From: Darby Weaver (ccie.weaver@gmail.com)
Date: Mon Nov 03 2008 - 19:45:45 ARST
1. Remember that QoS is called into play when and if the network is
experiencing congestion. Otherwise it is not in effect.
2. LLQ is an enhancement of all three legacy queuing algorithms: Priority
Queueing, Custom Queueing, and Weighted Fair Queueing.
3. LLQ is CBWFQ with a strict Priority Queue. So remember the "negative
with PQ", that is, that traffic is assigned with the command "Priority" will
be serviced first and to the effect of starving all other CBWFQ's are
servicesd.
Think about that for a moment. Savor it a little. How does it taste?
What I mean is one of the practices that we have come to assume is that
Voice Traffic needs to be serviced first. But is is small and predicatable.
Now try this with FTP, HTTP, or SQL application-based traffic on a busy
network.
Does any other traffic ever get a chance in this theoretical example?
Finally consider this tidbit:
LLQ is designed "specifically" for converged networks that carry Voice and
Interactive Video.
It has 2 components:
1. PQ for real-time sensitive traffic.
2. CBWFQ for data applications.
Also remember that LLQ has a built-in Policer. This feature is also enacted
during times of network congestion. If not then the traffic assigned to the
PQ would effectively starve the other classes of traffic as I mentioned
above.
If and when this happens, traffic is dropped with no preferences whatsoever.
Does that help a bit?
Darby
On Mon, Nov 3, 2008 at 4:22 PM, <akberali.cisco@gmail.com> wrote:
> Hi,
>
> Can any one plz tell me when do we use CBWFQ & LLQ in MQC -QOS.
>
> What are their advantages & disadvantage.
>
> Which is the best feature in QOS if want to prioratise my DATA traffic , i
> donot have voice passing through my data trafic.
>
>
>
> Regards,
> Akber Mirza.
>
>
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