[SIPForum-discussion] Using UPDATE for call transfers

[Victor Pascual Avila]

On Fri, Jun 26, 2009 at 2:55 PM, Richard<dude at mr.net> wrote:
> Caller A (UAC) connects a caller B's via UAS which caller B has call
> forwarded to Caller C.  The UAS sends a new INVITE to Caller A, Call A
> replies with 100 Trying and 180 ringing (SDP profile), UAS replies with a
> PRACK and 200 OK, Then Caller A sends another 180 ringing (SDP profile),
> Then Caller A sends an UPDATE (SDP profile) changing the Media port, The UAS
> then sends 504 Server timeout.
>
> Shouldn't the UAC (Caller A) do a RE-INVITE instead of an UPDATE?  RFC 3311
> section 5.1 recommends sending a re-INVITE instead of an UPDATE.
>
> My question is should UAC conform to this standard or is it grey area as
> it's "recommended?"
>
> Much Thanks!

I'd recommend taking a look at RFC5589 (Call Transfer)

Cheers,
-- 
Victor Pascual Ávila