Hi,
I have any questions about sending offer by UPDATE request.
RFC3311/5.1 Sending an UPDATE says,
The rules for inclusion of offers and answers in SIP messages as
defined in Section 13.2.1 of RFC 3261 still apply. These rules exist
to guarantee a consistent view of the session state. This means
that, for the caller:
o If the UPDATE is being sent before completion of the initial
INVITE transaction, and the initial INVITE contained an offer,
the UPDATE can contain an offer if the callee generated an
answer in a reliable provisional response, and the caller has
received answers to any other offers it sent in either PRACK or
UPDATE, and has generated answers for any offers it received in
an UPDATE from the callee.
o If the UPDATE is being sent before completion of the initial
INVITE transaction, and the initial INVITE did not contain an
offer, the UPDATE can contain an offer if the callee generated
an offer in a reliable provisional response, and the UAC
generated an answer in the corresponding PRACK. Of course, it
can't send an UPDATE if it has not received answers to any
other offers it sent in either PRACK or UPDATE, or has not
generated answers for any other offers it received in an UPDATE
from the callee.
o If the UPDATE is being sent after the completion of the initial
INVITE transaction, it cannot contain an offer if the caller
has generated or received offers in a re-INVITE or UPDATE which
have not been answered.
According to the description above, The following scenarios seem
to be allowed.(before sending PRACK)
A B
| |
|ini-INVITE (offer0) |
|------------------------------>|
| |
| 1xx-rel (answer0)|
|<------------------------------|
| |
|UPDATE (offer1) |
|==============================>|
| |
A B
| |
|re-INVITE (offer0) |
|------------------------------>|
| |
| 1xx-rel (answer0)|
|<------------------------------|
| |
|UPDATE (offer1) |
|==============================>|
| |
A B
| |
|re-INVITE (no offer) |
|------------------------------>|
| |
|UPDATE (offer1) |
|==============================>|
| |
and for the callee:
o If the UPDATE is being sent before the completion of the INVITE
transaction, and the initial INVITE contained an offer, the
UPDATE cannot be sent with an offer unless the callee has
generated an answer in a reliable provisional response, has
received a PRACK for that reliable provisional response, has
not received any requests (PRACK or UPDATE) with offers that it
has not answered, and has not sent any UPDATE requests
containing offers that have not been answered.
o If the UPDATE is being sent before completion of the INVITE
transaction, and the initial INVITE did not contain an offer,
the UPDATE cannot be sent with an offer unless the callee has
sent an offer in a reliable provisional response, received an
answer in a PRACK, and has not received any UPDATE requests
with offers that it has not answered, and has not sent any
UPDATE requests containing offers that have not been answered.
o If the UPDATE is being sent after the completion of the initial
INVITE transaction, it cannot be sent with an offer if the
callee has generated or received offers in a re-INVITE or
UPDATE which have not been answered.
According to the description above, The following scenarios seem
to be allowed.(before receiving PRACK)
A B
| |
| re-INVITE (offer0)|
|<------------------------------|
| |
|1xx-rel (answer0) |
|------------------------------>|
| |
|UPDATE (offer1) |
|==============================>|
| |
A B
| |
| re-INV (no offer)|
|<------------------------------|
| |
|UPDATE (offer1) |
|==============================>|
| |
Is my understanding correct?
Some scenarios seem to be allowed only for re-INVITE.
is this what the author intended?
If not, which is not intended scenario?
Regards,
Shinji
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