Re: [Sipping] Possible Solution to HERFP

Hi Vijay,

On Jul 11, 2005, at 9:52, Vijay K. Gurbani wrote:
> Rohan Mahy wrote:
>> Hi Folks,
>> I just submitted a new individual I-D that describes a possible  
>> solution to the Heterogeneous Error Response Forking Protocol.  Until 
>>  it appears in the archives, you can find it here:
>> https://scm.sipfoundry.org/rep/ietf-drafts/rohan/herf-fix/draft-mahy- 
>> sipping-herfp-fix-00.txt
>> https://scm.sipfoundry.org/rep/ietf-drafts/rohan/herf-fix/draft-mahy- 
>> sipping-herfp-fix-00.html
>
> Rohan:
>
> Interesting approach to the problem.  After a quick reading, it
> strikes me that a long time ago, we had a SIP mantra that was oft
> repeated: "Every transaction completes independent of others."
>
> Did we break this mantra?  In Figure 4, there are two INVITEs
> leaving the UAC, the second in response to the 130.  However,
> there is only one final response coming back to the UAC (the
> 200 OK).  Since the draft states that the original INVITE request
> is unaffected by the new request, it would seem that the UAC
> will wait for another final response to balance out the original
> request?

I don't think we broke that mantra.  The original INVITE request still 
needs to receive the "best final response" from the proxy.  If the UAC 
sent INVITE requests to repair any of the branches, the target-set just 
uses 487 instead of the actual 4xx or 5xx for the branch for the 
purpose of best-response processing.  A 2xx or 6xx will always win the 
best-response war, and hopefully most 4xx responses will win instead of 
a 487.

thanks,
-rohan

> Before proposing any solutions, wanted to make sure that we do
> indeed have a dangling INVITE problem...
>
> Thanks,
>
> - vijay
> -- 
> Vijay K. Gurbani, Ph.D.  
> vkg@{lucent.com,research.bell-labs.com,acm.org}
> Wireless Networks Group/Internet Software and Services
> Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
> Naperville, Illinois 60566     Voice: +1 630 224 0216

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