X2 Signalling Transport
X2 signalling bearer provides the following functions:
- Provision of reliable transfer of X2-AP message over X2 interface.
- Provision of networking and routeing function
- Provision of redundancy in the signalling network
- Support for flow control and congestion control
L2 - Data link layer
Support of any suitable data link layer protocol, e.g. PPP, Ethernet
- The eNB supports IPv6 and/or IPv4
- The IP layer of eNB-eNB only supports point-to-point transmission for delivering X2-AP message.
- The eNB supports the Diffserv Code Point marking
SCTP is supported as the transport layer of eNB-eNB signalling bearer.
- SCTP refers to the Stream Control Transmission Protocol developed by the Sigtran working group of the IETF for the purpose of transporting various signalling protocols over IP network.
- There is only one SCTP association established between eNB pairs.
- The eNB establishes the SCTP association. The SCTP Destination Port number value assigned by IANA to be used for X2AP is 36422.
3GPP TS 36.420 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 general aspects and principles
3GPP TS 36.421 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 layer 1
3GPP TS 36.422 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 signalling transport
IETF RFC 2460: "Internet Protocol, Version 6 (IPv6) Specification"
IETF RFC 791 (September,1981): "Internet Protocol"
IETF RFC 2474 (December 1998): "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers"