5 LCS-AP Message Transport

29.1713GPPLCS Application Protocol (LCS-AP) between the Mobile Management Entity (MME) and Evolved Serving Mobile Location Centre (E-SMLC)Location Services (LCS)Release 17SLs interfaceTS

5.1 General

The LCS-AP is a logical interface between the MME and the E-SMLC. This clause specifies the standards for signaling transport to be used across LCS-AP.

5.2 Protocol Layering

Figure 5.2-1 below shows the protocol layering used to support the transfer of LCS-AP PDUs between an E-SMLC and a MME. The LTE Positioning Protocols (LPP and LPPa) can be carried in LCS-AP messages which are transparent to the MME.

Figure 5.2-1 Protocol Layering for LCS-AP

5.3 Usage of SCTP Associations

SCTP (see IETF RFC 4960 [4]) shall be supported as the transport layer of LCS-AP messages.

Semi-permanent SCTP associations shall be established between MME and E-SMLC, i.e. the SCTP associations shall remain up under normal circumstances.

Local multi-homing should be supported. Remote multi-homing shall be supported.

Multiple local SCTP endpoints may be supported. Multiple remote SCTP endpoints shall be supported. When multiple local or remote SCTP endpoints are configured, several simultaneous SCTP associations shall be supported between MME and E-SMLC.

The MME shall establish the SCTP association. Since under normal operation there should always be an SCTP association established between an MME and an E-SMLC, if the E-SMLC needs to initiate a message towards an MME it shall do so over an existing SCTP association already established with that MME.

When an entity detects that an SCTP association has been lost, all resources for transactions open on that association shall be released.

The registered port number for LCS-AP is 9082. The registered payload protocol identifier for LCS-AP is 29.