LLQ: Priotity-Queue for VoIP, higher than 33% ?

Unanswered Question
Jul 17th, 2009

Is it possible to increase the LLQ Priortiy-Queue for VoIP higher than 33% (best practice?) of the total bandwith ?

...

Bandwith(AR): 1Mbit, 2Mbit, 4Mbit

WAN-Link: G.703 or G.SHDSL or 10/100/1000 Ethernet

HW: 1841/2821/38xx/7201

...

any URL on CCO ?

any expirience ?

Thanks for any comment !

I have this problem too.
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Giuseppe Larosa Fri, 07/17/2009 - 12:11

Hello Ralf,

it is possible for example for protection: we did so for a mobile provider to allows voip to have resources in case the parallel link fails: that is in normal conditions we had half on each link.

Actually we were using faster links 45 Mbps or 155 Mbps.

Be aware that LLQ and CBWFQ has elastic behavior and not used resources are used by other traffic classes

Hope to help

Giuseppe

rnolden Fri, 07/17/2009 - 12:58

there is only one active WAN-Link

so this scenario isn't possible !

....

can i increase the PQ for VoIP above 33% ?

until which value ?

Giuseppe Larosa Sun, 07/19/2009 - 08:23

Hello Ralf,

>> can i increase the PQ for VoIP above 33% ?

until which value ?

Until other traffic classes don't suffer starvation.

As I wrote for the elasticity of CBWFQ with LLQ when VoIP traffic is less then provisioned percentage resources are left to the other traffic classes.

Hope to help

Giuseppe

Joseph W. Doherty Sun, 07/19/2009 - 16:40

"there is only one active WAN-Link

so this scenario isn't possible ! "

Why do you think that?

"Is it possible to increase the LLQ Priortiy-Queue for VoIP higher than 33% (best practice?) of the total bandwith ?"

Yes, it is.

"any URL on CCO ? "

To tell you what?

The TelePresence Design Guide, has a section, http://www.cisco.com/en/US/docs/solutions/Enterprise/Video/tpqos.html#wp1050044, that discusses Cisco's "33% LLQ Rule" recommendation.

"any expirience ? "

Yes, I have quite a bit. Cookbook recommendations for X% don't often optimally satisfy real traffic QoS needs. I've used more and used less LLQ bandwidth %. What's important with QoS is the combination of using bandwidth management and bandwidth provisioning to meet service requirements.

"can i increase the PQ for VoIP above 33% ?

until which value ?"

Not sure I understand the question. If you're asking about PQ, each class preempts all lower classes. If you placed VoIP into the highest class, you've effectively guaranteed such traffic 100%.

[edit]

If you meant LLQ, not PQ, you could set it to whatever the platform supports for its CBWFQ. Without checking, and using max reserved bandwidth, I assume you might be able to configure LLQ to 99 or 100%. Further assuming you can, does this make sense? It might, again depends on what you're trying to accomplish.

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