3GPP Glossary

3GPP Specific Proxy Mobile IPv6 Error Code

A standardized error code defined within the Proxy Mobile IPv6 (PMIPv6) protocol for 3GPP-specific error conditions. It enables network elements to communicate precise failure reasons during mobility management procedures, facilitating troubleshooting and network optimization in 3GPP Evolved Packet Core (EPC) and 5G Core (5GC) networks.

5G Mobility Management

5GMM is the control-plane protocol in 5G that manages the mobility and registration states of a UE (User Equipment) in the 5G Core Network. It handles procedures like registration, deregistration, and service requests, enabling the UE to access network services and maintain connectivity while moving. It is a fundamental protocol for session management and network access in 5G.

5G Session Management

5GSM is the protocol for managing PDU Sessions in 5G networks. It handles session establishment, modification, and release between the UE and the SMF. It is crucial for enabling diverse 5G services with specific QoS requirements.

ATM Adaptation Layer

AAL is a protocol layer in the ATM protocol stack that adapts higher-layer protocols to the underlying ATM layer. It segments data into ATM cells and reassembles them, providing different service classes for various traffic types like voice, video, and data. It was crucial for early 3GPP networks using ATM transport.

ATM Adaptation Layer type 1

AAL1 is an ATM Adaptation Layer protocol designed for constant bit rate (CBR) services requiring timing synchronization between source and destination. It provides circuit emulation over ATM networks, enabling transport of traditional TDM traffic like voice and video. This protocol is crucial for legacy network integration and maintaining service quality in hybrid ATM/IP networks.

ATM Adaptation Layer type 2

AAL2 is a protocol layer that adapts variable-bit-rate, delay-sensitive traffic like voice and video for transport over an Asynchronous Transfer Mode (ATM) network. It enables efficient multiplexing of multiple low-bit-rate connections into a single ATM Virtual Channel Connection (VCC), optimizing bandwidth usage. It was crucial for early 3GPP UMTS networks where ATM was the primary transport technology for the lu and lub interfaces.

ATM Adaptation Layer type 5

AAL5 is a protocol layer in the ATM stack designed for efficient, connection-oriented transport of variable-length data packets, primarily IP datagrams, over Asynchronous Transfer Mode networks. It provides segmentation and reassembly with low overhead, crucial for early 3GPP core network interfaces like Iu-PS and Gn, enabling reliable data transport in 2G/3G systems.

Asynchronous Balanced Mode

ABM is a data link layer operational mode in the LAPDm protocol, used for signaling in GSM. It establishes a balanced, peer-to-peer connection between two entities, enabling simultaneous two-way communication with error detection and recovery. This is essential for reliable signaling exchanges in mobile networks.

Augmented Backus-Naur Form

ABNF is a formal syntax specification language used extensively in 3GPP technical specifications to define protocol message formats, data structures, and encoding rules. It provides a precise, machine-readable way to describe complex telecommunications protocols, ensuring interoperability between different network elements and vendors. Its importance lies in eliminating ambiguity in protocol implementations.

Accelerated H.245 Procedures

ACP is a 3GPP protocol enhancement that accelerates the establishment of H.245 control channels for multimedia sessions, such as video calls, in mobile networks. It reduces call setup delays by optimizing the negotiation of codecs and capabilities, improving user experience for real-time services. This is particularly important for ensuring responsive and efficient multimedia communication over 3G and 4G systems.

Association Control Service Element

ACSE is an OSI application-layer protocol that establishes, maintains, and terminates associations between application entities. It provides reliable connection management for services like SMS, enabling secure and orderly communication sessions between network elements in 3GPP systems.

Access Link Control Application Protocol

ALCAP is a transport network signaling protocol used in 3GPP UMTS networks to dynamically establish, manage, and release transport bearers for user plane traffic. It operates between network elements like the RNC and Node B to set up AAL2 connections over Iub and Iur interfaces. Its role is crucial for efficient resource utilization and supporting real-time services.

Acknowledged Mode Data

AMD is a Radio Link Control (RLC) protocol mode in 3GPP networks that ensures reliable data delivery through automatic repeat request (ARQ) mechanisms. It provides error correction, in-sequence delivery, and duplicate detection for control signaling and user data requiring guaranteed delivery. This mode is fundamental for maintaining connection integrity and quality of service in UMTS, LTE, and 5G NR systems.

Answer Message

ANM is an ISUP signaling message used in circuit-switched telephony to indicate that a called party has answered a call. It is a critical part of call setup and teardown procedures, allowing billing to commence and resources to be allocated for the conversation. Its role is foundational in legacy SS7-based networks for managing call state.

Access Network Query Protocol

ANQP is a query/response protocol used by mobile devices to discover information about available access networks before connecting. It enables efficient network selection by providing metadata about network capabilities, services, and policies. This protocol is crucial for seamless Wi-Fi offloading and network discovery in 3GPP-WLAN interworking scenarios.

Additional Protocol Configuration Options

APCO is a mechanism in 3GPP standards that allows network operators to configure additional protocol parameters beyond the basic PDP context. It enables flexible protocol stack configuration for user sessions, supporting diverse services and applications. This capability is crucial for implementing advanced network features, service differentiation, and supporting legacy or proprietary protocols.

Application Protocol Data Unit

APDU is a structured data unit used for communication between a smart card (e.g., UICC/USIM) and an external application or network entity. It enables secure, standardized commands and responses for operations like authentication, subscription management, and application execution, crucial for mobile security and services.

Application Transport Mechanism / Application Transport Message

APM is a 3GPP protocol mechanism for transporting application-level data, such as signaling for supplementary services, over IP-based networks. It enables the delivery of service-specific information between network entities, ensuring interoperability and reliable transport. This is crucial for maintaining legacy service functionality in modern all-IP core networks.

Application-defined RTCP packet

An extension mechanism for the Real-time Transport Control Protocol (RTCP) that allows applications to define custom packet types for session-specific control information. It enables richer media session control beyond standard RTCP reports, facilitating enhanced monitoring, feedback, and signaling for multimedia services.

Automatic Repeat Request

ARQ is an error-control protocol used in data link and transport layers to ensure reliable data transmission over unreliable channels. It works by detecting errors in received packets and automatically requesting retransmissions from the sender. This mechanism is fundamental to maintaining data integrity in wireless communication systems where channel conditions are variable.

Asynchronous Transfer Mode

ATM is a cell-switching, connection-oriented networking protocol used in early 3GPP releases for core and access network transport. It provided deterministic Quality of Service (QoS) for voice and data by using fixed-size 53-byte cells. It was foundational for UMTS transport before being superseded by IP-based solutions.

Attribute-Value Pair

AVP is a fundamental data structure used in Diameter-based protocols to encode information elements. It consists of an attribute header identifying the data type and a value field containing the actual data. AVPs are essential for flexible and extensible signaling, enabling the transport of diverse parameters like subscriber identities, QoS settings, and charging information across network interfaces.

Backhaul Adaptation Protocol

BAP is a layer 2 protocol introduced in 3GPP Release 16 for Integrated Access and Backhaul (IAB) networks. It enables the dynamic routing of data and control packets between IAB nodes and the donor node over wireless backhaul links. It is crucial for creating flexible, multi-hop, and self-organizing wireless backhaul topologies.

Bearer Association Transport

BAT is a protocol mechanism that enables the association of multiple IP flows or bearers to specific transport resources in 3GPP networks. It ensures proper mapping between service data flows and underlying transport bearers, optimizing resource utilization and supporting QoS differentiation across different network domains.

Bearer Capability Information Element

BCIE is a structured information element within 3GPP signaling protocols that defines the characteristics and requirements of a bearer service. It is transmitted during call setup and bearer establishment procedures to negotiate and configure the appropriate transport resources between network entities. Its standardized format ensures interoperability across different network nodes and vendors.

Basic Communication Part

BCP is a protocol component within 3GPP's Mission Critical Push to Talk (MCPTT) service, standardized in TS 24.275. It provides the fundamental communication mechanisms for establishing, maintaining, and terminating group or private MCPTT calls. It is crucial for ensuring reliable, low-latency voice communication in public safety and mission-critical scenarios.

Basic Encoding Rules

BER is a set of standardized rules for encoding data structures defined in ASN.1 (Abstract Syntax Notation One) into a serialized binary stream. It is a fundamental encoding scheme used extensively in 3GPP protocols for signaling messages, ensuring unambiguous data exchange between network elements regardless of their internal hardware or software architecture.

Basic Encoding Rules - Tag Length Value

BER-TLV is a standardized data encoding format used in 3GPP specifications, particularly for smart card applications like USIMs. It structures data into a tag (identifying the data object), a length (specifying its size), and a value (the actual data). This format is crucial for ensuring reliable, unambiguous, and flexible data exchange between network entities and UICCs.

Binary Floor Control Protocol

BFCP is a binary protocol for managing shared resources, like the 'floor' (permission to speak or transmit), in conferencing and real-time communication services. It is crucial for coordinating media transmission in IMS-based multimedia sessions, ensuring orderly and fair access among participants.

Block Header

The Block Header (BH) is a protocol data unit structure used in 3GPP specifications for data transmission, particularly in the context of Short Message Service (SMS) and other bearer-independent core network protocols. It provides essential control information for the segmentation, reassembly, and routing of data blocks within the network. Its standardized format ensures reliable and interoperable message handling across different network elements and releases.

BootstrappingInfo-Answer message

The BootstrappingInfo-Answer (BIA) is a Diameter protocol message used in the 3GPP Generic Authentication Architecture (GAA). It is sent by the Bootstrapping Server Function (BSF) to the Network Application Function (NAF) to securely deliver bootstrapping information, enabling application-layer authentication and key agreement. This message is critical for establishing secure sessions between user equipment and network-based applications without requiring separate user credentials.

Broadcast/Multicast Control

BMC is a sublayer in the UMTS protocol stack responsible for managing broadcast and multicast data delivery over the air interface. It handles scheduling, segmentation, and reassembly of broadcast/multicast messages, enabling efficient point-to-multipoint transmission. This protocol is essential for services like cell broadcast SMS and multimedia broadcast/multicast services (MBMS).

Binding Revocation Acknowledgement

BRA is a Diameter-based protocol message used in the 3GPP Evolved Packet Core (EPC) to acknowledge the successful revocation of a mobility binding. It is a critical component of the Gx interface, ensuring that policy and charging control (PCC) rules are properly terminated when a user's IP-CAN session ends, preventing resource leaks and billing errors.

Binding Revocation Indication

BRI is a signaling message used in the GPRS Tunneling Protocol (GTP) to explicitly request the revocation of binding information between network nodes. It ensures proper cleanup of mobility and session contexts when connections are terminated or resources need to be released, preventing stale bindings that could cause routing errors or resource leaks.

Base Station Subsystem Application Part

BSSAP is a signaling protocol used in GSM and UMTS networks to manage communication between the Base Station Subsystem (BSS) and the Mobile Switching Center (MSC). It handles critical functions like call setup, handover, and location updating, ensuring seamless mobility and service continuity. Its role is fundamental for circuit-switched voice and data services in 2G/3G networks.

Base Station System Application Part Location Services Extension

BSSAP-LE is a protocol extension to BSSAP that enables location services (LCS) in GSM networks. It facilitates communication between the Serving Mobile Location Center (SMLC) and the Base Station Controller (BSC) for positioning operations. This protocol is essential for implementing emergency services, location-based services, and lawful interception capabilities in 2G networks.

Base Station System GPRS Protocol

BSSGP is a layer 3 protocol that operates between the SGSN and BSS across the Gb interface in 2G/3G GPRS and EDGE networks. It provides connectionless transport for LLC PDUs and supports mobility management, paging, and radio resource management functions. It is crucial for separating radio network and core network functions.

Base Station System Application Part

BSSLAP is a signaling protocol used for location services (LCS) in GSM and early UMTS networks. It operates between the Serving Mobile Location Centre (SMLC) and the Base Station Controller (BSC) to support positioning methods like Enhanced Observed Time Difference (E-OTD). It enables the network to determine a mobile device's geographical location.

Base Station Subsystem Management Application Part

BSSMAP is a signaling protocol used between the Base Station Controller (BSC) and Mobile Switching Center (MSC) in GSM networks. It manages radio resource allocation, handover control, and BSS operation and maintenance functions. This protocol is essential for coordinating mobility management and call control between the radio access and core network domains.

BSS GPRS Protocol Virtual Connection

BVC is a logical connection within the Gb interface that transports GPRS signaling and user data between the BSS and SGSN. It provides virtual point-to-point connectivity for BSSGP protocol messages, enabling efficient packet data routing and mobility management in 2G/3G networks. This abstraction layer separates physical transport from logical connections, allowing multiple BVCs to share the same physical resources.

Block Waiting Time

Block Waiting Time (BWT) is a timer parameter used in 3GPP protocols, particularly in the Radio Link Control (RLC) layer, to manage retransmissions of data blocks. It defines the maximum time the transmitter waits for an acknowledgment before retransmitting a block, ensuring reliable data delivery. This mechanism is crucial for controlling latency and optimizing throughput in wireless communication.

Command Application Protocol Data Unit

C-APDU is a standardized command structure used in 3GPP networks for communication between applications and smart cards (UICC/USIM). It enables secure execution of commands like authentication, file access, and applet management. This protocol ensures interoperability between network equipment and subscriber identity modules across different manufacturers and network generations.

Control Service Access Point

The Control Service Access Point (C-SAP) is a logical interface defined in the Radio Link Control (RLC) sublayer of the UTRAN protocol stack. It provides a standardized access point for the upper layer (RRC) to exchange control information with the RLC layer, enabling reliable signaling and control plane operations. Its definition ensures a clear separation of control and user plane functions within the radio interface protocols.

Command Transport Protocol Data Unit

C-TPDU is a protocol data unit used for control signaling within the transport layer of 3GPP networks. It carries commands for connection establishment, release, and management between network entities, ensuring reliable control plane communication.

Command/Response field bit

The C/R bit is a single-bit field in the Layer 2 protocol data unit (PDU) header, primarily in protocols like LAPDm and its derivatives. It distinguishes between a command frame sent by one entity and a response frame sent by another, defining the direction and control relationship for data link layer operations. This fundamental bit is crucial for establishing and managing logical connections, ensuring proper frame sequencing, and enabling error recovery procedures in cellular signaling.

