Submission Date: April 24, 2008 From: IETF SIGTRAN WG (Lyndon Ong ) To: 3GPP TSG CT WG4 (Zhao yuyi ) CC: Gonzalo Camarillo Jon Peterson (IETF RAI Area Director) Cullen Jennings (IETF RAI Area Director) Response Contact: Lyndon Ong Technical Contact: Michael Tuexen [tuexen@fh-muenster.de] Purpose: For Information Deadline: None Body: Dear Mr. Zhao, The SIGTRAN working group discussed your liaison regarding M3UA and reached the following conclusions: Regarding the liaison?s first scenario we agree that the signalling gateway SG1 must send a DUNA message to SP1 if a point code of SP2 is not reachable via SG1. It does not matter whether the point code represents a node in the SS7 network or a node in the IP network. Regarding your second scenario it should be noted that neither DUPU nor DUNA messages can be sent from ASPs (marked as SPs in your figures) to SGs. They can only be sent from SGs to ASPs. When an AS serves a point code, only the whole point code can be available or unavailable. Under our current procedures, it is not possible to make only a part of the point code unavailable. If it is desired that specific user parts can become unavailable, then configuring the AS to serve a particular point code and service indicator combination could solve the problem within the existing procedures. Such configuration is already supported by M3UA without any extensions. However, this approach has some drawbacks, expecially if multiple SGs are used. There was some discussion within the Working Group about potential extensions to overcome these drawbacks, but no consensus was reached. The SIGTRAN working group is currently not chartered to develop new protocol. However, developing a new protocol via individual submissions is a possible alternative. The SIGTRAN mailing list provides a way of reviewing such submissions and providing comments. We would appreciate your thoughts on the above suggestions and would like to know whether they address your requirements and concerns. Sincerely Lyndon Ong (SIGTRAN chair)