QOS appyling on fast ethernet in mpls network(Urgent)

Unanswered Question
Mar 30th, 2008

Hi,all

Thanks in advance

Their is some confusion in qos configuration in mpls network.

One of my customer wants to deploy qos for bandwidth management in mpls network.

Scenario is like below.

MPLS sp provides 18 mb ethernet connection to customer.Bandwidth is controlled by MPLS sp.customer wants to reserve 16 mb for video traffic and remaining for data.But connection is comming on fastethernet port on 2811 router.I am plaaning to use CBLLQ.is it right solution or not?

I have this problem too.
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Goutam Sanyal Mon, 03/31/2008 - 00:04

Sandeep, Okay, but you need to ask the ISP to allow the QoS traffic over there MPLS network Thanks Goutam

Pavel Bykov Mon, 03/31/2008 - 00:35

The most critical to your design is shaper. There will be bottleneck on the ISP side, where ISP will not let more than 18Mb through, probably by policing. So what you need is create shaper on the output.

That is good news, since CBWFQ or CBWFQ+LLQ is not supported on the Ethernet itself very well, and almost not at all on subinterfaces.

Under shaper there should be a child map with all the policies.

So it will be like this:

PARENT: Shape average 18M

CHILD: class video

class data

It is a normal scenario, and you primarily to take care of your bottlenecks.

royalblues Mon, 03/31/2008 - 01:25

I agree with Pavlo that you need to use nested policies with the parent policy shaping the traffic and LLQ+ CBWFQ for prioritising the traffic

BTW, reserving 16MB out of 18 seems to be a bit too high for video. Recommendation for LLq is about 33% bandwidth

Narayan

san_dec21 Mon, 03/31/2008 - 02:45

thanks all of you for quick reply

But can i get some documentaion about nested policies under the parent policy, i mean can i get config example?

And what is meaning of "Recommendation for LLq is about 33% bandwidth"

royalblues Mon, 03/31/2008 - 03:11

Have a look here

http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfmcli2.html#wp1022062

From the QoS SRND

Cisco Technical Marketing testing has shown a significant decrease in data application response times

when realtime traffic exceeds one-third of link bandwidth capacity. Extensive testing and customer

deployments have shown that a general best queuing practice is to limit the amount of strict priority

queuing to 33 percent of link capacity. This strict priority queuing rule is a conservative and safe design

ratio for merging realtime applications with data applications.

http://www.cisco.com/univercd/cc/td/doc/solution/esm/qossrnd.pdf

HTH

Narayan

Joseph W. Doherty Mon, 03/31/2008 - 05:34

There are two issues you need to address. First, what to do with the traffic you send to MPLS. Second, what happens to the traffic as it exits MPLS.

For the former, much as the other posters have also noted, a hierarchical shaper, with the parent's shaper configured for 18 Mbps, and the child's video class provided 16 Mbps, would often be the norm. If the video is not real-time, an ordinary CBWFQ class reservation of the necessary bandwidth usually works fine. If the video is real-time, e.g. video conferencing, LLQ is often the choice, but at these bandwidth levels, it's often not necessary.

e.g. (pseudo config)

policy-map parent

class class-default

shape 18 Mbps

policy-map child

class video

bandwidth 16 Mbps (or priority 16 Mbps)

class class-default

no fair-queue (FQ, on most platforms, seems to disturb non-LLQ bandwidth reservations)

fastethernet 0/0

service-policy output parent

The latter issue, what happens at MPLS egress, can be just as important. If your MPLS environment is multi-point, it's crucial too. If there are only two sites, your outbound policy, alone, might be all you need, but you still need to confirm what the MPLS provider does. For instance, they might rate-limit the MPLS egress bandwidth, and if their burst intervals differ from your shaper's, even though you both are configured for 18 Mbps, they might still drop some of your traffic.

If you're working with multi-point MPLS, then you need to consider how to obtain the bandwidth reservation you need within that environment which is very dependent on what the MPLS vendor offers. The latter is usually accomplished by usage of some type of CoS/QoS marking, for which the MPLS provider guarantees some service level for particular markings.

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