CCITT Signalling System No. 5

C5 is an early digital common channel signalling system standardized by CCITT (now ITU-T) for international telephone networks. It enables out-of-band signalling between international switching centers, separating call control information from voice channels to improve efficiency and enable advanced services. Though largely superseded by later systems like SS7, it represents a foundational step in digital signalling evolution.

Capacity Allocation Acknowledgement

Capacity Allocation Acknowledgement (CAA) is a protocol message used in 3GPP networks to confirm the successful allocation of radio resources. It is a critical component of the Radio Resource Control (RRC) and Radio Link Control (RLC) protocols, ensuring reliable data transmission and efficient spectrum utilization.

CAMEL Application Part

CAP is a signaling protocol used in CAMEL (Customized Applications for Mobile networks Enhanced Logic) to enable real-time, intelligent service control in mobile networks. It connects network elements like the SSF (Service Switching Function) to external platforms such as the OCS (Online Charging System) or SCP (Service Control Point), allowing for advanced prepaid services, number translation, and other value-added services.

Channel Associated Signalling

Channel Associated Signalling (CAS) is a legacy telephony signalling method where control information travels within the same physical channel as the voice/data traffic. It contrasts with Common Channel Signalling (CCS) systems like SS7, where signalling uses separate dedicated channels. CAS was foundational in early digital telephony but has been largely superseded by more efficient packet-based signalling in modern 3GPP networks.

Concise Binary Object Representation

CBOR is a compact binary data format designed for constrained environments like IoT devices. It provides efficient encoding of structured data with minimal overhead, enabling resource-efficient communication in 5G networks. Its importance lies in reducing bandwidth consumption and processing requirements for devices with limited capabilities.

Cell Broadcast Service Protocol

CBSP is a protocol used in 3GPP networks to deliver Cell Broadcast messages, such as Public Warning System alerts, to all devices in a specific geographical area. It operates between the Cell Broadcast Center (CBC) and the core network (e.g., MME, AMF). Its primary purpose is to enable efficient, reliable, and immediate mass notification services for emergency and commercial information.

Control Channel Segmentation and Reassembly Layer

CCSRL is a protocol layer in 3GPP IMS that segments and reassembles control messages for reliable transmission over transport protocols with size limitations. It ensures complete delivery of large SIP messages by breaking them into manageable packets and reconstructing them at the receiver. This is essential for maintaining signaling integrity in IMS networks.

Concise Data Definition Language

CDDL is a standardized data modeling language used in 3GPP specifications to define data structures and their constraints. It provides a human-readable and machine-processable format for describing JSON and CBOR data formats, ensuring interoperability between network functions and applications. Its adoption enables consistent implementation of data models across different vendors and systems.

Compressed Data Stream Length

CDSL is a parameter defined in 3GPP TS 23.042 for SMS compression, specifying the length of a compressed data stream. It is essential for efficient SMS transmission by enabling the network to correctly parse compressed messages, reducing payload size and conserving radio resources. This mechanism supports reliable delivery of compressed text and data in legacy GSM and UMTS networks.

Capabilities Exchange Request

A Diameter protocol message used to initiate a capabilities exchange between Diameter peers. It allows nodes to discover each other's supported applications, vendor-specific features, and security mechanisms, ensuring interoperability and proper session handling in 3GPP networks.

Connectionless Network Protocol

CLNP is an OSI network layer protocol standardized by 3GPP for connectionless data transfer in early GPRS networks. It provides datagram services, enabling packet routing without establishing a dedicated circuit, which was foundational for mobile packet data. It was later superseded by IP in 3GPP architectures.

Connect Acknowledgement

CONNACK is a protocol message used in 3GPP networks to acknowledge the successful establishment of a connection. It is a critical component of connection management signaling, confirming that a connection request has been processed and accepted by the network. This acknowledgement mechanism ensures reliable session setup and enables subsequent data transfer.

Character Oriented Non‑Transparent Protocol

CONTP is a 3GPP protocol for transmitting character-oriented data over wireless networks without transparency requirements. It enables reliable transmission of terminal-to-terminal character data, supporting applications like teletype and legacy text-based systems. This protocol ensures data integrity while maintaining compatibility with character-based communication systems.

Common Open Policy Service

COPS is a client-server protocol defined by the IETF and adopted by 3GPP for policy control and resource management in mobile networks. It enables policy decision points (PDPs) to communicate policy decisions to policy enforcement points (PEPs), ensuring consistent application of QoS, charging, and access control rules across network elements. This protocol is fundamental for implementing dynamic policy control in 3GPP architectures like IMS and PCC.

Common Part Convergence Sublayer

The Common Part Convergence Sublayer (CPCS) is a protocol layer within the Iub interface's transport network layer, standardized in 3GPP. It provides common data transport services for different user plane protocols between the RNC and Node B, enabling efficient multiplexing and reliable data transfer. Its role is crucial for maintaining consistent transport mechanisms across various radio access network services.

Command Protocol Data Unit

A standardized protocol data unit used for test equipment control and measurement commands in 3GPP conformance testing. It enables automated testing of UE RF performance by providing a structured format for test commands and responses between test systems and devices under test.

SCCP Connection Refused

A Signaling Connection Control Part (SCCP) message indicating a connection establishment request has been rejected. It is a critical error response in the SS7 signaling network, used to manage signaling connections between network nodes like MSCs and HLRs. It ensures signaling resources are not wasted on unsuccessful connections.

Conditional on Value

CV (Conditional on Value) is a protocol mechanism in 3GPP's Radio Resource Control (RRC) layer, specified in TS 25.331. It enables the network to send configuration messages to the User Equipment (UE) where certain information elements are included or omitted based on the value of other parameters. This optimizes signaling overhead by avoiding the transmission of redundant or unnecessary data, improving air interface efficiency.

Destination ADdress

DAD is a field in packet headers that specifies the final recipient's address in 3GPP network protocols. It ensures accurate routing and delivery of user data and control messages across interfaces like Gn and S5/S8. This fundamental addressing mechanism is critical for maintaining end-to-end connectivity and session management in mobile networks.

Diameter Base Protocol Accounting

DBPA is the Diameter protocol's accounting framework within 3GPP networks, enabling the collection, correlation, and transport of usage data for billing and charging. It provides a standardized, reliable, and secure method for network elements to report resource consumption to charging systems. This is fundamental for monetizing services and ensuring accurate subscriber billing.

Dedicated Control Service Access Point

DC-SAP is a logical service access point in the UTRAN protocol stack, specifically within the Radio Resource Control (RRC) layer. It provides a defined interface for exchanging dedicated control signaling messages between the RRC entity and its upper layers, ensuring reliable and structured communication for UE-specific procedures like connection establishment, handover, and measurement control.

Diameter Credit Control

DCC is a Diameter-based protocol defined in 3GPP for real-time credit control and online charging in packet-switched networks. It enables network operators to manage subscriber spending, enforce quotas, and support prepaid and hybrid billing models by interacting with charging systems during service sessions. This is crucial for monetizing data services and preventing revenue leakage.

Diameter Credit Control Application

DCCA is a Diameter-based protocol for real-time credit control in 3GPP networks. It enables service providers to manage prepaid and postpaid billing, enforce spending limits, and control service usage. This is essential for monetizing network services and preventing revenue leakage.

Data Channel Establishment Protocol

DCEP is a 3GPP protocol used to establish, manage, and tear down data channels for services like IMS and MCPTT. It operates as an application layer protocol, typically over TCP or SCTP, to negotiate channel parameters and ensure reliable data delivery. Its importance lies in providing a standardized mechanism for session-oriented data services within the 3GPP ecosystem.

Data Description Indicator

The Data Description Indicator is a protocol element used in 3GPP RRC signaling to describe the characteristics of a data flow or radio bearer. It provides essential information to the network and UE for proper data handling, including traffic class, QoS parameters, and logical channel mapping. Its correct interpretation is crucial for establishing and maintaining the appropriate radio bearer configuration to meet service requirements.

Distinguished Encoding Rules

DER is a set of encoding rules for ASN.1 (Abstract Syntax Notation One), used to serialize structured data into a deterministic, unambiguous binary format. It ensures data integrity and interoperability for 3GPP protocols by providing a canonical encoding that eliminates redundancy and allows for exact binary comparisons, which is crucial for digital signatures and security operations.

Dynamic Host Configuration Protocol

DHCP is a network management protocol used to dynamically assign IP addresses and other network configuration parameters to devices. In 3GPP networks, it automates IP address allocation for User Equipment (UE) and network functions, enabling efficient resource management and seamless connectivity.

Disconnect

DISC is a specific frame type within the LAPDm (Link Access Procedure on the Dm channel) protocol used in GSM. It is a command sent to logically terminate a data link layer connection between a mobile station and the network, ensuring an orderly release of layer 2 resources before the physical channel is released or reassigned.

Data Link Connection

A logical connection established at the data link layer (Layer 2) between two network entities, such as a mobile station and a network node. It provides a reliable, sequenced data transfer service for user data and signaling. It is a fundamental transport mechanism in legacy GSM and GPRS systems.

Disconnected Mode

A frame type in 3GPP protocols indicating a state where a connection is logically maintained but the physical link is inactive. It is crucial for power saving and efficient resource management, allowing devices to temporarily suspend communication without fully releasing network resources.

Diameter Routing Message Priority

An attribute within the Diameter protocol that allows a Diameter node to assign a priority level to a request message. This enables intermediate Diameter Routing Agents (DRAs) to perform load balancing, overload control, and priority-based routing decisions.

Digital Subscriber Signalling System No. One

A signalling protocol used in Integrated Services Digital Network (ISDN) for call control and supplementary services between a subscriber terminal and the local exchange. In 3GPP, it is relevant as the basis for certain legacy circuit-switched signalling adaptations and for understanding the evolution towards all-IP signalling like SIP.

Digital Subscriber Signalling System No. 2

DSS2 is a signalling protocol used in the core network, specifically for establishing, managing, and releasing packet-switched connections in the NGN/IMS architecture. It is a 3GPP adaptation of the ITU-T Q.2931 standard for B-ISDN, enabling call control and bearer control functions over the Nc interface.

Direct Transfer Application Part

DTAP is a core network protocol used for transparently transferring non-call-related signaling messages, such as mobility management and session management messages, between the mobile station and the core network across the radio access network. It is a key component of the BSSAP and RANAP protocols in GSM and UMTS, enabling the separation of radio-specific and core network-specific signaling.

Datagram Transport Layer Security

A security protocol providing communications privacy for datagram protocols. It is used in 3GPP to secure delay-sensitive, unreliable transport like UDP, crucial for real-time services such as VoLTE and IoT data. It prevents eavesdropping, tampering, and message forgery.

Second Generation Digital Video Broadcasting - Return Channel via Satellite

The second-generation DVB standard for interactive satellite systems, specifying the return link from user terminals to the satellite network. It provides enhanced bandwidth efficiency, support for IP-based services, and improved QoS for broadband satellite communications. Integrated in 3GPP for satellite backhaul and NTN scenarios.

Distance Vector Multicast Routing Protocol

DVMRP is an interior gateway multicast routing protocol that builds source-specific distribution trees using a distance-vector algorithm. In 3GPP, it is referenced for IP multicast routing in interworking scenarios with external IP networks, such as between a GGSN/PDN-GW and an external multicast source. It enables efficient multicast data delivery across routed domains.

Explicit Congestion Notification-Capable Transport

A transport layer capability, primarily for TCP, that allows network nodes to signal impending congestion to endpoints before packet loss occurs. It enables more efficient congestion control, reducing latency and improving overall network throughput.

Ethernet Header Compression

EHC is a 3GPP protocol that compresses Ethernet frame headers over the air interface to reduce overhead and improve spectral efficiency. It is crucial for supporting Ethernet-based services, like industrial IoT and fronthaul, in 5G and beyond, enabling more efficient use of radio resources for time-sensitive traffic.

Error Indication

A protocol layer primitive used to signal an error condition from a lower layer to a higher layer within the 3GPP protocol stack. It is a fundamental mechanism for error reporting and recovery procedures, ensuring reliable data transfer and signaling.

Elementary Procedure

A fundamental, indivisible unit of communication between network entities in 3GPP systems. It defines a complete interaction, such as a request and its response, and is the basic building block for all signaling protocols, ensuring reliable and standardized message exchange.

Extended Protocol Discriminator

A field in 5G NAS (Non-Access Stratum) messages used to identify the protocol type of a message. It extends the traditional Protocol Discriminator to support a wider range of protocols and future enhancements, ensuring backward compatibility and flexibility in 5G core network signaling.

External Protocol Data Unit

An External Protocol Data Unit is a container used in protocol layer encapsulation, particularly in the Service Data Adaptation Protocol (SDAP) in 5G NR and the LTE Positioning Protocol (LPP). It carries higher-layer protocol data, including headers and payload, as a single unit for processing by a peer entity. It is fundamental for efficient data unit handling and protocol transparency.

Encoding Symbol Identifier

The Encoding Symbol Identifier (ESI) is a key field within the Forward Error Correction (FEC) framework, specifically in Raptor and RaptorQ codes. It uniquely identifies each encoding symbol (source or repair) within a source block, enabling the receiver to correctly reconstruct the original data after transmission over an unreliable channel.

Extension payload

An Extension payload, a protocol data unit used in 3GPP specifications to carry optional or additional information within a message or packet structure. It provides a flexible mechanism for future enhancements and vendor-specific extensions without breaking existing protocol formats, ensuring backward and forward compatibility.

F1 Application Protocol

F1AP is the application layer protocol operating over the F1-C interface between a gNB-CU and a gNB-DU. It defines the signaling procedures for UE management, bearer control, and mobility, enabling coordinated operation in a disaggregated 5G RAN.

Final Block Indicator

A control bit used in data link layer protocols, notably in GSM's Radio Link Protocol (RLP) and related standards. It signals that the current block is the final one in a sequence or higher-layer packet, allowing the receiver to properly reassemble data units and manage the data window.

