[SIPForum-discussion] Issue to use Tag

[sunil singh]

Tag is for UA (user agent) to identify the trasaction.Branch is for first hop i.e. sip proxy or sip server. if you have a phone with multiple lines that time tag is usefull so that phone identify the tag in the transaction.
 
by RFC section 19.3  "This is needed in order for a UA to  invite itself to a session, a common case for "hairpinning" of calls
   in PSTN gateways.  Similarly, two INVITEs for different calls will  have different From tags, and two responses for different calls will
   have different To tags.
"
 
Thanks,
Sunil

   

________________________________
 From: Dinesh Rao <dinesh2022 at gmail.com>
To: Stephen James <sjames_1958 at yahoo.com> 
Cc: "discussion at sipforum.org" <discussion at sipforum.org> 
Sent: Friday, 28 September 2012 12:29 AM 
Subject: Re: [SIPForum-discussion] Issue to use Tag
  

But proxies don't deal with tags and call ID's, they use branches to distinguish different transaction.Only UAC/UAS knows about call ID and tags.

Regards
C.Dinesh

On Fri, Sep 28, 2012 at 12:22 AM, Stephen James <sjames_1958 at yahoo.com> wrote:

Since 18x can establish early dialog then it is pertinent to that time. 
>
>Sent from my iPhone
>
>On Sep 27, 2012, at 13:36, Dinesh Rao <dinesh2022 at gmail.com> wrote:
>
>
>
>>Hi Stephen,
>>
>>I have one question to you.As you said, In case of forking for two 18x responses there will be 2 unique totags.Bu there is branch parameter too in the via headers which is used by proxies to distinguish between two forked calls before dialog establishment.I think tags and callid is something used after dialog is established but before dialog establishment, branches are used to distinguish different transaction in case of forking before dialog establishment.Please correct me if I am wrong. 
>>
>>Regards
>>C.Dinesh
>>
>>On Thu, Sep 27, 2012 at 4:54 PM, Stephen James <sjames_1958 at yahoo.com> wrote:
>>
>>The tags (along with the CALL-ID) identify a dialog, please see RFC 3261 for complete description.
>>>Since there can be more than one dialog in a "call" the call ID is not sufficient. 
>>>
>>>The most obvious case is a forking situation, where the INVITE is forked and there are two 18x responses establishing a dialogue.
>>>The From tag from the sender and each of the To tags from each of the responders would establish two dialogs under the same Call-id
>>>
>>>Call-Id, From, ToA and Call-Id, From and ToB
>>>
>>>
>>>Stephen James 
>>>sjames_1958 at yahoo.com
>>>
>>>We are not princes of the earth, we are the descendants of worms, and any nobility must be earned.
>>>
>>>
>>>
>>>
>>>
>>>
>>>________________________________
>>> From: Kareena K <kareenaf1 at gmail.com>
>>>To: discussion at sipforum.org
>>>Sent: Wed, September 26, 2012 5:23:34 PM
>>>
>>>Subject: [SIPForum-discussion] Issue to use Tag
>>>
>>>
>>>Hi all,
>>>
>>>
>>>why tag(i.e to-tag and from-tag) had been used if we can identity the call by using Call-id.
>>>
>>>
>>>
>>>  
>>>_______________________________________________
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>>>
>>
>>
>>-- 
>>C.Dinesh
>>Sr. Software Engineer
>>Panterra Networks
>>
>>


-- 
C.Dinesh
Sr. Software Engineer
Panterra Networks


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