Hi
Consider the following topology
UA1 ----- Call-stateful-proxy ------ UA2
UA1 does not support session timer, Make a call to UA2.
Call-stateful-proxy adds Session-Expires:100 header and forwards to UA2. UA2
minimum session expires is 900. But in this case INVITE will not contain
"support: timer". According section 9, UAS can reject with 422 only if there is
a timer tag in supported header
<Snip from RFC>
If an incoming request contains a Supported header field with a value
'timer' and a Session Expires header field, the UAS MAY reject the
INVITE request with a 422 (Session Interval Too Small) response if
the session interval in the Session-Expires header field is smaller
than the minimum interval defined by the UAS' local policy. When
sending the 422 response, the UAS MUST include a Min-SE header field
with the value of its minimum interval. This minimum interval MUST
NOT be lower than 90 seconds.
</Snip from RFC>
Also UAS cannot increase the session expires duration
<Snip from RFC>
The UAS MUST
NOT increase the value of the Session-Expires header field.
</Snip from RFC>
What should be the behavior of UAS here?
1) accept the call with 100 seconds?
2) Increase the duration to 900 seconds while sending 200 Ok?
Note: Session timer should not be turned-off
Regards
S.Radha krishna
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