Clustering over the WAn - CUCM

[Kiley Arena]

Hello there,

I'm not sure if this is the right area to post this question, please let me know if it is not and I will repost it elsewhere....

We are currently using Clustering over the WAN for 5 metropolitan sites for 2 different networks - one uses gatekeepers, the other does not.  My colleague and I differ an how calls are physically handled for other sites within the cluster.  In both networks, there is a route pattern: [2-9]xxxxxx.  This pattern encompasses numbers that are within the cluster as well as sites outside of the cluster.  For example, a number within the cluster might be:  449xxxx and a number outside of the cluster might be 431xxxx.  I remember being told by another voice engineer eons ago that there should not be route patterns for devices within the cluster.  I can understand that but, and here is the actual question, how are our intra cluster calls getting routed if they aren't using a route pattern?  It seems like it should actually use the the route patterns since we're all connected over WAN links but I don't know enough about this network and VoIP in general to know where to look for information.

I've tried looking up clustering over the WAN and just find the generc stuff  like the RTT has to be less than 80ms but I can't seem to find an answer to my question.  It's probably something obvious like they ARE using the route pattern...but if they are, I don't understand WHY!

Any enlightenment would be very greatly appreciated!!!!

Thanks,

Kiley

[Ayodeji Okanlawon]

Route patterns are only used for anything outside of the cluster. ie PSTN calls, calls to another cluster via ICT (gatekeeper or non GK controlled), SIP etc

All device local to a cluster register with CUCM and CUCM route calls internally to those devices. CUCM knows where they are....

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[Jaime Valencia · Accepted solution]

The answer is that it's because of the routing algorithm, which uses best match routing

[2-9]xxxxxx covers A LOT of numbers, (8,000,000 to be exact)

Whereas if you have a DN configured as 4491111 on a phone, it's only ONE match.

CUCM will find and use the pattern (wherever it might be configured) that is the best match for the digits you dialed.

If you dial 4312222 and it goes via the RP, that's because in all your dial plan, that RP was the best match for those digits.

If you want further reading, read the dial plan chapter from the SRND

HTH

java

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[Kiley Arena]

Jaime,

Thanks for the information - even though we're a cluster, we're clustering over the wan so a route pattern of some sort would be needed - makes sense now that it's spelled out.  I'm not sure what the SRND is as I'm starting the CCNP Voice track with CIPT1 but I'll sniff it out on the web.

V/R,

Kiley 

[ronpatel]

Hi Kiley

SRND is the document which has all the required/tested/supported information about the Cisco CUCM.

Below is the link for Dial plan for CUCM 9.0

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/9x/dialplan.html

Regards
Ronak Patel

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[Kiley Arena]

Thansk Ronak!  I've put the link into my bookmarks!

Kiley

[Jaime Valencia]

In ANY deployment model, assuming you want to reach something outside CUCM (another CUCM cluster, PSTN, SIP trunks, a PBX, etc) you need route patterns, the fact this is CoW has nothing to do with whether you need route patterns or not.

HTH

java

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[Kiley Arena]

Jaime,

I understand the need for route patterns when going anywhere outside of the cluster (PSTN, other cluster, etc) - am I misunderstanding the need for route patterns when CoW then, within a cluster?

Thanks,

Kiley

[Terry Cheema]

Hi Kiley,

My friends Deji, Jamie and Ronak have already answered your queries. But still if you have any confusion will try to  explain:

I remember being told by another voice  engineer eons ago that there should not be route patterns for devices  within the cluster. 

Yes thats right. For dialing the VoIP phones in a cluster you dont need to have any route patterns.

I can understand that but, and here is the actual question, how are our 
intra cluster calls getting routed if they aren't using a route 
pattern?  It seems like it should actually use the the route patterns 
since we're all connected over WAN links but I don't know enough about 
this network and VoIP in general to know where to look for information.

Intra cluster calls are routed by the call manager according to internal database. All the phones inside a cluster register to the call manager servers. The call manager knows about the Directory Numbers (DNs - as configured by the users in CUCM) and is able to route the calls between each other without having need for routing the calls anywhere else (gateways, Trunks etc.).

Even though you have a CoW deployment and your servers are located at different sites as long as they are part of the same cluster, they have same copy of the database (which has records of all internal numbers and associated phones) which is achieved through dbreplication. So all the Call Manager servers have the records of all the internal numbers and can route calls between each other.

I've tried looking up clustering over the WAN and just find the generc 
stuff  like the RTT has to be less than 80ms but I can't seem to find an
 answer to my question.  It's probably something obvious like they ARE 
using the route pattern...but if they are, I don't understand WHY!

Clustering over WAN or Centralised CUCM servers make no difference. As explained above as long as they are part of the same cluster they have the same copy of the database irrespective of their location and have the records for all the internal directories.

I understand the need for route patterns when going anywhere outside of 
the cluster (PSTN, other cluster, etc) - am I misunderstanding the need 
for route patterns when CoW then, within a cluster?

Yes as already explained there is no need for route patterns for routing calls between phones inside a cluster. As you have configured specific extensions as directory numbers, associated to phones, the call manager server knows which phone to alert when a match is found.

Please let us know if you still have further queries.

Thanks,

Terry

[Kiley Arena]

Terry,

Obviously, I'm dense as dirt....

Let me try and lay out the topology of one of our networks - there are 5 subscribers and 1 Publisher spread over a large metropolitan area.  Each subscriber is at one of the 5 locations (I'm stating the obvious, I'm sure!) with one location having a subscriber and the publisher.  All data communication between sites are via L3 MPLS links.  Typical data communications between sites go from each  site's core L3 switch up to an ASR and out to WAN (although, it's really a MAN, I suppose!) and over to the remote site's stack.

Now for my denseness.....Terry, you say "So, all the Call Manager servers have the records of all the internal numbers and can route calls between each other."  I'm getting hung up on the word "route"... HOW are the calls routed between each other or....are they not and the call managers do call control between each other (using the data path to communicate?) and the one sub tells the other sub: "I have a call to one of your DNs from one of my DNs?" and the local subscriber places the call?

Thanks so much for having the patience to explain these concepts - I greatly appreciate it!

Kiley

[Terry Cheema]

Hi Kiley,

All the call manager servers inside a cluster have the same database.So once they analyse the number, lookup in the database and find the associated phone - its alerted. How they communicate with each other? - The call manager servers communicate with each other via Intra cluster communication signaliing (ICCS) which is a real-time protocol. It uses a TCP connection thats setup between all call control servers (full mesh).

Hope that clarifies.

Thanks,

Terry

[Kiley Arena]

Terry,

Ahhhhh -  that makes sense!!!  Intracluster calls aren't actually "routed" to each other - regardless of what kind of cluster you have. The subs actually do the brunt of the work by using ICCS to set up call control. Hence, no route patterns are needed/used for intra-cluster calls.  The lights have finally come on!

Most awesome Terry; I cannot thank everyone enough for having the patience to clarify the process for me.

V/R,

Kiley