Frame Checking Sequence

A Frame Checking Sequence is a checksum or error-detecting code appended to a data frame or packet at the physical or link layer. It allows the receiver to detect transmission errors caused by noise or interference, ensuring data integrity by verifying that the received bits match the sent bits before processing.

Format Identifier

A field in protocol data units (PDUs) that indicates the structure and encoding of the subsequent data. Used in layers like PDCP and MAC to enable multiplexing, efficient header compression, and correct interpretation of packets in 3GPP systems.

First Input First Output

A fundamental queuing discipline where packets are processed in the exact order they arrive. In 3GPP, it's a baseline scheduling and buffering method used in protocol layers (e.g., RLC, PDCP) to ensure in-order delivery, providing simplicity and fairness for data flows without strict latency requirements.

First Missing PDCP SN

A PDCP status report field indicating the first missing PDCP Sequence Number (SN) in a reception window. It is crucial for efficient ARQ-based loss detection and retransmission in LTE and NR, enabling reliable data delivery over the radio interface.

Feedback Message Type

A field in MBMS feedback reports sent by UEs to indicate the type of feedback being provided, such as decoding status or channel quality. It enables efficient multicast/broadcast service delivery by allowing the network to collect receiver performance data and optimize transmissions.

Frame Reject

A control frame type in the GSM data link layer (LAPDm protocol) used to report unrecoverable errors in a received frame. It initiates retransmission procedures, ensuring data integrity over the radio interface for signaling and packet data services.

Finite State Model

A formal model used to define the behavior of communication protocols, where a system can be in one of a finite number of states and transitions between them based on events. It is crucial for specifying unambiguous protocol procedures in 3GPP standards, ensuring interoperability.

Frame Sequence Number

A number assigned to data frames in a sequence to ensure correct ordering, detect loss, and support retransmission mechanisms. It is a fundamental element in link-layer and transport protocols within the UTRAN Iur and Iub interfaces for reliable data delivery.

Frame Tunnelling Mode

A mode of operation for the Terminal Adaptation Function (TAF) in 3GPP that allows the transparent tunnelling of complete data link layer frames between a Mobile Terminal (MT) and an Interworking Function (IWF). It is used to support legacy data services like GSM Circuit Switched Data over 3G/UMTS networks.

File Transfer Protocol

A standard network protocol used within 3GPP systems for transferring files between network elements, management systems, and user equipment. It is used for software updates, configuration management, log retrieval, and lawfully intercepted data delivery. It provides reliable, bulk data transport over IP connections.

GTP encapsulated user Plane Data Unit

A data unit that encapsulates user plane traffic within the GTP protocol for transport across the core network. It is fundamental for carrying user data (e.g., IP packets) between network nodes like the SGW and PGW in EPS, or the UPF in 5GS, enabling efficient tunneling and mobility management.

Generic Access - Resource Control

A protocol within the Generic Access Network (GAN) framework, also known as UMA, for managing resources and controlling connections between a mobile device and a GAN Controller (GANC) over unlicensed wireless IP networks like Wi-Fi. It enables secure, seamless handovers of voice and data sessions between cellular and IP-based access, extending service coverage.

Generic Access - Radio Resource Control

A protocol in the Generic Access Network (GAN) that manages radio resources and mobility for the IP-based access leg. It adapts cellular RRC principles to control the unlicensed radio link (e.g., Wi-Fi), handling measurements, handover preparation, and system information for seamless service continuity between cellular and IP domains.

Generic Address Parameter

A parameter used in signaling protocols to carry address information in a generic, flexible format. It enables the transport of various address types, such as IP addresses or E.164 numbers, within control messages, ensuring interoperability across different network elements and services.

General Control (SAP)

A Service Access Point (SAP) used in the protocol architecture of UMTS and LTE radio access layers. It denotes the logical interface and service primitives for general control signaling between the Radio Resource Control (RRC) layer and lower layers (RLC, MAC, PHY). This matters for the configuration and control of radio bearers and physical channels.

General Control Service Access Point

GC-SAP is a service access point defined in the Radio Resource Control (RRC) protocol layer. It provides the interface for the transfer of general control information between the RRC and the upper layers, specifically for broadcast and multicast services. It is essential for managing system information and cell broadcast messages in UMTS networks.

Gateway Control Protocol

Gateway Control Protocol (GCP) is a 3GPP adaptation of the ITU-T H.248/Megaco protocol. It defines the signaling interface between a Media Gateway Controller (MGC) and a Media Gateway (MGW) for controlling bearer resources. It is fundamental for separating call control from media transport in modern telecommunications networks.

Generic Routing and Encapsulation

Generic Routing and Encapsulation (GRE) is a tunneling protocol used to encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an IP network. In 3GPP, it is used for encapsulating user plane and control plane packets between network functions, particularly in EPS and 5G architectures for backhaul and interconnect.

GPRS Radio Resources service access point

GRR is a service access point (SAP) within the GPRS protocol stack, specifically between the LLC and RLC/MAC layers. It defines the primitives for managing radio resources, enabling data transfer and signaling over the air interface. It is a foundational interface for packet-switched data services in 2G/3G networks.

GPRS Tunnelling Protocols

A suite of IP-based protocols used in 3GPP mobile networks to encapsulate and tunnel user data and control signaling between network nodes, primarily between the core network and radio access network. It enables mobility and session management by creating secure, logical connections over the IP backbone.

GPRS Tunnelling Protocol for Control Plane

The control plane component of the GTP protocol suite, responsible for signaling procedures such as tunnel establishment, modification, and deletion between core network nodes. It manages session and mobility contexts, enabling dynamic user plane path management in mobile networks.

GPRS Tunnelling Protocol for User Plane

The user plane component of the GTP protocol suite, used to tunnel actual user data packets between network nodes such as RAN and core gateways. It encapsulates IP packets within GTP headers for transport over the mobile backbone, enabling efficient data forwarding and mobility support.

Hypertext Application Language

Hypertext Application Language (HAL) is a media type and format for representing resources and their relationships in RESTful APIs, using hyperlinks for navigation. It standardizes API responses with embedded links and resources, improving discoverability and client-server decoupling. In 3GPP, HAL is used in service-based interfaces for network function communication.

Header Compression

A technique that reduces the size of packet headers (e.g., IP, UDP, RTP) before transmission over a radio link to save valuable bandwidth and reduce latency. It is essential for efficient transport of voice (VoIP) and other real-time, small-packet traffic over wireless links.

High Level Data Link Control

A bit-oriented, synchronous data link layer protocol standardized by ISO. In 3GPP, it is used for framing and reliable data transfer over various interfaces, particularly in early UMTS and GSM core network signaling links. It provides error detection, flow control, and data transparency.

Host Identity Protocol

HIP is a host identification and mobility management protocol that separates a host's identity from its network location. It introduces a cryptographic Host Identity (HI) to decouple the transport layer from internetworking, enabling secure host mobility, multihoming, and improved security for IP communications.

Home Node B Application Part

HNBAP is a control plane protocol used between a Home Node B (HNB) and the HNB Gateway (HNB-GW) in 3GPP femtocell networks. It manages the registration, configuration, and control of the HNB, enabling secure and efficient operation of small cells in residential or enterprise environments. It is crucial for integrating femtocells into the mobile core network.

High Reliability Protocol

A transport layer protocol designed for ultra-reliable low-latency communication (URLLC) in 5G networks. It operates above the IP layer, providing enhanced reliability through mechanisms like packet duplication, advanced forward error correction (FEC), and stringent latency control for critical industrial and vehicular applications.

High Speed Protocol

A security protocol defined in 3GPP for securing high-speed data transfers, particularly for Lawful Interception (LI) and similar applications. It ensures the integrity, confidentiality, and reliable delivery of intercepted data between network functions and mediation/collection systems.

Hypertext Transfer Protocol

The application-layer protocol for distributed, collaborative, hypermedia information systems. It is the foundation of data communication for the World Wide Web and is the primary protocol used for transporting web traffic, including HTML, over 3GPP mobile networks.

Hyper Text Transfer Protocol Secure

HTTPS is HTTP/1.1 secured with SSL/TLS, operating on port 443. It provides encrypted and authenticated communication for web-based services in 3GPP networks, protecting user data and signaling integrity between network functions and user equipment.

Initial Address Message

An ISUP (ISDN User Part) signaling message used in circuit-switched telephony networks to initiate a call. It carries essential call setup information like called party number, calling party number, and bearer capability. It is fundamental for establishing voice calls in legacy GSM and early UMTS networks.

Internet Control Message Protocol

A network-layer protocol used for diagnostic and error reporting in IP networks. It enables devices to communicate network status, such as unreachable destinations or time exceeded, and supports utilities like ping and traceroute. It is essential for network troubleshooting and management.

Information Element

A fundamental data structure in 3GPP protocols, used to encapsulate specific pieces of information exchanged between network entities. It is the basic building block of protocol messages, enabling the transmission of parameters like identifiers, configuration settings, and measurement results. Its standardized format ensures interoperability across different vendors and network generations.

Information Element Data

Refers to the actual value or content part of an Information Element (IE) within a 3GPP protocol message. While the IE defines the structure and meaning, the IED is the specific instance of data carried within that structure for a particular message exchange. It is the payload that enables dynamic configuration, signaling, and control in the network.

Information Element Identifier

A fundamental field in 3GPP protocol messages that uniquely identifies a specific Information Element (IE) within a protocol data unit. It allows the receiver to interpret the content, type, and structure of the following data, enabling extensible and structured communication between network entities.

Information Element Identifier Data Length

A protocol field in 3GPP specifications that defines the length of the data portion for a specific Information Element (IE). It is a fundamental component for parsing and constructing protocol messages, ensuring data integrity and interoperability between network elements.

Internet Engineering Task Force Standard

Refers to standards developed by the IETF, an open international community that designs and promotes voluntary Internet standards. In 3GPP, IETF standards (like SIP, Diameter, IPsec) are adopted and profiled for use in mobile network architectures, enabling internetworking with the global Internet.

Information Field Sizes

Standardized definitions for the maximum bit lengths of data fields within 3GPP protocol messages and information elements. They ensure interoperability between network elements and user equipment by defining precise data structures for encoding and decoding signaling and user data.

Information Field Size for the UICC

A subset of Information Field Sizes specifically defining the maximum lengths of data fields used in communications with the Universal Integrated Circuit Card (UICC), including the SIM/USIM. It standardizes commands and responses between the mobile terminal and the UICC for secure authentication, subscription management, and application toolkit operations.

Internet Group Management Protocol

A network-layer protocol used by IP hosts and adjacent multicast routers to establish and manage multicast group memberships. It enables efficient one-to-many data distribution, which is critical for services like IPTV, video conferencing, and software updates within 3GPP networks, reducing bandwidth consumption compared to unicast.

Internet Inter-ORB Protocol

IIOP is a protocol enabling communication between distributed objects using the Common Object Request Broker Architecture (CORBA) over TCP/IP networks. It is used in 3GPP for certain management and charging interfaces, allowing interoperability between network elements from different vendors.

Internet Message Access Protocol, version 4

IMAP4 is a standardized protocol for accessing and managing email messages on a remote mail server. It enables users to view, organize, and manipulate messages without downloading them to the client, supporting offline operation and server-side folder management. Its inclusion in 3GPP standards facilitated mobile email services.

Intelligent Network Application Protocol

A signaling protocol used for communication between Intelligent Network (IN) functional entities, such as between a Service Switching Point (SSP) and a Service Control Point (SCP). It carries queries and instructions for executing advanced telecommunication services like call forwarding and number translation.

INFormation field

The INF is a variable-length field within certain 3GPP protocol data units used to carry essential control or user information. Its structure and interpretation are defined by the specific protocol and message type, making it a fundamental, flexible container for payload in signaling and data transmission.

IP Bearer Control Protocol

A protocol used within the 3GPP IMS framework for negotiating and controlling the characteristics of IP-based media bearers (e.g., voice over IP streams) between endpoints or network nodes. It enables dynamic resource reservation and parameter agreement for media flows.

IP Control Protocol

IP Control Protocol (IPCP) is a Network Control Protocol (NCP) within the Point-to-Point Protocol (PPP) suite, specifically used for configuring, enabling, and disabling the IPv4 protocol modules on both ends of a PPP link. It is essential for establishing IPv4 connectivity over serial point-to-point links, commonly used in legacy dial-up and some backhaul scenarios.

Internet Protocol Stack

The Internet Protocol Stack (IPS) is the standardized suite of protocols enabling IP-based communication within 3GPP networks. It defines the layered architecture for data transmission, ensuring interoperability between network elements and external IP networks. Its specification is foundational for delivering all packet-switched services, from basic internet access to IMS-based voice.

IPv6 Control Protocol

IPV6CP is a Network Control Protocol (NCP) within the Point-to-Point Protocol (PPP) suite, used to establish, configure, test, and terminate the IPv6 protocol over a PPP link. It negotiates IPv6-specific parameters like interface identifiers between two peers, enabling IPv6 connectivity on serial links.

MIME ISDN User Part Multi-purpose Internet Mail Extension

ISUP, in the context of MIME extensions, refers to the adaptation of the traditional ISDN User Part signaling protocol for transport over IP-based networks using MIME encapsulation. It enables the carriage of legacy circuit-switched call control signaling within SIP or other IP messaging frameworks, facilitating network interworking.

JSON Content Rules

JSON Content Rules (JCR) is a formal language defined in 3GPP for specifying the structure, constraints, and validation rules for JSON data used in network APIs and service interfaces. It provides a standardized way to describe JSON schemas, ensuring data consistency and interoperability between different network functions and external applications.

JavaScript Object Notation

JSON is a lightweight, text-based data interchange format used extensively in 3GPP for service-based interfaces (SBI), network function (NF) communication, and management data representation. It enables structured data exchange in APIs, replacing older, bulkier formats like XML in many 5G core network protocols.

Layer 2 (Data Link Layer)

The second layer in the protocol stack, responsible for node-to-node data transfer, error control, flow control, and logical link management over the physical layer. In 3GPP, it is subdivided into sublayers: MAC, RLC, and PDCP. It ensures reliable and efficient data transmission between the UE and the network.

