Need help with QoS configuration

[elizabethf]

Hi, my teacher gave me the task to create a MPLS VPN network. I have successfully done everything he asked for, except for the QoS configuration. Since I'm a beginner I'm not familiar with QoS whatsoever. I have been trying to figure out how to do it for the past couple of days but I can't seem to figure it out so I'd be very glad if someone here could help me out. I'm supposed to configure QoS on both PE and CE routers. The QoS needs to have 3 classes - Real Time, Default and Data. I need to make it so that the CE router switches the DSCP values to EXP values for the PE router, and the other way around for PE - it needs to switch from EXP values to DSCP for the CE router. The topology is as shown below. Any instructions will be appreciated. Thanks in advance! 

[MHM Cisco World]

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[elizabethf]

What? 

[Joseph W. Doherty]

"Since I'm a beginner I'm not familiar with QoS whatsoever."

Your a beginner working a task with MPLS VPN, CE, PE, P routers, RR routers?  While working with the forgoing, you've not familiar with QoS, at all?

What kind of course is this?  What level, college, industry, other?

With regard to your questions, although I have some experience with QoS, it doesn't extend to using QoS with MPLS, although I have a very light knowledge of it, such as I know the EXP bits are often used for QoS purposes.  I also recall (?) conversion from IP ToS to MPLS EXP is relatively simple, although you lose ToS granularity (6 bits to 3 bits).  I also recall, original ToS is preserved, so unless you need to change MPLS EXP within the MPLS cloud, and update ToS upon MPLS cloud egress, I believe you shouldn't need to concern yourself with converting EXP back to ToS (which cannot be done, fully, i.e. 3 bit to 6 bits).

You describe a requirement to have 3 classes, RT, data and default.  What kinds of traffic map into RT and data?  What are your treatment requirements for these 3 classes?

Since your note you're just a beginner and totally unaware of QoS, this presentation might help.

A task of this sort, might also find some help in the Service Providers Forums, where working with MPLS topologies, is more common.

[mlund]

I found this sentence " I need to make it so that the CE router switches the DSCP values to EXP values for the PE router" difficult to understand. Because the CE does not use labels, where EXP is used. The CE use DSCP and when packet arrives to PE, the PE will copy the DSCP:s first 3 bits (TOS bits) and use them in the EXP bit in the label/labels. This happens by default in cisco routers, without any need to configure it. The other way around is that when PE receives the packet from P router, it removes the labels and forward the packet to CE with DSCP unchanged. This is also default, and called PIPE mode. This behavior can be changed, so if EXP bits have been changed in transit this change can be reflected down to DSCP bits before transfer the packet. This is called HALF PIPE mode.