CUCM 7 Qsig with Nortel

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Feb 9th, 2010
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i must migrate from Nortel CS1000M (4.5) to CUCM 7.0. I read many docs about it and how to accomplish this using QSIG. I need to use a different method to migrate with qsig. I explain:

1. Initial situation: Nortel PBX connected to PSTN by E1 (all is working!!!)

2.    Now i must start migration using interoperability: consider i want to use QSIG but with this type of connections: (all CUCM servers are operational  and configured)

   2.1  Disconnect 1 PRI cable form Nortel and connect it to my Voice Gateway 3845 with VWIC2-2MFT-T1/E1 card (so connect PRI to the first port of the voice card)

   2.2 Connect the second port of the voice card to Nortel by QSIG

the map is :

PSTN----------connection to 1st port of VWIC2-2MFT--------------------> 3845-----------------------------> IP connection to CUCM and LAN

                                                                                                                               | (Qsig on 2nd port of  VWIC2-2MFT)



                                                                                                                         Nortel PBX

Can this configuration work ? CUCM controls 3845 voice gateway and, when there is a call directed for Nortel DN's, it is routed to QSIG channel.

My problem is that all configuration examples deals with PBX directly connected to PSTN and a QSIG connection to voice gateway that is AFTER the PBX and not connected to PSTN.

Do you know if there is any documentation explaining this configuration ?

Thank you,


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Tommer Catlin Tue, 02/09/2010 - 09:00
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Any PBX migration I have done in the past, I dedicated a router between CUCM and the PBX.

CUCM-----QSIG/H323/MGCP router-------PBX

Then on CUCM, I have a dedicated PSTN router for in/out calls.

Its a delicate balance when you migrate DNs from one PBX to CUCM.  You have to be careful to overload the trunk between CUCM and the PBX.   Once you reach that breaking point, you should PORT the DNs from the PBX pstn connection to the CUCM PSTN PRI connections.

This is assume you have ordered a new PRI(s) for your CUCM router.

robmas0871 Tue, 02/09/2010 - 10:32
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You mean that i must double my PRI lines to do this migration ? Let me me ask you if i understand your solution:

         CUCM-----QSIG/H323/MGCP router-------PBX------------1st PRI Line------------>PSTN





      MGCP Router



             | Other PRI Line to avoid overload on QSIG Trunk




This is the solution you used to migrate ? I have 20 PRI lines on PBX: can i setup 1 QSIG trunk for every PRI ?

Tommer Catlin Tue, 02/09/2010 - 10:48
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I wouldnt say double.....     Let me see if I can explain this:

For example, I have 2,000 DNs on my Nortel PBX.  Approx call volume through PSTN is around 1 channel per 10 DNs.

If i were to migrate 100 DNs to the CUCM, Im looking at approx 10 channels for PSTN connectivity and then misc station to station calls.

To provide connectivty, I need to have (1) QSIG T1 between CUCM and Nortel to make this work and still have bandwidth.

On the CUCM, I install a new PRI on a new router. (Say MGCP).   When my CUCM callers make an outside call, they will use this PRI.  But all incoming calls will still come from the Nortel via the QSIG trunk.

If your PSTN Carrier will allow you to break up the DID Banks and migrate them to the new PRI, even better!  Most carriers are starting to allow the breaking of DID banks between PRI groups.  So for example, I had the range 555-1000-1999.   But I was moving DID numbers 1050, 1060, 1061, 1072 to the new PRI.  Most will allow it.  Some do not.. all depends.

At some point though, you will have more phones and DNs than on the Nortel, at this point, you should move all the PRIs over to the CUCM and route traffic *back* to the Nortel as needed.  For example, I had 1200 DIDs on the CUCM (phones) and 800 on the Nortel, it would make more sense to move all PRI traffic to the CUCM and push traffic back through the QSIG as needed.

The trick here to balance the trunk between CUCM and Nortel, and also the PSTN traffic incoming/outgoing. 

You will also need to figure out voicemail.   I typically do (and Cisco recommendeds) you migrate everyone to a common voicemail platform FIRST, before turning up phones.  This way, whether they are on CUCM or Nortel, the voicemail is the same.  If you have (2) different voicemail platforms, then you have to deal with AMIS or VPIM or?  But all depends on the scenario, budget, business drivers, etc... you may have to use AMIS or VPIM if required.

Hope I have not confused you.

In the end, you will probably pay a little more for PRIs than you would hope to be paying, but it will help your migration.  Those costs assocaited to the "double PRIs" will only be temporary.

Rob Huffman Tue, 02/09/2010 - 12:09
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Hey Tommer,

Great answer my friend! Worthy of 5 points for sure

We used the method given by Tommer for our Notel to CUCM migration, and used DSC's

(Distant Steering Codes) on the Nortel side to route incoming calls to DN's that had moved over

to CUCM. Worked sweet!



robmas0871 Tue, 02/09/2010 - 12:51
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Thank you,

your explanation was clear about how QSIG channel can go busy when overloading it with additional calls. But consider my migration architecture showed below: (i have an MGCP router with a 2 port VWIC2-2MFT: one connected to PSTN and the other for QSIG Trunk connected to Nortel)


PSTN----------to 1st port of VWIC2-2MFT---------> MGCP Router--------------> CUCM--------> Cisco DN's


                                                                                                         | (QSIG on 2nd port of  VWIC2-2MFT)



                                                                                                   Nortel PBX




                                                                                                  Nortel DN's

I have calls going into QSIG channel in these 4 situations: (Cisco DN's are Phones migrated to CUCM and Nortel DN's are Phones not yet migrated)

1.   Cisco DN's to Nortel DN's

2.   Nortel DN's to Cisco DN's

3.   Nortel DN's to PSTN

4.   Voicemail channels

So, it's true that i can overload the QSIG channel because of additional station to station calls but not for "Cisco DN's to PSTN" calls. Consider that i have 6 MGCP routers with 18 VWIC2-2MFT cards, so i must set up many QSIG channels as possible.

So, my final questions are:

1.    Do you think my migration architecture  (with special handling of QSIG congestion) can work ?

2.    have you got a link to any documentation about configuring CUCM and MGCP router for my migration architecture ? (i read every documentation about it, but all are dealing with this type of architecture: PSTN------->PBX---------->MGCP Router---------->CUCM and not with mine that is a little bit different)

Thank you and Good Luck to Packers!!!!


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