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The BGP Monitoring Protocol (BMP)

If you run connections to the ‘net at any scale, even if you are an “enterprise” (still a jinxed term, IMHO), you will quickly find it would be very useful to have a time series record of the changes in BGP at your edge. Even if you are an “enterprise,” knowing what changes have taken place in the routes your providers have advertised to you can make a big difference in tracking down an application performance issue, or knowing just when a particular service went off line. Getting this kind of information, however, can be difficult.

BGP is often overloaded for use in data center fabrics, as well (though I look forward to the day when the link state alternatives to this are available, so we can stop using BGP this way). Getting a time series view of BGP updates in a fabric is often crucial to understanding how the fabric converges, and how routing convergence events correlate to application issues.

One solution is to set up the BGP Monitoring Protocol (BMP—an abbreviation within an abbreviation, in the finest engineering tradition).

BMP is described in RFC7854 as a protocol intended to “provide a convenient interface for obtaining route views.” How is BMP different from setting up an open source BGP process and peering with all of your edge speakers? If you peer using eBGP, you will not see parroted updates unless you look for them; if you peer using iBGP, you might not receive all the updates (depending on how things are configured). However you peer, you will not get a “time series” view of the updates along your edge that can be correlated with other events in your network. Any time you peer using BGP, you are receiving routes after bestpath.

When you pull a BMP feed, in contrast, you are getting the BGP updates as the speaker sees them—before bestpath, before inbound filters, etc. This means you receive a full feed just as the edge speaker receives it. This is all provided in a format that is easily pushed into a database and correlated through timestamps—a huge wealth of information that can be quite useful not only to monitor the health of your network edge, but for troubleshooting. BMP includes messaging for:

  • An initial dump of the current BGP table, called route monitoring
  • Peer down notification, including a code indicating why the peer went down
  • Stat reports, including number of prefixes rejected by inbound policy, number of duplicate prefixes, number of duplicate withdraws, etc.
  • Peer up notification
  • Route mirroring, in which the speaker sends copies of updates it is receiving

To set BMP up, you need to start with a BGP speaker that supports sending a BMP feed. Juniper supports BMP, as does Cisco. The second thing you will need is a BMP collector, a handy open source version of which is available at openbmp.org.

You will note that the openbmp collector has interfaces to a RESTful database interface, as well as a KAFKA producer. One of these two interfaces should allow you to tie BMP into your existing network management system, or set up a new database to collect the information.

BMP is becoming a bit of an ecosystem in its own right; the GROW working group has already a draft to extend BMP to report on the local routing table, which would allow you to see what is received by BGP but not installed. Another draft accepted by the GROW WG extends BMP to support the adj-rib-out, which would allow you to see the difference between what a BGP speaker receives and what it sends to its peers.

Several other drafts have been proposed but not accepted by GROW, including adding a namespace for the BGP peer up event, and using BMP as part of a BGP based traffic engineering system.

Hopefully, at some point in the future, I’ll be able to follow this post up with a small lab showing what BMP looks like in operation. For now, though, you should definitely try setting BMP up in your network if you have any sort of ‘net edge scale, or a data center using BGP as its IGP.

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