Greetings,
We have discovered a second interop problem in our testing; this one
is less easily explainable to me in terms of SEMS mechanics, so I am
hoping some light can be shed, or it can be marked as an actual bug.
Raphael and Stefan, I have privately e-mailed you a packet capture of
the scenario I am about to describe, but I prefer not to post it on
the public list.
Here is the flow:
PBX --> SEMS --> PSTN_GW
PBX supports timer, and PSTN_GW does not.
1. PBX sends an initial INVITE, in which it says that it supports
timers. SEMS relays this INVITE onto PSTN_GW with Session-Expires:
240 and Min-SE headers added.
2. PSTN_GW responds with 100/183/200, and no reference to timer
support in any of them. No Session-Expires header, no Supported:
timer, none of it.
Critically, the 200 OK that is received from PSTN_GW is modified by
SEMS to contain:
Supported: timer
Session-Expires: 240;refresher=uas
This seems to suggest to me that SEMS has designated PSTN_GW the
refresher, even though it does not support timers!
3. At 120 sec in, SEMS sends a reinvite to PBX and gets 200 OK back
that contains Session-Expires: 240;refresher=uas.
4. At 126 sec in, SEMS sends reinvite to PSTN_GW and gets 200 OK back
as well. Again, no indication that the PSTN_GW supports timers in any
way.
5. At 246 sec in, SEMS sends another reinvite to PSTN_GW, gets same
200 OK back.
6. At 360 seconds, SEMS sends BYE to both endpoints. Since step #3,
there were no other reinvites to the PBX.
...
This leads me to believe that SEMS has for some reason decided that
the refreshes are going to come from PSTN_GW, and ends the call when
it does not see them after 240 seconds. Why does it do that? If that
is in fact the assumption, why send a reinvite to the PSTN_GW at all
as in step #4?
I am unable to explain this behaviour. Any help would be appreciated!
Cheers,
--
Alex Balashov - Principal
Evariste Systems LLC
1170 Peachtree Street
12th Floor, Suite 1200
Atlanta, GA 30309
Tel: +1-678-954-0670
Fax: +1-404-961-1892
Web: http://www.evaristesys.com/
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