episode-69.xml

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  <title>User-Configurable Protocol Support for OVS, or Why Doesn't OVS Support P4?</title>
  <description>
    <p>
      There are several challenges toward making it easy for users to add
      support for new protocols in OVS or, equivalently, adding P4 support to
      OVS.  This talk, given at the Dagstuhl seminar on programmable data
      planes in April 2019, explains the reasons that OVS doesn't already have
      these features, what's changing, and likely future directions.  The talk
      includes considerable discussion with the audience.
    </p>

    <p>
      An early statement summarizes the message of the talk:
    </p>

    <blockquote>
      ...I think that it's too hard to add support for new protocols and I
      think users should be able to do that fairly easily.  Currently, it's
      really hard--it's hard for me in some cases, and if it's hard for me then
      I'm sure it's hard for everyone else.
    </blockquote>

    <p>
      A little later, this quote covers Ben's philosophy on P4:
    </p>

    <blockquote>
      Why I like P4 is because of my own personal experience with OpenFlow.  At
      Nicira when we started out designing OpenFlow, we designed it for very
      much a fixed match over basically IPv4 and related fields.  We knew from
      day 1 that that wasn't good enough, I mean, not to mention existing
      protocols like IPv6 that we couldn't handle, but it seemed pretty obvious
      that people would want to add their own.  Over a couple of years, in my
      spare time I started tinkering with ideas for how to write a language for
      specifying what protocols a switch supports. It seemed like there were
      two possibilities that kept coming up, and yet neither one of them seemed
      very good.  One was basically based on fixed offsets; people kept
      suggesting this, I think maybe even Nick McKeown suggested this at one
      point.  I kept pointing out that fixed offsets are not going to work very
      well because offsets change from one packet to another.  The other end of
      the spectrum was somebody just provides a program in some general-purpose
      language that extracts the headers that you want, and that also seems
      pretty unsatisfying because it's really hard to take a general-purpose
      program and look at it in terms of some of its emergent properties.  You
      can't do much with it other than run it.  I tried to come up with some
      languages that fit in between and then when I first saw one of the drafts
      of the P4 specification, I looked at it and said, &quot;I wish I'd written
      this.&quot;  It seems to me that it strikes a really good balance there.
    </blockquote>

    <p>
      The remainder of the talk covers the possible directions forward for OVS
      and flexible protocol support, including eBPF and AF_XDP.
    </p>

    <p class="attribution">
      OVS Orbit is produced by <a href="mailto:blp@ovn.org">Ben Pfaff</a>.  The
      intro music in this episode is <a href="http://dig.ccmixter.org/files/AlexBeroza/43098">Drive</a>,
      featuring cdk and DarrylJ, copyright 2013, 2016 by Alex.  The bumper
      music is <a href="http://dig.ccmixter.org/files/speck/42100">Yeah Ant</a>
      featuring Wired Ant and Javolenus, copyright 2013 by Speck.  The outro
      music is <a href="http://dig.ccmixter.org/files/Kirkoid/43005">Space
      Bazooka</a> featuring Doxen Zsigmond, copyright 2013 by Kirkoid.  All
      content is licensed under a Creative Commons <a href="http://creativecommons.org/licenses/by/3.0/">Attribution 3.0
      Unported (CC BY 3.0)</a> license.
    </p>
  </description>
  <pubDate>Mon, 03 Jun 2019 12:00:00 GMT</pubDate>
</item>