4 Protocol Stack

29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS

4.1 Introduction

The protocol stack for the control plane over the Sxa, Sxb, Sxc, combined Sxa/Sxb, N4 and N4mb reference points shall be as depicted in Figure 4.1-1. Clauses 4.2 and 4.3 further specify the related UDP and IP requirements.

Figure 4.1-1: Control Plane stack over Sxa, Sxb, Sxc, combined Sxa/Sxb, N4 and N4mb

The protocol stack for the user plane over the Sxa, Sxb and N4reference points (see clause 5.3) shall be as depicted in Figure 4.1-2. 3GPP TS 29.281 [3] further specifies the related GTP-U, UDP and IP requirements. Both IPv4 and IPv6 shall be supported.

Figure 4.1-2: User Plane stack over Sxa, Sxb, combined Sxa/Sxb and N4

4.2 UDP Header and Port Numbers

4.2.1 General

A User Datagram Protocol (UDP) compliant with IETF RFC 768 [4] shall be used.

4.2.2 Request Message

The UDP Destination Port number for a Request message shall be 8805. It is the registered port number for PFCP.

The UDP Source Port for a Request message is a locally allocated port number at the sending entity.

NOTE: The locally allocated source port number can be reused for multiple Request messages.

4.2.3 Response Message

The UDP Destination Port value of a Response message shall be the value of the UDP Source Port of the corresponding Request message.

The UDP Source Port of a Response message shall be the value from the UDP Destination Port of the corresponding message.

4.3 IP Header and IP Addresses

4.3.1 General

In this clause, "IP" refers either to IPv4 as defined by IETF RFC 791 [5] or IPv6 as defined by IETF RFC 2460 [6]. A PFCP entity shall support both IPv4 and IPv6.

4.3.2 Request Message

The IP Destination Address of a Request message shall be an IP address of the peer entity.

During the establishment of a PFCP Session, the CP and the UP functions select and communicate to each other the IP Destination Address at which they expect to receive subsequent Request messages related to that PFCP Session. The CP and the UP functions may change this IP address subsequently during a PFCP Session Modification procedure.

The IP Source Address of a Request message shall be an IP address of the sending entity.

4.3.3 Response Message

The IP Destination Address of a Response message shall be copied from the IP Source Address of the corresponding Request message.

The IP Source Address of a Response message shall be copied from the IP destination address of the corresponding Request message.

4.4 Layer 2

Typically Ethernet should be used as a Layer 2 protocol, but operators may use any other technology.

4.5 Layer 1

Operators may use any appropriate Layer 1 technology.