Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
New Member

QoS Capabilities in MPLS – 2


Based on paper titled "L3 MPLS VPN Enterprise Consumer Guide" page 16 ( My SP has only 3 CoS for its VPN service. I have classified up to 10 different classes on my sites using a BW Manager device. I need to carry my CoS (based on DSCP or other way) through the MPLS VPN transparently.

1) Is it possible to map my CoS values to the CoS values used by the SP so that they can be mapped back to my network at the opposite end of the VPN?

2) If yes, How? Who would it be responsible to do that? Please explain.


Re: QoS Capabilities in MPLS – 2

It is possible, but it requires that the provider does customised re-marking on egress. I don't think too many providers will do that.

A better alternative is to configure an ingress service-policy on your CE devices that re-marks the packets to your desired scheme based on whatever classification method you used to mark them in the first place.

Hope that helps - pls rate the post if it does.


New Member

Re: QoS Capabilities in MPLS – 2

Hi Paresh:

Assuming that my SP re-marks the DSCP bits on egress. Then my BW Manager receives "untrusted" DSCP markings from the SP at the opposite site. So I must reclassify all the traffic (with the ingress service-policy you mentioned) again to recover my 10 COSes. That means double work for each site (output and input policies). Is that correct?


Re: QoS Capabilities in MPLS – 2

From my experience, no SP remarks customer DSCP in MPLS-VPN. Most of them ensure diffserv transperancy as they mark their EXP based on your DSCP. But yes if the SP does remark ur DSCP, it surely is more work as you or ur SP will have to rewrite


Re: QoS Capabilities in MPLS – 2

Hi Mate,

As I indicated earlier, I don't know of any providers who tinker with the customer's DSCP bits on egress. However, that is not your question, is it ? You are asking what happens if it does (hypothetical case, I presume).

In that case, I stand by what I said earlier. You would have to re-classify on ingres at the other end, meaning double-work. But in such a case, there is no other workaround, is there ?

Hope that helps - pls do rate the posts if it does.


Re: QoS Capabilities in MPLS – 2


As a MPLS SP I would not like to deal with customer DSCP values in any place in my PE routers except the input interface from a pure operational point of view.

So SPs offering QoS will either remark on ingress OR transparently transport DSCP values of the customer across the MPLS domain. For transparent DSCP transport MPLS exp bits are set along with the SP policy and service purchased on the ingress interface. The trick on the egress interface, where a pure IP packet needs to be handled, is to map incoming MPLS exp (in the VPN label) to a qos group and use the qos group in the egress class-map for traffic classification. This way a SP does not need to mess with customer DSCP values.

But this is technology ... your specific SP product and technical implementation might differ, f.e. because he has other vendor PEs not able to offer those features.

Hope this helps! Please rate all posts.

Regards, Martin

CreatePlease to create content