SIP Record Route Header

[@flowzyytube7276]

Very good video explaining the Record-Route header usage in SIP. Keep up the good work Vishal Patel!

[@ashutosh567]

very detail oriented explanation.......excellent job Vishal!!

[@yesu007das]

hi vishal if 200 ok is retrasmitting and no ack from the caller what could be reason

[@vark4you]

Hi Vishal, nice and clear explanation. Thanks Vishal!

[@karteekkota6924]

Very clear.now I got much more idea on the topic.

[@ericgamess275]

Thank you Vishal. I can see that you have a good experience of installing and configuring OpenSIPs. Will it be possible for you to make some videos on how to setup basic labs with OpenSIPs or Kamailio. For example a lab with one proxy SIP and two telephones, where each telephone can call the other.

[@gowthamvema923]

In the BYE Transaction the proxies have deleted their route header, how will 200 OK will go for BYE, as there are no ROUTE headers...

[@nivinsebastian]

this record Route is only applicable to P CSCF ? what about other SIP nodes in between like S_CSCF and may be some BGCF etc ? all those Route addresses also will be stored ?

[@luckystrings4328]

Hi Vishal, Can you explain in detail diff between route,via,record route?

[@manishkrbhadani]

Hi vishal, Seen your videos and having some doubt...can you expalin it My question is can record route header added without route header in invite. As i followed ietf doc, it shows that to generate a record route you must add route header in invite itself. If you will not add route header in invite then it will treate at stateless proxy and follows the same. If you want it to be stateful then route header is mandetory in invite request.

[@arunmishra6342]

Thanks vishal . Can you explain in more detail about lr/sr (louse routing and strict routing .

[@vinayakkolhapure150]

I understood how RR header helps to route the call through proxy but what is the difference between Record Route header and Contact header ? How do they differ from each other ? And one more question is we already have VIA header(mandatory one) to do routing via Proxy, then why do we require RR header ? Thanks !!

[@flowzyytube7276]

In terms of routing priority, SIP prioritizes the Route details first, then Contact header (if there is no Route header) and finally the From header (if there is no Contact header). In the first example, when proxies P1 and P2 rewrote/forward the SIP INVITE onward to B, they did not add the Route header. So when A received the 200 OK, it only has the Contact header to work with, which is why it sends the ACK back directly to B. In the second example, proxies P1 and P2 wants to be part of all the subsequent transactions between A and B, maybe P1 has billing service, P2 is the PSTN gateway and B is a phone on the PSTN. So P1 says, hey I need to track this call for billing purposes, I'll add a Record Route header with my IP so that all SIP transactions pertaining to this call passes through me. P2 says, hey I need to do SIP to ISUP conversion, so I need to be part of any future transactions in order for this call to work, I'll add a Record Route header with my IP too! The rest is as the video explains. Regarding the Via header, Via headers are used for loop detection, not routing. In both the examples above, P1 and P2 adds the Via headers in the INVITE message. So when the INVITE hits B, it will have 3 Via header lines, P2's IP address, P1's IP address and A's IP address, in that order. The subsequent 100 Trying, 180 Ringing, 200 OK etc. responses from B will traverse through P2, P1 and finally hit A. But along the way, the Via headers are removed on each hop. P2 receives the response with 3 Via lines, will check the Via header if his IP address appears FIRST in the Via list, if it is, it will forward the response onward and REMOVE its own Via header. P1 receives the response with 2 Via lines, again checks the Via header if his IP address appears FIRST in the Via list, if it is, it will forward the response onward and Remove its own Via Header. A receives the response with only 1 Via line, which is its own. If P1 or P2 receives requests/response that has its own IP address in the Via header but not as the First entry, it will send a 482 Loop Detected response to the sender. Hope this helps!

[@abhshekSnha]

Hi, Vishal , Very informative. Just One query why the response to INV msg is 100 trying/180 ringing /200 ok... Why these numeric number any specific reason ?

[@vikasjarugumalli3174]

these are the RESPONSE codes for SIP as per RFC 3261

[@jyotiprasad5340]

Nice and simple video

[@banavathpeddareddeppa5133]

awesome. Thanks. can you please brief on Request URI.

[@dharambirku]

awesome info. really great

[@rajjipadma5144]

Hi Vishal, I have been following your videos.. 1> Can u explain the difference between the Route and Record route header 2> Can we invoke the route and record route headers in the initial invite itself. Can you please explain Thanks, Rajji Padma

[@VishalPatel4487]

Thanks Rajji. 1. Record route- it is the function of sip proxy to add this header in initial request, if proxy wants to be the part of the future transaction. That means, proxy wants to be the part of all transaction.That's why,it recorded it's ip in this header. Once, the initial invite reaches to the final destination. Final destination knows the path from where the request coming (from how many different proxy) using record-route header. Using this record-route header, it makes route header & also sends detail of record-route header to originating phone. Originating phone also makes route header. Now if any proxy finds route header, it follows that path. That means it gives first priority to route header. 2. As per my knowledge, we can't invoke both in same header.

[@ajitkumar-db8wr]

awesome