Re: AW: [Sip] From and To-header confusion in draft-ietf-sip-replaces-04.txt

[Cullen Jennings <[e-mail]>]

Sounds like we need to fix the draft.

On 11/28/03 2:19 AM, "Christian Stredicke" <[e-mail]> wrote:

> Hi Paul,
>  
> correct. The problem is that users get angry if the pickup does not work just
> because of standards confusion.
>  
> Our current workaround is to relax the requirement a little bit and accept to-
> and from-tags exchanged. That works fine, however there is some risk that this
> can lead to some false pickups. However, I don¹t know a scenario where this
> can be an issue.
>  
> Christian
>  
> 
> -----Ursprüngliche Nachricht-----
> Von: Paul D.Smith [mailto:[e-mail]]
> Gesendet: Freitag, 28. November 2003 11:05
> An: 'Christian Stredicke'
> Cc: '[e-mail]'
> Betreff: RE: [Sip] From and To-header confusion in
> draft-ietf-sip-replaces-04.txt
>  
> 
> Christian,
> 
>  
> 
> If I understand you correctly, you are pointing out the following.
> 
>  
> 
> If a target receives an INVITE with Replaces headers, it has to somehow use
> the Replaces To/From fields to identify a dialog.  If this dialog were
> originally started by the target then there may be a mapping of:
> 
>  
> 
> To field of original INVITE ==> target's idea of remote tag
> 
> From field of original INVITE ==> target's idea of local tag.
> 
>  
> 
> However if the target did not start the dialog, the mapping is reversed.
> 
>  
> 
> To field of original INVITE ==> target's idea of local tag
> 
> From field of original INVITE ==> target's idea of remote tag.
> 
>  
> 
> And your question is... how does the Replaces To/From get mapped to the
> targets idea of local/remote tags?
> 
>  
> 
> Unfortunately, this can't be resolved into a simple mapping.  A third party
> REFER modifying an INVITE may not know who started the dialog and so renaming
> the Replaces fields makes no difference since the referrer still doesn't know
> which tag to place in which field.  The target has to perform a lookup using
> both mappings - often one will find a dialog and the other will not.
> 
>  
> 
> There is a possible issue with "loopback" type dialogs where a UA, with
> multiple personalities (i.e. a gateway) may have two dialogs, one in each
> direction.  In this case, it may be impossible to map to a single dialog,
> which is where the following sentence from page 5 of the draft is headed...
> 
>  
> 
>   "If the Replaces header field matches more than one dialog, the UA MUST act
> as if no match is found."
> 
>  
> 
> Is this a correct understanding of your posting?
> 
>  
> 
> Regards,
> 
> Paul DS.
> 
> Paul D.Smith 
> Network Protocols Group
> Data Connection Ltd (DCL)
> Tel: [phone]  Email: [e-mail]
> Fax: [phone]  Web:   http://www.dataconnection.com
> <http://www.dataconnection.com/>
> -----Original Message-----
> From: Christian Stredicke [mailto:[e-mail]]
> Sent: 27 November 2003 17:45
> To: SIP (E-mail)
> Subject: [Sip] From and To-header confusion in draft-ietf-sip-replaces-04.txt
>> 
>> Hi!
>>  
>> I think there is some from and to-header confusion in the Replaces header.
>>  
>> Depending on who initiates the call, the to and from must be exchanged. Maybe
>> it would be better to use the term local and remote-tag instead or to allow
>> mixing from and to.
>>  
>> Christian
>> --
>> Christian Stredicke
>> tel:[phone] (ENUM & PSTN)
>