Hello, I am looking for SRVCC PS to CS Cancel (and Ack) messages example (gtpv2) in order to understand how this packet is built. Can I find these Wireshark traces> BR, Diana asked 24 Nov '14, 09:25  Dianalab9 |
One Answer:
I can't get it to you as a pcap, but I could probably answer field questions if you have specific things you're not sure on. That's the best I can do. :/ Also see section 5.2.6 and 5.2.7 of TS 29.280 for the IE breakdown of those two messages. There's really not a lot to it. http://www.etsi.org/deliver/etsi_ts/129200_129299/129280/12.02.00_60/ts_129280v120200p.pdf answered 25 Nov '14, 21:24  Quadratic edited 25 Nov '14, 21:25 |
Hi, yes, I do have a specific question:
It is stated in the standard 29.280 that: "The TEID field in the SRVCC CS to PS Cancel Notification message header shall be set to "0" if the message is sent before reception of the acceptance response to the SRVCC CS to PS Request" From the possible IEs in Cancel Notification message, it doesn't include any address for Control (for the other direction) so what I don't understand is on which TEID-C the Cancel Acknowledge message will ride.
Do you have an explanation on this?
The request and response messages are tied together by the GTP sequence numbers. Because one UE can have only one control TEID pair on an Sv interface (mandatory, section 5.2.1), and because the cancel message contains the UE's permanent identifier (IMSI or, for emergency scenario, IMEI), there's no need for the acknowledgement to specify any control TEID for both sides to cleanly map the exchange to a given subscriber and handover attempt.
One thing to keep in mind here is that Sv is indirectly governed by TS 29.274. Fields inherent to GTPv2c apply here as well (such as request/response sequence numbers).