[Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps?

[Jim Gettys]

I've been watching all the discussion of different TCP flavours with a 
certain amount of disquiet; this is not because I think working on 
improvements to TCP are bad; in fact, it is clear for wireless we could 
do with improvements in algorithms.  I'm not trying to discourage work 
on this topic.

My disquiet is otherwise; it is:
     0) the buffers can be filled by any traffic, not necessarily your 
own (in fact, often that of others), so improving your behaviour, while 
admirable, doesn't mean you or others sharing any piece of your won't 
suffer.
     1) the bloated buffers are already all over, and updating hosts is 
often a very slow process.
     2) suffering from this bloat is due to the lack of signalling 
congestion to congestion avoiding protocols.

OK, what does this mean?  it means not that we should abandon improving 
TCP; but that doing so won't fundamentally eliminate bufferbloat 
suffering.  It won't get us to a fundamentally different place, but only 
to marginally better places in terms of bufferbloating.

The fundamental question, therefore, is how we start marking traffic 
during periods when the buffers fill (either by packet drop or by ECN), 
to provide the missing feedback in congestion avoiding protocol's servo 
system. No matter what flavour of protocol involved, they will then back 
off.

Back last summer, to my surprise, when I asked Van Jacobson about my 
traces, he said all the required proof was already present in my traces, 
since modern Linux (and I presume other) operating systems had time 
stamps in them (the TCP timestamps option).

Here's the off the wall idea.  The buffers we observe are often many 
times (orders of magnitude) larger than any rational RTT.

So the question I have is whether there is some technique whereby 
monitoring the timestamps that may already be present in the traffic 
(and knowing what "sane" RTT's are) that we can start marking traffic in 
time prevent the worst effects of bloating buffers?
             - Jim