Can I send out an ethernet packet with over 1500 bytes in linux ?

For a special test, I need to send out jumbo packet with over 1500
bytes packet size. Can I do this? how?

If a general 10/100M ethernet card cannot do it, how is a 1000M
ethernet card?

Or can I use a cisco router to generate this kind of packet? ( I tried
to change MTU in the ethernet interface of Cisco router 2611, but it
said "Interface Ethernet0/0 does not support user settable mtu". )


Any response will be very appreciated!

On 20 Dec 2004 18:59:43 -0800, (E-Mail Removed) (Hans Yin) wrote:

>For a special test, I need to send out jumbo packet with over 1500
>bytes packet size. Can I do this? how?
>
>If a general 10/100M ethernet card cannot do it, how is a 1000M
>ethernet card?
>
>Or can I use a cisco router to generate this kind of packet? ( I tried
>to change MTU in the ethernet interface of Cisco router 2611, but it
>said "Interface Ethernet0/0 does not support user settable mtu". )
>
>
>Any response will be very appreciated!

I'm not certain this is what you're looking for, but the recent
Realtec 8169 (Linksys GA311) NICs support something they refer to as
"jumbo frame". You need to use the most recent drivers - the standard
SuSE 9.2 and earlier drivers haven't got the jumbo frame support yet.
I didn't hunt thru the Realtec site to find out exactly what that is
(fell over it while I was looking for something else), but it sounds
like it might be what you're looking for.

Mike-

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Hans Yin wrote:
> For a special test, I need to send out jumbo packet with over 1500
> bytes packet size. Can I do this? how?
>
> If a general 10/100M ethernet card cannot do it, how is a 1000M
> ethernet card?

A GigE nic is mandatory to succesfully use jumbo frames -- at _all_
points from start to end! CAT7 cable or fiber optic also.

> Or can I use a cisco router to generate this kind of packet? ( I
tried
> to change MTU in the ethernet interface of Cisco router 2611, but it
> said "Interface Ethernet0/0 does not support user settable mtu". )

Jumbo frames (if enabled on the interface) will be part of the auto
negotiation at startup. You can't "manually" force it even with a GigE
nic.

> Any response will be very appreciated!

If you just need a "simple" test environment, you _might_ get by using
a good crossover cable between two boxes with the same brand of GigE
nic. These days even different brands _should_ work at 30-40% rated
capability.

These speeds are very sensitive to anything that upsets the full data
rate flow. It seems you get 80-85% throuput (after much fiddling) or
you get less than 50% (also after much fiddling ;-)

You may also have to change a number of the default TCP perf settings.
http://www.psc.edu/networking/projects/tcptune/
hth,
prg
email above disabled

Sorry for the bad link -- must be getting too old to do cut-n-paste :-(
http://www.psc.edu/networking/projects/tcptune/

prg

[vodafone@Dreamlin1 test]# ping -c 3 -s 1500 61.95.203.xx
PING 61.95.203.xx (61.95.203.xx) 1500(1528) bytes of data.
1508 bytes from 61.95.203.xx: icmp_seq=1 ttl=64 time=3.15 ms
1508 bytes from 61.95.203.xx: icmp_seq=2 ttl=64 time=3.04 ms
1508 bytes from 61.95.203.xx: icmp_seq=3 ttl=64 time=3.05 ms


--- 61.95.203.xx ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2020ms
rtt min/avg/max/mdev = 3.041/3.085/3.158/0.082 ms
[root@Dreamlin1 test]#