COP L2R Character Orientated Protocol

A character-oriented data link layer protocol used for reliable point-to-point communication, often for management or control signaling. It frames data as sequences of characters, providing error control and link management functions, and is a foundational protocol for certain legacy 3GPP interfaces.

Layer 2 Relay Character Oriented Protocol

A protocol for relaying character-oriented data link layer frames, enabling the extension or interconnection of Layer 2 links. It operates by receiving, potentially processing, and forwarding L2R frames, facilitating network topologies beyond simple point-to-point connections for management and control traffic.

Layer Two Tunneling Protocol

An IETF-derived tunneling protocol used within 3GPP networks to transport Layer 2 packets (like PPP frames) over IP networks. It is primarily used in the Packet Data Network Gateway (PGW/PGW-U) to establish tunnels for user data sessions between the network and external packet data networks.

Layer 3

In the OSI model, Layer 3 is the network layer responsible for logical addressing, routing, and forwarding of data packets across different networks. In 3GPP, it primarily refers to the IP layer and the control-plane signaling protocols (like RRC, NAS) that operate at this layer to manage connectivity and mobility.

Link Access Procedure Balanced

LAPB is a data link layer protocol used in 3GPP systems for reliable, error-controlled point-to-point connections, often for signaling transport. It is a balanced-mode adaptation of HDLC, ensuring data integrity between network elements. Its structured frame handling is foundational for legacy circuit-switched and packet data interfaces.

Link Access Procedure on the D-channel

LAPD is a data link layer protocol used in ISDN and adapted in 3GPP for signaling transport, particularly over the D-channel. It provides reliable, multiplexed communication between multiple endpoints over a single physical interface. In mobile networks, it's crucial for layer 2 signaling in interfaces like the A-bis.

Link Access Procedure for Modems

LAPM is a data link layer protocol used for error correction and data compression in modem communications, standardized by ITU-T V.42. In 3GPP, it is referenced for circuit-switched data services, ensuring reliable data transfer over analog modem connections. It enhances throughput and reliability for fax and dial-up data.

Layer Convergence Information

LCI is a protocol mechanism used to convey information about the convergence of protocol layers, particularly for efficient data transmission and session management. It enables the network and user equipment to align on layer configurations and capabilities, ensuring optimized resource usage and service continuity across different access technologies.

LCS Application Protocol

The LCS Application Protocol (LCS-AP) is a control plane protocol defined by 3GPP for location services. It facilitates communication between network entities like the Gateway Mobile Location Centre (GMLC) and the Mobile Management Entity (MME) or Serving GPRS Support Node (SGSN) to request and deliver location information for a target UE. It is fundamental for enabling emergency services, lawful intercept, and commercial location-based applications.

Location Services User Plane Protocol

The Location Services User Plane Protocol (LCS-UPP) is the application-layer protocol that operates over the LCS User Plane (LCS-UP). It defines the format and exchange procedures for positioning-related data packets (PDUs) containing measurement data, assistance data, and location results between the UE and the Location Management Function (LMF) via the 5G user plane.

Local Descriptor

A protocol element within the H.248/Megaco media gateway control protocol. It describes the properties of a termination on the media gateway (MG) that are specific to its local context, such as IP address, port, and codec details, enabling the media gateway controller (MGC) to manage media streams.

Lightweight Directory Access Protocol

An open, vendor-neutral application protocol for accessing and maintaining distributed directory information services over an IP network. In 3GPP systems, it is widely used for subscriber data provisioning, equipment identity register (EIR) access, and network configuration management.

Label Distribution Protocol

A protocol defined by the IETF (RFC 5036) and referenced by 3GPP for distributing labels in MPLS (Multi-Protocol Label Switching) networks. It enables routers to establish Label Switched Paths (LSPs) by exchanging label mappings. In 3GPP architectures, it's used for traffic engineering and transport network control.

SM Low Layer Source Specific Multicast (address)

LLC is a logical link control protocol layer in GPRS and UMTS, providing a reliable data link between the mobile station and the SGSN. It handles segmentation, reassembly, and error correction for user data and signaling. It is essential for ensuring data integrity and flow control over the radio interface.

Logical Link Entity

LLE is a conceptual entity within the GPRS logical link control layer, representing an instance of a logical link between a mobile station and the network. It manages the state, parameters, and data flow for a specific logical connection. It is fundamental for handling multiple concurrent data sessions and signaling channels.

Logical Link Management

Logical Link Management (LLM) is a protocol layer defined in 3GPP specifications for managing logical links in mobile networks, particularly in the GPRS core network. It handles the establishment, maintenance, and release of logical connections between network entities, ensuring reliable data transfer and resource allocation. Its role is critical for efficient packet-switched communication and mobility management.

Logical Link Management Entity

Logical Link Management Entity (LLME) is a functional entity within the GPRS protocol architecture that implements Logical Link Management (LLM) procedures. It resides in both the Mobile Station and the Serving GPRS Support Node, responsible for executing link control operations like establishment and release. This entity ensures reliable logical connectivity for packet data transmission across the network.

LTE Positioning Protocol

LPP is a point-to-point protocol used between a location server (e.g., E-SMLC) and a target device (UE) to determine the device's geographical position. It supports multiple positioning methods like OTDOA, A-GNSS, and E-CID, enabling high-accuracy location services for emergency calls, navigation, and IoT applications.

Local Source

A term from the H.248/Megaco media gateway control protocol denoting a logical entity within a Media Gateway that represents the source of media (e.g., audio, video) originating locally within that gateway. It is used in context associations to describe the flow and termination of media streams.

Length and Value

A fundamental encoding scheme used in 3GPP protocols to represent information elements (IEs) in messages. It consists of a length field indicating the size of the subsequent value field, which contains the actual data. This TLV-like structure ensures efficient and flexible parsing of protocol messages.

LTE-WLAN Aggregation Adaptation Protocol

LWAAP is a protocol layer in LTE-WLAN Aggregation (LWA) that adapts PDCP PDUs for transmission over a WLAN link. It enables the eNB to split and route user data traffic simultaneously over LTE and WLAN radio bearers, improving user throughput and network efficiency by leveraging unlicensed spectrum.

LTE WLAN Radio Level Integration with IPsec Tunnel

In the context of LTE-WLAN Radio Level Integration with IPsec Tunnel (LWIP), the term LWIP refers to a Protocol Data Unit generated by the LWIPEP entity for secure transmission over WLAN. It represents the encapsulated user data packet that is routed via an IPsec tunnel between the UE and the eNB, enabling secure and integrated WLAN data transmission under LTE control.

LWIP Encapsulation Protocol

LWIPEP is the protocol entity responsible for generating and processing LWIP PDUs in the LTE-WLAN Radio Level Integration with IPsec Tunnel feature. It resides in the UE and the eNB, handling the encapsulation and decapsulation of user data into the IPsec-secured format for transmission over an untrusted WLAN link under eNB control.

Light-weight Protocol

LWP is a streamlined protocol introduced in 3GPP Release 17 for resource-constrained devices, particularly in IoT and industrial applications. It reduces signaling overhead and power consumption, enabling efficient communication for massive numbers of simple sensors and actuators.

Mobile Header Compressor

Entity in the mobile terminal (UE) that performs header compression on uplink data packets. It reduces IP/UDP/RTP header overhead, improving spectral efficiency and reducing latency for real-time services over the radio interface.

Mobile Header Compressor/Decompressor

A combined entity in the mobile terminal (UE) that performs both header compression for uplink and header decompression for downlink. It is the integrated functional block within the UE's PDCP layer handling bidirectional header optimization.

Mobile Header Decompressor

Entity in the mobile terminal (UE) that performs header decompression on downlink data packets received from the network. It reconstructs full IP/UDP/RTP headers from compressed formats, enabling efficient use of radio bandwidth for downlink services.

Message Transfer Part 2 - User Peer-to-Peer Adaptation Layer

M2PA is a protocol adaptation layer enabling SS7 MTP2 signaling transport over IP networks. It provides reliable, sequenced delivery of MTP3 messages between signaling points, facilitating the migration from TDM to IP-based core networks. This is crucial for modernizing legacy SS7 infrastructure.

SS7 MTP3 – User Adaptation Layer

M3UA is a SIGTRAN adaptation layer that enables SS7 MTP3 signaling messages to be transported over IP networks to IP-based application servers. It allows telephony applications like ISUP or SCCP to run over IP, separating signaling from legacy TDM infrastructure. This is key for modern softswitch and IMS architectures.

PDU Multi-Access PDU

A protocol data unit that supports multi-access connectivity, enabling a single data session to utilize multiple network access types simultaneously. It is fundamental for ATSSS (Access Traffic Steering, Switching and Splitting) and 5G multi-access integration.

Mobile Application Protocol

A core network signaling protocol used for communication between network elements like HLR, VLR, and MSC in GSM, UMTS, and early LTE networks. It enables subscriber data management, mobility services (like location updates and handovers), and supplementary services (like call forwarding). It was foundational for 2G/3G circuit-switched and packet-switched core operations.

Media Burst Control Protocol

A control protocol used in Mission Critical Push-To-Talk (MCPTT) services over 3GPP networks. It manages the floor control for group communications, arbitrating which user in a talkgroup has permission to transmit media (the 'floor') at any given time.

Multi-Class Multi-Link PPP

A Point-to-Point Protocol (PPP) extension that aggregates multiple physical links into a single logical bundle and supports multiple traffic classes. It enhances bandwidth and provides QoS differentiation for backhaul and access networks in early 3GPP releases.

MEdia GAteway COntrol

A master-slave protocol defined by IETF and adopted by 3GPP for controlling Media Gateways (MGWs) from a Media Gateway Controller (MGC). It separates call control intelligence from media processing, enabling scalable and flexible circuit-switched to packet-switched network interworking.

Media Gateway Control Part

Media Gateway Control Part (MGCP) is a protocol, standardized by IETF and referenced in 3GPP, used for controlling Media Gateways from external call control elements like Media Gateway Controllers or Softswitches. It is a predecessor to the H.248/MEGACO protocol and was used in early decomposed network architectures.

Multi-purpose Internet Mail Extensions

An Internet standard that extends the format of email messages to support text in character sets other than ASCII, as well as attachments of audio, video, images, and application programs. In 3GPP, it is widely used to encapsulate and describe multimedia content and signaling payloads within messaging and IMS services.

Multilink-Multiclass PPP

A Point-to-Point Protocol (PPP) extension that enables the bundling of multiple physical links into a single logical link and supports multiple traffic classes. It enhances data throughput and provides differentiated QoS for various traffic types over Iub and Iur interfaces in UTRAN.

Multi-Link/Multi-Class Point-to-Point Protocol

A protocol enabling the bonding of multiple physical connections and support for traffic class prioritization over a single logical PPP link. It provides scalable bandwidth and QoS for transport networks in 3GPP systems, primarily used in earlier releases for UTRAN backhaul.

Multicast Listener Discovery

A protocol enabling IPv6 routers to discover multicast listeners on directly attached links. It is essential for efficient IP multicast group management, allowing routers to learn which nodes wish to receive traffic for specific multicast addresses, thereby optimizing network resource usage.

Mobile Location Protocol

An application-level protocol standardized by the Open Mobile Alliance (OMA) and referenced by 3GPP for exchanging location information between a Location Server (e.g., GMLC) and a Location Service client (LCS Client). It enables standardized access to mobile device positioning for value-added services.

Multimodal Synchronization Protocol

MMSP is a protocol defined by 3GPP for synchronizing multiple media components (like audio, video, and text) in a multimedia presentation or service. It ensures that different media streams are presented to the user in a coordinated, time-aligned manner. This is essential for delivering a coherent and immersive user experience in applications like synchronized slide shows with audio narration.

MPEG Media Transport

MMT is an MPEG standard for packaging and delivering multimedia content over IP networks. It is designed for efficient streaming and broadcasting of high-quality video and audio, supporting features like multiplexing, synchronization, and error resilience. It is relevant in 3GPP for enabling advanced media delivery services.

MPEG Media Transport Protocol

MMTP is the delivery protocol within the MMT standard, used for transporting multimedia data over IP networks. It handles packetization, multiplexing, and timing synchronization of media streams, ensuring efficient and reliable delivery. It is key for streaming applications, particularly in broadcast and broadband convergence scenarios.

Mobile Network Signalling

A fundamental protocol layer within the 3GPP architecture that carries control plane signalling for circuit-switched (CS) mobile services. It operates as the network layer (Layer 3) in the control plane protocol stack, responsible for establishing, maintaining, and releasing connections for services like voice calls and SMS. MNS is essential for the basic operation and mobility management of 2G (GSM) and 3G (UMTS) circuit-switched networks.

IKEv2 Mobility and Multihoming Protocol

MOBIKE is an extension to the Internet Key Exchange version 2 (IKEv2) protocol that enables an IPsec Security Association (SA) to survive changes in the underlying IP addresses of the endpoints. It is crucial for mobile VPN clients, allowing seamless IPsec connectivity during handovers between different networks (e.g., Wi-Fi to cellular) without re-establishing the entire VPN tunnel.

Media Orientation Negotiation Acceleration

A protocol enhancement within the IMS framework that accelerates the setup of media sessions, particularly for voice and video calls. It reduces call setup delays by optimizing the Session Description Protocol (SDP) offer/answer exchange during session negotiation.

MC service Off-Network Protocol

A set of protocols defined for Mission Critical (MC) services, such as push-to-talk (MCPTT), to enable direct communication between user equipment (UE) when outside network coverage or when the network is unavailable. It supports off-network, device-to-device (D2D) operation for public safety and professional users.

Multicast Open Shortest Path First

A multicast routing protocol extension to OSPF used within 3GPP packet-switched networks, primarily for IP multicast group management and distribution tree calculation. It enables efficient delivery of multicast traffic across the core network infrastructure.

Mandatory Present

A protocol field indicator specifying that a particular information element or parameter must be included in a message for the message to be considered valid and processable. It ensures syntactic and semantic correctness in signaling exchanges.

