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<div class="moz-cite-prefix">On 28-03-2013 17:31, Daniel Havey
wrote:<br>
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<blockquote
cite="mid:1364502699.15279.YahooMailClassic@web163001.mail.bf1.yahoo.com"
type="cite">
<pre wrap="">Having just finished my proposal and regained the ability to think about stuff, I'm going to agree with Oliver.
I have no studies and I have no evidence. However, I have a nice analysis ;^) The ISP's edge router has a rate limiter because they want to sell us bandwidth. However, they also don't want to drop those packets because they already did all the work of getting them to the edge router.
This is a very likely place for bloat.</pre>
</blockquote>
<br>
I don't know ... if the "excessive" packets are part of a long
living flow (large file xfer, voice conference, etc...) the ISP
would rather drop a few packets early, and doing so signal the
source that it must packet rate, than allow a big buffer to grow and
mess up all flows. <br>
<br>
<blockquote
cite="mid:1364502699.15279.YahooMailClassic@web163001.mail.bf1.yahoo.com"
type="cite">
<pre wrap="">
Hmmmm, actually I do have a study:
End-to-end Detection of ISP Traffic Shaping using Active and Passive Methods, Partha Kanuparthy and Constantine Dovrolis
This is a large study with lots and lots of users all over the place. Check the paper for details, but, it indicates that token buckets are prevalent. If this is true, it is easy to imagine that the ISP's are configuring the queues on their edge routers so that they don't drop packets easily.
...Daniel
--- On Thu, 3/28/13, Oliver Hohlfeld <a class="moz-txt-link-rfc2396E" href="mailto:oliver@net.t-labs.tu-berlin.de"><oliver@net.t-labs.tu-berlin.de></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">From: Oliver Hohlfeld <a class="moz-txt-link-rfc2396E" href="mailto:oliver@net.t-labs.tu-berlin.de"><oliver@net.t-labs.tu-berlin.de></a>
Subject: Re: [e2e] Do we have buffer bloat on edge routers or on core routers?
To: <a class="moz-txt-link-abbreviated" href="mailto:end2end-interest@postel.org">end2end-interest@postel.org</a>
Date: Thursday, March 28, 2013, 11:38 AM
Hi,
</pre>
<blockquote type="cite">
<pre wrap="">Perhaps my question is a stupid one, however, can
</pre>
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<pre wrap="">someone help me here?
While there is a lack of evidence, I tend to believe the
answer
is no for most networks.
Let me briefly elaborate on this issue. It is hard to
provide a
definite answer due to the multitude of possible devices
and
configurations. I tried conducting a survey of typical
hardware
combinations and talk to more operators, but had to give up
at some
point.
Signs of buffer bloat:
- I remember having read reports of queuing delays of up to
one second in the Level 3 network. Unfortunately, I
can't
find the reference any more.
Contra buffer bloat:
- By working with a tier-1 network, I never found evidence
for potential
buffer bloat in their core and aggregation network
(might be
different for other networks). The aggregation
network has been put
under load and none of the devices showed excessive
queuing. In
fact, queuing delays were minimal.
In the core, the buffers are "reasonably" sized and
don't allow for
excessive queuing.
- Typical buffer sizes are around 100ms. Juniper "M-Series"
routers
are at 200ms.
- While it is theoretically possible to have bloated buffers
in the
core, affording excessive buffering is getting more
expensive /
infeasible with increasing line card speed (e.g.,
100GE).
- The switching infrastructure in the aggregation network
is
typically not equipped with a lot of buffer space.
In conclusion, from what I have seen so far, I believe that
buffer
bloat is mostly a problem at the edge.
Oliver
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<pre wrap="">
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