QOS over 4MB MPLS LINK for VOIP and Video conferencing

[awadmohammad5]

Hello Experts,

we have HQ and a BR all the IP phones in BR registered with CUCM cluster which is in HQ (version 10.5)

and we are also regularly conducting Video conference calls between HQ and BR using Cisco Telepresence as well as Huwaei and Polycom TP.

we have 4 MB link between HQ and BR and the issue is we are facing some distortation in the video coference video and voice is not that clear sometimes even users on the call voice breaks and ip phone gets unregister from cucm and register back within few minutes.

when i check the bandwidth utilisation of 4MB utilsation is around 2.5 to 3 MB not more than that 

but i am unable to understand why this issue is happening? i checked with my Service provider they said there is no packet drops on the link to.

any help help with QOS ?? i think QOS only comes into effect when there is a congestion.

[Nick Halbert-Lillyman]

Firstly, you should be able to login to the web interface of your TP endpoint during a call to check for packet loss - optimally, it should be at 0% or very close to (less than 1 - 2%)

What are you using to monitor your bandwidth?  Most tools will look at a 5-minute average, so a 5 minute average of 3Mbps will likely include many shorter duration spikes.

How much bandwidth are you using per video call?  If you only have a 4Mbps link, most QoS policies won't allocate more than 30% of bandwidth to real time traffic, so if you're running any more than around 1Mbps per call you would likely exceed this, and that's assuming your switches and routers are configured properly for QoS.

QoS is unfortunately a complicated beast, and you're likely to have difficulties running video on a 4Mbps link if you're sharing the link with other applications.