[SIPForum-discussion] sip prack

Wed Nov 20 23:28:19 UTC 2013

Really thanks Paul.

Guillermo

-----Mensaje original-----
De: Paul Kyzivat [mailto:pkyzivat at alum.mit.edu] 
Enviado el: miércoles, 20 de noviembre de 2013 06:30 p.m.
Para: Zuñiga, Guillermo; discussion at sipforum.org
Asunto: Re: [SIPForum-discussion] sip prack

On 11/20/13 1:47 PM, Zuñiga, Guillermo wrote:
> Really I did it, but this was I make a couple of questions, just to ensure concepts.

OK. Then see comments inline below.

> Thanks Paul.
>
>
>
>
> Guillermo Zuniga
> Especialista de Soporte Técnico
> Gerencia de Soporte Técnico
> Cable & Wireless Panamá, S. A.
> Tel:    +507 263-6671
> Fax:    +507 265-3295
> Cel:    +507 6670-0481
> Email:  Guillermo.Zuniga at cwpanama.com
>
> -----Mensaje original-----
> De: discussion-bounces at sipforum.org 
> [mailto:discussion-bounces at sipforum.org] En nombre de Paul Kyzivat Enviado el: martes, 19 de noviembre de 2013 11:33 a.m.
> Para: discussion at sipforum.org
> Asunto: Re: [SIPForum-discussion] sip prack
>
> It sounds like you haven't read RFC3262.
> Read that carefully, and then come back if you still have questions.
>
> Actually, a better place for such questions is:
> sip-implementors at lists.cs.columbia.edu
>
>          Good Luck,
>          Paul
>
> On 11/14/13 9:01 PM, Zuñiga, Guillermo wrote:
>> Hi fellows.
>>
>> I would like to understand the following.
>>
>> I have the scenarios A call B.
>>
>> In the first invite I am seeing that include the header "Supported:
>> 100rel" and then my GW is sending back a 180Ringing/SDP  with "Required:
>> 100rel",  and after 7 more 180 my GW is killing the session with 504 
>> Server Time Out.
>>
>> Question:
>>
>> 1-What means that "Supported: 100rel" in the first invite coming from 
>> the Peer?

It means the UAC is capable of generating reliable provisional responses, if requested to do so.

>> 2-What means that "Required: 100rel" back in the 180 from my GW? What 
>> my GW are expecting receive from the Peer? Why is sending 7 more 180 
>> to the Peers?

This means that the UAS requires that the UAC support reliable provisional responses. I think that you will find that the 180 also includes an RSeq header field. The RSeq is what makes the response a
*reliable* provisional.

Because the UAC has said that it supports 100rel, it MUST recognize the RSeq as indicating a reliable provisional, and send a PRACK indicating that it has received it.

>> 3-Why then after a timer is killing the session with 504 Server Time out?

Presumably because it hasn't received the PRACK it is expecting.

>> 4-What could happen is don’t send back from my GW "Required: 100rel"
>> in the 180, session could continue? What should send me Peer in this case?

If the UAC doesn't include Supported:100rel in the INVITE, then the UAS should not use reliable provisionals. IOW, don't indicate support unless you really do.

Now go back and read 3262 again. This is all in there.

	Good Luck,
	Paul

>> Thanks a lot for all the feedback.
>>
>> Thanks
>>
>> Guillermo
>>
>> Guillermo Zuniga
>> Especialista de Soporte Técnico
>> Gerencia de Soporte Técnico
>>
>> Tel:  +507 263-6671
>> Cel:  +507 6670-0481
>> Fax:  +507 265-3295
>> Email:        Guillermo.Zuniga at cwpanama.com
>>
>> <http://www.cwpanama.com>
>>
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