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Home networks, according to the Aug. 15 Stavance R&D
Newsflash, have recently reached the 10.5 million mark worldwide, and are
expected to grow to 16.6 million by 2006.
Many of you have been on the leading edge of this trend,
first pulling cable for 10 megabits/second Ethernet (often called 10bT). Or you
may have dabbled with HomePNA networking (see below). Or more recently, you may
have climbed on the 10 megabits/second wireless networking bandwagon under the
moniker of WiFi or 802.11b. But you probably haven't yet experimented with
networking that uses the existing electricity wires in the wall (the power line)
to carry data. Because power line networking is a relatively new home and small
office option, in this issue we'll see how it works, and try to put it in
perspective alongside other, more familiar networking contenders.
Let's begin by reviewing the common home and small office
networking technologies so that we have a sense of their strengths and
weaknesses:
l10bT (Ethernet, or
Category 5) wire is, for all reasonable purposes, very secure and delivers a
pretty error-free 10 megabits/second of raw data (or ten-times greater, if your
network cards support 100bT). But you have to pull a wire to every spot you want
a PC.If you use an "Ethernet switch" at the central point where all
the wires come together, then the full media speed will be available to each
device (a "hub," instead of a "switch," shares the media's
bandwidth among all PCs).
Each PC requires an Ethernet card (if one isn't built-in),
or something like a USB-Ethernet adapter. Most cable/DSL "modems"
provide an Ethernet jack. (Note that for all of the network configurations we'll
be discussing in this article, not only do you need a network adapter on each
PC, but you also need one more "box" if you want to share your cable/DSL
connection -- a "router." It could be a standalone box, a part of the
cable/DSL modem, or even a PC running the appropriate software.
For this discussion though, we'll assume that the router is
a part of the cable/DSL modem.)
l HomePNA (http://www.homepna.org
) piggybacks data onto your existing home telephone wiring (without interfering
with phone calls). Until recently, it ran at only one to two megabits/second,
but its V2 devices are now rated at 10 megabits/second. You plug a HomePNA
"modem" between each PC and a phone jack in the wall, and the PCs are
then networked together. If you have a cable/DSL modem/router, then another
HomePNA modem goes between the cable/DSL modem/router and a phone jack.
l However, according
to Intel technical support (Intel is one of the manufacturers of HomePNA
devices), encryption is not a part of the current HomePNA products. Because the
signals degrade over distance, this may not be a huge security risk in a rural
area, but in high density apartment buildings most phone lines show up on a
common "punch block" where unencrypted signals could be siphoned
off.
l HomePNA devices
are available as PCI cards, USB adapters, and Ethernet to phoneline
"bridges."
l WiFi, or 802.11b,
offers 10 megabits/second of data and the ultimate in flexibility, especially
where wandering notebooks are concerned. You connect a "wireless access
point" to your cable/DSL modem/router via an Ethernet cable, and then
"wirelessly-enable" each PC or notebook with a built-in PCI card, a
PCMCIA card for notebooks, or a USB adapter. But depending on the building
layout and construction, its coverage can be spotty, and documented flaws in the
current WEP encryption make it susceptible to hacking.
Power Line Networking.
Under the standardizing influence of the HomePlug Powerline Alliance,
several companies now offer products that use the existing electricity wires
within our walls to carry data at a maximum raw data rate of 14 megabits/second,
without affecting the power.
(One company, Phoenix, explains that the overhead
associated with networking over the very data-unfriendly power lines reduces
that "raw" 14 megabits/second to an effective data throughput of 8
megabits/second, but more on the speed issue in a moment.) The recommendation
for maximum distance between powerline modems seems to be about 150 feet,
although HomePlug indicates that they have yet to run into a house where it
didn't work. And a practical (if not an absolute) limit of 16 powerline modems
seems to be what's claimed for home or small office powerline networks.
Similar to the other technologies, you need a "powerline
modem" between your cable/DSL modem/router and the wall, and another
powerline modem between each PC and the wall; various companies make versions
that connect to an existing Ethernet jack, to a PC's USB connector, or that can
be installed into a PCI slot.
Behind the tests.
Unlike the carefully controlled benchmark-driven tests conducted by many
"testing laboratories" (which are also valuable), I focus on pragmatic
real-world testing that uses the same type of equipment you probably have,
configured in similar ways. For example, I don't use PCs stripped of all of
their background tasks to keep normal CPU activity from affecting test results
(although I do make an effort to see that no unusual activity takes place during
the tests.) And for these file transfer speed tests, I didn't configure an FTP
or other specialized server. Instead, I used Window's File Sharing and
Explorer's "drag and drop" to copy a large 338 megabyte (aprox.) test
file between the two systems in the same way you'd likely transfer a file. Tests
were conducted in both directions and repeated twice, with the results averaged.
So while absolute test numbers might be better in optimized environments, these
results reflect how I would expect the technology to actually work for you.
For most tests I used powerline modems from the same
vendor, one attached to my cable/DSL modem/router and the other to the test PC
running Windows XP; each powerline modem was plugged into a different electrical
circuit (meaning that the signals had to travel down to the circuit breaker box
and back up.) The second PC in the file transfer tests was connected by wired
Ethernet directly to the router, and used Network Neighborhood to gain access to
the test PC.
Installation.
Powerline modems that connect directly to an Ethernet jack, either on a
cable/DSL modem/router or to an existing Ethernet jack on a PC, didn't require
any setup or software install at all -- they were transparent to the machines.
Installing a USB version did require a typical software installation, which
proved flawless on a Windows XP machine. However, when I originally attempted to
install the ST&T USB software on a "well-used" Windows Millennium
system, the installation process repeatedly failed and eventually corrupted the
system. This may have been more an indictment of the state of this old Windows
Me machine than of the powerline modem software, and I didn't pursue it since
this seemed a good time to upgrade the machine to Windows XP. J But all of the
powerline modems did work fine under XP.
The Results.
To begin, I ran a benchmark file transfer between the two systems using only
standard wired 10bT Ethernet (no powerline modem), resulting in an end-user
throughput of 7.2 megabits/second. (Don't be surprised that wired Ethernet
doesn't live up to its "raw data rate" promise of 10 megabits/second
-- protocol and operating system overhead always take a toll on the
"end-user data rate," which is why we're going to be comparing actual
end-user file transfer performance.) For comparison, a previous similar test of
802.11b wireless Ethernet (high signal strength and only one wireless PC active)
yielded an end-user throughput of 7.0 megabits/second.
I then installed pairs of powerline modems and tested the
file transfer throughput as described above, yielding the following end-user
data rates: Asoka PL9610-ETH / PL9710-USB 4.0 megabits/second Phoenix Broadband
NeverWire 14 4.6 megabits/second ST&T M51 / U21 4.9 megabits/second 10bT
wired Ethernet only 7.2 megabits/second 802.11b 10 megabits/second wireless 7.0
megabits/second (You may well experience faster or slower speeds, depending on
your electrical system.)
Analysis.
The most important result of this experiment, to me, is that these powerline
modems provided exactly what they promised -- simple, no-new-wires networking.
You might be concerned that the end-user data throughput of the powerline modems
(in my tests) was slower than wired or wireless Ethernet, but let's put that in
perspective -- if you do intend to transfer large files or expect to stream lots
of multimedia at speeds faster than your cable/DSL connection, the increased
speed of wired Ethernet might well justify the hassle of pulling cable. But for
most typical small network activities, such as sharing a cable or DSL
connection, remote-printing, and typical file transfers, the slower speeds of
the powerline modems may be unnoticeable compared to the flexibility of being
able to compute anywhere you can plug-in to an electrical socket.