MAC Protocol Data Unit

A Protocol Data Unit (PDU) at the Medium Access Control (MAC) layer, representing the data packet exchanged between peer MAC entities. In 3GPP contexts, it often refers to the structured data unit containing a MAC header, zero or more MAC Service Data Units (SDUs), and optionally padding and a CRC. It is the fundamental unit for data transmission and logical channel multiplexing in the radio interface protocol stack.

Multiplex Payload Length

A parameter in the 3GPP codec specifications that defines the length of the payload within a multiplexed data frame. It is crucial for the proper assembly and parsing of speech and audio data packets in mobile communication systems, ensuring interoperability between network elements and user equipment.

Multi-Path QUIC

MPQUIC is a transport protocol extension enabling simultaneous data transmission over multiple network paths, such as 5G and Wi-Fi. It enhances throughput, reduces latency, and improves connection resilience by aggregating bandwidth and providing seamless failover. This is crucial for demanding applications like AR/VR and real-time communications.

Multi-Path TCP Protocol

A transport layer protocol extension that allows a TCP connection to use multiple network paths simultaneously, increasing throughput, resilience, and mobility support. It enables devices with multiple interfaces (e.g., Wi-Fi and cellular) to aggregate bandwidth and seamlessly switch paths without breaking the connection.

Move Receiving Window

A protocol mechanism in the RLC layer to manage the sequence number space for acknowledged mode data transfer. It ensures reliable in-order delivery by controlling the receiver's buffer window, preventing buffer overflow and sequence number exhaustion.

Multiple Stream Registration Protocol

A session management protocol used in the IP Multimedia Subsystem (IMS) to establish and control multiple media streams within a single multimedia session. It enables applications like video conferencing and file transfer by managing the registration and negotiation of individual media components.

Message Transfer Part

A core signaling protocol in the SS7 (Signaling System No. 7) stack, responsible for the reliable, connection-oriented transfer of signaling messages between network nodes. It provides routing, error detection/correction, and flow control, forming the backbone for traditional telephony and early mobile network signaling.

Message Transfer Part layer 1

MTP1 is the physical layer of the SS7 signaling protocol stack, responsible for the electrical and physical transmission of signaling messages over a digital link. It defines the physical interface, line coding, and clock synchronization, ensuring raw bitstream delivery between signaling points. Its reliability is foundational for all higher-layer SS7 signaling functions.

Message Transfer Part layer 2

MTP2 is the data link layer of the SS7 signaling protocol, providing reliable point-to-point transfer of signaling messages over a single link. It handles error detection/correction, sequencing, and flow control, ensuring error-free delivery between directly connected signaling points. It is crucial for maintaining signaling link integrity.

Message Transfer Part layer 3

MTP3 is the network layer of the SS7 protocol, responsible for routing signaling messages across the signaling network and managing the availability of signaling links and routes. It provides functions like message discrimination, distribution, and routing, ensuring messages reach their correct destination node even via multiple hops.

Message Transfer Part level 3 (for Q.2140)

MTP3-B is a protocol layer within the 3GPP signaling system, specifically adapted for the Q.2140 adaptation layer used in B-ISDN User Part (B-ISUP) signaling. It provides reliable, connectionless message transfer and routing for signaling messages in the core network, particularly for ATM-based transport. Its role is crucial for establishing and managing call control and bearer services in early 3G networks.

Maximum Transmission Unit

MTU is the largest size of a data packet that can be transmitted over a network interface without requiring fragmentation. It is a fundamental parameter in IP networking, affecting performance, efficiency, and protocol behavior. Proper MTU configuration is crucial for optimizing throughput, minimizing latency, and avoiding fragmentation-related issues in 3GPP and IP networks.

Modify UE Context Answer

MUA is a Diameter protocol message used in the 3GPP Policy and Charging Control (PCC) architecture. It is sent by a Policy and Charging Rules Function (PCRF) to a Traffic Detection Function (TDF) in response to a Modify UE Context Request (MUR). This message confirms the application of updated policy and charging rules for a user session.

H.223 Multiplex layer

The multiplexing layer defined in the ITU-T H.223 standard, adopted by 3GPP for circuit-switched video telephony over UMTS. It multiplexes audio, video, data, and control streams into a single bitstream for transmission over the network.

Network Protocol Data Unit

A Network Protocol Data Unit (N-PDU) is a packet or data unit exchanged between peer entities at the network layer (Layer 3) within the 3GPP protocol architecture. It contains user data and network layer header information for routing and delivery. It is a fundamental construct for data transmission in packet-switched domains like GPRS and EPS.

Non-3GPP Connection

A protocol layer entity in the 5G NR user plane stack that manages data transmission over non-3GPP wireless links. It adapts higher-layer PDCP packets for transport over alternative access media like Wi-Fi or satellite, enabling integrated multi-RAT operation.

Negation ACKnowledgement

A control message indicating a transmission failure or error, used in ARQ/HARQ protocols for reliable data delivery. It prompts the sender to retransmit the missing or corrupted data block, ensuring data integrity and efficient link adaptation across 3GPP radio interfaces.

Node Address byte

A one-byte field used in certain 3GPP protocol data units to identify a network node or endpoint within a communication session. It facilitates multiplexing and routing of messages between peer entities, particularly in legacy circuit-switched and packet-switched control protocols.

Negative Acknowledgement

A control message in communication protocols indicating that a transmitted data block (e.g., a packet or frame) was not received correctly or was lost. It triggers retransmission of the missing data, forming the basis of Automatic Repeat Request (ARQ) and Hybrid ARQ (HARQ) error control mechanisms essential for reliable data delivery.

Naming Authority Pointer

NAPTR is a DNS resource record used for dynamic delegation and service discovery, enabling the mapping of domain names to URIs or other domain names based on rules. In 3GPP, it is utilized for ENUM (E.164 Number Mapping) and service selection, such as routing SIP calls or discovering IMS application servers.

Non-Access Stratum

The NAS is a functional layer in the protocol stack between the UE and the core network (MME/AMF). It handles signaling for mobility management, session management, and subscriber identity management, independent of the underlying radio access technology. It is fundamental for establishing and maintaining connectivity.

Node B Application Protocol

A signaling protocol used in UMTS Radio Access Network (UTRAN) for communication between the Radio Network Controller (RNC) and Node B. It manages radio resource control, cell configuration, and measurement reporting, enabling efficient operation of the air interface. NBAP is critical for UTRAN functionality, supporting mobility and quality of service.

Network Control Protocol

A protocol used for establishing, maintaining, and terminating network connections, particularly in early 3GPP systems. It manages control plane signaling for data sessions, ensuring proper session setup and teardown. It was foundational for early packet-switched services.

NG Application Protocol

NG-AP is the control plane protocol between the 5G Next Generation NodeB (gNB) and the Access and Mobility Management Function (AMF) over the NG interface. It manages procedures like UE context management, paging, and handovers. It is fundamental for 5G network signaling and mobility.

Next Generation Application Protocol

NGAP is the signaling protocol between the 5G Core Network (5GC) and the Next Generation Radio Access Network (NG-RAN). It is essential for establishing, managing, and releasing UE contexts, handling mobility, and transferring NAS messages, enabling the control plane functionality of the 5G system.

Nature Of Address indicator

A parameter within signaling protocols (like ISUP, BICC, SIP) that classifies the type of an address, such as a phone number. It distinguishes between national, international, subscriber, or network-specific numbers, which is crucial for correct call routing and service handling.

Network Service Data Unit

A protocol data unit (PDU) used within the context of network service protocols, such as the Base Station System Application Part (BSSAP). It represents a unit of data exchanged between network entities to convey service-related information. Its role is fundamental in enabling structured communication and service execution across network interfaces.

RLC Non-Transparent Mode

An operating mode of the Radio Link Control (RLC) protocol in GSM/EDGE networks where the RLC layer provides limited error correction, primarily for acknowledged data transfer. It is designed for non-real-time services where some delay for retransmissions is acceptable, offering a balance between reliability and complexity compared to transparent mode.

Network Time Protocol

A widely used protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. In 3GPP systems, it provides precise time references for network elements, enabling coordinated operations like handovers, time-stamped billing, and lawful interception.

Null Information Frame

A specific frame type in the LAPDm protocol used on the radio interface in GSM/UMTS networks. It carries no user data but is essential for maintaining the data link layer connection and performing supervisory functions like acknowledging received frames or indicating receiver status.

Original Dialog Identifier

A unique identifier used in the IP Multimedia Subsystem (IMS) to correlate multiple related SIP dialogs or transactions that belong to the same communication session. It is essential for session continuity, forking, and service logic execution across different SIP signaling legs.

Open Systems Interconnection

A foundational, seven-layer conceptual model (ISO/IEC 7498-1) for standardizing communication functions of a telecommunication or computing system. 3GPP standards often reference the OSI model to describe protocol stacks and layer responsibilities.

Octet Stream Protocol

OSP is a transport protocol used in 3GPP networks, primarily within the GPRS Tunneling Protocol (GTP) framework, to carry octet-aligned user data and signaling. It provides a reliable, connection-oriented mechanism for data transfer between network nodes, ensuring efficient and structured communication essential for core network operations.

Poll/Final Bit

A single-bit control field in the Layer 2 (L2) protocol headers of 3GPP systems, such as RLC and LAPDm. It regulates frame transmission in acknowledged mode, controlling when a receiver should send an acknowledgment or when a transmitter can send a new frame.

Piggy-backed Ack/Nack message

A message used in GSM/EDGE Radio Access Network (GERAN) to acknowledge (ACK) or negatively acknowledge (NACK) received data blocks. It is transmitted by piggy-backing the control information onto an uplink data block, improving spectral efficiency by reducing the need for standalone control messages.

Piggy-backed Ack/Nack Indicator

A control field within an uplink radio block header in GERAN that signals the presence of a Piggy-backed Ack/Nack (PAN) message in the same block. It acts as a flag, informing the receiver to decode the subsequent PAN message multiplexed with the data payload.

Reversed HTTP binding for SOAP

PAOS is a SOAP binding that reverses the typical HTTP client-server roles, allowing a server to send SOAP requests to a client. It is defined in 3GPP for use with Liberty Alliance Project (LAP) and Security Assertion Markup Language (SAML) protocols, enabling secure, asynchronous service interactions in mobile networks.

Proxy Binding Acknowledgment

A message sent by the Local Mobility Anchor (LMA) in a PMIPv6 network to the Mobile Access Gateway (MAG) to confirm successful binding registration or update for a mobile node. It is a critical component for signaling mobility session establishment and ensuring the mobile node's reachability.

Protocol Control Byte

PCB is a control byte used in certain 3GPP protocols, particularly in GSM/EDGE Radio Access Network (GERAN) data transmission. It manages protocol state, frame synchronization, and error control within data link layer frames, ensuring reliable communication over the air interface.

Protocol Discriminator

A field in the protocol header used to identify the type of protocol data unit being carried, enabling multiplexing of different protocols over a single logical connection. It is crucial for the correct routing and processing of messages within the network layer.

Packet Data Convergence Protocol

A layer 2 protocol in 3GPP radio access networks (UTRAN, E-UTRAN, NG-RAN) responsible for header compression, ciphering, integrity protection, and in-order delivery of user and control plane data. It sits between the Radio Resource Control (RRC) layer and the underlying radio link layer (RLC), optimizing data transmission over the air interface.

Packet Detection Information

Packet Detection Information (PDI) is a key component within the Packet Forwarding Control Protocol (PFCP) used in 5G and 4G core networks. It defines the set of rules and information used by the User Plane Function (UPF) or Packet Gateway (PGW) to identify packets belonging to a specific service data flow. This enables precise traffic steering, policy enforcement, and charging based on deep packet inspection criteria.

Protocol Data Unit

A fundamental concept in telecommunications representing a unit of data exchanged between peer entities at a specific protocol layer, consisting of protocol control information and user data. It is the basic building block for all data communication in 3GPP systems, enabling structured interaction between network functions and the UE. Understanding PDUs is essential for protocol analysis, network troubleshooting, and system design.

Packet Forwarding Control Protocol

A 3GPP protocol used in 5G Core and EPC to separate the control plane from the user plane. It enables the control plane (SMF/CP-function) to program forwarding rules, QoS policies, and charging instructions into the user plane (UPF/UP-function) over the N4/Sx interface.

PHS Internet Access Forum Standard

A protocol standard for data communication over PHS (Personal Handy-phone System) networks, enabling internet access and data services. It defines modulation, framing, and error control for reliable data transmission, bridging PHS with IP networks for mobile connectivity.

Packet Identification

A field within a protocol data unit that uniquely identifies a specific packet or data flow. It is used for multiplexing, demultiplexing, routing, and applying specific processing rules to packets traversing the network, such as in header compression contexts.

Protocol-Independent Multicast

Protocol-Independent Multicast (PIM) is a family of multicast routing protocols used to build distribution trees for efficient multi-destination data delivery in IP networks. It is 'protocol-independent' as it can operate over any underlying unicast routing protocol, creating scalable multicast forwarding paths.

Protocol-Independent Multicast - Dense Mode

PIM Dense Mode (PIM-DM) is a flood-and-prune multicast routing protocol where data is initially flooded to all network branches and then pruned back where there are no receivers. It is efficient in environments with densely distributed multicast group members.

Protocol Independent Multicast – Sparse Mode

A multicast routing protocol used in 3GPP networks for efficient group communication. It operates in sparse mode, meaning it builds distribution trees only where receivers are present, optimizing bandwidth. It is protocol-independent, working over various underlying unicast routing protocols.

Post Office Protocol, version 3

POP3 is an Internet standard protocol used by email clients to retrieve messages from a mail server. In 3GPP, it's referenced for email service support in early mobile data services, enabling basic email access over mobile networks.

Primitive Procedure Entity

A fundamental architectural concept in 3GPP protocol design, representing a basic, indivisible unit of procedure or operation. It defines the atomic actions that can be requested or performed within a protocol layer, forming the building blocks for more complex service interactions and signaling flows.

Payload Protocol Identifier

A field in protocol headers (like GTP-U, PDCP, or RoHC) that identifies the type of data payload being carried. It enables the receiving entity to correctly interpret and process the encapsulated user data or control information, ensuring proper multiplexing and protocol handling.

