In this post I’ll be sharing my experiences with the ZyXEL PLA4201 powerline networking starter kit.  ZyXEL calls this their HD networking kit claiming that it is ideal for media streaming and gaming.

They claim a max throughput of 500Mbps which is more than double that of most other powerline kits with a max transfer rate of 200Mbps.

The concept of powerline networking is pretty simple, plug in a pair of the adapters to the electrical outlets in your home and send ethernet packets over your homes electrical system.  The technology these adapters use is based on the IEEE P1901 standard.

Whats Included in the Kit
  • Two Powerline Ethernet Adapters
  • Two Ethernet Cables
  • Quick Start Guide
  • Support CD
The Adapters

The adapters are a lot smaller than I expected them to be, they are about the size of a credit card , or ac adapter.  On the front of the adapters are three LED status lights, power, homeplug status, and ethernet status.

One of the nice things about powerline networking is that the adapters don’t require a separate AC adapter giving them a nice clean look.

On the side of the adapters there is a reset / encrypt button.  This is used to pair the adapters to create an encrypted channel between them using 128-bit AES encryption.

Encryption is important for powerline adapters deployed in environments where shared electrical wiring exists, such apartments and office buildings.

There are also several ventilation holes on each side of the adapters to keep them cool.  After operating for a while they tend to get a bit warm.  If the adapter detects a loss of link they will enter a  power savings mode, making them “green”.

 

On the back of the unit is a label which contains the serial number, ethernet MAC address, and the DEK number (device encryption key).  In order to use the configuration utility you need to enter the DEK for each of the units.  Having the security key visible on the adapter is a security risk since anyone with physical access could easily record the key.

To prevent the hastle of disconnecting them later you may want to write down the key from each unit, or just take a picture.  All of these numbers are unique to each individual adapter.

Installing the Adapters

Setting up the adapters is pretty quick and easy to do.  For a basic setup with only two adapters there are only three things you need to do.

  1. Plug each of the adapters into an electrical outlet
  2. Connect an ethernet cable to the ports on the bottom of the adapter.
  3. Press the reset / encrypt button on each adapter (they must be pressed within two minutes of each other)

Since the adapters act like an ethernet bridge there is no need for drivers or software to be installed.  For more complex configurations with multiple adapters you will probably want to use the configuration utility.

You can add additional adapters as needed, the procedures for syncing multiple units is described in the users guide.

Adapters in Action

Test Setup

To test the performance of the adapters I connected one adapter directly to a Cisco 3750G switch. I connected a Linux host to the same switch to function as an iPerf server.

The second adapter was placed at two different locations in my home.

  1. Both adapters on the same electrical circuit (breaker)
  2. Each adapter on a different circuit (one upstairs, one on the main level)
I connected my Alienware laptop to the remote adapter and used the Windows version of iPerf to connect to the remote iPerf server.
Performance Test Results

TCP and UDP throughput was measured in Megabits per second (higher is better).  Latency numbers are indicated in milliseconds (lower is better).  For the control test I connected my laptop directly to the switch and set the speed to 100Mb full duplex (more on that later).

Single Session iPerf (Mbps) Parallel Sessions iPerf (Mbps) UDP iPerf (Mbps) Average Latency (ms) Flood Ping Average Latency (ms)
Same Electrical Circuit 62.9 82 85 3.523 2.698
Different Electrical Circuit 57.7 66 72.1 3.614 2.600
Control Test 94.9 94.6 95.4 0.448 0.388
Analyzing The Results

Maximum Throughput

The maximum transfer rate I was able to achieve using the powerline adapters was 85Mb/s during the UDP test.  Unfortunately the PLA4201 units will never achieve any throughput over 100Mb because this is the highest speed supported by the ethernet port on the devices.

The manufacturers claim that they can support 500Mbps is completely false.  The hardware specifications clearly indicate the interface consists of a single RJ45 connector that supports 10/100 Auto MDI/MDIX.

It turns out that ZyXEL does produce a similar model, the PLA4205 which does offer gigabit ethernet ports.  The gigabit kit only costs about $20 more than the fast ethernet kit which is absolutely worth it!  With gigabit ports it should certainly be possible to achieve speeds somewhere closer to the 500Mbps they claim.

ZyXEL PLA4205 Gigabit Adapter Kit

Performance VS Location

Based on my testing it’s clear that these adapters do perform better when they are connected to the same electrical circuit.  When I placed one of the adapters on a different floor in my home the transfer rates did drop a bit.

ZyXEL claims the maximum distance the adapters will work is up to 300 meters.  In general as distance increases I suspect transfer rates will decrease.

Latency

I found that the powerline adapters introduced about 2-3 milliseconds of latency.  A couple of milliseconds won’t be noticeable to most users.  If you’re a gamer looking for the fastest connection possible you might want to avoid these and run an ethernet cable instead.

The latency numbers were fairly consistent though with less variation then I would expect from a busy wireless connection.

Commands Used for Testing

Below are the iPerf commands I used during the testing.  The iPerf server was running on a Linux host and the client ran on Windows.

Single Session iPerf iperf -c <server ip> -w 90000 -t 30
Parallel Sessions iPerf iperf -c <server ip> -P 10 -t 30
UDP Iperf iperf -c <server ip> u -b 100000000
iPerf Server TCP Mode iperf -s
iPerf Server UDP Mode iperf -su

The ping tests were ran from the Linux host using the standard ping utility.  The reason I used the Linux host to send the pings is because the standard Windows ping utility does not have time resolution below 1ms.

Average Latency ping <client ip> -c 30
Flood Ping Average Latency ping <client ip> -c 100000 -f
Conclusion

Overall I found these adapters to work better than I expected them too.  It was disappointing to discover they only have a 100Mb ethernet port though.  I would like to test the adapters with gigabit ports to see how much faster they perform.

dual band wireless N bridge would probably be a better option than the PLA4201 kit.  For situations where wireless isn’t an option then these adapters would be a decent option.  Overall they are quick to install and they actually work surprisingly well.

With a maximum distance of 300 meters these adapters can reach locations that ethernet (100 meter max), and wireless may not be able to reach.  Keep in mind that speed will decrease as distance increases.

ZyXEL PLA4201 Documentation Links

Sam graduated from the University of Missouri – Kansas City with a bachelors degree in Information Technology. Currently he works as a network analyst for an algorithmic trading firm. Sam enjoys the challenge of troubleshooting complex problems and is constantly experimenting with new technologies.

Circle Sam on Google+!

Facebook Twitter YouTube