How much should one set aside for call control QOS bandwidth?

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Feb 27th, 2009
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I'm setting up some QOS classes to use with LLQ on some router ports. I've used 95k for each g.711 call in the EF priority queue, but I'm unsure how much bandwidth to use for the call control for each call. We're marking call control at CS3, and the Cisco QoS SRND v3.3 only mentions "150pbs (plus Layer 2 overhead) per phone call of guarandeed bandwidth is required for voice control traffic; more may be required, depending on the call signaling protocol(s) in use."

So for a 100MB ethernet link which 300 VoIP g.711 calls will be traversing, I've 30mb of priority queueing (rounded up) and 60k for call control bandwidth, using 200bps for each call.

Does 200bps per call for call control sound like it will be enough?

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Overall Rating: 5 (1 ratings)
Hythim Ali El Hadad Sat, 02/28/2009 - 06:01
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Hi Jim,

Instead of all of your calculation

please refer to this URL

It will help you calculating the required bw for any number of calls you will need through yuor links

We won't be able to determine that from here as you'll find it is depending on the link type and if you will change your voice payload size from 160 and if there is a media security or tunneling

Wish this URL be helpful

jkeeffe Mon, 03/02/2009 - 06:59
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I've worked with this bandwidth calculator and appreciate you confirming it. However, it is the call control part of the QOS that I'm concerned about. This calculator doesn't address how much call control for each call - at least it is not evident. Any idea where I can look to find out how to calculate bandwidth so I can intelligently size the Call Control class?

iptuser55 Mon, 03/02/2009 - 09:26
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I forgotten where I`ve seen this - in soem Cisco IPT book/SRND but around 31/37k for 100 handsets, also I`ve seen 150bps per handset which if you do the maths it does not add up to 31-37k for 100 but I would go with the 31,37K figure.

jkeeffe Mon, 03/02/2009 - 09:35
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I think if I use 200bps per handset I can't go wrong - that would add up to 20k for 100 sets, and 600k for 300. Thanks for the help!


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