Protocol and Parameter Select

PPS is a response message in the UICC/USIM initialization sequence, sent in reply to an Answer To Reset (ATR) command. It allows the terminal to negotiate and select the communication protocol and parameters for the smart card interface, ensuring compatibility and optimal performance between the device and the SIM.

Provisional Response Acknowledgement

PRACK is a SIP method defined in RFC 3262, used within the IMS to reliably acknowledge the receipt of provisional responses (1xx) like 180 Ringing. It ensures reliable delivery of provisional signaling, which is critical for services like call progress indication and early media.

Procedure Code

A 1-octet unsigned enumerated value used in the Xn Application Protocol (XnAP) to uniquely identify a specific procedure or message type. It enables efficient decoding and processing of signaling messages between gNBs in 5G NR, ensuring correct protocol handling.

PDU Set Integrated Handling Information

A protocol mechanism in 5G-Advanced that provides integrated control information for handling sets of Protocol Data Units (PDUs) in the user plane, optimizing data transmission for applications with specific processing requirements. It enhances efficiency by enabling network and UE to coordinate the handling of PDU sets based on application-layer semantics.

Protocol State Machine

A formal model defining the states and transitions of a communication protocol entity. It ensures reliable and orderly message exchange between network nodes by managing connection establishment, data transfer, and error recovery procedures. It is fundamental to the deterministic behavior of network interfaces.

PDU Set Sequence Number

A sequence number used in 5G NR to ensure the in-order delivery and integrity of Protocol Data Unit (PDU) Sets, which are groups of PDUs belonging to the same application data unit. It is crucial for ultra-reliable low-latency communication (URLLC) services.

Protocol Type

A field within the GTP' (GPRS Tunnelling Protocol prime) header used to distinguish between different types of payload protocols being carried. It is essential for billing systems (Charging Data Function) to correctly interpret and process charging records in mobile packet networks.

Procedure Transaction Identity

A unique identifier used within signaling protocols to correlate messages belonging to the same transaction or procedure. It is essential for managing concurrent signaling exchanges between network entities, ensuring correct message routing and state management.

Payload Unit

A fundamental data unit in the Radio Link Control (RLC) protocol layer. It is the formatted block of data (including header and payload) that is transferred between peer RLC entities over the logical channels. It is the core unit for RLC's segmentation, concatenation, and error correction operations.

Quick UDP Internet Connections

QUIC is a transport layer network protocol standardized by the IETF and adopted by 3GPP. It operates over UDP, providing reduced connection and transport latency, improved security with mandatory TLS 1.3, and multiplexed streams without head-of-line blocking. Its integration into 5G systems aims to enhance application performance, particularly for web, video, and real-time services.

Response Application Protocol Data Unit

A response message in the Application Protocol Data Unit format, used for secure communication between a UICC/SIM card and an external entity like a network application server. It is a fundamental component of the SIM Application Toolkit (SAT) and OTA (Over-The-Air) protocols, enabling secure command-response transactions for services like profile management and authentication.

Response Transport Protocol Data Unit

A Transport Protocol Data Unit (TPDU) sent in response to a request, forming part of the dialogue in various 3GPP signaling protocols. It is a fundamental messaging construct used to convey acknowledgment, results, or data in protocols like the Transaction Capabilities Application Part (TCAP). It ensures reliable and structured communication between network entities.

Regional Signalling System No. 1

A regional variant of the ITU-T Signalling System No. 7 (SS7) protocol stack, standardized by 3GPP for use in telecommunications core networks. It defines the message transfer part (MTP) and signalling connection control part (SCCP) layers for reliable signalling transport in specific geographical regions.

Regional Signalling System 2

R2 is a legacy digital channel-associated signalling (CAS) protocol used for trunk connections in telephony networks. It was standardized by ITU-T and adopted in 3GPP for interconnecting circuit-switched network elements, particularly in specific geographic regions. It matters as it represents a key historical signalling system that supported international telephony before the dominance of SS7.

Rate Adaptation Functions

Rate Adaptation Functions dynamically adjust the data transmission rate over a wireless link based on channel conditions. This ensures efficient spectrum usage and maintains connection reliability by matching the data rate to the available signal quality and network load. It is a fundamental mechanism for optimizing throughput and user experience in mobile networks.

Re-Auth-Answer

The Re-Auth-Answer (RAA) is a Diameter protocol message sent by a Diameter server (e.g., PCRF) in response to a Re-Auth-Request (RAR). It is a critical component of the Policy and Charging Control (PCC) architecture, used to acknowledge the application of new policy rules or charging instructions to a user session.

Remote Authentication Dial In User Service

A widely deployed networking protocol that provides centralized Authentication, Authorization, and Accounting (AAA) management for users connecting to a network. In 3GPP, it is used for interworking with non-3GPP access networks (like WLAN) and for certain policy control functions.

Radio Access Network Application Protocol

RANAP is the signaling protocol between the Core Network (CN) and the UMTS Radio Access Network (UTRAN). It manages radio access bearers, mobility, and security functions, enabling the CN to control the RAN and deliver services to the user.

Resource Allocation Protocol

A protocol for managing and allocating network resources, primarily defined for media delivery services. It ensures efficient utilization of bandwidth and network elements by coordinating resource requests and assignments between functional entities, such as application servers and media processors.

Re-Auth-Request

A Diameter protocol command used in the Policy and Charging Control (PCC) architecture. It is sent by the Policy and Charging Rules Function (PCRF) to request re-authorization of an ongoing service session, typically to modify QoS policies, charging rules, or service parameters based on changing network conditions or subscriber policies.

Rate Control Procedure Acknowledgement

The Rate Control Procedure Acknowledgement (RC) is a control plane message used on the Iu interface in UMTS networks to acknowledge the receipt and processing of a Rate Control command. It is part of the Radio Access Bearer (RAB) management procedures, ensuring reliable negotiation of data rates for user connections between the RNC and core network.

Remote Descriptor

A protocol element in the H.248 (Megaco) media gateway control protocol used to describe remote network entities or endpoints. It enables media gateways and controllers to exchange information about far-end capabilities and parameters for session establishment and management.

Reject Frame

A Reject (REJ) frame is a Layer 2 protocol data unit used in 3GPP networks to indicate the rejection of a received frame due to errors or protocol violations. It is part of the data link layer procedures, such as in the Radio Link Control (RLC) or Link Access Protocol (LAP) protocols, to manage error control and flow control. REJ frames help maintain reliable data transmission by signaling the need for retransmission of specific frames.

Remap Frame

REMAP is a specific frame structure defined in 3GPP TS 24.022 for the Radio Link Protocol (RLP) in GSM and UMTS circuit-switched data services. It is used for signaling and control purposes within the RLP layer to manage data transmission reliably over the air interface. Its role is crucial for maintaining the integrity and flow of circuit-switched data connections.

Representational State Transfer

REST is an architectural style for designing networked applications, adopted by 3GPP for northbound and service-based interfaces. It uses HTTP methods (GET, POST, PUT, DELETE) to operate on resources identified by URIs. In 3GPP, it enables flexible, scalable, and web-friendly APIs for network function exposure and management.

Remote Electrical Tilting Application Part

RETAP is a protocol within the AISG framework that standardizes communication between RET controllers and antenna units for remote electrical tilt control. It ensures interoperability across vendors, enabling precise and reliable antenna adjustments in mobile networks.

Request For Comments

A series of documents published by the Internet Engineering Task Force (IETF) that include proposed standards, best practices, and informational memos. RFCs form the foundational technical and organizational documentation for the Internet and many protocols used in 3GPP systems, such as SIP, Diameter, and HTTP.

Response Header Identifier

A protocol element defined in 3GPP TS 23.048 for the Mobile Station Application Execution Environment (MExE). It identifies the type of header in a response message from a server to a mobile device. This enables structured communication for service provisioning and management.

Response Header Length

A protocol field defined in 3GPP TS 23.048 for MExE that specifies the total length, in octets, of the header section in a server response message. It allows the receiving client to accurately locate the start of the message body for processing.

Radio Link Control

Radio Link Control (RLC) is a Layer 2 protocol in the radio access network that ensures reliable data transfer over the air interface. It operates between the MAC and PDCP layers, providing segmentation, reassembly, error correction, and in-order delivery. RLC is critical for maintaining link quality, adapting to radio conditions, and supporting diverse services from voice to high-speed data in 3GPP systems.

Radio Link Control - Protocol Data Unit

The data unit exchanged between the Radio Link Control (RLC) sublayer and its peer entity. It is the structured packet containing user data or control information, formatted according to the RLC mode (Transparent Mode, Unacknowledged Mode, Acknowledged Mode). This is fundamental for reliable data transfer over the radio interface.

Radio Link Control Protocol

The Layer 2 protocol responsible for transferring data between the UE and the network over the radio interface. It provides error correction via ARQ, segmentation, reassembly, and in-sequence delivery. It operates in three modes (TM, UM, AM) to suit different service requirements.

Radio Link Protocol

A data link layer protocol defined in GSM (04.22) for circuit-switched data services. It provides a reliable, sequenced data transfer service over the inherently error-prone radio interface by using error detection and retransmission (ARQ). It was fundamental for early mobile data services like fax and dial-up networking.

Resynchronization Marker

A marker inserted into a data stream, particularly in the Radio Link Control (RLC) layer, to indicate a resynchronization point for the receiving entity. It is crucial for recovering from transmission errors, enabling the receiver to correctly realign and decode subsequent data units after a failure.

Receive Not Ready

A frame type used in data link layer protocols, particularly in GSM/UMTS, to indicate a temporary inability to accept incoming data frames. It is a flow control mechanism that signals a receiver's buffer congestion or processing delay, allowing the sender to pause transmission and prevent data loss. This ensures reliable data transfer over the radio interface.

Radio Network Subsystem Application Part

A signaling protocol used in UMTS and GSM networks to manage communication between Radio Network Subsystems (RNS), specifically between Radio Network Controllers (RNCs). It handles functions like soft handover, relocation, and resource management across different RNS entities. RNSAP ensures seamless mobility and efficient resource utilization in the radio access network.

Robust Header Compression

A protocol that significantly reduces the header overhead of IP packets (e.g., IPv4, IPv6, UDP, RTP, TCP) over bandwidth-constrained wireless links. It operates by establishing a compression context between compressor and decompressor, sending full headers only initially, then transmitting small identifiers for subsequent packets. This improves spectral efficiency and reduces latency.

Remote Operations Service

A service element within the CAMEL (Customised Applications for Mobile network Enhanced Logic) and IP Multimedia Subsystem (IMS) service layer that enables the execution of operations on a remote network entity. It provides a structured, object-oriented framework for invoking actions like subscriber data management, service control, and event reporting between network nodes, such as an SCP and an MSC.

Remote Operation Service Element

ROSE is an OSI application-layer protocol for remote operations, enabling client-server interactions like request, response, and error reporting. It is used in 3GPP for CAMEL and other intelligent network services, providing a standardized framework for executing procedures on remote network entities.

RP Message Type Indicator

A field within the Relay Protocol (RP) used in Short Message Service (SMS) delivery via the IP Multimedia Subsystem (IMS). It identifies the specific type of RP message being transmitted, such as a data message, delivery report, or error indication, enabling proper routing and processing between network entities.

RP User Information

The payload field within a Relay Protocol (RP) DATA message that carries the actual content of a Short Message (SM). This includes the text, binary data, or protocol data of the SMS itself, along with its associated header (TPDU). It is the core user data transported between the SMSC and the UE via IMS.

Response Packet Identifier

A protocol identifier used in 3GPP networks, introduced in Release 5, to tag response packets in specific messaging exchanges. It ensures correct association between requests and responses, aiding in reliable communication and error handling within network signaling procedures.

Radio Resource Control

The Radio Resource Control (RRC) protocol is a layer 3 signaling protocol in the radio interface between the UE and the network (gNB/eNB/NodeB). It is responsible for establishing, configuring, maintaining, and releasing radio bearers, and for controlling all lower-layer protocols related to radio resource management and mobility.

Radio Resource LCS Protocol

The Radio Resource LCS Protocol (RRLP) is a positioning protocol used in GSM and UMTS networks to exchange location-related information between a Mobile Station (MS) and the network. It supports network-assisted and MS-based positioning methods like Cell-ID, OTDOA, and A-GPS.

Remote Source

A term from the H.248/Megaco protocol naming convention used in 3GPP Media Gateway control. It refers to a logical entity that represents an inbound media stream endpoint on a Media Gateway, such as the audio received from a circuit-switched network leg or an IP stream.

Retransmission Sequence Number

A sequence number used in 3GPP radio link protocols (like PDCP and RLC) to identify and order data packets for retransmission. It ensures reliable delivery by allowing the receiver to detect missing packets and the transmitter to track which packets need to be resent.

Ranging and Sidelink Positioning Protocol

RSPP is a protocol defined for direct device-to-device (sidelink) communication to perform ranging and positioning. It enables accurate distance measurement and location determination between UEs without network infrastructure, supporting V2X, public safety, and commercial proximity services.

Rapid Spanning Tree Protocol

RSTP is a network protocol that prevents loops in Ethernet networks by creating a loop-free logical topology. It ensures network reliability and stability by rapidly converging to a new topology after a link failure, minimizing downtime.

Resource ReserVation Protocol

RSVP is a signaling protocol used to reserve network resources along a data path, ensuring quality of service (QoS) for specific data flows. It enables applications to request bandwidth and latency guarantees from the network, crucial for real-time services like VoIP and video streaming.

Real-time Transport Control Protocol

RTCP is the control protocol companion to RTP, providing out-of-band statistics and control information for real-time media sessions. It is essential for monitoring QoS, synchronizing media streams, and providing minimal session control, enabling adaptive streaming and participant awareness.

RTP Control Protocol

RTCP is the control protocol that works alongside RTP in multimedia sessions. It provides out-of-band statistics, control information, and synchronization data for participants in an RTP session. It is essential for monitoring QoS, synchronizing multiple media streams, and conveying participant identity in 3GPP IMS services like VoLTE and ViLTE.

