SIP Trunking with CUCM

[Music]

Welcome back.

In the previous lecture we worked on advanced SIP registration with multiple softphones.

In this lecture we’ll integrate multiple Q-SYS softphones with  

a real SIP proxy using what’s called SIP trunking.

This is useful for situations where you need to configure more than 8 softphones.

It can also be used to talk to a proxy that does not use registration.

In this lecture we’ll show how this is done using CUCM.

A quick review of the basic topology of a typical VoIP deployment is shown above.

Everything here stays the same when we are working  

with multiple softphones using trunking instead of only one.

Here we see a network switch in the middle, a core,  

a CUCM server, and a laptop which can configure the core or run another softphone.

Keep in mind the topology here is greatly simplified from an  

actual enterprise VoIP deployment,

but the basic concepts shown here should apply to any running CUCM implementation.

The steps will be as follows:

Biggest difference here is that there is no registration taking place.

Without registration things happen a bit differently with the proxy.

In this case both sides use what is called an “OPTIONS Ping” to check the status of each other.

This is similar to a more standard network ICMP ping but using SIP signaling instead.

Both sides will respond with an  

‘OK’ message to let the other know that they are ready to make calls.

As mentioned before, SIP trunking is useful when you need lots of softphones in your design.

For example, CUCM only supports 8 softphones with an advanced setup and with

20 or 30 softphones typing in credentials would be time consuming as well!

Here we have the CUCM side.

The setup here is going to look very simple but there are some issues that can come up.

In CUCM you would go to Device -> Trunk to create a new trunk.

First, the basics. This will be a trunk and it needs a name.

A couple things we want to note here.

The ‘Destination Address’ will be the LAN  

interface of the core you are going to use for the softphone.

The destination port will normally be 5060 and is the same one configured on the core.

We use a basic SIP Trunk Profile here and a Standard SIP Profile.

Last, and important, we have the DTMF signaling method.

We normally use RFC2833 on the core and this should match what the core is using.

Otherwise we won’t be able to send or receive DTMF.

On the core side many things remain the same but there are important differences.

Here the Username only functions as the phone number.

The proxy IP address is where SIP signaling messages will be sent.

‘Register with Proxy’ is not checked since with a trunk we are not doing registration.

We can still have a backup proxy if one is needed.

Since we are not doing registration how do both sides know that they can place calls?

They use what is called ‘OPTIONS’ pings.

These are not the same as ICMP messages that you might be used to and are SIP signaling messages.

Both sides will periodically send out ‘OPTIONS’ messages  

and the other side will reply with a ‘200 OK’.

This lets both sides know they are ready for calls.

On the previous slide we saw an example of the OPTIONS message  

and here we see the ‘200 OK’ indicating a good status.

If the ‘200 OK’ does not come back check connectivity between the core and the CUCM server.

Here we see that the trunk setup failed because  

we did not see a response to the OPTIONS message that the core sent.

Again here we need to check connectivity between the core  

and the CUCM server and make sure all IP addresses and ports are correct.

Once we get our configuration right then at this point you should be able to  

open the softphone and see it in ‘OK’ status again.

You should be able to place and receive a call.

Also note again that a trunk supports more than 8 softphones  

so you could have many softphones in your design.

You can also refer back to the basic CUCM training for reference.

Again, nothing changes in the call itself with a trunk. It’s just how we perform the setup.

That’s it.

In these workshops we’ve covered the basic types of SIP setup with the core.