Subject: [Sipping] 100 and retransmissions

From: Terry L Anderson <[email-masked]>
Date: Tue, 11 Sep 2001 13:01:19 -0400

Should a UAC cease retransmission of INVITE after receiving a 100
response?

bis-04 14.4.1 says:
    "The client ceases retramissions if it receives a provisional..."
and the state diagram in Figure 10 indicates the same.  These do not
appear to make 100 an exception.  However, 100 will often come from a
proxy rather from the far UAS.  I  believe that even a state-less proxy
will may send 100 but does not retransmit, so if the UAC also ceases
retransmissions, a single lost request may fail the transaction.

11.1 also states (with regard to 1xx):
    "...and clients can inquire about the current state of call
processing by re-sending the request."

which sound like UAC are at least allowed to retransmit after any 1xx.

It seems reasonable to cease retransmission after non-100 1xx's, but NOT
after receiving 100.  Am I missing something?

--

------------------------------------------------------------
Terry L Anderson              mailto:[email-masked]
Tel:908.582.7013   Fax:908.582.6729
Lucent Technologies/INS/Voice Over IP Access Networks
Rm 2B-121, 600 Mountain Av, Murray Hill, NJ 07974
http://its.lucent.com/~tla (Lucent internal) http://www.gti.net/tla

---

From: "Brett Tate" <[email-masked]>
Date: Tue, 11 Sep 2001 14:38:33 -0400

> Should a UAC cease retransmission of INVITE after receiving a 100

Yes, it should cease retransmission of 
the INVITE.  The UAC is no longer 
responsible for delivery of the INVITE 
or final response. 

If a UAC wants to help ensure receiving 
subsequent 1xx responses, it should 
support draft sip-100rel instead of 
periodically resending the INVITE.

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