QPPB in MPLS VPN

TL&DR: QPPB works in MPLS VPNs… with a few limitations (at least in Cisco IOS implementation).

And now for the long story: A while ago I’ve noticed that my LinkedIn friend Joe Cozzupoli changed his status to something like “trying to get QPPB to work in MPLS VPN environment”. I immediately got in touch with him and he was kind enough to send me working configurations; not just for the basic setup, but also for Inter-AS Option A, B and C labs.

Knowing that QPPB relies on CEF, I doubted it would work as well on VRF interfaces as it does in pure IP environments, so I decided to do a few tests of my own. Here are the limitations I found:

QPPB in MPLS/VPN: Limitations

The following limitations apply to QPPB used in MPLS VPN environment:

  • QPPB can be used to classify CEF-switched IP packets. It can thus be used on ingress traffic entering PE router through a PE-CE interface. Egress (PE-to-CE) MPLS VPN traffic is label-switched and thus not classified by QPPB.

  • QPPB can also be used on ingress interfaces of Inter-AS option-A links (autonomous systems linked with numerous VRFs), but not when option-B or option-C are used (these options use label switching between ASBR PE-routers).

  • QPPB was developed before MPLS VPN functionality and its route-map processing was never upgraded to support extended BGP communities. The match extcommunity statement cannot be used in the route-map specified in the table-map BGP router configuration command; you have to use standard BGP communities.

Configure QPPB in MPLS VPN environment

To configure QPPB in MPLS VPN environment, perform the following steps:

  1. Configure propagation of standard BGP communities between PE-routers in the VPNv4 address family.
  2. Mark target networks with BGP communities when inserting them in the VPNv4 BGP table on the egress PE-router.
  3. Configure a QPPB route-map that sets QoS groups based on BGP attributes on the ingress PE-router.
  4. Apply QPPB route-map to BGP routes in individual VRFs.
  5. Configure ingress QPPB on VRF interfaces.
  6. Configure MQC class maps and policy maps.
  7. Apply inbound MQC service policy to VRF interfaces.

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4 comments:

  1. stretch 04 March 2010 18:36
    "Quick link for the attention-challenged"

    I'll have you know, sir, that the politically-correct term for this disability is "differently attentive." In the future, please show more compassion for those of us who--ooh look, a kitty!
  2. Ivan Pepelnjak 04 March 2010 19:22
    ROFL :-D Thank you, you've made my day 8-)

    OTOH, you can't imagine how hard it is to properly address these difficult areas when English is not your native language O:-)
  3. JCC 11 May 2011 16:25
    Ivan, this is an old post, but, do you have any examples or just thoughts on MPLS Inter-AS Option C. Does it really saves all the operational work? Is it really used in practice?
  4. Ivan Pepelnjak 11 May 2011 20:59
    Inter-AS Option C is used in practice and is definitely a better option than (A). Whether you prefer (B) or (C) depends on what you want to ASBR routers to do and how much you trust the other AS.
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