Point-to-point service

Description

Point-to-point service is a service type defined in 3GPP TS 21.905, the vocabulary specification. It describes a communication service in which data is sent from a single network termination to another network termination. This is the service-level realization of the point-to-point communication configuration, providing a dedicated, typically bidirectional, path between two endpoints.

In 3GPP networks, a point-to-point service is characterized by a one-to-one relationship between the communicating parties. This means that the network establishes a connection that is dedicated to the two endpoints, ensuring that data sent by one is received by the other, and vice versa. This is in contrast to point-to-multipoint services, where data from one source is delivered to multiple destinations, or multipoint services, where multiple parties can communicate with each other.

The point-to-point service is fundamental to many telecommunication applications. Classic examples include voice calls, video calls, SMS, and interactive data sessions such as web browsing or file transfer. In each case, the communication is between two specific parties: the calling and called parties for voice, or the client and server for data. The network must provide a reliable, often bidirectional, channel to support these services.

From an architectural perspective, a point-to-point service can be implemented using various bearer technologies. In circuit-switched networks, a dedicated circuit is established for the duration of the call. In packet-switched networks like GPRS, UMTS, LTE, and 5G, a point-to-point service is typically carried over a dedicated bearer or a set of bearers that provide the necessary QoS. For example, in LTE, an EPS bearer provides a point-to-point connection between the UE and the P-GW, and multiple bearers can be used to support different QoS flows within the same service.

In the context of 5G, a point-to-point service can be realized through a PDU session, which provides connectivity between the UE and a data network. The PDU session can be of type IPv4, IPv6, or Ethernet, and it can support multiple QoS flows. Each QoS flow can be considered a point-to-point service instance if it carries traffic between two specific endpoints. The 5G system also supports point-to-point services over non-3GPP access, such as Wi-Fi, through the N3IWF.

The point-to-point service is also relevant in the context of multicast and broadcast. For instance, in MBMS, the network can choose to deliver a service using point-to-point bearers to individual users if the number of users is small, or using a point-to-multipoint bearer if the number is large. This decision is based on radio resource efficiency and is a key aspect of MBMS operation.

In summary, point-to-point service is a basic service type that provides a dedicated communication path between two network terminations. It is a cornerstone of many telecommunication services and is supported across all 3GPP generations.

Purpose & Motivation

The point-to-point service concept exists to provide a standardized way to describe and implement services that involve exactly two parties. In the early days of telecommunications, most services were inherently point-to-point, such as voice calls. However, as networks evolved to support multicast and broadcast, there was a need to explicitly define and distinguish point-to-point services from other types. This distinction is crucial for service definition, capability negotiation, and resource management.

Before the formal definition in TS 21.905, the term "point-to-point" was used informally, but its precise meaning varied. The introduction of a standardized definition ensured that all stakeholders—network operators, equipment vendors, and service providers—had a common understanding. This is particularly important for interoperability, as it allows different networks and devices to correctly interpret service requests and allocate resources accordingly.

Moreover, the point-to-point service concept addresses the need for efficient resource utilization. By clearly identifying a service as point-to-point, the network can allocate dedicated resources and apply appropriate QoS and security policies. This ensures that the service meets its performance requirements while optimizing the use of network resources. For example, a point-to-point voice call requires a dedicated bearer with stringent delay and jitter requirements, whereas a point-to-multipoint broadcast can use a shared bearer with different QoS characteristics.