[45807] in North American Network Operators' Group
Re: Cisco PPP DS-3 limitations - 42.9Mbpbs?
daemon@ATHENA.MIT.EDU (Iljitsch van Beijnum)
Wed Feb 20 16:28:16 2002
Date: Wed, 20 Feb 2002 22:28:22 +0100 (CET)
From: Iljitsch van Beijnum <iljitsch@muada.com>
To: Jon Mansey <jon@interpacket.net>
Cc: <nanog@merit.edu>
In-Reply-To: <BFB8DD49-2641-11D6-9FCA-003065477C74@interpacket.net>
Message-ID: <20020220215726.R64519-100000@sequoia.muada.com>
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Errors-To: owner-nanog-outgoing@merit.edu
On Wed, 20 Feb 2002, Jon Mansey wrote:
> OMG! Arent we missing the point here? What about never running links above
> 60% or so to allow for bursts against the 5 min average, and <shudder>
> upgrading or adding capacity when we get too little headroom.
> And here we are, nickel and diming over a few MBps near to 45M on a DS3...
And why not? Obviously there is a reason why they're not upgrading,
because there is plenty of traffic to fill up a second or faster circuit
if packets are being dropped because of congestion. (Which has not been
confirmed so far.)
There shouldn't be any problems pushing a DS3 well beyond 99% utilization,
by the way. With an average packet size of 500 bytes and 98 packets in the
output queue on average, 99% only introduces a 9 ms delay. The extra RTT
will also slow TCP down, but not in such a brutal way as significant
numbers of lost packets will. Just use a queue size of 500 or so, and
enable (W)RED to throttle back TCP when there are large bursts.
