Re: [Bloat] [tsvwg] how much of a problem is buffer bloat today?

[Oliver Hohlfeld <oliver@net.t-labs.tu-berlin.de>]

On 03/13/2013 03:23 PM, Eliot Lear wrote:
> I don't have an answer to that question, but Mark Allman from ICIR did
> attempt to characterize buffer bloat on the Internet through an
> empirical study that appeared in the January edition of CCR.  You can
> find a reference to that paper at the following URL:
> 
> http://www.sigcomm.org/ccr/papers/2013/January/2427036.2427041

The full extend of the answer is still unclear to me. We have recently
attempt to complement the rather technical and QoS centric view on the
buffer bloat problem by estimating the user experience impact:

BufferBloat: How Relevant? A QoE Perspective on Buffer Sizing.
Oliver Hohlfeld, Enric Pujol, Florin Ciucu, Anja Feldmann, Paul Barford
http://downloads.ohohlfeld.com/paper/bufferbloat-qoe-tr.pdf

The paper studies the impact of buffer sizes on VoIP, IPTV, and web
browsing Quality of Experience (QoE). We find that:

- oversized buffers indeed degrade QoE when they are sustainable filled.
- however, large buffers do not always degrade user experience.
- the level of congestion significantly degrades QoE, oftentimes more
  than buffer sizes.

One example discussed in the paper is web browsing. When the level of
congestion is low, HTTP transactions benefit from "large" buffers as
they reduce losses by absorbing transient bursts. When the level of
congestion is high, transfer times become RTT dominated and the queuing
delays start to kick in.

Note that objective QoE metrics used in our paper also do not provide
the full picture:
(i) objective QoE metrics and subjective user experience are not
    always correlated.
(ii) the influence memory effects is still unclear (e.g., for how
     long will a user be influenced by a single degradation and how
     does it alter his behavior?). Psychological insights are only
     available for short-time scales.
(ii) even if service degradations exist that would degrade the user
     experience, the user might not always notice them.

In summary, the question on how much of a problem buffer bloat currently
is cannot be fully answered and still requires further research.

Oliver