Real-time Transport Protocol

RTP is a standardized packet format for delivering audio and video over IP networks. It provides end-to-end network transport functions suitable for applications transmitting real-time data, such as interactive audio and video. It is fundamental for Voice over LTE (VoLTE), Voice over NR (VoNR), and multimedia streaming in 3GPP networks.

Real-time Streaming Protocol

An application-layer network control protocol designed for establishing and managing media sessions between endpoints, such as streaming servers and clients. It enables control over real-time multimedia delivery, including play, pause, and record functions, and is used in 3GPP for streaming services like video and audio over mobile networks.

RANAP User Adaptation

RUA is a protocol layer that transports RANAP messages over IP-based signaling transport networks, such as Iu-flex. It enables the separation of control and user planes and supports efficient signaling between the RNC and CN in 3G UMTS networks.

S101 Application Protocol

S101-AP is the application-layer protocol that defines the signaling messages and procedures exchanged over the S101 interface between an LTE MME and a CDMA HRPD Access Network. It is essential for executing optimized inter-RAT handovers, enabling session context transfer and resource preparation.

S1 Application Protocol

S1 Application Protocol (S1AP) is the control plane signaling protocol used over the S1 interface between the E-UTRAN (eNodeB) and the Evolved Packet Core (EPC), specifically the MME. It manages UE context, bearer establishment, handovers, and paging. It is fundamental for LTE and 5G NSA network operation.

Server Assignment Answer

A Diameter protocol message used in the Cx interface within the IMS. It is sent by the Home Subscriber Server (HSS) to the Interrogating-Call Session Control Function (I-CSCF) in response to a Server Assignment Request (SAR), providing user authentication and service profile data.

Signalling ATM Adaptation Layer

A set of ATM Adaptation Layer (AAL) protocols, specifically AAL5 and the Service Specific Coordination Function (SSCF) and Service Specific Connection Oriented Protocol (SSCOP), used to transport signalling messages (e.g., for B-ISDN and early 3GPP Iu, Iur, and Iub interfaces) over ATM networks.

Signalling ATM Adaptation Layer – Network Node Interface

A protocol layer that adapts signalling messages for transport over ATM networks at the Network Node Interface. It ensures reliable, connection-oriented signalling between network nodes in UMTS and early mobile networks, crucial for core network communication.

Set Asynchronous Balanced Mode frame

A Layer 2 frame in GSM and UMTS used to establish a logical link connection in Asynchronous Balanced Mode between a mobile station and the network. It initiates data link layer setup for signalling communication, a fundamental step in call and session establishment.

Service Area Broadcast Protocol

SABP is a 3GPP protocol used for broadcasting messages, like Cell Broadcast Service (CBS), over a specific service area in UMTS networks. It enables efficient, one-to-many delivery of public warning or location-based information to multiple UEs simultaneously, which is critical for emergency alerts.

Selective ACKnowledgement

A TCP/IP protocol mechanism that allows a receiver to acknowledge non-contiguous blocks of data received correctly. It improves efficiency in lossy networks by enabling the sender to retransmit only specific missing segments, rather than everything after a gap.

Single Association Object

A protocol data unit used in the Diameter protocol for 3GPP interfaces. It encapsulates a single Diameter command and its associated Attribute-Value Pairs (AVPs) for reliable transport and processing between network functions, such as between a Policy and Charging Rules Function (PCRF) and an Application Function (AF).

Service Access Point

A conceptual point within a protocol layer where services are provided to the layer above. It defines the interface and primitives (e.g., request, indication, response, confirm) for communication between adjacent layers in the OSI or 3GPP protocol stack, enabling layered network architecture.

Signalling Connection Control Part

A network layer protocol within the SS7 and SIGTRAN signaling frameworks, providing connectionless and connection-oriented services. It enables the routing of signaling messages between network nodes (like MSCs and HLRs) based on subsystem numbers, supporting global title translation for flexible addressing beyond point codes.

Stream Control Transmission Protocol

SCTP is a reliable, message-oriented transport layer protocol used extensively in 3GPP core network signaling interfaces. It provides multi-homing, multi-streaming, and enhanced security compared to TCP, making it ideal for carrying critical signaling protocols like S1-AP, NG-AP, and Diameter.

Service Data Adaptation Protocol

SDAP is a protocol layer introduced in 5G NR to manage QoS flows between the core network and the UE. It maps QoS flows to data radio bearers and marks packets with QoS Flow Identifiers, enabling fine-grained service differentiation and support for network slicing. It is crucial for meeting diverse 5G service requirements.

Service Discovery Protocol

A Bluetooth protocol used by devices to discover what services other Bluetooth devices offer and to determine the characteristics of those available services. It is a fundamental part of the Bluetooth stack, enabling dynamic ad-hoc networking and interoperability between diverse devices.

Signalling Data Unit

A protocol data unit (PDU) used for carrying signalling information between peer entities in a 3GPP network. It is the payload passed between protocol layers, containing control plane messages for call setup, mobility management, and session control. Its standardized structure is fundamental for reliable network operation.

Session Initiation Protocol

SIP is an IETF-defined application-layer signaling protocol used to create, modify, and terminate multimedia sessions such as voice and video calls over IP networks. In 3GPP, it is the core protocol for IP Multimedia Subsystem (IMS) services, enabling rich communication services over cellular and fixed networks.

Session Initiation Protocol with encapsulated ISDN User Part

SIP-I is a protocol for interworking between SIP-based IP networks and traditional ISDN/SS7 telephony networks. It encapsulates ISUP messages within SIP, enabling seamless call signaling and feature transparency across network boundaries, which is crucial for migration from legacy to all-IP networks.

Service Location Protocol

A protocol defined by 3GPP for discovering and selecting location-based services and servers within a network. It enables User Equipment (UE) to locate services like positioning servers (e.g., SLP) and is fundamental for location-based applications and emergency services. It ensures efficient service discovery and network resource utilization.

Signalling Link Test Message

A protocol message used in SS7-based signalling networks to verify the operational status of a signalling link. It is a crucial maintenance and diagnostic tool, ensuring reliable signalling connectivity between network nodes like MSCs and HLRs.

Short Message Control Protocol

A protocol within the CAMEL (Customised Applications for Mobile network Enhanced Logic) framework that enables the intelligent network to control SMS service logic. It allows the CAMEL Service Environment (CSE) to monitor and influence SMS routing and delivery for value-added services.

Session Management Client

The Session Management Client is a functional entity, typically residing in the User Equipment (UE), responsible for initiating, maintaining, and terminating Packet Data Unit (PDU) sessions. It interacts with the network's Session Management Function (SMF) to manage the data connectivity required for the UE's applications and services.

SMLC Peer Protocol

A protocol used for direct communication between two Standalone Mobile Location Centers (SMLCs) over the Lp interface in GSM networks. It defines the messages and procedures for SMLC-to-SMLC interactions, enabling coordination for location services, particularly when a UE roams into an area served by a different SMLC.

Short Message Peer-to-Peer Protocol

Short Message Peer-to-Peer Protocol (SMPP) is an open, industry-standard protocol designed for exchanging SMS messages between Short Message Service Centers (SMSCs) and external messaging entities like ESMEs. It enables high-volume SMS submission, delivery, and query operations, forming the backbone for many value-added SMS services.

Simple Message Transfer Protocol

A 3GPP-defined adaptation of the IETF's Simple Mail Transfer Protocol, used for transporting Short Messages (SMS) over IP networks. It enables SMS interworking between traditional circuit-switched mobile networks and IP-based messaging systems, facilitating services like email-to-SMS and application-originated messaging.

SubNetwork Dependent Convergence

A functional layer in the GPRS and UMTS protocol stack that adapts upper-layer network protocols (like IP) for transmission over the underlying mobile network. It handles functions such as compression and segmentation to optimize data transfer for the radio interface. It is a key component for enabling efficient packet data services.

Sub-Network Dependent Convergence Protocol

The protocol that implements the SNDC layer functions in GPRS and UMTS. It defines the detailed procedures and packet formats for data compression, segmentation, and protocol discrimination between the MS and SGSN. SNDCP is essential for optimizing data transfer efficiency over the radio interface.

Simple Network Management Protocol

SNMP is a widely adopted IETF standard protocol used for monitoring and managing network devices. In 3GPP networks, it is commonly used for the management of IP-based network elements, allowing managers to query status information (GET) and apply configurations (SET) to managed devices.

Set Normal Response Mode

SNRM is a specific frame type in the High-Level Data Link Control (HDLC) protocol suite, used to establish a data link connection in Normal Response Mode (NRM). It configures secondary stations for communication under the control of a primary station, fundamental for reliable point-to-point and multipoint link management in telecom backhaul and control interfaces.

Simple Network Time Protocol

A simplified version of NTP used for clock synchronization in 3GPP networks. It provides accurate time distribution for network elements and user equipment, which is critical for time-sensitive applications, billing, security, and network operation.

Simple Object Access Protocol

An XML-based messaging protocol used within 3GPP specifications for web services communication, particularly in the context of Open Service Architecture (OSA) and Parlay/OSA Gateway interfaces. It defines a standardized envelope structure for exchanging structured information in a decentralized, distributed environment. Its use in 3GPP enables standardized northbound APIs for network capability exposure.

Sidelink Relay Adaptation Protocol

A protocol layer in 5G NR sidelink communications that enables relay functionality between UEs. It adapts data for transmission over the sidelink relay interface, supporting ProSe services and extended coverage for public safety and V2X applications.

Signalling Radio Bearer

A logical channel in cellular networks dedicated to carrying control plane signalling messages between the UE and the network. It ensures reliable delivery of critical signalling for connection establishment, mobility, and configuration.

Signalling Radio Bearer 2

A specific signalling radio bearer used in UMTS and LTE for carrying NAS messages after security activation. It is established post-RRC connection setup and handles non-access stratum signalling like session management.

Selected REJect frame

SREJ is a control frame used in data link layer protocols like LAPDm and LAPD for selective retransmission. It requests the retransmission of a specific, identified frame that was received out-of-sequence, improving efficiency over rejecting all subsequent frames.

Signalling System Number 7

SS7 is a set of telephony signaling protocols used to set up and tear down telephone calls, provide services like caller ID, and enable roaming. It is the foundational out-of-band signaling system for traditional circuit-switched networks, including 2G and 3G core networks, enabling reliable call control and supplementary services.

Supplementary Service Application Part

SSAP is a signaling protocol within the 3GPP Core Network, specifically part of the CAMEL (Customised Applications for Mobile network Enhanced Logic) architecture. It facilitates the control and management of supplementary services, such as call forwarding and barring, by enabling communication between network entities like the gsmSCF and the MSC or SGSN. Its role is crucial for delivering advanced, operator-specific telephony features beyond basic call handling.

Service Specific Co-ordination Function

The Service Specific Co-ordination Function (SSCF) is a protocol adaptation layer defined in the Iu interface for UMTS and the Iur interface between RNCs. It maps the service-specific requirements of the upper layer (SSCOP - Service Specific Connection Oriented Protocol) to the generic capabilities of the underlying network layer (e.g., MTP3-B or SAAL). It is essential for ensuring reliable, connection-oriented data transfer for control plane signaling in the Radio Access Network.

Service Specific Connection Oriented Protocol

A transport protocol within the Iu interface's ATM-based transport layer, providing reliable, in-sequence data transfer for control plane signaling. It ensures error-free delivery and flow control between the RNC and core network, crucial for stable network operation.

Service Specific Convergence Sublayer

A sublayer within the ATM Adaptation Layer (AAL) that adapts higher-layer protocols to the underlying ATM service. In 3GPP, it often houses SSCOP to provide reliable signaling transport over the Iu interface, ensuring protocol-specific requirements are met.

Secure Socket Layer

A cryptographic protocol designed to provide secure communication over a computer network, notably the Internet. It ensures privacy, authentication, and data integrity between two communicating applications, such as a web browser and a server.

Synchronization Source Identifier

A unique identifier for the source of a media stream within Real-time Transport Protocol (RTP) sessions. It distinguishes between multiple concurrent media sources (e.g., different speakers in a conference call), enabling proper synchronization, mixing, and playback by receivers. It is fundamental to multimedia communication in IMS and VoLTE/VoNR.

Service Specific Segmentation and Re-assembly sublayer

A protocol sublayer in the Iu interface user plane, part of UMTS. It segments and reassembles service data units (SDUs) from higher layers (like the RLC) into packets suitable for transport over the underlying ATM/AAL2 network. It ensures efficient bandwidth utilization for circuit-switched services.

Session-Termination-Answer

A Diameter protocol message used in 3GPP networks to acknowledge the termination of a session. It is sent in response to a Session-Termination-Request (STR), confirming that session resources have been released and charging records are finalized, crucial for accurate billing and resource management.

Session-Termination-Request

Session-Termination-Request (STR) is a Diameter command used in 3GPP networks to explicitly request the termination of an established Diameter session, such as an IP-CAN session or a credit control session. It is a critical component of the Diameter base protocol for proper session cleanup, resource release, and final accounting.

SUper FIeld

SUFI is a variable-length control field used in the Radio Link Control (RLC) protocol layer in 3GPP UMTS. It carries status information, primarily for RLC Acknowledged Mode (AM), to facilitate selective retransmissions. It is a key mechanism for implementing ARQ (Automatic Repeat Request) and ensuring reliable data delivery over the radio interface.

Synchronization User Plane Protocol

A user plane protocol used in UTRAN Iur and Iub interfaces for transporting synchronization information, such as timing and frame alignment, between network nodes. It ensures coordinated transmission and reception, which is critical for radio resource management and handover procedures.

Terminating IP Multimedia Basic Call State Model

The Terminating IP Multimedia Basic Call State Model (T-IM-BCSM) is a finite state machine used in the IP Multimedia Subsystem (IMS) call session control. It models the events and points of control for a terminating (incoming) SIP session from the perspective of the serving CSCF, defining where service logic can be invoked.

RLC Transparent Mode

A Radio Link Control (RLC) operational mode in 3GPP UMTS and LTE where the RLC sublayer does not perform segmentation, concatenation, or error correction. It simply passes data through transparently, used for delay-sensitive services like voice where lower-layer reliability is sufficient.

