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SubjectRe: Gigabit Linux Server Bottlenecks

On 08-Feb-2000 Jonathan Disher wrote:
>>maddening to the CPU. As I recall, the host must be able to process
>>around 82,000 packets (read "CPU interrupts") per second to fill the
>>pipe unidirectionally. Try this in a full duplex setting with a 2 gig
>>pipe to fill and you (at least) double the amount of work the CPU needs
>>to accomplish every second.
> IIRC, gigaether is actually 500mbit ethernet in full duplex mode.

More complicated:

In Full Duplex: it is 1 GBit

In Half Duplex:
Packets smaller than 640 (or 512, sorry do not remember) are padded to this
value. So if you transmit 40 byte packets in half dupplex you get approx the
performance of a 100 MB in Full Duplex.

Also, both the switch (hub) and the host can exercise flow control and request
actual transmission rate to be dropped (modulations stays same as for 1GB).

The figure you quote is the value implemented via flow control on most "GigE"
hubs like PE 1xxx. They usually send back a flow control signal to drop speed
around half a gig. This is in their specs ;-)

Anyway, this is OT.

On Topic: you can deliver 1GigE with Linux and it works. To be more exact -
works great ;-). The question being: is there any chance to get 802.1Q in 2.4?
Current code is for 2.2.

Correct me if I am wrong but I do not recall it on the feature list.

Thanks in advance,

- ----------------------------------
Anton R. Ivanov
IP Engineer Level3 Communications
RIPE: ARI2-RIPE E-Mail: Anton Ivanov <>
@*** Cushman's Law ***
A fail-safe circuit will destroy others.

- ----------------------------------
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