3Com Remote Network Adapter Kullanıcı El Kitabı - Sayfa 18
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3 C
I
O M
M P A C T
3Com Impact External Digital Modems and Adapters
Give You Speed and Reliability
Basic ISDN Advantages
ISDN service —offered by major
telephone companies around the
world— offers many advantages
over analog telephone connections.
Performance and Economy
ISDN is fast. Using a single tele-
phone connection, Basic Rate ISDN
provides two B channels for digital
calls, each carrying up to 64 Kbps
of data or voice communication.
Combining the two channels via
Multilink PPP creates a 128 Kbps
data pipe between two sites.
For Internet users and teleworkers,
ISDN speeds the process of locat-
ing data resources and download-
ing files. ISDN saves money, too,
by reducing telephone line usage
time and associated charges. A
data file that takes four minutes to
transmit with the fastest analog
modem (28.8 Kbps) takes less than
one minute with an ISDN external
digital modem or ISA adapter
using Multilink PPP.
With ISDN, calls connect in a mat-
ter of seconds. Analog modems
must negotiate the speed that the
telephone line will support, which
can take up to 30 seconds to set up
a connection.
Analog Modems
2400 bps
14.4 Kbps
ISDN digital modems and adapters are four times as fast as the fastest analog modems —
and nearly 50 times as fast as many analog devices.
18
I S D N A
Digital Reliability
ISDN is a digital technology, trans-
mitting 0s and 1s over the tele-
phone line instead of modem tones.
As a result it is inherently very reli-
able, like an audio CD or a CD-
ROM. By contrast, analog phone
lines pick up noise from their sur-
roundings, which can block connec-
tions, slow transmission, and cor-
rupt data.
Digital
Modems
and
Adapters
One
ISDN
Channel
28.8 Kbps
64 Kbps
D A P T E R S
A N D
Multilink PPP—Getting the
most out of ISDN
To give you the highest possible
transmission speed over an ISDN BRI
connection, all 3Com Impact adapters
and digital modems support the
Multilink PPP (Point-to-Point Protocol)
and IETF Internet Standard. With
Multilink PPP on both ends of a BRI
connection, two 64 Kbps ISDN chan-
nels are combined into one 128 Kbps
data pipe, without additional hard-
ware or lines from your ISDN
provider.
Multilink PPP, combined with 3Com's
bandwidth on-demand technology,
lets you utilize your ISDN resources
Two
how and when you need them. In
ISDN
cooperation with 3Com's
Channels
(Multilink
AccessBuilder 4000-ISDN, your 3Com
PPP)
ISDN ISA adapter can automatically
open a second B channel to handle a
sudden transmission load, then trans-
parently close the second connection
when network requests are satisfied.
Just as easily, a Multilink PPP session
makes room for an outgoing voice call
or fax transmission starting over the
3Com Impact external modem's
Phone Out port, then resumes full
bandwidth when the call or fax ends.
Compared with other ISDN multiplex-
ing schemes, the Multilink PPP stan-
dard offers superior flexibility and
interoperability, giving you transpar-
ent channel aggregation—simply and
inexpensively. And with 3Com's con-
128 Kbps
tinuing support for Multilink PPP you
can count on interoperability for all
your ISDN networking, now and in the
future.
M
O D E M S