DRMP

Diameter Routing Message Priority

Protocol →
Introduced in Rel-13

DRMP is a Diameter protocol attribute that allows a node to assign a priority level to a request, enabling routing agents to perform load balancing, overload control, and priority-based routing.

Category
Protocol
Introduced
Rel-13
Where
Core Network › Evolved Packet Core
Specifications
25 specs
DRMP Description Purpose Related Classification Detected Changes Specifications

Description

Diameter Routing Message Priority (DRMP) is a protocol extension defined in 3GPP to enhance the capabilities of Diameter-based signaling networks, particularly within the IP Multimedia Subsystem (IMS), Evolved Packet Core (EPC), and 5G Core (5GC). It is implemented as an Attribute-Value Pair (AVP) that can be included in Diameter request messages. The DRMP AVP carries an integer value representing the message's priority, with lower numerical values typically indicating higher priority (e.g., 0 for highest priority). The primary function of DRMP is to provide a standardized, in-band signaling mechanism for conveying priority information, allowing Diameter nodes to make more intelligent routing and processing decisions.

Architecturally, DRMP operates within the Diameter base protocol framework (RFC 6733). When a Diameter client or server generates a request (e.g., a Credit-Control-Request (CCR) or an AA-Request (AAR)), it can populate the DRMP AVP based on local policy, the type of service, or subscriber profile. This message is then sent into the Diameter network, often traversing one or more Diameter Routing Agents (DRAs). These intermediate DRAs, which are crucial for scalability and routing in large networks, inspect the DRMP value. Using this information, a DRA can implement priority-aware routing logic. For example, during periods of network congestion or node overload, the DRA can prioritize the forwarding of high-priority messages (like emergency service requests or messages for premium subscribers) while potentially delaying or rejecting lower-priority traffic. This is a key tool for implementing overload and congestion control mechanisms as specified in 3GPP.

The DRMP value influences behavior at multiple points. Beyond routing agents, the destination Diameter server can also use the DRMP to prioritize the order in which it processes incoming requests from its queue. The specifications define procedures for how DRMP values should be generated, forwarded, and potentially modified by trusted nodes. Its introduction formalized what was previously often handled via proprietary or network-local mechanisms, ensuring interoperability between equipment from different vendors in multi-vendor core networks. DRMP is a critical component for achieving carrier-grade reliability and service differentiation in all-IP core networks that rely heavily on Diameter signaling for authentication, authorization, accounting, and policy control.

Purpose & Motivation

DRMP was created to address the challenges of managing signaling load and ensuring service availability in increasingly complex and high-scale Diameter signaling networks. As 3GPP networks evolved to all-IP architectures (IMS, EPC), Diameter became the primary protocol for real-time AAA and policy functions. Without a standardized priority mechanism, all Diameter signaling messages were treated with equal importance by routing agents. This posed a significant problem during signaling storms or node failures, as critical messages (e.g., for emergency calls, handovers, or high-value customers) could be dropped indiscriminately alongside less important traffic, degrading essential services.

The development of DRMP in Release 13 provided a standardized solution to this problem. It was motivated by the need for explicit overload control mechanisms within the Diameter protocol itself. DRMP allows network functions and operators to implement policy-based priority marking. This enables the network to gracefully degrade under load by protecting high-priority sessions and services, a fundamental requirement for telecom-grade resilience. It addressed the limitations of previous ad-hoc approaches and provided a tool for fulfilling regulatory requirements for emergency service support and for implementing commercial service differentiation within the signaling plane.

Classification

Part ofIMS

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (91 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Studied in Rel-13, normative work from Rel-15.

Rel-15 17 changes

In Release 15, the DRMP (Diameter Routing Message Priority) function was corrected and clarified, specifically addressing its procedures and the handling of a Diameter race condition. The corrections ensured proper operational behavior, such as defining the MME/SGSN action upon receiving a DIAMETER_UNABLE_TO_COMPLY response for a NOR message. This provided more reliable priority-based routing for Diameter signaling.

  • EPS mobile identity and UE status in the ATTACH REQUEST message TS 24.301CR3028
  • Correcting message definition of messages including EENL TS 24.301CR3061
  • Correction on transmission failure of IDENTITY RESPONSE message TS 24.301CR3078
  • Handling of attempt counter upon receipt of the ATTACH ACCEPT message TS 24.301CR3138
  • Establishment of secure exchange of NAS messages during inter-system change from N1 mode to S1 mode TS 24.301CR3139
  • Use of 5G-GUTI in creation of an ATTACH REQUEST message TS 24.301CR3152

+ 11 more changes

Rel-16 10 changes

In Release 16, the enhancements for the Diameter Routing Message Priority (DRMP) function are not described within the provided grounding context or the listed Change Request titles. The available material focuses on other areas, such as NAS message security handling, 5GMM parameter procedures, and QoS priority for VAL service traffic flows, but does not contain specific technical details on DRMP changes from the previous release.

  • TAU REQUEST message security handling during mobility S1 to N1 TS 24.301CR3202
  • Clarification for EMM cause #3, #6, and #8 in the SERVICE REJECT message TS 24.301CR3211
  • Procedure associated with a back-off timer started upon receipt of a PDN CONNECTIVITY REJECT message TS 24.301CR3222
  • Correction of parameters in the registration request message while disabling EUTRA TS 24.301CR3231
  • Handling of 5GMM parameters for non-integrity protected reject messages in EPS TS 24.301CR3237
  • Deletion of RAND and RES on receiving Service Accept message TS 24.301CR3239

+ 4 more changes

Rel-17 12 changes

In Release 17, the DRMP (Diameter Routing Message Priority) function was enhanced to address superfluous AVPs in re-used Diameter AVPs tables, ensuring cleaner and more efficient message structures. A correction was also made to the message name associated with this function for improved clarity and alignment within the signaling framework. These updates specifically refined the Diameter-based signaling procedures used for transport and routing within the core network.