Transmission side Terminal Adaptation Function

The T-TAF is a functional entity in 3GPP networks responsible for adapting data streams from a terminal for transmission over the network. It handles protocol conversion and data formatting, ensuring compatibility between the terminal and the network infrastructure. This function is crucial for supporting various data services and applications.

Transaction Capabilities Application Part

TCAP is a signaling protocol used in SS7 and SIGTRAN networks to facilitate transaction-oriented, connectionless communication between network nodes. It enables the exchange of non-circuit related information, such as database queries (e.g., for number portability) or intelligent network (IN) service triggers, independent of voice call paths.

Transmission Control Protocol / Internet Protocol

The foundational suite of internet communication protocols. It defines how data is packetized, addressed, transmitted, routed, and received across networks. It is essential for enabling IP-based services and internet connectivity in 3GPP systems.

Trivial File Transfer Protocol

A simple, lock-step file transfer protocol used in 3GPP networks for downloading configuration files, software updates, and bulk data to network elements and user equipment. It provides a lightweight alternative to FTP, operating over UDP, which is crucial for automated provisioning and management tasks.

Transaction Identifier

A unique identifier used in various 3GPP protocols to correlate messages belonging to the same transaction or procedure between network entities. It is fundamental for dialog management, session control, and ensuring reliable message exchange in signaling protocols.

Transport Independent Call Control

Transport Independent Call Control (TICC) is a 3GPP architecture and protocol framework that separates call control logic from the underlying transport technology. It enables the creation and management of multimedia sessions (like voice and video calls) over various IP-based and circuit-switched networks, providing network convergence and service flexibility.

Type Length Instance Value

A fundamental encoding format used in 3GPP protocol messages, particularly in the GPRS Tunneling Protocol (GTP). It structures information elements (IEs) as a TLV (Type-Length-Value) triplet, with an added Instance field to distinguish between multiple IEs of the same Type. This ensures efficient, extensible, and unambiguous data parsing.

Type, Length, Value

A flexible data encoding format used extensively in 3GPP protocols, particularly in GTP headers. It structures information into a self-describing triplet, enabling efficient and extensible message parsing. This is fundamental for protocol evolution and interoperability across network nodes.

Transparent Mode Data

TMD is a service provided by the Radio Link Control (RLC) layer in 3GPP protocols. It offers unacknowledged data transfer without segmentation, reassembly, or retransmission, providing a simple, low-latency path for streaming or broadcast traffic where error recovery is handled at higher layers.

Transfer Mode Entity

The Transfer Mode Entity (TME) is a protocol layer entity defined in UTRAN RRC specifications. It manages the transfer mode for data bearers, handling the mapping between logical channels and transport channels, and is crucial for establishing and reconfiguring radio bearers in 3G UMTS networks.

Temporary Maximum Media Stream Bit Rate Notification

A Real-time Transport Control Protocol (RTCP) packet type used in RTP-based media sessions to notify a media sender about a temporary limit on the bit rate it should use for a specific media stream. It is a key feedback mechanism for managing congestion and adapting to receiver or network constraints.

Temporary Maximum Media Stream Bit Rate Request

A Real-Time Transport Control Protocol (RTCP) feedback message used in multimedia sessions to dynamically request a peer to limit its maximum sending bit rate for a specific media stream. It is crucial for congestion control and adapting to network conditions in real-time communication services like Voice over IP (VoIP) and video conferencing.

Transmission Medium Requirement

A parameter within the 3GPP Bearer Binding and Event Reporting Function (BBERF) and Policy and Charging Control (PCC) architecture. It specifies the required QoS characteristics for a bearer transporting IP flows, enabling policy enforcement and resource allocation.

Transmission Object Identifier

Transmission Object Identifier (TOI) is a protocol field in FLUTE/ALC used for identifying data objects within a broadcast/multicast session. It enables receivers to request specific objects for repair or to identify components of a multimedia service. It is crucial for efficient file delivery over unidirectional transports.

Transport Protocol Data Unit

The TPDU is a fundamental data unit in 3GPP transport protocols, representing a packet of user data or control information exchanged between peer protocol entities. It is crucial for the structured encapsulation and reliable delivery of information across network interfaces, forming the basis for various service data flows.

Tree and Tabular Combined Notation

TTCN is a standardized, abstract, and protocol-independent testing language developed by ETSI and adopted by 3GPP. It is used to specify test cases and test suites for conformance testing of telecommunications protocols and systems. TTCN enables the creation of precise, executable test specifications that verify if an implementation meets its standard.

Tree and Tabular Combined Notation version 2

TTCN-2 is the second major version of the TTCN testing language, maintaining the original tabular format but with significant enhancements in structuring and expressiveness. It was used for the majority of 3GPP conformance test suites through the 3G and 4G eras. TTCN-2 is defined in the ISO/IEC 9646 series and ETSI standards.

Telephone User Part

TUP is a component of the SS7 signaling protocol, used for call setup and teardown in traditional circuit-switched telephony networks. It handles basic call control functions like address signaling and supervision, enabling reliable voice communication between exchanges.

Traversal Using Relays around NAT

TURN is a protocol that enables real-time communication (e.g., voice, video) between devices behind NATs or firewalls by relaying data through a public server. It acts as a fallback when direct peer-to-peer connections are blocked, ensuring connectivity for IMS and WebRTC applications.

Type and Value

TV is a compact encoding format used in 3GPP protocols to represent information elements with a type identifier and associated value. It optimizes message size by omitting length fields for fixed-length values, improving efficiency in signaling and management interfaces.

Two Way Alternate

TWA is a communication mode defined in 3GPP for data link layer protocols, enabling bidirectional data exchange where devices take turns transmitting. It ensures orderly communication by preventing collisions and managing transmission rights. TWA is used in interfaces like X2 and S1 for efficient signaling and data transfer.

Unnumbered Acknowledgement

A frame type used in data link layer protocols for reliable data transmission without sequence numbers. It acknowledges the receipt of frames, enabling flow control and error recovery in signaling and data transfer. It is a fundamental mechanism for ensuring data integrity in various 3GPP interfaces.

User Authorization Request

A Diameter protocol command used within the IMS (IP Multimedia Subsystem) core network. It is sent by an Interrogating-CSCF (I-CSCF) to a Home Subscriber Server (HSS) to request authorization information for a user attempting to register to or establish a session in the IMS.

Unnumbered Acknowledgement

A control frame used in data link layer protocols (like those in 3GPP TS 27.010) to acknowledge receipt of frames without using sequence numbers. It provides a simple, efficient acknowledgement mechanism for reliable data transfer.

User Data Header Indicator

A single-bit field within SMS TP-UDH that signals the presence of a User Data Header. It is essential for enabling advanced SMS features like concatenation, port addressing, and application identifiers by indicating that the message payload contains structured header information.

User Data Header Length

An 8-bit field that specifies the total length (in octets) of the User Data Header in an SMS message. It directly follows the UDHI indicator and is critical for correctly parsing the header's information elements before accessing the actual message text.

User Datagram Protocol

A core transport-layer protocol providing connectionless, unreliable datagram services for IP networks. It offers minimal overhead with no handshaking, ordering, or retransmission, making it ideal for low-latency applications like VoIP, DNS, and real-time streaming in 3GPP systems.

Facsimile UDP Transport Layer

A protocol defined by 3GPP for transporting facsimile (fax) data over IP networks using UDP. It enables real-time fax transmission in packet-switched environments like IMS, providing error recovery and adaptation to network conditions without the overhead of TCP.

SCCP Unitdata Message

A connectionless SCCP message used for transporting signaling data without establishing a virtual circuit. It provides a basic datagram service for signaling network elements, enabling efficient, low-overhead transfer of short messages in scenarios where connection-oriented services are unnecessary.

Universal Decompressor Virtual Machine

A virtual machine defined by the SigComp protocol to execute decompression algorithms on compressed signaling messages. It provides a standardized, safe environment for running bytecode decompressors, enabling efficient compression of text-based protocols like SIP and HTTP in constrained wireless networks.

UE Initiated Report Indication

UE Initiated Report Indication (UEIRI) is a protocol mechanism introduced in 3GPP Release 19. It allows the User Equipment (UE) to proactively initiate and send measurement reports or status indications to the network without waiting for a specific request from the base station. This enhances network awareness of UE conditions, supports more dynamic resource management, and is particularly relevant for advanced mobility and power-saving features.

Unnumbered Information frame

An Unnumbered Information (UI) frame is a type of frame in data link layer protocols, such as those used in 3GPP for signaling transport. It carries information without requiring sequence numbers or acknowledgments, making it suitable for connectionless, low-overhead data transfer. It is fundamental for certain control plane and user plane messaging within the network architecture.

Unnumbered Information with Header Check

A frame type in the 3GPP 27.010 multiplexing protocol used for data transfer between a Terminal Equipment (TE) and a Mobile Termination (MT). It carries user data with an error-checked header, providing a reliable data link service for serial communication in legacy mobile devices.

User Plane Location Protocol

ULP is a protocol defined by 3GPP and OMA for delivering location information over the user plane. It enables positioning services like emergency calls, navigation, and location-based services by carrying positioning-related messages between a device and a location server. It is a key enabler for standardized, network-assisted positioning.

Unacknowledged Mode

Unacknowledged Mode (UM) is a radio link control (RLC) protocol mode that provides unacknowledged data transfer service. It ensures in-sequence delivery of upper layer protocol data units (PDUs) but does not guarantee delivery, making it suitable for delay-sensitive, error-tolerant traffic like voice or streaming video. Its operation is crucial for efficient radio resource usage in scenarios where retransmissions are undesirable.

Unacknowledged Mode Data

Unacknowledged Mode Data (UMD) refers to the specific Protocol Data Unit (PDU) format used by the Radio Link Control (RLC) layer when operating in Unacknowledged Mode (UM). It is the packet structure that carries user or control plane data, containing a header with sequence number and segmentation information, and the payload. UMD PDUs are the fundamental units transmitted over the air interface for UM services.

Unbalanced Operation Normal Response Mode Class

UNC is a protocol class within the Unbalanced Operation for Normal Response Mode, used in data link layer communications. It defines a specific master-slave relationship for managing data transfer, ensuring orderly and controlled exchange between primary and secondary stations in a network.

Update Notification Acknowledgment

A Diameter protocol command (Update-Notification-Answer) used in the 3GPP S6a/S6d interface between an MME/SGSN and an HSS. It is the acknowledgment message sent in response to an Update Notification Request (UPR), confirming the successful processing of a subscriber data change notification.

Update Notification

A GTPv2-C message used in the S5/S8 interface between SGW and PGW to notify the PGW of changes in the SGW's state or configuration. It ensures session continuity and proper bearer management during mobility events or network updates.

Virtual Connection

Virtual Connection (VC) is a logical communication path established between endpoints in a transport network, such as an ATM or IP network, to carry user data and signaling. It provides a reliable, connection-oriented service for transporting 3GPP protocol data units (PDUs) between network elements, ensuring data integrity and sequence.

Virtual Concatenation

Virtual Concatenation (VCAT) is a transport network technique that groups multiple independent virtual containers (e.g., in SDH/SONET or OTN) into a single logical pipe to achieve higher bandwidth efficiency and flexible capacity allocation. It allows network operators to combine lower-order signals to match service requirements, optimizing resource utilization in backhaul and core networks.

Codec Mode Request for Adaptive Multi-Rate Wideband

WB-CMR is a control mechanism used in AMR-WB voice calls where the receiver sends requests to the transmitter to switch to a specific codec mode (bitrate). It optimizes voice quality and bandwidth usage dynamically based on network conditions and receiver capabilities.

WAP Binary XML

WBXML is a compact binary representation of XML, standardized by the WAP Forum and adopted by 3GPP. It is designed to efficiently encode XML documents for transmission over bandwidth-constrained wireless networks, reducing payload size and parsing overhead. This protocol is crucial for mobile services like WAP browsing and device management, enabling structured data exchange on early mobile networks.

Wireless Datagram Protocol

WDP is a transport-layer protocol in the WAP architecture that provides a consistent datagram service over various underlying wireless bearers. It adapts to different network technologies (like GSM SMS, USSD, or packet data) to offer a unified interface for upper WAP layers. This abstraction enables WAP applications to operate independently of the specific bearer network, promoting interoperability across diverse mobile environments.

Wireless LAN Control Plane Protocol

A GTP-based control plane protocol used between the Trusted WLAN Access Gateway (TWAG) and the UE over the SWw reference point. It manages the establishment, modification, and termination of PDN connections and bearers for UEs connected via trusted WLAN access.

Wireless Transaction Protocol

A lightweight transaction-oriented protocol in the WAP stack, providing reliable request/response services. It manages the efficient exchange of data units between a WAP client and server, optimizing performance over wireless links with mechanisms for segmentation and reassembly.

XML Configuration Access Protocol

An HTTP-based protocol defined by the IETF and adopted by 3GPP that allows a client to read, write, and modify application configuration data stored in XML format on a server. It is fundamental for managing subscriber service settings in IMS, such as call forwarding rules and presence authorization.

XML Encoding Rules

XER is a set of standardized rules for encoding Abstract Syntax Notation One (ASN.1) data structures into XML format. It provides a human-readable and platform-independent XML representation of ASN.1-defined protocol messages and data. This is crucial for management interfaces, configuration data exchange, and debugging in telecom networks.

Exchange Identification frame

An Exchange Identification (XID) frame is a control frame used in data link layer protocols, such as those based on HDLC, to negotiate and exchange configuration parameters between two connected entities. In 3GPP, it is used in legacy circuit-switched data services and certain control plane interfaces to establish link characteristics before data transfer.

Extensible Markup Language

XML is a W3C-standardized markup language used extensively across 3GPP specifications for data representation and exchange. It provides a flexible, text-based format to structure configuration data, service descriptions, and management information in a human-readable and machine-parsable way. Its adoption enables interoperability and automation in network management, service provisioning, and device configuration.

SCCP Extended Unitdata

XUDT is a Signaling Connection Control Part (SCCP) message type used in SS7-based core networks for connectionless data transfer with enhanced capabilities. It extends the basic UDT message by including optional parameters for segmentation/reassembly and hop counter control, enabling the reliable transfer of larger data units across the signaling network.