>Hi,
>Refering to bis03:
>The definition of a transaction is
>"... all messages from the first request
> sent from the client to the server up to a final (non-1xx)
> response sent from the server to the client. A transaction
> is identified by the CSeq sequence number (Section 10.20)
> within a single call leg ..."
>Consider the scenario that I am a UAC, I send an INVITE to my outbound
>proxy. The proxy forks it to n other servers.
>Now, I could end up getting n 18Xs ( or even n 200 ) responses. All
>these will have the same Cseq no. So, do all these 18Xs & 200s form a
>part of the same transaction? Going by definition the transaction
>should end the moment it gets the first 200. Which means the other 200s
>belong to a NULL ( already deleted) transaction!
As you mentioned,"a transaction is identified by the Cseq number within a
Call Leg."
Whenever a proxy forks a request, the response for each request forms a
different Call Leg.
This is identified by the tag in the To Header of the response. So,CSeq
within the Call Leg will
uniquely identify a transaction.
>Also, I as the UAC don't know how many people the proxy had forked the
>request to. So, for how long should I maintain the state of the
>transaction, I could get n 180s for that transaction. I don't know
>whether the 200s belong to the same transaction or not.
Now that you can match the response to the request with the To header
tag which identifies a call leg, and cseq header which identifies a
transaction within a call leg,the proxy can maintain state untill
it recieves a final response for the request sent or if the retransmissions
timeout.
>The draft 03 on pg. 121 says "Responses are processed as follows. The
>process completes (and state
> can be freed) when all requests have been answered by final status
> responses (for unicast) or 60 seconds have elapsed (for multicast). "
>But this is for the proxy, he knows to how many people he has forked the
>request to. What about the UAC, I as a UAC also have to process the
>multiple 18X/200 responses the proxy might send to me. For how long
>should I keep the state of the transaction & even the call, just to
>respond to these multiple responses.
>I can not wait infinitely, or should I destroy the transaction state
>immediately upon getting the first 200. But then what about the next
>200s that can follow. It is even possible that I could have destroyed
>the call context and even after that I keep receiving 200s for an INVITE
>that the proxy forked. I can't even keep expecting processing 200s for a
>call in active/deleted phase forever.
>--
>Regards,
>
>Harpreet Ahluwalia,
>Consultant,
>Lucent Technologies
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