6 Transport

29.4053GPPNq and Nq' Application Protocol (Nq-AP)Release 17Stage 3TS

6.1 General

This subclause specifies the standards for signalling transport to be used across Nq/Nq’ interface. Nq/Nq’ interface is a logical interface between the RCAF and the MME/SGSN. All the Nq-AP messages described in the present document require an SCTP association between the RCAF and the MME/SGSN.

6.2 IP layer

The RCAF shall support IPv6 (see IETF RFC 2460 [7]) and IPv4 (see IETF RFC 791 [6]).

6.3 Transport layer

SCTP (see IETF RFC 4960 [8]) shall be supported as the transport layer of Nq-AP messages.

Semi-permanent SCTP associations shall be established between the RCAF and MME/SGSN, i.e. the SCTP associations shall remain up under normal circumstances when the RCAF needs to use the Nq-AP procedures towards the MME/SGSN.

The RCAF shall initiate establishment of the SCTP association.

Transport network redundancy can be achieved by SCTP multi-homing between two end-points, of which one or both is assigned with multiple IP addresses. SCTP end-points shall support a multi-homed remote SCTP end-point. For SCTP endpoint redundancy, an SCTP endpoint (in the RCAF or MME/SGSN) may send an INIT, at any time for an already established SCTP association, which the other SCTP endpoint shall handle as defined in IETF RFC 4960 [8].

RCAF and MME/SGSN shall support a configuration with a single SCTP association per RCAF/MME (or RCAF/SGSN) pair. Configurations with multiple SCTP endpoints per RCAF/MME (or RCAF/SGSN) pair may be supported.

Within the SCTP association established between one RCAF and one MME/SGSN, both RCAF and MME/SGSN shall reserve several stream identifiers, based on the INIT message exchange for the sole use of Nq-AP procedures.

The registered port number for Nq-AP is 36424.

The payload protocol identifier to be used for Nq-AP is 0.