ethernet and switches, was Re: [rescue] Mozilla Firefox

Nathan Raymond nate at
Fri Apr 23 11:22:20 CDT 2004

On Fri, 23 Apr 2004, Joshua Boyd wrote:

> I wonder how much inappropriate legacy stuff is really left inside of
> GigE.

The CPU speed limits gigabit ethernet performance because of the
processing overhead. Standard ethernet packets are a maximum of 1,500
bytes long, which means a computer must process more than 80,000 packets
every second to achieve gigabit ethernet's full throughput. Many systems
can only process about a fifth of that, limiting performance to less than
100 Mbps in a lot of scenarios. To circumvent this problem, gigabit
ethernet supports larger packets called jumbo frames, which can be up to
9,000 bytes each. However, not every ethernet card/driver supports jumbo
packets, and not every gigabit switch supports jumbo packets, and as far
as I know it's not something that's turned on by default in cards that do
support it.

> Unless I luck out on a switch, I don't expect to ever be able to afford
> that, and that seems to leave only GigE.

I think that a gigabit ethernet network with cards and drivers that have
jumbo frames enabled, and switches that support jumbo frames, would
address one of the last roadblocks to making ethernet decent.

Nathan Raymond

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