[SIPForum-discussion] SIP Transaction Layer

[Donald Lee]

refer to RFC3261 section 17.1.1.2:
   If an unreliable transport is being used, the client transaction MUST
start timer A with a value of T1.If a reliable transport is being used, the
client transaction SHOULD NOT start timer A (Timer A controls request
retransmissions).  For any transport, the client transaction MUST start
timer B with a value of 64*T1 seconds (Timer B controls transaction
timeouts).
I think it can answer your query.


On 5/8/08, gaurav katiyar <gaurav_katiyar at yahoo.com> wrote:
>
> Hi Banu,
>     In case of un-reliable transport, as you know that there are chances
> of dropping sip message on network. Because of that SIP ensures that if a
> UAC won't get response in a certain period of time it would retransmit the
> message. Because transport is not ensuring the packet delivery so SIP takes
> this responsibility and ensures deliver a message on other end. But in case
> of reliable transport, transport ensures delivery of sip message on other
> end and takes care of any data loss. So there is no need to start timer to
> re-transmit data as it is ensured by transport layer.
>
> is what i understand.
>
> Gaurav
>
>
> *banu Priya K <banupriya at tataelxsi.co.in>* wrote:
>
> Hi,
>
> In case of reliable transport, why timer A is not set to fire.. i.e
> retransmission timer,
> Only timer B is set.
>
> Regds,
> Banupriya K
>
>
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>   *Gaurav Katiyar* | *Lead – Engineering | GlobalLogic Inc.*
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-- 
BR
Donald
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