MGCP, Call Manager , Voice Gateway questions

[wilson_1234_2]

In a scenario of

Main Branch has Call Manager controlling Main Site and branch phone functions.

Branch sites have voice gateways connected to Main site via MPLS with IP Phones for branch users and configured with MGCP.

Each branch has a PRI for ouside local and LD calls.

Questions:

The voice gateway, when configured with MGCP is a remote control mechanism for call manger to have control of all ports on the gateway, correct?

When configured this way, and the remote sites have their own PRI, is considered PRI Backhauling?

Do the remote branch phones register with Call Manger or the remote gateway ?

Does the remote gateway notify Call Manager that a phone is taken of hook, or the phone does it directly?

When a call comes in to a remote branch via the branch PRI, would the process be:

1. Call hits remote gateway

2. Remote gateway contacts Call Manager via MGCP.

What does MGCP do at this point?

3. Call data is carried via tcp port 2428 from Branch gateway to Call Manager.

4. Call Manager communicates vi skinny with remote phone.

[Jaime Valencia]

I strongly recommend you to start reading documentation from http://www.cisco.com to understand how things work.

Questions:

The voice gateway, when configured with MGCP is a remote control mechanism for call manger to have control of all ports on the gateway, correct?

A: MGCP is ALWAYS a master-slave protocol independently of LAN/WAN

When configured this way, and the remote sites have their own PRI, is considered PRI Backhauling?

A: MGCP ALWAYS backhauls Q931 info to CUCM

Do the remote branch phones register with Call Manger or the remote gateway ?

A: With the call control agent, CUCM.

Does the remote gateway notify Call Manager that a phone is taken off hook, or the phone does it directly?

A: NO, SCCP is between CUCM and phones

When a call comes in to a remote branch via the branch PRI, would the process be:

1. Call hits remote gateway

2. Remote gateway contacts Call Manager via MGCP.

What does MGCP do at this point?

A: Handles Q921 and backhauls Q931 to CUCM to determine routing based on IEs.

3. Call data is carried via tcp port 2428 from Branch gateway to Call Manager.

4. Call Manager communicates via skinny with remote phone.

Again, you need to read documentation to understand the differences between a call agent, a GW, a phone and how the communications and protocols are handled between them.

HTH

java

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[wilson_1234_2]

Thanks,

Is there any documentation that shows the call flows and answers the questions I have here:

"differences between a call agent, a GW, a phone and how the communications and protocols are handled"

"A: With the call control agent, CUCM. "

How do I know if I have the Call Control Agent?

[Jaime Valencia]

Cisco Call agents are only CUCM or CUCME, so you most likely will have one.

Read the overview of CUCME or CUCM to understand what a call agent does and provides.

Using Call Flows to Resolve Call Processing Problems

http://www.cisco.com/iam/unified/ipt611/Using_Call_Flows_to_Resolve_Call_Processing_Problems.htm

Sample of Debug MGCP Packets

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_tech_note09186a0080174804.shtml

The study material for CCVP is also a very good reference to understand all this.

HTH

java

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[wilson_1234_2]

Yes,

Very helpful, thanks.

Couple more questions,

When checking to see if the gateway is registered in Call Manager, on the Gateway end we can entr "sh ccm-manager"

But on the Call Manger end, we can go to gateway from the Management application and the only thing you see is

Status-Ready

Is this the only way to determine if the Gateway is registerd on the Call Manager end?

Sometimes I will see logs in the gateway showing the phone has unregistered normally and registered.

Jul 12 20:40:08.543: %IPPHONE-6-UNREGISTER_NORMAL: ephone-3:001FCAE77A1C IP:10.2.1.4 Socket:2 DeviceType:Phone has unregistered normally.

Jul 12 20:40:09.051: %IPPHONE-6-UNREGISTER_NORMAL: ephone-1:001FCAE779E6 IP:10.2.1.5 Socket:4 DeviceType:Phone has unregistered normally.

Jul 12 20:40:09.307: %IPPHONE-6-UNREGISTER_NORMAL: ephone-4:001FCAE7797D IP:10.2.1.1 Socket:1 DeviceType:Phone has unregistered normally.

Jul 12 20:40:20.151: %IPPHONE-6-UNREGISTER_NORMAL: ephone-2:001FCAE7798A IP:10.2.1.3 Socket:3 DeviceType:Phone has unregistered normally.

Jul 13 13:40:49.836: %IPPHONE-6-REGISTER_NEW: ephone-3:SEP001FCAE77A1C IP:10.249.120.4 Socket:3 DeviceType:Phone has registered.

Are these registrations in Call Manager?

[Jaime Valencia]

That might be CME or SRST you're running.

HTH

java

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[wilson_1234_2]

Yes SRST is configured to fail back to the PRI when the link to the main site is lost.

Is this registration on the gateways?

If so, is it seperate or in addition to the registration of the phones in Call Manager?

Also, this question:

When checking to see if the gateway is registered in Call Manager, on the Gateway end we can entr "sh ccm-manager"

But on the Call Manger end, we can go to gateway from the Management application and the only thing you see is

"Status-Ready"

on that particular gateway page.

Is this the only way to determine if the Gateway is registerd on the Call Manager end?

[Jaime Valencia]

SRST is a mechanism for phones to fallback to a router that provides basic call functionality because the communication phone-CUCM is down.

Search srst in CCO for greater details if you want further info

sh ccm-manager only proves the keepalives are being sent between the MGCP GW and CUCM, a sh mgcp endpoints is better command for registration.

On CUCM simply go to the endpoint page and see if it shows as registered or not.

HTH

java

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[wilson_1234_2]

Yes, I knew that SRST was the failback mechanism, but I had specific questions about it.

For example, if Call Manager is remotely controlling the gateway, are the dial peers needed in the router config without SRST?

Or are the dial peers in the config to be used by the SRST function only when the gateway looses connectivity with Call Manager?

[Jaime Valencia]

Yes, if the GW is MGCP and you have SRST the dial-peers that are not marked for MGCP are for SRST

MGCP GW without SRST only contains MGCP related dial-peers

HTH

java

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[wilson_1234_2]

Excellent,

Thanks.

So in the below examples,

Dial peers 1, 9010 and 61 are for Call Manager to control and the rest are for SRST failback,

is that correct?

dial-peer voice 1 pots

description MGCP Inbound Calls from PSTN

service mgcpapp

incoming called-number .

direct-inward-dial

port 0/1/0:23

!

dial-peer voice 2 pots

description Emergency 911 dialing

translation-profile outgoing CALLERID

destination-pattern 9911

incoming called-number .

direct-inward-dial

port 0/1/0:23

forward-digits 3

!

dial-peer voice 9010 pots

description MGCP Dial-peer for 0/1/0

service mgcpapp

port 0/1/0:23

!

dial-peer voice 61 pots

description FAX line

service mgcpapp

destination-pattern 1234567

port 0/2/0

!

dial-peer voice 3 pots

description 7 digit Local Dialing

destination-pattern 9[2-9]......$

incoming called-number .

direct-inward-dial

port 0/1/0:23

[Jaime Valencia]

Yes, that's correct.

HTH

java

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