[SIPForum-discussion] Question on Target refresh

[Ramesh Kandasamy]

Thanks for your response, Justin !

I don't change the media attributes. It is just that initial SIP INVITE
from UAC to UAS goes from source TCP port say P1. Call gets established
fine. After a period of time, P1 gets closed and a new TCP port P2 is
opened at source (UAC). Subsequent SIP messages goes from this new TCP port
P2. Please note that media attributes and Contact header info doesn't
change from the initial INVITE. However. looks like UAS accounts this as
target refresh. As the first SIP message that goes out of UAC to UAS after
the port change @ UAC is SIP INFO, UAS thinks that SIP INFO is being used
for target refresh.

My question is
1. Is this really accounted as target refresh here? I believe no, as there
is no change in media attributes or Contact header info.
2. How this TCP port change is usually handled by any SIP UAs?

Thanks
Ramesh

On Thu, Jun 20, 2019 at 3:05 PM Justin Davies <justin at futureblue.com> wrote:

> Hi Ramesh,
>
> If I understand you correctly, you are using an INFO method to change the
> media attributes?
>
> Only re-INVITES and UPDATES can change the media. See rfc3311 for
> information on UPDATES.
>
>
>
> --
> Justin Davies
> justin at futureblue.com
> +447427629649
>
> On 20 Jun 2019, at 18:40, Ramesh Kandasamy <ramelcom at gmail.com> wrote:
>
> Reposting the query below.
>
> Thanks
> Ramesh
>
> On Thu, May 2, 2019 at 2:03 PM Ramesh Kandasamy <ramelcom at gmail.com>
> wrote:
>
>> Hi all,
>>
>> I have a question on the below call flow and if it is related to target
>> refresh.
>>
>> SIP UA establishes a TCP connection with SIP Proxy to initiate the call.
>>     INVITE from SIP UA was sent from TCP port, say p1.
>> Call got answered and ongoing.
>> At some point, SIP UA closes TCP port p1 by exchanging TCP FIN/FIN ack.
>> Later within the same dialog, SIP UA establishes another TCP connection
>> with the same SIP Proxy for the same call to send SIP INFO.
>>    INFO from SIP UA was sent from TCP port, say p2.
>> SIP Proxy sends back the INFO response to this new TCP port p2.
>> But subsequent SIP requests are not routed from SIP Proxy to this new TCP
>> port p2 of SIP UA. Rather, it attempts to send on p1 which fails.
>>
>> My question is, is this INFO above considered as target refresh? Please
>> note that Contact and dialog-id (From, To, Call-Id, R-uri) between the
>> initial INVITE (from p1) and INFO (from p2) remains the same. IP address
>> doesn't change either.
>>
>> My thought is that the above flow is allowed and this is not a target
>> refresh. So, So, any subsequent SIP requests from SIP Proxy should ideally
>> be sent to this new TCP port p2.
>>
>> Please advise.
>>
>> Thanks
>> Ramesh
>>
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