The present document specifies or references the necessary information to provide a reliable transfer of signalling messages between the Serving GPRS Support Node (SGSN) and the Visitors Location Register (VLR). This reliable transfer of messages is provided by the Network Service Part (NSP) of the Signalling System No 7 (SS7). This documents specifies or references the subset of MTP and SCCP to be used in the Gs interface.
The present document specifies or references the subset of MTP and SCCP which is used for the reliable transport of BSSAP+ messages in the Gs interface. The present document references the TS 29.202
which specifies alternative transport layers that can be applied instead of the MTP. The present document also specifies the SCCP addressing capabilities to be provided in the Gs interface.
The present document is divided into two main parts, clause 5
dealing with the use of MTP and clauses 6
and 7 dealing with the use of SCCP.
of the present document deals with the subset of the MTP that is required between an SGSN and a VLR. It is intended that this implementation of MTP is compatible with a full MTP implementation. Clause 4
references the TS 29.202
which specifies alternatives to the MTP.
The SCCP is used to provide message routing between the SGSN and the VLR. The SCCP routing principles specified in the present document allow to connect one SGSN to several VLR. No segmentation at SCCP level is needed on the Gs interface. Only SCCP class 0 is used on the Gs interface. Clauses 6
and 7 identify the SCCP subset that should be used between an SGSN and an VLR.
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
Unless listed below, the definitions, symbols and abbreviations are listed in TR 21.905
and TS 23.060
The Gs interface connects the Serving GPRS Support Node (SGSN) to the Visitors Location Register (VLR). This interface is defined in the 64 kbit/s for E1 interface and for 64 kbit/s or 56 kbit/s for T1 interface boundary of an SGSN to a VLR or of a VLR to an SGSN. The configuration of the Gs interface shall not impose any restriction on the number of VLRs or SGSNs to be connected by the Gs interface. The Gs interface definition shall support an early implementation of GPRS when one SGSN may be connected to several VLRs or a more mature implementation when several SGSNs may be connected to one VLR. Therefore the interface shall support the use of an STP.
The level of resilience in the Gs interface is determined by the operator, however it is recommended that the operator considers the use of more than one multiplex system between the SGSN and the VLR. Each multiplex system should be used to carry one signalling link and routing diversity should be provided among the signalling links to increase the resilience of the system.