Global UCCX deployment - maximum network latency permitted?

Answered Question
Jan 20th, 2010

We are looking at a global deployment of UCCX. The number of agents will be small, around 25 in total, but globally dispersed.

What is the maximum network latency UCCX can tolerate?

We would be looking to have the UCCX server, PSTN connection and CUCM in a datacentre in London and agents in London, Toronto, Singapore and Santiago.

There would be QoS set on the WAN but latency between London and Santiago could be an issue as it may be 200ms or worse.

Any feedback would be appreciated.

Thanks

Andy

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Correct Answer by Jonathan Schulenberg about 6 years 10 months ago

Above 150ms, or esspecially 200ms your voice quality will begin to degrade. This is not a CCX limitation.

What will really get you is the amount of CAD signaling. It is a "chatty" application; delay will slow it down. Here is an excerpt from the CCX SRND:

Impact of delays inherent in the applications themselves. 25 seconds is the initial Cisco Unified
CCX agent login setup time with no WAN delay. The overall time to log in agents and base delay
adds approximately 30 seconds of delay per 30 milliseconds of WAN delay.

From page 108 of the Solution Reference Network Design for Cisco Unified CCX and Cisco Unified IP IVR, Release 7.0.

I do not recall there being a documented maximum in the SRND because the BU likely expected the voice RTT delay limit of 150ms to become a problem first.

Also remember that all reporting in CCX is recorded and displayed in server time. Global deployments could be somewhat annoying because all reporting for an agent in another timezone would have to be mentally offset by the person viewing the report. There are similar issues with time-of-day/day-of-week code within scripts but these can be overcome with some work at least.

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Correct Answer
Jonathan Schulenberg Wed, 01/20/2010 - 05:51

Above 150ms, or esspecially 200ms your voice quality will begin to degrade. This is not a CCX limitation.

What will really get you is the amount of CAD signaling. It is a "chatty" application; delay will slow it down. Here is an excerpt from the CCX SRND:

Impact of delays inherent in the applications themselves. 25 seconds is the initial Cisco Unified
CCX agent login setup time with no WAN delay. The overall time to log in agents and base delay
adds approximately 30 seconds of delay per 30 milliseconds of WAN delay.

From page 108 of the Solution Reference Network Design for Cisco Unified CCX and Cisco Unified IP IVR, Release 7.0.

I do not recall there being a documented maximum in the SRND because the BU likely expected the voice RTT delay limit of 150ms to become a problem first.

Also remember that all reporting in CCX is recorded and displayed in server time. Global deployments could be somewhat annoying because all reporting for an agent in another timezone would have to be mentally offset by the person viewing the report. There are similar issues with time-of-day/day-of-week code within scripts but these can be overcome with some work at least.

andyhibbert Wed, 01/20/2010 - 07:07

Thanks for replying.

My main concern with latency is that if UCCX is constantly talking to the Agent workstations then there may be missed poll responses or timeouts and UCCX assumes that the Agent has gone off-line etc. I was hoping that there were some published recommendations, but 150ms is probably as good a figure as any.

Andy

Jonathan Schulenberg Wed, 01/20/2010 - 11:02

I asked a TME from the BU for a little clarification and here is what I got.

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CAD sends a heartbeat every 30 secs. There is a timeout of 120 secs, which means the server will drop the connection if no heartbeat is received after 120 secs.

I still feel that the latency will slow you down so much that this will never happen unless the link goes down.

andyhibbert Thu, 01/21/2010 - 01:52

I agree, it looks like voice quality is likely to be the issue with this deployment.

I'm puzzled by one thing about this 150ms limit though.

Tthe UCCX SRND mentions on page 7-1;

Total delay budget for latency (taking into account WAN latency, serialization delays for any local area network traversed, and any forwarding latency present in the network devices). The generally agreed-upon limit for total (one-way) latency for applications in a network is 150 milliseconds.

In this case are they including voice as one of the applications ?

My understanding of this would be that if the one way latency is 150ms then the total RTT could be 300ms. Or have I completely misinterpreted this?

Thanks

Andy

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