[asterisk-users] SDP bug

[Raj Jain]

 Olle,

It depends on how strictly the UA adheres to the offer/answer model. The
issue would be that a RE-INVITE from Asterisk will have the version
number incremented by more than one, which will break the following rule.

Quoting from RFC 3264 Section 8:

   When issuing an offer that modifies the session,
   the "o=" line of the new SDP MUST be identical to that in the
   previous SDP, except that the version in the origin field MUST
   increment by one from the previous SDP.

That said, I agree that most UAs do not check this. What's a bit more
alarming fundamentally is that Asterisk is creating a new answer SDP to
respond to an INVITE retransmission. An RFC 3261 compliant
implementation MUST send an exact copy of the previous SIP response. Anyway,
I realize that Asterisk is not inherently RFC 3261 compliant.

Raj



>
> > Asterisk sends 200 OK:
> > o=root 16300 16300 IN IP4 203.89.nnn.nnn
> >
> > Asterisk sends 200 OK (retransmission):
> > o=root 16300 16301 IN IP4 203.89.nnn.nnn
> >
>
> Raj,
> That's an interesting observation. Do you think this will cause any
> issues? Even though it's not
> beautiful, I fail to see why a UA would check that.
>
> /O
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