Re: [Sip] When does the registrar have to create GRUUs ?

[Jonathan Rosenberg <[e-mail]>]

What Paul and Dale said.

Indeed previous versions of GRUU did only create gruu when the Supported 
header field was present, but Paul K. found the issue described below 
and so it was changed to do so even when Supported is not there.

-Jonathan R.

Paul Kyzivat wrote:

> 
> 
> [e-mail] wrote:
> 
>> Hi Jonathan,
>>
>> GRUU draft tells the registrar to create a public GRUU and a
>> temporary GRUU whenever it receives a REGISTER request with
>> "+sip.instance" Contact header parameter but only return
>> them is the REGISTER request contains Supported: gruu.
>>
>> Does this make any sense ? Why would the registrar have to
>> create those GRUUs if it would not return them to the UA ?
>>
>> The use case I am thinking is:
>>
>> - A registrar which supports both GRUU and Outbound - An UA which 
>> supports Outbound but not GRUU
>>
>> Such an UA would send its Contact header with "+sip.instance"
>> parameter but it would not include Supported: gruu in its
>> REGISTER. Strictly speaking GRUU draft currently tells
>> the registrar to create GRUUs but not to return them to the UA.
>>
>> I would assume GRUU draft needs a small fix to tell the
>> registrar to create the GRUUs only if the REGISTER
>> request contains "gruu" option tag in Supported header.
>>
>> Do you agree or have I missed something ?
> 
> 
> This is partially one of those questions like "does a tree that falls 
> make any noise if nobody is listening?"
> 
> If in fact nobody will learn about this gruu then there is no need to 
> create it. But that is all about the difference between the conceptual 
> model and the implementation, so it doesn't need to be stated.
> 
> The problem arises when there are multiple observers of registration 
> state. There are at least two ways this can happen:
> - other UAs that register
> - subscribers to the reg event package
> 
> After you register, if others register they will get your contact back 
> in the response to their register request, along with their own. If they 
> support gruu, then they will will see the permanent gruu and latest temp 
> gruu for your contact.
> 
> Similarly, when you register, any subscribers to the reg event package 
> will get a notify telling of the change in registration state, including 
> your contact and the gruus that were "assigned" to you.
> 
> Everything hangs together better this way. Still, if nobody is looking 
> you don't have to assign these, as long as you do assign them when 
> somebody does start looking.
> 
>     Paul
> 

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[e-mail]                              FAX:   [phone]
http://www.jdrosen.net                         PHONE: [phone]
http://www.cisco.com

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