Hi All,
This is a B2BUA scenario.
This issue is as shown below
UE1 ----- INVITE [no SDP, Require:100 Rel] ------------ > B2BUA -------
INVITE [no SDP, Require:100 Rel] -----------> UE2
B2BUA <------- 183
[no SDP] ------------- UE2
When an INVITE is sent with require 100rel and without an offer, misbehaving
UE2 sends 18x without SDP.
RFC 6337 does not define the behavior of UAC in this case.
There could be 2 possible solutions:
1. Tear down the call by sending CANCEL on egress leg and 420 Bad extension
response on ingress leg as shown below
UE1 ----- INVITE [no SDP, Require:100 Rel] ------------ > B2BUA------- INVITE
[no SDP, Require:100 Rel] -----------> UE2
UE1 <----- 420 Bad extension ------------------------------ B2BUA<-------
183 [no SDP] ---------------------------------- UE2
B2BUA ------- CANCEL ------------------------------------------> UE2
2. Ignore 18x received and wait for reliable response containing SDP on the
egress leg. On receiving the response, send 18x reliably with SDP followed by
200 OK with the same SDP on the ingress leg. This ensures backward
compatability.
UE1 ----- INVITE [no SDP, Require:100 Rel] ------------ > B2BUA -------
INVITE [no SDP, Require:100 Rel] -----------> UE2
B2BUA <----------
183 [no SDP] ---------------------------------- UE2
UE1 <----- 183 [with SDP] --------------------------------- B2BUA
<----------- 200 [with SDP] ------------------------------ UE2
UE1 <----- 200 [with SDP] --------------------------------- B2BUA
I would appreciate if you could share your comments on both the solutions and
propose alternate solution if any.
Regards
Hemanth
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Kumar,
Hemanth
Sent: Wednesday, January 04, 2012 8:39 PM
To: [email protected]
Cc: Paul Kyzivat
Subject: [Sip-implementors] Expected behavior for an INVITE sent without an
offer
Hi,
What should be the behavior of UAC when an INVITE is sent without offer and
Require 100rel and it receives non-reliable/reliable 18x response without SDP?
Should the transaction be terminated by sending CANCEL?
The same scenario was given as comment which has not been addressed in
offer/answer draft-ietf-sipping-sip-offeranswer-03
http://www.softarmor.com/sipping/process/wg-review/reviews/draft-ietf-sipping-sip-offeranswer-03-seth.txt
" 3. Section 1.1 :
Comment :- We should define the behavior for a UAC which sends out an INVITE
without SDP and receives the first non-failure reliable response without an
Offer, due to the UAS not conforming to the draft. As this being an open point
can lead to multiple different implementations. Does the UAC clear the call or
send a PRACK and wait for the offer in subsequent reliable responses."
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