[SIPForum-discussion] Sip Proxy Server

[prasanna c]

When checking for loop, you need to check all the via headers for branch matching, not just the top via header. sent-by field would only indicate the via headers placed by this proxy. On top of it you should check branch parameter as well to detect between loop & spiral.


From: priyankam at tataelxsi.co.inTo: mjhorse at qq.com; c_prasanna_c at hotmail.com; discussion at sipforum.orgSubject: RE: [SIPForum-discussion] Sip Proxy ServerDate: Thu, 24 Apr 2008 16:33:06 +0530

If only sent by is checked it can be either loop or spiral.. but for loop branch parameter will also match,
in case of spiral.. branch parameter will have different value.
hence to detect a loop we need to store the branch parameter of all request that was sent via proxy.
its a hectic job.. any better way to detect a loop.

-----Original Message-----From: mjhorse at qq.com [mailto:mjhorse at qq.com]Sent: Thursday, April 24, 2008 3:30 PMTo: priyankam; 'prasanna c'; discussionSubject: Re: [SIPForum-discussion] Sip Proxy Server
Hi
 
But if all Via header is check, proxy will know for sure that if it is already on the way of the message. So, why loop cant be detected?
 
 
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by mj
 
 
------------------ Original ------------------

From:  "Priyankam"<priyankam at tataelxsi.co.in>;
Date:  Thu, Apr 24, 2008 05:54 PM
To:  "'prasanna c'"<c_prasanna_c at hotmail.com>; "discussion"<discussion at sipforum.org>; 

Subject:  Re: [SIPForum-discussion] Sip Proxy Server
 



You are trying to say if the sent-by matches loop is detected? what about branch parameter? shouldn that also match with Via..
One more doubt if only sent by check is done.. then it can also be spiral detection.. in this we cant discard the request?
 
Please solve these issues.

-----Original Message-----From: prasanna c [mailto:c_prasanna_c at hotmail.com]Sent: Thursday, April 24, 2008 2:05 PMTo: priyankam at tataelxsi.co.in; discussion at sipforum.orgSubject: RE: [SIPForum-discussion] Sip Proxy ServerYou should check all the via headers that has sent-by value placed by proxy in earlier forwarding to detect the loop.


From: priyankam at tataelxsi.co.inTo: discussion at sipforum.orgDate: Thu, 24 Apr 2008 12:39:15 +0530Subject: [SIPForum-discussion] Sip Proxy Server


Hi,
 
  we have a confusion regarding loop detection by proxy server. As per the RFC 3261 we create key for branch parameter using , To tag, From tag, Call-ID header
field, the Request-URI of the request received (before translation), the topmost Via header, and the sequence number from the CSeq header field.
 
But the confusion is if the request traverses through several proxies and the same request comes back to the previous proxy, the top most via gets changed,
so the Key generated will be different, hence loop detection is not possible.
 
Please suggest a solution for this issue.
 
Regards,
Priyankam
Tata Elxsi Ltd.
Bangalore
 

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