Re: [Bloat] Bufferbloat Paper

[Mark Allman <mallman@icir.org>]

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Let me make a few general comments here ...

(0) The goal is to bring *some* *data* to the conversation.  To
    understand the size and scope of bufferbloat problem it seems to me
    we need data.

(1) My goal is to make some observations of the queuing (/delay
    variation) in the non-FTTH portion of the network path.  As folks
    have pointed out, its unlikely bufferbloat is much of a problem in
    the 1Gbps portion of the network I monitor.

(2) The network I am monitoring looks like this ...

       LEH -> IHR -> SW -> Internet -> REH

    where, "LEH" is the local end host and "IHR" is the in-home router
    provided by the FTTH project.  The connection between the LEH and
    the IHR can either be wired (at up to 1Gbps) or wireless (at much
    less than 1Gbps, but I forget the actual wireless technology used on
    the IHR).  The IHRs are all run into a switch (SW) at 1Gbps.  The
    switch connects to the Internet via a 1Gbps link (so, this is a
    theoretical bottleneck right here ...).  The "REH" is the remote end
    host.  We monitor via mirroring on SW.

    The delay we measure is from SW to REH and back.  So, the fact that
    this is a 1Gbps environment for local users is really not material.
    The REHs are whatever the local users decide to talk to.  I have no
    idea what the edge bandwidth on the remote side is, but I presume it
    is general not a Gbps (especially for the residential set).

    So, if you wrote off the paper after the sentence that noted the
    data was collected within an FTTH project, I'd invite you to read
    further.

(3) This data is not ideal.  Ideally I'd like to directly measure queues
    in a bazillion places.  That'd be fabulous.  But, I am working with
    what I have.  I have traces that offer windows into the actual queue
    occupancy when the local users I monitor engage particular remote
    endpoints.  Is this representative of the delays I'd find when the
    local users are not engaging the remote end system?  I have no
    idea.  I'd certainly like to know.  But, the data doesn't tell me.
    I am reporting what I have.  It is something.  And, it is more than
    I have seen reported anywhere else.  Folks should go collect more
    data.

    (And, note, this is not a knock on the folks---some of them my
    colleagues---who have quite soundly assessed potential queue sizes
    by trying to jam as much into the queue as possible and measuring
    the worst case delays.  That is well and good.  It establishes a
    bound and that there is the potential for problems.  But, it does
    not speak to what queue occupancy actually looks like.  This latter
    is what I am after.)

allman




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