Netgear GA620T, GA620 SUPPLEMENTARY GUIDE

White Paper on GA620/GA620T Gigabit Ethernet Card
Performance

Gigabit Ethernet adapters represent the next step in the evolution of
network performance. The widespread adoption of Fast Ethernet at the desktop
has created a bottleneck at the server, specifically at the Server adapter. Some
companies have created Server adapters with multiple 100 Mbps connections,
while others have populated several PCI slots with 100 Mbps adapters to boost
Server bandwidth beyond Fast Ethernet. Gigabit Ethernet delivers performance

beyond these aggregation band-aids, by delivering speeds approaching 1 Gbps.

Network Configurations

Due to the fact that Servers benefit most from Gigabit speeds, the adapter
card drivers are optimized for that environment. In most networks, the server
distributes information to multiple clients. For this reason, the driver has been
optimized to perform best in a one-to-many environment. Using the test program

Chariot running against twenty -five 100 Mbps clients, Gigabit speeds are
consistently reproduced in lab.

Test results will vary depending on a number of factors including the type
of test, the speed and performance of the computers being used, and the
network topology. To measure the capabilities of the adapter, the test should
stress the network and not the other components of your system. Programs
such as Ganymede’s Chariot, and Microsoft’s NTTTCP accomplish this goal
quite well. These tools provide a multi-threaded, asynchronous performance
benchmark for measuring achiev able data transfer rate.

Back-to-Back Test

One test that does not accurately measure adapter performance is a back­to-back test. The driver is optimized for one-to-many scenarios, so testing in a
back-to-back environment will yield slower results. More than 500 Mbps
throughput is still possible using a multi-threaded testing program for testing
network performance, such as Microsoft’s NTTTCP program. While one is
unlikely to see the full capabilities of a Gigabit Ethernet card when tested back­to-back, it is still possible to get a feel for the capabilities of the adapter.

File Transfer

Another test that does not accurately measure adapter capability is a file
transfer. Copying a file from one computer to another tests a hard drive’s
performance rather than network performance. In a test like this, the limiting
factor is the performance of the computers, rather than the performance of the
network. The copying process adds the overhead of the disc drives, as well as
the operating system handling the copy. The test results indicate the computers’
ability to process these additional requirements rather than the abilities of the
connection between them. In a test like this it is possible to see results less than
20 Mbps on any card, which is slow for both a 100 Mbps card and the 1000 Mbps
card. Surprisingly, the Gigabit adapter will probably be the slower of the two
cards in this test.

The reason a 1000 Mbps adapter would perform below a 100 Mbps
adapter is quite simple in this test. In order to achieve Gigabit performance,
Gigabit adapter drivers contain additional intelligence beyond Fast Ethernet
drivers. This intelligence creates more overhead than a standard 10/100 card.
When stressing the network at higher speeds, this overhead is negligible, and
improves to the performance of the network. When the cards are run at minimal
performance, such the file copy test, the Gigabit card will have slightly more
overhead than a standard 10/100 card, causing slower performance. However,
as more stress is placed on the network, such as video or multiple system file
transfers, the gigabit card will start to outperform a 10/100 card. Ultimately, the
Gigabit adapter can deliver 10 times the network throughput of a Fast Ethernet
adapter.