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.
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.
If you repeat offer 3 from message 7, again - how could that help
anybody?
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?
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?
RjS
Caller Callee
| |
| |
|(1) INVITE with offer 1 |
|---------------------------->|
| |
| |
|(2) 180 with answer 1 |
|<----------------------------|
| |
| |
|(3) PRACK |
|---------------------------->|
| |
| |
|(4) 200 PRACK |
|<----------------------------|
| |
| |
|(5) UPDATE with offer 2 |
|---------------------------->|
| |
| |
|(6) 200 UPDATE with answer 2 |
|<----------------------------|
| |
| |
|(7) UPDATE with offer 3 |
|<----------------------------|
| |
| |
|(8) 200 UPDATE with answer 3 |
|---------------------------->|
| |
| |
|(9) 200 INVITE |
|<----------------------------|
| |
| |
|(10) ACK |
|---------------------------->|
| |
| |
| |
| |
Figure 1: UPDATE Call Flow
On Nov 21, 2007, at 11:20 PM, Dean Willis wrote:
On Nov 21, 2007, at 10:57 PM, Robert Sparks wrote:
There can be several UPDATEs with their associated 200-UPDATES
before the 200-INVITE.
Remember that UPDATE is a nonINVITE transaction and there may be a
_long_ time between the UPDATE and the 200-INVITE.
Paul drew the arrow backwards for the 200-UPDATE though - did that
mislead you?
Ah, yes, I read that Alice had sent a second conflicting offer in
UPDATE.
However, even with this directionality, the answer in the
INVITE-200, if present, would have to be a copy of the answer in
the 183. This doesn't create any error I can see, it just
illustrates the UPDATE race condition that would have existed even
had there not been an answer in the 183. Early media, early
session, and UPDATE were all bad ideas (probably all because of
forking and PSTN interactions) IMHO, and I'm pretty sure reliable
provisionals are on that list too.
Alice Bob
| INVITE offer1 |
|----------------->|
| 183 answer1 |
|<-----------------|
| PRACK |
|----------------->|
| 200 PRACK |
|<-----------------|
| UPDATE offer2 |
|<-----------------|
| 200 UP answer2 |
|<-----------------|
| 200 IN SDP? |
|<-----------------|
Now what should be in the 200 for the invite?
Its better to do what is already required - send no SDP in the
200 for the invite.
--
Dean
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