SIP topolgy

[Pointbreak]

Experts,

Can any one help me with SIP toplogy. Any good example.

I need clear idea on the device connection, From SP side where it is terminating in our environment. What configuration we do in router. Is SBC i used in every cisco sip topology.

Looks funny to you guys. But i am totally  confused on this

[Vivek Batra · Accepted solution]

It's hard to reply in couple of lines here, but let me try.

SIP doesn't define any sort of topology, it's a application layer protocol used to create, modify and terminating the VoIP sessions.

SBC is something which connects the enterprise VoIP network to service providers network and hence sits in between. 

In Cisco installation, you will frequently see CUBE doing this role. So call manager like CUCM instead of interacting directly to service providers network, communicate to CUBE and then CUBE further interacts with service provider network. In other than Cisco environmnet, you may see Sonus, Genband etc doing this job.

Please let us know if you still have any questions.

- Vivek

[Pointbreak]

Thanks Batra for your reply. The above was the answer i was looking for !But not fully cleared with the concept.

So  from cube to SP it will be a sip trunk right?. What about the connetion between cucm and cube?[which protocol]

Since you mentioned it is application layer protocol it will be recognized by name@domain.com. Where these manipulation done.

What is the role of registrar server,proxy server. Is it a mandatory nodes when you deploy a SIP implimentation. 

[Vivek Batra]

Yes, it will be SIP between CUBE and service provider. Between CUCM and CUBE, you've a choice of either H.323 or SIP. SIP is more preferred now because of ease of implementation and troubleshooting.

Most of the user part headers in SIP like Request-URI, To, From etc are based on what you said. Name is generally the number which is being called and domain could be either domain or IP address. SIP is based on UAC and UAS architecture and each client takes care of manipulating SIP headers.

Try referring RFC 3261 for detailed explanation of registrar, redirect and proxy server but in real world, you would mostly found B2BUA (Back To Back User Agent) which compromises of all required SIP servers embedded into one. Both CUCM and CUBE acts as B2BUA and process SIP messages independently.

- Vivek

[Pointbreak]

CUCM and CUBE acts as B2BUA? Means it will do the functions of registrar and proxy servers ryt?

Correct me if above statement is rubblish!

[Vivek Batra]

No, your statement is not rubbish :)

Yes, CUCM acts as registrar server for SIP phones although I won't say it acts as strict proxy server too (as per RFC). Since it's B2BUA and hence when it recieves any SIP request, it becomes UAC to process/generate/forward the request further.

Out of the above statements, CUBE doesn't act as registrar server because of the fact that it doesn't need to be. None of the device actually registers with CUBE. Since CUBE co-resides on IOS, registrar server functionality is supported by CME (which is another small call manager product). From CUBE perspective, its primary role is to process calls only or you can say, it's IP to IP gateway.

- Vivek

[Pointbreak]

Thanks for the info sir!

My last question before we wind up

So in a ideal scenario there will be a Cusp server to do the proxy function,right?

[Vivek Batra]

I'm sorry. What you're referring as Cusp? 

Do you mean CUPS (Cisco Unified Presence Server) or something else?

- Vivek

[Pointbreak]

Cisco unified sip proxy!

[Vivek Batra]

I don't have much exposue on Cisco Unified SIP Proxy however as far as I know, its main application is to aggregate all SIP based devices in a network and acts as a centralized dial plan hence all call routing is done through it. Moreover it's stateless SIP proxy which means that it doens't maintain the SIP dialog state and hence it's not B2BUA. This is opposite to what CUCM and CUBE can do.

- Vivek