[OpenSIPS-Users] DIfference between R-URI and Destination URI in openSIPs

[Alex Balashov]

Hi,

The Request URI is a SIP concept, while the destination URI might be best described as a fictive invention of OpenSIPS configuration script. It represents the next-hop destination to which the request will be forwarded on the network and transport layer, as you correctly surmised, while the request URI is a logical destination. The destination URI supersedes the request URI, but if the destination URI is not set, the domain/port/transport attributes of the request URI are consumed to determine the forwarding destination.

An RURI is not the same thing as an Address of Record; an AoR refers to a logical URI entity in the location service (registrar) context. The purpose of a registrar is to map an AoR (such as sip:mohamed at sip.opensips.org) to one or more Contact URIs (e.g. sip:line1 at 192.168.1.100;user=phone), which indicate how to reach a given device on the network and transport layer.

Hopefully that helps!

-- Alex

> On Jul 30, 2024, at 9:26 PM, Mohamed OUALLA <oualla.simohamed at gmail.com> wrote:
> 
> Hello all,
> 
>   I have a technical question about the difference between Request URI and Destination URI in SIP. In my understanding of SIP, the R-URI (Request URI) is located in the start line of the SIP request and is also known as the Address of Record (AoR). However, I am unclear about what the Destination URI is for openSIPs. Is it the same as the Request URI, or is it related to an added route header, or the destination address in the transport protocol, I am not sure about it?
> 
>   Additionally, I have observed that when I change the $du pseudo variable in OpenSIPS, it relays the request to the UAS without changing the R-URI (change it with the sip uri I gave to $du pseudo variable). This behavior is the same as using the t_relay() method, which also does not change the R-URI but sends the request to the UAS. I guess that changes have been done only for the destination address in the transport layer.
> 
>   Could someone please explain these observations and clarify the difference between R-URI and Destination URI?
>   And the best way to route calls from UAC to UAS in simple VoIP call components (Caller - SIP Proxy - Callee), actually I change the $ru, then I forward() the request stateless or t_relay() stateful.
> 
> Thank you.
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-- 
Alex Balashov
Principal Consultant
Evariste Systems LLC
Web: https://evaristesys.com
Tel: +1-706-510-6800