[6535] in North American Network Operators' Group
Re: NAP/ISP Saturation WAS: Re: Exchanges that matter...
daemon@ATHENA.MIT.EDU (alex@relcom.EU.net)
Wed Dec 18 05:07:06 1996
Date: Wed, 18 Dec 96 12:45:45 +0300
To: avg@pluris.com, cnordin@vni.net
Cc: doleary@cisco.com, nanog@merit.edu
From: alex@relcom.EU.net
As for me, congestion exists if long TCP sessions can't adapt their
window sizes and packet drop if more than 3 - 5 % over connection line.
This means more than 1,000 - 2,000 tcp sessions through 2 Mbit link, for
example. Yes, IP is connectionless protocol, but Internet is not connectioonless
network in real life...
> Craig Nordin <cnordin@vni.net> wrote:
>
> >> Er. There's no such thing as perfect transport as long as TCP is
> >> concerned. If end-hosts support large windows, even a single
> >> TCP session will load the network to the point where it'll lose
> >> packets.
>
> >What you say here makes sense to me. But, out of a 500
> >ping sample over the course of half a day, I was getting well
> >below one percent loss -- six months ago.
>
> Most TCP sessins are pretty short, in fact. They simply have
> no chance to open window. Also, there's a lot of old TCP
> implementations which have window limited to 64Kb (or less!).
>
> >Now, my same sample group is going for more than three percent,
> >with many ten percent loss routes showing...
>
> Well, nobody argues that Internet is overloaded. But the question
> of how to measure the congestion is not as simple as just pinging.
>
> The problem is that there's no reasonable way to learn loss
> statistics from routers.
>
> --vadim
>
---
Aleksei Roudnev, Network Operations Center, Relcom, Moscow
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