What is the recommended Delay/Latency between Call manager and The SRST setup

[Velu Sanjeevirayan]

Hi ,

Need to understand the readability between the CUCM and SRST.

What is the recommended Delay/Latency, Bandwidh  between Call manager and The SRST gateway setup.

Regards,

Velu S

[Manish Gogna]

Hi Velu,

An RTT of 80 ms or less is ideal. SRND provides details about SRST as well as all Deployment models of CUCM.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/collab09/models.html#wp1053477

HTH

manish

[Manish Gogna]

Bandwidth would depend on the codec being used for calls destined to or from SRST gateway as well as the number of phones / calls that is supports. Example , a g711 call would take around 80 kbps while a g729 would take around 24 kbps bandwidth.

HTH

Manish

[Aman Soi]

Hi Velu,

In addiiton to what Manish has said,

You can also refer the link and look for "Observations During Cisco Unified Communications Manager WAN Outage"

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/vcallcon/ps2169/prod_qas0900aecd8028d113.html

regds,

aman

[joao.wilson.rocha]

Hi Manish,

I've been struggling to get this information and what I could understand from the SRND is that this 80ms is just related to the Intra-Cluster communications (Between Servers UCS), there is no relation with SRST Gateways:

"The maximum one-way delay between any two Unified CM servers should not exceed 40 ms, or 80 ms round-trip time."

From that I assume that the RTD between the SRST and the Cluster should be based on the affirmation below:

"If a voice service is hosted across a WAN where the one-way latency is 200 ms, for example, users might experience issues such as delay-to-dialtone or increased media cut-through delays. For other services such as presence, there might be no problem with a 200 ms latency."

[Patrick Wherry]

Velu,

This doc is what Cisco and other telephony companies use for a benchmark.  150ms is one-way delay is the limit before the experience starts breaking down.  Latency that is greater than this effects performance not just for the call quality, but also for call setup, DTMF tones, call features during the call, and termination. 

Hope that helps,

Patrick

http://www.cisco.com/c/en/us/support/docs/voice/voice-quality/5125-delay-details.html