In steps 3
and 4 read send in lieu of retransmit (it's a typo error).
Dushyant
Dushyant Dhalia wrote:
1. There
are
two cases - based on whether offer1 is carried in INVITE or 200OK.
2. In any case INVITE or Re-INVITE should be differentiated/identified
as any other transaction.
3. It's a race. Rest of the flow is as follows -
1. Callee will retransmit 200OK (INVITE).
2. Caller will retransmit ACK (INVITE).
3. Callee will retransmit 200OK
(Re-INVITE).
4. Caller will retransmit ACK (Re-INVITE).
4. It's an implementation issue - UAC may wait for some timer [till UAS
is in Moratorium state]. UAC may delink subscriber behaviour (pressing
some key on mobile let's say for hold) from sending Re-INVITE to avoid
such race.
RFC 5407 is what you are looking for.
Dushyant P S Dhalia
Rancore Technologies, Gurgaon, INDIA
zabi wrote:
Caller (A) Callee(B)
| INVITE |
|---------------------------> |
| 200 OK |
|<---------------------------- |
| ACK(dropped) |
| ------------x-> |
| re-INVITE |
| ----------------------------->|
| 200 OK |
| (retx for 1st Invite) |
|<------------------------------|
The scenario is follows
1. A sends Invite to the B
2. B responds with 200 Ok(invite txn terminated)
3. A sends ACK for 200 Ok which gets dropped on the network ( B is
retransmitting 200 OK).
4. Since A has already send ACK A sends re-INVITE.
5. Meanwhile A receives 200 OK for the 1st INVITE.
6. Since the there is no txn existing for the the 1st invite, the
transport sends the response to the UA.
7. Now the UA behaves as though the 200OK is received for the
re-invite!!!!!
How to differentiate b/w 200 OK for INVITE or re-INVITE???.
What should be the behavior of the UA for handling of this response.
Pls Correct if i am wrong....
RFC3261 Snippet:
Note that a UAC MUST NOT initiate a new INVITE transaction within a
dialog while another INVITE transaction is in progress in either direction.
1. If there is an ongoing INVITE client transaction, the TU MUST
wait until the transaction reaches the completed or terminated state before
initiating the new INVITE.
Regards,
Zabi
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