37.4723GPPRelease 16TSW1 signalling transport
For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905  and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905 .
ng-eNB: as defined in 3GPP TS 38.300 
SCTP association: as defined in IETF RFC 4960 (2007-09) 
SCTP endpoint: as defined in IETF RFC 4960 (2007-09) 
W1: interface between a ng-eNB-CU and a ng-eNB-DU, providing an interconnection point between the ng-eNB-CU and the ng-eNB-DU.
W1-C: Reference point for the control plane protocol between ng-eNB-CU and ng-eNB-DU.
For the purposes of the present document, the abbreviations given in 3GPP TR 21.905  and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in 3GPP TR 21.905 .
DiffServ Differentiated Service
IANA Internet Assigned Number Authority
IP Internet Protocol
PPP Point to Point Protocol
SCTP Stream Control Transmission Protocol
4. W1-C signalling bearer
4.1 Function and protocol stack
The W1-C signalling bearer provides the following functions:
– Provision of reliable transfer of W1AP messages over the W1-C interface.
– Provision of networking and routeing function.
– Provision of redundancy in the signalling network.
– Support for flow control and congestion control.
The protocol stack for W1-C Signalling Bearer is shown in figure 4.1-1 and details on each protocol are described in the following clauses.
Figure 4.1-1: W1-C signalling bearer protocol stack
The Transport Network Layer is based on IP transport, comprising SCTP on top of IP.