[TriLUG] OT: what is a gigabit ethernet server?

[Aaron S. Joyner]

Brian Henning wrote:

> ----- Original Message ----- From: "Christopher L Merrill" 
> <chris at webperformanceinc.com>
>
>>
>> "Gigabit Ethernet: This term does not connote an actual operating speed
>> of 1GB/sec. For high-speed transmission, connection to a Gigabit 
>> Ethernet
>> server and network infrastructure is required."
>>
>> What does that mean?  Does that mean I need something besides a switch
>> with a gigabit port?
>
> I think the description was trying to explain the maxim that a chain 
> is only as strong as its weakest link...  There are plenty of 
> consumers (/idiots) out there that would not immediately grasp why 
> they only get 10Mbit through their 10Mbit hub to their 10Mbit server 
> when their workstation has 1Gbit. Dell's just trying (vainly, 
> probably) to point out that you'll only get gigabit performance if all 
> the steps along the way are gigabit.
>
> Cheers,
> ~B
>
Brian does a good job of pointing out the actual purpose of Dell's 
statement, but there's a greater subtlety that bears mentioning.  If you 
use cheap hubs, and regular PCI Gigabit NICs, you won't see 1,000 Mbits 
/ second.  In order to get up into that range, you're going to need to 
overcome two bottlenecks.

First the PCI bus can't really handle that much throughput, so you're 
going to need to use something like Intel's CSA architecture (which ties 
the Gig-E controller into the north bridge chipset, bypassing the PCI 
bus), or go straight to PCI-X, preferably on a well-designed motherboard 
using AMD's HyperTransport.

Second, you'll also need to up the MTU of the interface and use what are 
commonly referred to as "Jumbo Frames", meaning that you send data in 
packets larger than the standard 1500 byte chunks.  The maximum 
practical MTU for Gig-E is usually 9000 bytes, but take note that most 
inexpensive Gig-E switches won't support the larger frame sizes (and 
will drop or truncate those packets).

Hopefully this will help someone who's looking into Gig-E understand how 
to set their expectations accordingly.  :)

Aaron S. Joyner