60% of BW for voice

[Krzysztof Zaleski]

Hello,

I am just wondering, how much impact on the network/devices (for example 3945E with 80Mb WAN link) would have a specific QoS configuration, where I have a branch with contact center agents, and the amount of voice traffic reaches over 60% of existing WAN link. Is it OK to define 60% of BW for priority queue?

Cheers,

Krzysztof

[Terry Cheema · Accepted solution]

It depends on your requirements totally. There are guidelines by Cisco, other best practices etc. but they are for a reference only. Only you know what type of traffic your site is generating, what is critical and the bandwidth required for each type.

If your site hosts a high priority critical contact center, and its most important one, you can assign 60% or the required bandwidth to that traffic. During congestion, the contact center traffic will have 60% of the bandwidth and rest of the traffic will have 40% to share.

Just break down different types of traffic/bandwidth needs and assign bandwidth priority according to your needs.

Go through the below document, it has some recommendations/best practices from Cisco, use these as a reference:

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND_40/QoSIntro_40.html#pgfId-61104

-Terry

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[Krzysztof Zaleski]

That's what I thought, thanks. I wonder how such locations like contact centers are configured in real life. Agents are usually located in different site that DC, and usually there is not much other traffic, except some email maybe. So, do people reserve 60-70% to voice aor just upgrade WAN links so they can have no more than 30% for voice (doesn't make sense to me, as lot's of BW is wasted).

Krzysztof

[Joseph W. Doherty]

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Posting

I'm unable to say how other call (contact) centers are bandwidth provisioned, but ours have lots of excess bandwidth.  (We might be unusual as we're also a service provider.)  If fact, the last year or so, we be even adding more because our customer reps have had their PC applications moved to VDI applications, which for great performance, you want to provision it much like VoIP.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Cisco warns against allocating more than one third of the bandwidth for LLQ; this recommendation is to insure you leave sufficient bandwidth for your other traffic.  However, as Terry also notes, this is really only a guideline, much would depend on the needs of your other traffic.

However, once you get to about two thirds of the bandwidth for LLQ, you're likely to start to queue your LLQ traffic (against itself).  For something like VoIP, you're also impacted by how variable the CODEC's bandwidth utilization being used is (e.g. G.711 vs. G.729) and also by whether you have call management that insures the number of call won't oversubscribe your bandwidth.

So, to your question is 60% OK for LLQ being used by VoIP; well maybe, maybe not.  I would say it's likely borderline, just for VoIP needs.  I cannot say at all relative to your other traffic's service needs.