QoS implementation with VRF

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May 20th, 2009
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We want to implement QoS in our network. Have read "a few" doc's regarding QoS, but still have some unaswered questions.

The network is built up with several Catalyst 3560-E, and we are using VRF-lite.

The network is divided into several VRFs. Each VRF has it's own ospf routing instance, and inside each VRF the data is routed from 3560 to 3560....

In VRF "vhf" we have speach (a local radio system),

VRF "voip" and VRF "video" is also real time applications. We also have an "office" VRF and a "guest" VRF

plus some more VRFs, eight all in all.

What we trying to achieve, is that we would like to give priority to VRF=vhf first of all,

then "voip" and "video" and finally "office"/"guest" to be the least important nettwork/routing instance.

Is there any way to realize "VRF based QoS" like the way we want.

Or, could there be another way to solve what are trying to do.

Perhaps in near future, we would like to give priority to softphones inside the "office" VRF,

but this is not a issue at the moment.

Thanks in advance.

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Joseph W. Doherty Wed, 05/20/2009 - 11:48
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I don't know if QoS is VRF-Lite aware. If not, you probably could use DSCP to reflect the importance of VRF and/or traffic type. Then just prioritize based on DSCP.

Don't forget, DSCP provides 64 values, so, if necessary, you should be able to classify VRF and traffic types.

Giuseppe Larosa Wed, 05/20/2009 - 12:07
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Hello Rune,

with VRF lite you are not using MPLS frames: packets belonging to different VRFs travel on 802.1Q frames on trunks (back to back logical link for each VRF).

802.1Q frames have the usual 802.1p CoS so QoS should apply exactly as in single routing table case.

You should verify that voip traffic is marked with DSCP EF.

for video recommendation is to use AF41.

Another possibility could be to match on vlan-id (if supported):

a VRF-lite is mapped to specific Vlan-id.

But as I noted at the beginning you should be able to apply the usual QoS framework with marking in the edge (setting DSCP), trusting DSCP (or rewriting) to set internal DSCP.

mapping of internal DSCP to CoS (global)

mapping of CoS to port queues



Hope to help


runeaagesen Sun, 05/24/2009 - 07:28
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Hi, thanks to both of you.

Well, I have to admit I'm having some difficulties understanding this. Even if I have read the QoS doc from Cisco, it seem to be a bit tricky to configure.

You wouldn't know of any configuration examples that explain the different parts of QoS?

Joseph W. Doherty Mon, 05/25/2009 - 03:20
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". . . it seem to be a bit tricky to configure."

Yes, it can be; often tedious too. Have you considered Cisco's AutoQoS? (It would need to be modifed to best suit your requirements, but might be easier then building all QoS configurations from scratch.)

"You wouldn't know of any configuration examples that explain the different parts of QoS?"

There are snippets of QoS configurations scattered thoughout Cisco documentation but I'm unsure such would well explain "different parts of QoS".

It's probably best to well understand QoS conceptionally first, and then determine what the platform supports.

You might start with both QoS design quides and other additional information on QoS, e.g.:



Then perhaps the QoS chapter from your device's configuration guide, e.g.:



Learning QoS to the implementation level might take the same effort and time as learning routing to the implementation level. Basic concepts for both are simple, but both share "the devil is in the details".


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