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Of the two main flavors of DSL, asymmetric (ADSL) and
symmetric (SDSL), ADSL has been the most deployed,
mainly because residential customers mostly need
bandwidth on the downstream end so have little need
for the line to be symmetric. On the other hand,
businesses have needs for both downstream and upstream
data, but SDSL has not taken off because of problems
associated with standardization of the service. The
latest incarnation of SDSL aims to change all of that.
Both the ITU (G.SHDSL) and the ETSI (TM6) are
currently uniformly standardizing SHDSL, which stands
for Single-Pair High-Speed Digital Subscriber Line.
Targeting the small business market, some of the major
characteristics of SHDSL is the ability for it to
combine multiple voice and data channels as well as
functionality for video conferencing, remote LAN
access, Web page hosting, and leased lines with
customer-specific data rates.
Varying from 192 Kbps to 2.32 Mbps, SHDSL can work
with other DSL connections and can work across greater
distances than past DSL flavors. This is a blessing
for those businesses and residencies that could not
get DSL access because they were just beyond the
service provider's boundaries, but there are still
major limitations to where DSL can be deployed. With
products such as Net to Net's Voice Over G.SHDSL
Network Extender, these limitations are being
addressed because they provide the ability to add DSL
service to a network.
INSTALLATION
For our tests, we received a point-to-point solution
that was equipped with a service unit and a provider
unit, which acted as a 1-port DSLAM. For these units,
there was no built-in management, so the installation
was only that of setting up the connections
appropriately. Under normal circumstances, the
provider unit is located at the ISP, but for our
purposes, we kept it right here in our labs and used a
regular Ethernet cable to act as the copper wire
connecting the units. When the cable was connected,
this SHDSL connection consistently linked up in
approximately twenty seconds.
The rest of our set up consisted of plugging in the
power adapters, verifying the switch configuration of
the provider unit, and connecting the voice and
Ethernet connections. From the service unit, we
connected a regular Ethernet cable to a PC and an
analog line to a regular telephone (the voice over DSL
that we received digitizes and extends a single voice
line over an SDSL or G.SHDSL line). From the provider
unit, we connected a crossover cable to an Ethernet
port in the wall and a voice line to an analog jack.
We made sure that the correct LEDs were on and were
ready to test the DSL connection. For this set up, the
most difficult part was knowing that we needed to use
a crossover Ethernet cable from the provider unit. We
did not have any configuration issues at all.
DOCUMENTATION
There is not much to the documentation, nor does there
have to be. Once the set up is complete, the DSL
connection should work without need of further
assistance. Net to Net Technologies provides accurate
installation instructions that go through a
step-by-step procedure of the set up. Although there
is a page that describes the LED indicators and some
information associated with them, we would like to see
more troubleshooting guidance just in case the SHDSL
or voice over DSL line does not work right away.
FEATURES
The following are the major features of the Voice Over
G.SHDSL Network Extender:
- Supports selectable data rates up to 2.32 Mbps (SHDSL).
- Provides a voice over DSL (VoDSL) connection.
- Extends DSL lines across greater distances to
allow for quality connections that were not
possible before.
- Connects to a PC or LAN directly through any
Ethernet port.
- Configuration-free operation.
- Can be used in point-to-point configurations or
with any Net-to-Net IP DSLAM.
- IPacket technology -- reduces network
administration and configuration costs and regains
around 20 percent of bandwidth previously lost to
transport overhead.
- AutoIP architecture -- if using a larger DSLAM,
includes AutoSync line provisioning, AutoConfig
configuration management, and AutoRestore
backup/recovery.
OPERATIONAL TESTING
Once we completed the set up, there was very little
that we needed to do to test the network extender.
First, we accessed the Web from the PC that was hooked
up via an Ethernet cable to the service unit. The Web
pages came up just as fast as if we had connected the
PC directly to our network. Since this access could
only be established through the SHDSL connection going
from the service unit to the provider unit, we knew
that the units were working. However, we decided to
test this more thoroughly by changing one of the
jumper switches on the provider unit to the "up"
position, thereby blocking the SHDSL connection to
that unit and in theory, not allowing the PC to access
the Web. Indeed, access was not established until we
changed the jumper switch back to the "down" position,
proving the extension of our network though a
point-to-point SHDSL connection.
In a similar fashion, we tested the VoDSL line by
making both local and long distance calls. We also
used a number of different analog phones to see if the
quality was similar for all of them. For most of our
calls, the quality was quite good on both ends. We
knew this because our local calls were made within the
labs. While there was little to no latency, the voice
from the phone connected to the service unit sometimes
had a slightly lower volume than most regular PSTN
phone calls. Nevertheless, the communication was
always understandable. As a matter of fact, there was
a time during our testing when we were having trouble
with our T1 voice network. At that time, TMC Labs used
the VoDSL line for our business calls. The VoDSL calls
were much clearer than our troubled regular phone
lines.
ROOM FOR IMPROVEMENT
As it currently stands, there isn't that much we could
say that would greatly improve the Voice Over G.SHDSL
Network Extender. That's because its greatest strength
is its simplicity. For instance, if we were to suggest
some elaborate GUI, that would increase the
functionality but may sacrifice its core
functionality. In any case, Net to Net's other
products address such additional features. However, we
would go as far as to say that some type of simple
monitoring program would be helpful so that users
could see the packets being sent and notice if there
is any fluctuation on the SHDSL connection.
CONCLUSION
Net to Net's Voice Over G.SHDSL Network Extender does
exactly what it set out to do. Because of SHDSL and
the functionality of the chips inherent in the boxes,
this DSL connection can reach up to a 30,000-foot
distance. At this distance, the quality of the
connection is comparable to that of a 12,000-foot
distance using ADSL. Furthermore, the VoDSL line, the
ability to connect to a PC or LAN directly through any
Ethernet port, and the simplicity of the entire
operation makes the Voice Over G.SHDSL Network
Extender an effective and efficient product.
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