Unity Connection Clustering and TIMG Port Allocation Clarification

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Nov 23rd, 2009
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I need to get a clarification on port capacity particularly how it is affected (or not) by the combination of utilizing Connection clustering and TIMG integration(s).


Assumption – 144 ports max per cluster / 72 ports max per server (i.e., IMAP is licensed)


Both clusters have TIMG integration to legacy PBX and integration to CUCM.


I would envision a valid port configuration as follows (just looking at one cluster for simplicity)


Cluster 1 – 96 ports (TIMG) / 48 ports (CUCM)

Based solely on numbers and port capacities, this would appear to be valid.


However, what I need to clarify is if this a valid configuration based on the clustering and TIMG integration specifics?  According to Cisco documentation on Unity Connection cluster configurations, there are guidelines for server assignments and usage of voice messaging ports based on the integration type.


For example, for a SCCP integration the phone system is setup with twice the number of SCCP ports needed and they are split across the 2 servers.  For example, if you need 16 ports to handle all messaging traffic then you configure 32 ports and they are split across the 2 servers.  In this example, the loss of one server provides full redundancy from a port capacity perspective for the cluster.


With TIMG, the number of ports configured is the same as the number of ports on each server in the cluster so that the servers share ALL ports.  For example, if you have 16 TIMG ports then each server in the cluster uses the same 16 TIMG ports.  In addition, calls are load balanced between servers by the TIMG.  So, depending on how this is interpreted – this may bring upon a limitation on the number of ports that can be provisioned to a PBX via the TIMG (and subsequently the max ports used per Connection cluster).  For example, if a single server can only handle 72 ports and the TIMG ports are the same across each server then would this mean that Cluster 1 could only have 48 ports (TIMG) total?  Effectively, overall ports per cluster would be 48 ports TIMG (each server has to use the same TIMG ports) / 48 ports (24 ports per server for total of 72) CUCM.  Effectively, you are only using 96 out of 144 available ports due to TIMG.  Is this correct or no?

Correct Answer by ghorna229 about 7 years 8 months ago

I understand what you are saying.  Like I said, my account engineer that worked with us on the Unity install sat down with us and talked about this with us.  His recommendation was to point our stack of 4 TIMGS to one Connections server and then with our other sites that have PIMGs point them to the other server primary.  This would load balance in a normal time, but in a failure would hit one of the 2 hard since everything would home to the server that is up.


The information I got from Cisco is that each server could handle 144 ports so combined they could handle 288 in Connections 7.1.

Correct Answer by ghorna229 about 7 years 8 months ago

My understanding is that the T1MGs will not load balance unless you put them through a SIP Proxy, at least that is what Cisco told me.  So you would point the TIMG to the SIP Proxy and then that would load balance the traffic to the clustered servers.   If there is no SIP Proxy, the TIMG will always look to its primary endpoint and if that is not available it will go to its secondary endpoint.

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Correct Answer
ghorna229 Tue, 11/24/2009 - 07:51
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My understanding is that the T1MGs will not load balance unless you put them through a SIP Proxy, at least that is what Cisco told me.  So you would point the TIMG to the SIP Proxy and then that would load balance the traffic to the clustered servers.   If there is no SIP Proxy, the TIMG will always look to its primary endpoint and if that is not available it will go to its secondary endpoint.

David Hailey Tue, 11/24/2009 - 09:48
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Good info to know and I'll check into that.  However, it doesn't quite answer my question.  So let's take the last portion of your comment.  My question is centered more on how the provisioning of the ports works within the cluster.  Can I configure 48 TIMG ports to point to the Pub and 48 more to point to the Sub...OR like the info in the design guide says, can I only configure 48 for the cluster because the servers must use the same TIMG ports (i.e., no one server can handle 96 ports in a failover scenario + the CUCM ports it hosts because the IMAP port limit is 72 per server, 144 per cluster).


Make sense?

ghorna229 Tue, 11/24/2009 - 10:00
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What you are saying makes sense, but from my experience with TIMGs and PIMGs, we have had Unity 5.0 installed for 2 years and use only these types of connections, I dont see how you could point specific TIMG ports to a specific server.  I am assuming since you are talking 48 ports you are using dual span TIMGs since you are talking 48 ports.  Also are you using a serial connection for SMDI?  We are so that would cause a problem as will since the same server needs to recieve that SMDI information to correctly drop the calls in the right spot.


I am preparing to build a Connections Lab to evaluate this as a migration path, and my understanding is that each server could support 144 ports for a total between them of  288 ports.  You have made me think of some things I will need to check when I build this, because of the active active config and the smdi requirements.  I currently have 160 ports in production so were not worried about the blockage of the 16 ports.   We are more looking for the redundancy the Connections can give us over having 2 5.0 clusters.

David Hailey Tue, 11/24/2009 - 10:26
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I understand your take on it when you talk about Unity.  However, this is with Unity Connection and way the specs are written up on how integrations work when clustering is ambiguous as it relates to TIMG/PIMG integrations.  This would be 4 TIMG w/serial integration - 2 stacks of 2.  When you think of it by port counts and separate servers, you would think that you could effectively utilize all of your ports...however, that may not be the case which is what I'm trying to get a clarification on.  In other words, I may only be able to use 2 TIMG's for an integration of 48 ports and then 24 CUCM ports on each server.  Then, in a failover the server left standing wouldn't be oversubscribed (i.e., no more than 72 ports pointed at it - 48 shared TIMG ports and it's dedicated 24 CUCM ports).  I hope to get a solid answer on this soon.

Correct Answer
ghorna229 Tue, 11/24/2009 - 10:39
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I understand what you are saying.  Like I said, my account engineer that worked with us on the Unity install sat down with us and talked about this with us.  His recommendation was to point our stack of 4 TIMGS to one Connections server and then with our other sites that have PIMGs point them to the other server primary.  This would load balance in a normal time, but in a failure would hit one of the 2 hard since everything would home to the server that is up.


The information I got from Cisco is that each server could handle 144 ports so combined they could handle 288 in Connections 7.1.

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