> - memory copies. As I understand it, to switch a packet through a Linux
> router, there are at least 2 memory copies....the packet is received and
> stored in the nic buffer...from there it's copied into main memory...I'm
> assuming the Linux kernel is very efficient and doesn't do any copies of
> its own...from there its copied into the outgoing nic's packet buffer.
Most NIC's have only FIFO's . Main memory is their ram buffer. One card DMA's
it in, the other DMA's it back out when using the fastroute aware tulip
driver.
> Cisco hardware...being designed with IOS in mind, allows IOS to do zero
> memory copies....the packet is read from the incoming nic's packet
> buffer directly out the outgoing nic.
Benchmarks for the low end ciscos say either they dont or it doesnt matter
cos we kick them on IP 8)
> - extensive switching support. To my understanding, you can't have a
> linux box with 4 ethernet cards and bridge between eth0 and eth1, and
> then bridge between eth2, and eth3, and then route between the eth0/1
> combo and the eth2/3 combo. IOS handles that with no problem. Other
Correct. We don't support fancy switching. Linux is a router it doesnt really
have any pretense at switching. Measure the latency on a really good cut
through switch (like the big 3com ones) and you'll see why. For pure switching
the fancy dedicated hardware stuff beats us flat on latency and I guess always
will.
> speeds...I'm going with Cisco for reliability reasons (yes, I know, the
> LRP doesn't even need a hard drive...boots off a floppy, but I've found
Or flash. Which is nicer still.
Alan
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