[SIPForum-discussion] rport and received parameter in Via header

[Saurabh Shah (Software Development - Telecom)]

Gnana,

These both parameters do not affect Router functionality in any way unless
AGL(Application layer gateway) is enabled in Router.
These parameters are introduced in SIP to overcome NATing issue while STUN
is not used.

Lets take an example. UAC is behind NAT.
When UAC send a Request, Contact and Via contains its local IP/Port as STUN
is disabled. As per standard, UAS will send reply on Via which is local IP
and not routable.
As per guidelines for received parameter, if Source IP in IP header and
Contact/Via is different, UAS should send reply on Source IP from IP header
and add same in Via header with received="" field. By that way, UAC even
know its global IP and use same in next transactions.

When rport is present in Via header of any request, UAS should process
source Port same way as IP. It sends reply on global port and inform same
in Via header with rport="".


Hope this helps.

Regards,
Saurabh Shah



Regards,
Saurabh Shah

On Mon, Sep 25, 2017 at 9:26 PM, Gnana Guru Natarajan <
gnanaguru3012 at gmail.com> wrote:

> Hi,
>
>        What is the purpose of rport and received parameter in sip via
> header? Will it be needed if sip client is behind NAT router? If so, how
> router can process this sip header as router only handle the IP header but
> cannot application layer header?
>
> Thanks,
> Gnana Guru N.
>
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