Any PBX migration I have done in the past, I dedicated a router between CUCM and the 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.
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.
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)
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)
SIP traces provide key information in troubleshooting SIP Trunks, SIP
endpoints and other SIP related issues. Even though these traces are in
clear text, these texts can be gibberish unless you understand fully
what they mean. This document attempts to br...
Please find the attached HTML document, download and open it on your PC.
This provides an easy to use form where you simply answer a few
questions and it will render the proper jabber-config.xml file for you
to copy/paste. There is built in logic to verif...
CUCM Database Replication is an area in which Cisco customers and
partners have asked for more in-depth training in being able to properly
assess a replication problem and potentially resolve an issue without
involving TAC. This document discusses the bas...