[KLUG Members] Gigabit Ethernet, "Jumbo Frames" and IEEE802.1q VLAN -- WAS: SiS900 in SiS735 chipset on ECS K7S5A

[Bryan-TheBS-Smith]

Adam Tauno Williams wrote:
> Anyone use gigabit yet?  What do the actual utilization numbers look like?

I've been using 1000Base-SX (one type of 1000Base fiber **) on Linux for
over a year.  The _key_ to Gigabit performance is "Jumbo Frames" (9000
byte).  Otherwise, Gigabit will only give you a 1.5-3x boost over Fast
Ethernet, instead of 4-8x.  The problem with jumbo frames is that _all_
your cards must be using them ... *OR* ...

You get a _switch_ with multiple frame support aka _true_ IEEE 802.1q
VLAN (and not the "commodity" VLAN marketing crap on many switches out
there).  802.1q will handle switching your packets.  This is a good
"in-between" having all your clients talk with jumbo frames, which many
not be supported by many Fast Ethernet (let alone Ethernet) cards, let
alone there are performance issues in using 9000 byte frames at only
100Mbps (let alone 10Mbps).

BTW, for those of us who have UNIX networks, you'll note 9000 bytes
allows a 8KB NFS block to fit quite nicely.  As such, if you use NFS
with 8KB blocksize (or any other protocol with 8Kb blocks), you'll
probably get even a bigger boost closer to the 10x "theoretical" over
Fast Ethernet.  ;-P

-- TheBS

**NOTE:  1000Base-SX was the typical Gigabit topology before
1000Base-T[4] became available.  It allows upto ~350m runs using
multimode fiber.There is also a 1000Base-LX topology that allows runs
greater than 2km, although you'll pay extra for it.  Neither have the
wiring closet "issues" that 1000Base-T[4] has.  Don't think you can just
use UTP for 1000Base-T[4] "as usual" like 100Base-TX -- there are
various "maximum" bundling, proximity and other issues (not to mention
you _must_ have 4-pair UTP).

CC:  KLUG-HARDWARE

P.S.  We should probably follow-up to this on only the hardware list,
given it's non-Linux related.

-- 
Bryan "TheBS" Smith     mailto:b.j.smith@ieee.org    chat:thebs413
Engineer   AbsoluteValue Systems, Inc.   http://www.linux-wlan.org
President     SmithConcepts, Inc.     http://www.SmithConcepts.com
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