episode-46.xml

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  <title>In-band Network Telemetry</title>
  <guests>Chang Kim from Barefoot Networks</guests>
  <description>
    <p>
      Chang Kim is an engineer at <a
      href="https://barefootnetworks.com/">Barefoot Networks</a>, where he has
      been intimately involved in the design of the <a
      href="https://p4.org">P4</a> domain-specific language for controlling a
      network data plane.
    </p>

    <p>
      Whereas the control and management planes in a network system are
      general-purpose software implemented on CPUs, the data plane in a
      high-speed network is typically implemented in an ASIC dedicated to
      packet forwarding.  State-of-the-art switching ASICs can handle multiple
      Tbps (and Gpps).  Until recently, these ASICs were designed as
      fixed-function devices: they implemented the specific protocols they
      supported in a hardware description language such as Verilog.  Now,
      trends in hardware design have converged to make it possible to build
      much more general-purpose networking ASICs.  When this happens, some
      language is needed for programming the ASICs.  P4 is the leading
      candidate for a cross-platform language for this purpose.
    </p>

    <p>
      This episode focuses not on P4 itself but on In-Band Network Telemetry
      (INT), one application of P4.  INT is, according to Chang, a
      ``low-hanging fruit'' application of programmable network data planes,
      which can be conveniently implemented in P4.  INT embeds information
      about the conditions experienced by a particular packet traveling through
      the network into the packets themselves.  As a packet travels through the
      network, each intermediate switch collects relevant information, such as
      queuing information, arrival or departure timestamps, etc. and adds it to
      the packet.  When the packet leaves the network at a sink switch, it
      takes the accumulated information and, optionally, passes it along to a
      collector.  (Most applications will not pass every packet's information
      to a switch because that effectively doubles the amount of traffic in the
      network.)
    </p>

    <p>
      INT can offer real-time network monitoring information to administrators.
      Its reports can also be archived to set a baseline or for long-term
      storage.
    </p>

    <p>
      INT metadata can be integrated into a packet in a variety of ways.  The
      per-packet metadata is typically 16 to 20 bytes per hop, which is a
      significant amount of data that cannot easily be fit into existing
      fixed-size fields such as DSCP or PCP.  Geneve or NSH options are two
      reasonable places, and the metadata can also be inserted in nonstandard
      places (such as just after an L4 header) as long as the sink switch is
      configured to strip them before passing them along to an end host.
    </p>

    <p>
      To encourage industry-wide implementation of interoperable versions of
      INT, Barefoot has made available a <a
      href="http://p4.org/wp-content/uploads/fixed/INT/INT-current-spec.pdf">specification</a>,
      which includes a working implementation in P4, and released it to the P4
      consortium.  The specification will continue to be developed and
      maintained by the <a
      href="https://p4.org/members/announcing-the-p4-applications-working-group/">new
      P4 Applications Working Group</a>.  IETF also has a new <a
      href="https://datatracker.ietf.org/wg/ioam/about/">In-Situ OAM (ioam)</a>
      working group with related goals.
    </p>

    <p>
      To get involved with P4, including the new P4 Applications Working Group,
      please visit <a href="https://p4.org/">p4.org</a>.
    </p>

    <p>
      For more OVS Orbit discussion of P4, please see <a href="#e11">Episode
      11: P4 on the Edge</a> and <a href="#e9">Episode 9: Adding P4 to OVS with
      PISCES</a>.
    </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>Thu, 16 Nov 2017 04:43:46 GMT</pubDate>
</item>