Re: [Bloat] Questions for Bufferbloat Wikipedia article

[Dave Collier-Brown <davecb.42@gmail.com>]

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To speak to the original question, I'd say bufferbloat

  * is undesirable latency
  * was discovered when adding buffers counter-intuitively /slowed
    /packet flow.

That's so as to catch the reader's attention and immediately cast light 
on the (memorable but mysterious) name.

--dave


On 2021-04-05 11:24 a.m., David Lang wrote:
> On Mon, 5 Apr 2021, Stephen Hemminger wrote:
>
>> On Mon, 5 Apr 2021 08:46:15 -0400
>> Rich Brown <richb.hanover@gmail.com> wrote:
>>
>>> Dave Täht has put me up to revising the current Bufferbloat article 
>>> on Wikipedia (https://en.wikipedia.org/wiki/Bufferbloat)
>>>
>>> Before I get into it, I want to ask real experts for some 
>>> guidance... Here goes:
>>>
>>> 1) What is *our* definition of Bufferbloat? (We invented the term, 
>>> so I think we get to define it.)
>>> a) Are we content with the definition from the bufferbloat.net site, 
>>> "Bufferbloat is the undesirable latency that comes from a router or 
>>> other network equipment buffering too much data." (This suggests 
>>> bufferbloat is latency, and could be measured in seconds/msec.)
>>>
>>> b) Or should we use something like Jim Gettys' definition from the 
>>> Dark Buffers article (https://ieeexplore.ieee.org/document/5755608), 
>>> "Bufferbloat is the existence of excessively large (bloated) buffers 
>>> in systems, particularly network communication systems." (This 
>>> suggests bufferbloat is an unfortunate state of nature, measured in 
>>> units of "unhappiness" :-)
>>> c) Or some other definition?
>>>
>>> 2) All network equipment can be bloated. I have seen (but not really 
>>> followed) controversy regarding the amount of buffering needed in 
>>> the Data Center. Is it worth having the Wikipedia article 
>>> distinguish between Data Center equipment and CPE/home/last mile 
>>> equipment? Similarly, is the "bloat condition" and its mitigation 
>>> qualitatively different between those applications? Finally, do any 
>>> of us know how frequently data centers/backbone ISPs experience 
>>> buffer-induced latencies? What's the magnitude of the impact?
>>>
>>> 3) The Wikipedia article mentions guidance that network gear should 
>>> accommodate buffering 250 msec of traffic(!) Is this a real "rule of 
>>> thumb" or just an often-repeated but unscientific suggestion? Can 
>>> someone give pointers to best practices?
>>>
>>> 4) Meta question: Can anyone offer any advice on making a wholesale 
>>> change to a Wikipedia article? Before I offer a fork-lift 
>>> replacement I would a) solicit advice on the new text from this 
>>> list, and b) try to make contact with some of the reviewers and 
>>> editors who've been maintaining the page to establish some bona 
>>> fides and rapport...
>>>
>>> Many thanks!
>>>
>>> Rich
>>
>> I like to think of Bufferbloat as a combination of large buffers and 
>> how algorithms react to those buffers.
>
> I think there are two things
>
> 1. what bufferbloat is
>
>    bufferbloat is the result of memory getting cheaper faster than 
> bandwidth increased, combined with throughput benchmarking that 
> drastically penalized end-to-end retries.
>
> I think this definition is pretty academic and not something to worry 
> about using.
>
> 2. why it's a problem
>
> the problems show up when the buffer represents too much time worth of 
> data to transmit (the time between when the last byte in the buffer 
> gets inserted into the buffer and when it gets transmitted)
>
> So in a high bandwidth environment (like a datacenter) you can use 
> much larger buffers than when you are on a low bandwidth line
>
> David Lang
>
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-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
dave.collier-brown@indexexchange.com |              -- Mark Twain


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