As I'm attempting to lay out in my posts, there are are a plethora of
problems, end-to-end in the network. Would that there was only one problem.
Excessive, unmanaged buffers afflict the user's OS's (Windows, Mac and
Linux alike), particularly on recent hardware. Home routers and the
broadband connections (as shown by netalyzr) all have problems.
The bottleneck may be anywhere in the path; with the (sometimes)
exception of Windows XP, all edge equipment now routinely congests the
edge.
Multiple seconds of latencies, in both directions, are dismaying
commonplace.
Retail operators have had a hidden major support problem: how many of
the "bad service" calls have been due to the problem? It tends to be
transient in behavior, and I've chased the problem personally at least 5
times in the last 3 years. I've placed service calls I now believe
likely due to bufferbloat. I've caught problems with crash dumps being
uploaded to the net; backup and downloads can all cause trouble.
Courtesy of the Netalyzr team, I've been able to post color versions of
their results on
http://gettys.wordpress.com/2010/12/06/whose-house-is-of-glasse-must-not-throw-stones-at-another/;
they first reported results at the NANOG meeting last summer.
Disentangling broadband data from home router and operating system
bufferbloat is difficult; I've found bufferbloat is present in all of
them. The power of two bufferbloat sizes are almost certainly all
broadband gear (since the OS buffer sizes are quantised in packets, not
bytes).
In the downstream direction, one of the possible causes is be failure to
run any AQM in the broadband head-ends; this is certainly also the case
in home routers.
Also, as outlined in: Characterizing Residential Broadband Networks
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.65.6825&rep=rep1&type=pdf
we have good reason to believe this is taking place.
Since I became aware that bufferbloat might have become a generic
problem last summer from anecdotal data and personal experiments, I've
probed networks wherever I've travelled. Some of what I've seen was
clearly broadband bufferbloat; but more disturbingly, I've also seen
other evidence further into several of the networks I've probed (from
hotels *not* using broadband for their service), further confirming the
initial anecdotal data I was given that queue management is far from
universal (and essentially unheard of in the home).
If the idea that the buffers have destroyed congestion avoidance doesn't
scare you, I don't know what will.
It's a major problem.
Best Regards,
- Jim Gettys
