I disbelieve that there are any UAs that claim support for 100rel and
don't pay attention to the answer in the 180.
Please show me one (send me traces please).
Are you mixing the non-reliable 18x case in here? (I think that might
be where you're coming from since you say "older" UAs).'
That's not what we're discussing. Repeating the answer in the 200
here makes sense.
And what do you mean "rejects the 180"? That makes no sense.
Do you have a UAS that's tries to send 100rel responses when the UA
hasn't indicated support?
RjS
On Nov 22, 2007, at 11:33 AM, Dean Willis wrote:
On Nov 22, 2007, at 2:25 AM, Robert Sparks wrote:
I'm still not sure what you originally objected to. Just to be
point out that the UPDATE can come from either side, I'm copying
figure 1 from the UPDATE RFC here.
Tell me what SDP you think is safe to put in message 9.
Either the SDP from message 2 (the answer that corresponds to the
offer from INVITE), or nothing. No other SDP can go there.
I _think_ you're saying it should be answer 1 from message 2. How
could that help anybody? The session described by offer1/answer1
is long long gone.
It's not particularly useful, though it might have been had the
UPDATE sequence not occurred. And for those UAs that neither
implement answer-in-provisional nor UPDATE, it will at least result
in a working call.
If you repeat offer 3 from message 7, again - how could that help
anybody?
That would be a state mismatch, so don't do it.
I'll accept that you don't like the whole idea of early dialogs
and early media. But that cat's so far out of the bag its
forgotten what the bag smells like.
Given that this stuff is now _deployed_, what's the best answer to
my original question?
Either the final answer has to match the provisional answer, or it
has to contain nothing. There are cases of not-quite-right UAs
where either will cause disaster. It's a probability game.
What Paul points out causes me to champion making a much clearer
MUST NOT put SDP in the 200-INVITE if you're using 100-rel.
And my questions about how the repeat of either of those SDPs is
earnest, not rhetorical. I really don't see how its helping
something work.
Can you diagram the scenario where not repeating the SDP you want
to repeat leads to abject failure?
It is not uncommon for older UAs to completely ignore SDP in a
provisional response. I think both the SIP phones at my house do
this (although one also doesn't do reliable provisional at all, but
I'm not sure it rejects the 180 correctly).
if we skip the SDP in 4, Caller thinks he has never received an
answer:
Caller Callee
| |
| |
|(1) INVITE with offer 1 |
|---------------------------->|
| |
| |
|(2) 180 with answer 1 |
|<----------------------------|
ans. | |
ignored | |
|(3) PRACK |
|---------------------------->|
| |
| |
| |
|(4) 200 INVITE with ans 1 |
|<----------------------------|
| |
| |
|(5) ACK |
|---------------------------->|
| |
| |
| |
| |
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