[Iccrg] Re: [tcpm] I-D Action:draft-hkchu-tcpm-initcwnd-00.txt

[Jerry Chu]

On Tue, Mar 9, 2010 at 7:35 PM, rick jones <perfgeek at mac.com> wrote:
>
> On Mar 9, 2010, at 11:25 AM, Jerry Chu wrote:
>>
>> I don't know about you, but imagine a simple change that can deliver a 10%
>> improvement
>> (in average) over ALL web traffic regardless of the response sizes (some
>> are much less than
>> 10 segments), access speed,..., etc. That is A LOT to me!
>
> Indeed, 10% average improvement is impressive.
>
> Is there a way to tease-out what the "typical" cwnd becomes in both the base
> and exp cases?  Say from those services with larger responses? Does it
> become 8*MSS?  12*MSS etc?  That would help show how "close to the edge" 10
> segments might be yes?

Yes it's certainly doable but one problem with most of the services is
that there are
fewer larger responses, interleaved with many smaller responses, and the vast
majority of HTTP connections don't persist long enough to allow cwnd/ssthresh to
converge in a more meaningful way.

In order to perform a more detailed analysis on some network properties, we are
thinking about instrumenting a bulk data service like Youtube to avoid the above
mentioned problem, as described in section 11.2 of the I-D. The idea
is to monitor
some key TCP parameters at various stage of a connection (and Linux kernel
already conveniently provide "TCP_INFO" socket option). But before we proceed
we like to first hear suggestions from the lists. This is because any
large scale
experiment can be very time/resource consuming. In this case we'll likely have
to set up a different logging system for Youtube, may even have to
build and deploy
a different kernel with the right instrumentation (TCP_INFO may not provide all
the info we'll need) to many thousand machines..., etc.

>
> WRT the retransmissions (table 7 in the paper), is it safe to ass-u-me that
> the increase in retransmissions means a corresponding increase in "Internet"
> bandwidth consumed to deliver the given quantity of data?

I don't see why not. (Am I missing something?)

Thanks,

Jerry

>
> rick jones
> there is no rest for the wicked, yet the virtuous have no pillows
> wisdom teeth are impacted, people and things are affected by the effects of
> events :)
>