[SR-Users] SIP basic flow question: R-URI in ACK

[Daniel-Constantin Mierla]

Hello,

there is an errata for that RFC, but it refers only to the BYE, where it
adds back the transport=tcp, but the ACK R-URI should follow the same
rules, see:

  * https://www.rfc-editor.org/errata/eid5294

Cheers,
Daniel

On 28.04.19 22:54, Yufei Tao wrote:
>
> Hi,
>
>  
>
> I have a question regarding basic SIP flow for establishing a call
> session, and wonder if anyone can help me clarify.
>
>  
>
> For normal call set up, INVITE-OK-ACK, from RFC3261, I believe the
> ACK’s R-URI should be a copy of the Contact header of the OK message.
>
>  
>
> However in RFC3665 sections 3.1 and 3.2 for example, the ACK’s R-URI
> missed the parameters from the Contact header of the OK, e.g.
>
>  
>
> In OK the Contact header is:
>
>    Contact: <sip:bob at client.biloxi.example.com;transport=tcp>
>
>  
>
> And  ACK the R-URI is:
>
> ACK sip:bob at client.biloxi.example.com SIP/2.0
>
>  
>
> Which has got the parameter ‘transport=tcp’ removed – why is this?
>
>  
>
> In this case if the proxy connected to Bob handles ACK in the usual
> way as it would for all in-dialog requests, i.e. based on routing
> headers only and not extra processing, it’ll try to relay the ACK
> message to Bob using the default transport UDP which is not expected
> and will fail.
>
>  
>
> Can anyone help explain why the parameters are removed in RFC3665
> examples please? Have I missed anything? Thank you very much!
>
>  
>
> Yufei
>
>
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-- 
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio World Conference - May 6-8, 2019 -- www.kamailioworld.com

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