  • UAS services not allowed indication in EPS NAS message TS 24.301CR3618
  • Forbidden TAI list IEs in ATTACH and TAU REJECT messages TS 24.301CR3761
  • Handling of cause #8, #14, #35 for non-integrity protected reject messages TS 24.301CR3487
  • Handling UE radio capability IDs in GUTI REALLOCATION COMMAND message TS 24.301CR3489
  • Add 5GMM SR procedure for non-integrity protected reject message TS 24.301CR3524
  • Storage of counters related to non-integrity protected reject messages TS 24.301CR3486

+ 6 more changes

Rel-18 16 changes

In Release 18, the DRMP (Diameter Routing Message Priority) function was extended to include the SLg and Lgd interfaces for location services. This enhancement specifically introduced Diameter message priority handling for transport and routing on these interfaces. The update ensures prioritized Diameter signaling for location management procedures, aligning with the existing use of HTTP-based signaling control plane reference points for such services.

  • Exchanging the SDNAEPC EAP message in ESM procedures TS 24.301CR3853
  • Resolving the EN related to exchanging the SDNAEPC EAP message TS 24.301CR3870
  • Transport of messages of network-requested UE policy management procedure TS 24.301CR3934
  • Introduce Maximum time offset IE in the TAU ACCEPT message TS 24.301CR3970
  • Diameter message priority over SLg and Lgd TS 29.172CR0050
  • Add SBI support Indication in S6c Routing Info for SM Answer TS 29.338CR0043

+ 10 more changes

Rel-19 36 changes

In Release 19, the enhancements for Diameter Routing Message Priority (DRMP) specifically introduced priority handling for Mobile Terminated SMS over NAS, ensuring prioritized messaging delivery. This is complemented by the new capability for initial paging with priority in EPS, which integrates the EMM TRANSPORT message into paging procedures to support these prioritized services. These updates provide a more granular mechanism for prioritizing specific message flows within the NAS transport layer.

  • 24.301 MPS for Messaging Paging Priority TS 24.301CR4169
  • Provisioning an S-NSSAI via the PDN CONNECTIVITY REQUEST message TS 24.301CR3655
  • New message for transferring data over NAS - Part 2: procedures TS 24.301CR4367
  • New message for transferring data over NAS - Part 1: message format TS 24.301CR4366
  • Handling of inactive PDP context in EMM TRANSPORT message TS 24.301CR4517
  • Alignment of EMM Transport message TS 24.301CR4459

+ 30 more changes

Explore further

Broader topics and technologies where DRMP plays a role.

Topics
Authentication (5G-AKA, EAP)IMS & Voice (VoLTE, VoNR)EPC (Evolved Packet Core)MEC (Edge Computing)Emergency ServicesDiameter & Radius
Technologies
5G

Defining Specifications

3GPP specifications that define or reference DRMP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.

SpecificationTitleRelease
TS 23.700 vk00 XR Services Application Enablement Layer Rel-20
TS 24.301 vj60 NAS protocol for Evolved Packet System Rel-19
TS 29.128 vj10 MME/SGSN-SCEF Diameter Interfaces for PDN Interworking Rel-19
TS 29.153 vj00 Ns Reference Point Protocol between SCEF and RCAF Rel-19
TS 29.154 vj00 Nt Reference Point Protocol Rel-19
TS 29.172 vj00 EPC LCS Protocol (ELP) specification Rel-19
TS 29.201 vj00 RESTful Rx Interface for AF-PC Communication Rel-19
TS 29.212 vj00 Gx/Gxx/Sd/St Diameter Protocol Rel-19
TS 29.213 vj20 PCC Signalling Flows and QoS Mapping Rel-19
TS 29.214 vj20 Policy and Charging Control over Rx Rel-19
TS 29.215 vj00 S9 Reference Point Stage 3 Specification Rel-19
TS 29.217 vj00 Policy and Charging Control (PCC) for Np Interface Rel-19
TS 29.219 vj00 Sy Reference Point Stage 3 Specification Rel-19
TS 29.228 vj20 Cx and Dx Interface Signaling Flows Rel-19
TS 29.229 vj10 Diameter Protocol for Cx/Dx Interfaces Rel-19
TS 29.272 vj40 Diameter Interfaces for MME/SGSN Rel-19
TS 29.273 vj10 AAA Protocols for Non-3GPP Access in EPS & 5GS NSWO Rel-19
TS 29.328 vj20 Sh and Dh Interfaces: HSS-AS Interactions Rel-19
TS 29.329 vj10 Diameter Protocol for Sh Interface Rel-19
TS 29.336 vj10 HSS Diameter Interfaces for PDN Interworking Rel-19
TS 29.337 vj00 Diameter T4 Interface for MTC Device Triggering Rel-19
TS 29.338 vj30 Diameter protocols for SMS in MME/5GS Rel-19
TS 29.344 vj00 Diameter-based PC4a interface specification Rel-19
TS 29.345 vj00 Diameter-based PC6/PC7 interfaces for ProSe Rel-19
TS 29.468 vj00 MB2 Reference Point Protocol Definition Rel-19