[SIPForum-discussion] SIP Transaction Layer

[gaurav katiyar]

Timer B is used for transaction. or we can say it controls transaction time out. while timer A is controls the request re-transmission. and which is not required in case of reliable transport. It may possible that server is eating sip request and not responding :-). In that case B timer timeout and uac transaction comes in terminated state and uac can start required clean up at their end.
  Not only timer A is used for re-transmission but there are some other simlar timer are used for un-reliable delivery like D, E etc.
   
  is that make sense ?
   
  Ok as you say it realiable transport ensures delivery of messages to other end, then why should we start timer B?
      -----Original Message-----
From: gaurav katiyar [mailto:gaurav_katiyar at yahoo.com]
Sent: Thursday, May 08, 2008 11:23 AM
To: banupriya at tataelxsi.co.in; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] SIP Transaction Layer


  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.
The Global Product Development Leader




    
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