Re: TCP/IP send, sendfile, RAW

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Thu, 4 May 2006, Jan Engelhardt wrote:

>> I would like to send ethernet packets with 1400 bytes payload.
>> I wrote a small program witch sends a buffer of 1400 bytes in a endless loop.
>> The problem is that a would like 100Mbits throughtput but when i check this
>> with ethereal.
>> I only get 40 MBits. I tried sending with an UDP socket and RAW socket. I also
>> tried sendfile.
>> The RAW socket gives the best result till now 50 MBits throughtput.
>
> Limitation of Ethernet.
>
>
>
> Jan Engelhardt

Maybe he can tell what he means by 100 MBits! If he is looking for
100 megabits per second, that's easy, That's 100/8 = 12.5 megabytes
per second. Anything, including Windows on a wet string, will
do that. If he is looking for 100 megabytes per second, that's
hard. He would need 100 * 8 = 800 megabits/second. A "gigabit" link
runs that fast if nobody else is on it, but there is a header and CRC
tail, in addition to the payload. UDP is the protocol to use to realize
this kind of bandwidth, but its possible for some packets to get lost and,
if they are routed, they could even be duplicated. Also, when testing
UDP, there must be a listener in order to realize the high speed.
You can't just spew out a dead-end link.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
New book: http://www.lymanschool.com
_


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