Linux router (don't laugh) WAS:Re: test

Jim Shankland jas at flyingfox.com
Wed Oct 28 18:06:43 UTC 1998


Znyx (www.znyx.com) and Adaptec both make quad cards based on
the DEC Tulip chip.  I think Intel has a dual 82558 card.  Expect
to pay a substantial premium over the per-interface cost of single
cards.  You have to weigh that against the convenience/efficiency/etc.
of getting all those ports into one box.

Can't say whether these will work with Linux.  I use FreeBSD.  I have
one box (a Pentium 133, if I recall correctly) with 14 Ethernet interfaces:
3 quad cards, 1 single, and an ISA NE-2000 clone on a particularly
lightly used network.  Works fine.

The limiting factor ends up being PCI bus bandwidth.  You'll be hard
pressed to squeeze more than 100-150 Mb/s of total throughput out
of the router, since every bit takes two trips across the PCI bus:
from the device to main memory, and back.  If you can figure out
how to diddle IP headers while the packet is in the card's buffers,
and then do a card-to-card PCI transfer (i.e., without going to main
memory), you can probably do a bit better.  I haven't tried this,
so consider it a hypothesis.

Jim Shankland
Flying Fox Computer Systems, Inc.



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