What on earth is this?

http://www.cyberciti.biz/faq/rhel-centos-debian-ubuntu-jumbo-frames-configuration/

I was under the impression that Ethernet frames can never be more than
1500 bytes.

Or is it some kind of stupid linux hack? Or does it have any meaning?

Is there real value in this?

I don't get it.

-Girish

Jumbo frames.  Ethernet frames with more than 1500 bytes of payload/ 



Fewer frames get corrupted, means less processing overhead per frame.  
Outside of that, the remaining advantage is fewer frames going over  
the line. It's not recommended on the same LAN as systems not using  
jumbo frames.

This is not correct. The relatively recent (2005) IEEE 802.3as spec
extends Ethernet frame length only to 2048 bytes, mainly to accommodate
VLAN stacking and various encap methods. It does not define a standard
for jumbo frame length.

Jumbo frame support is widely implemented but it's still not standard.


Perhaps because there is no standard, switches differ on jumbo MTU.

Most support 9216 bytes or more, but some top out at 9000.

dn

But the same amount of data(!) needs to be transmitted, and only if no 
collision(s) and
retransmission(s) occurs!  Anybody on the same LAN segment - who wants 
to transmit,
I know only a few HP routers which can handle efficiently jumbo frames 
(internally) - IF
enabled.  Ask yourself, what would happen with this jumbo frames outside 
a LAN segment?
How would the rest of  routers/switches/repeaters - like hubs/etc. would 
handle jumbo frames?

mufurcz

Use NICs capable of TCP checksumming and the appropriate drivers, that


A router in between jumbo and non-jumbo will break frames down to
non-jumbo sizes if need be. Even a wee Cisco 3750G we tested with does
so with minimal CPU hit (maybe it's done in hardware on those, I don't
know) We had problems when using is on the same segment with 1518 MTUs.
Much of what we read recommened against it but that's like sticking a
"DO NOT PUSH" sign above a big red button for me. :)

Anyhow to sum it up: jumbo is cool when used correctly. The throughput
difference can be quite impressive, we had a considerable boost in
speed on 4x GigE iSCSI RAID chassis to the front end box and with NFS.


gg

Huh? Haven't seen a network in YEARS that didn't use a switch for
interconnect - the 'segments' with most switches have two hosts - machine
& switch.

If you're running 1GB or 10GB, the switches you're using have backbones
well capable of running any framesize you can configure.

	Lee

Yes, there's value in it. NFS can benefit greatly if you can stuff a
single read/write block into a single ethernet frame (rather than
splitting it across 3 or 4). It's also helpful for wringing maximum
throughput out of your network at higher speeds. Think about the
interrupt rate to send 1Gb/s with 1500B frames and compare that to
6000B frames. Even if your card is totally insane, you've just got 4
times more data out of one interrupt.

Check the manpages for the various network drivers...

On Dec 29, 2007 11:41 PM, Girish Venkatachalam



-- 
GDB has a 'break' feature; why doesn't it have 'fix' too?

On Dec 29, 2007 11:41 PM, Girish Venkatachalam


Can be.


http://sd.wareonearth.com/~phil/net/jumbo/
http://en.wikipedia.org/wiki/Jumbo_frames

DS

Jumbo frames are very real. A simple google search will enlighten you :)

This should help you: http://sd.wareonearth.com/~phil/net/jumbo/

On Dec 30, 2007 12:11 PM, Girish Venkatachalam



-- 
Karthik
http://guilt.bafsoft.net