🚀 go-pugleaf

Hi David,

As you probably know, TCP slow start is an algorithm used by workstations to
learn the bandwidth between the two endpoints of the communication.  Using
RED or other congestion control mecanism within a router will help you if
your router's output buffers are filling too fast, which I doubt would be
the case as it's 10 Mbps on each side of it and the weakest part of the link
is the cable modem....  If you use mainly your router to download stuff
rather than uploading, you are probably having a bandwidth of approx. 3 mbps
from your ISP, and he is the one buffering and doing the RED and whatever
other technique CBWFQ, etc. on it's CMTS router so there is not much you can
do on your router to help.  Your router is now overwhelmed so it would
forward outbound packets at line rate (which is probably the case unless you
flood it with UDP packets in which there is no embedded flow control) and
output buffers don't fill up.

If you wan't to do a quick test, just have your PC directly connected to the
cable modem and see how it behaves with regards to XWindows.  The X client
application will open up a connection to your PC on tcp port 600X, and your
PC will answer to this requets, having a router in between will not slow
things down as your upstream bandwidth is at most 600kbps - and you are
probably sending most often TCP ACKs for this session as well as small info
with regards to kb input and mouse mouvement.  Depending on what your ISP is
offering, which is a lot less than the router can handle, it's buffers will
most likely be almost empty.  You can see it's buffers using "sh int eth..."
and see what they look like in heavy traffic periods to see what it looks
like.  As long as the router's buffer are empty, no queueing mecanism will
do a big difference on the behavior of the traffic.

I hope this helps !

Olivier





"David Arnstein" <arnstein@panix.com> wrote in message
news:b3hppm$63d$1@reader1.panix.com...
> I've got a little Cisco 806 router between my Windows 2000 PC and my
> cable modem.   I think that I'm seeing bitrate oscillations during
> heavy traffic (X-windows in particular) and I suspect that this is due
> to TCP/IP "slow starts."
>
> How does one configure traffic shaping (or RED, or whatever) to
> minimize slow starts?  The config file entries are probably the same
> for all Cisco routers, so I can just type the entries into my router
> and see if they have any effect.
>
> Thanks for any suggestions.
> --
> David Arnstein
> arnstein+usenet@pobox.com