Tag Archives: ethernet

Trendnet Compacts Powerline Adapter

At CES, TRENDnet has launched the world’s smallest 500 Mb/s Powerline adapter with the new TPL-406E model. Look at the picture below to see the difference in size between a standard Powerline adaptor and the new model on the left. When trying to get all the modern gadgets plugged in and networked, this will certainly help where there is limited space or close electrical sockets.

TPL-406E Trendnet Powerline adaptor

“Consumers are looking for solutions to help connect their TVs to the Internet and TRENDnet Powerline products couldn’t be easier-with no complicated CD installation required,” stated Sonny Su, technology director for TRENDnet. “The TPL-406E defines a new category of ultra-compact high performance 500 Mbps Powerline adapters.”

More and more audio-visual equipment needs to be networked. In my living room, I think there are three ethernet devices (TV, satellite decoder and Bluray player) and I use a 100 Mb/s Powerline device to take the network to them. For this kind of equipment, Powerline is much more convenient than trying to setup a wireless bridge.

Available from April at all good retailers, the TPL-406E will be $60 on its own or $100 in a twin pack, TPL-406E2K.

Network Switches and Data Transfer Speeds

I recently upgraded my home network from 100 Mb/s to 1 Gb/s by replacing the switches. The main house switch is an unmanaged 1U rack-mounted switch, with a second desktop switch. Out of pure interest, I took the opportunity to do a little bit of speed testing to see how much of a difference upgrading the switches made in terms of actual data transfer speeds.

A few basics to avoid confusion  – b/s is bits per second and B/s is bytes per second. All of the reported figures will be in MB, so converting b/s to B/s:
Fast Ethernet = 100 Mb/s = 12.5 MB/s
Gigabit Ethernet = 1 Gb/s = 125 MB/s

100 Mb/s and 1 Gb/s refer to the speed of the underlying technology but data transfers at these rates are never achieved because of protocol overheads and such. As a baseline, if I write a large file (8 GB) to my PC’s local disk, I get a data transfer of between 50-55 MB/s.

On my network, I have two Buffalo Linkstation NAS devices, one with a Fast Ethernet interface and one with a Gigabit Ethernet interface. 2 GB’s worth of data would be written to each of these devices with different Ethernet switches in place to see what actual data transfer speeds would be achieved. The following Linux command was used five times in each situation and the result averaged.

time dd if=/dev/zero of=testfile bs=16k count=16384
Switch Model Data Rate to Fast NAS Data Rate to Gigabit NAS
1U Rack
Dynamode SW240010-R(Fast) 6.2 MB/s 8.6 MB/s
TP-Link TL-SG1016 (Gigabit) 6.4 Mb/s 21.4 MB/s
D-Link DES-1008D (Fast) 6.2 MB/s 8.6 MB/s
Netgear GS605 (Gigabit) 6.5 MB/s 21.1 MB/s

I also carried out two further tests:

  1. With Gigabit Ethernet only, I wrote to both NAS devices at the same time. The data transfer speeds were unaffected.
  2. I connected the two Gigabit Ethernet switches in series and wrote to the NAS. Transfer speeds were reduced by 1 MB/s on the Gigabit NAS to 20 MB/s. The change on the Fast Ethernet NAS was minimal.

There are several things that can be deduced from the information shown in the table above and the other tests.

  1. Actual data transfer rates are considerably less than the theoretical maximums.
  2. There’s no performance difference between rack-mounted and desktop switches.
  3. The write speed of the NAS can be a limiting factor.
  4. Gigabit Ethernet switches give large improvements with Gigabit Ethernet devices.
  5. Gigabit Ethernet switches give small improvements even with Fast Ethernet devices.
  6. Keep the number of switches in the network path to a minimum.