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Network Connectivity
Glossary SDSL (Symmetric
DSL): This is a business-class DSL offering. "Symmetric"
means that both the upload and the download speeds are the same.
This type of service is also typically more reliable than ADSL, and
it usually comes with a Service Level Agreement. This is important
for transferring or sharing large files, web hosting, or running
servers that need a constant connection to the Internet with
consistently high upload
speeds.
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IDSL (ISDN Digital
Subscriber Line): DSL over an ISDN type of digital line. As ISDN
line has two B-channels that are 64k each, and one D-channel
that is 16k. IDSL effectively combines these two B-channels to
provide 128Kbps of synchronous bandwidth, and some varieties
of IDSL can also combine the B- and D-channels to provide a
total of 144Kbps. The ISDN-type line allows this variety of
DSL to reach a much greater distance, but the cost of having
an ISDN-type line is high.
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ISDN: This technology is faster than
regular modems, but it is digital and it is a dialup. Not meant to
be a true permanent connection, in that it can lose the connection
and then just dial back up. An ISDN line has two B-channels that are
capable of 64Kbps each. It also has a D-channel which is 16Kbps,
used for carrying signaling information. Each channel also has an
associated phone number with it, which can be used like a regular
analog voice line when hooked up to the appropriate hardware. You
can subscribe to service for either one channel or both..
Frame Relay: A very reliable,
secure, digital service. The rock-solid reliability of
tried-and-true Frame Relay service makes it excellent for
"mission-critical" applications and corporate servers. Another
benefit of Frame Relay is that you can have your connection hooked
up to the Internet, and you can also add PVC (Permanent Virtual
Circuits) to multiple other sites that also have Frame Relay. This
way, you can connect to your ISP and also connect directly to
multiple branch offices of a business, all using the same Frame
Relay connection. This is great for interconnecting multiple
locations.
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