3com 7000 Manual De Usuario
1
-
2
C
H
A
P
T
E
R
1:
B
R
I
D
G
E
/R
O
U
T
E
R
M
O
D
U
L
E
Typically, the Bridge/Router module is used to interconnect LANs
running protocols such as Transmission Control Protocol/Internet
Protocol (TCP/IP) or Novell Internetwork Packet Exchange (IPX). The
module offers full LAN-to-LAN connectivity at speeds up to 64 Kilobits
per second (Kbps) on each ISDN channel (128
Kbps i
n total) and up to
2 Megabits per second (Mbps) on the WAN port.
The maximum bandwidth of the Bridge/Router Module is 2 Mbps. If you
have a single leased-line link running at 2 Mbps connected to a WAN
port, you must disable the ISDN ports and the second WAN port.
In the USA, some ISDN services run over 56 Kbps channels. Basic Rate
ISDN therefore offers connectivity of 112 Kbps in total.
Benefits of ISDN
ISDN is an extension of the national and international public switched
telephone network, which offers a digital end-to-end telecommunication
system, providing a better quality service than available using the analog
telephone network. The principal benefits of ISDN are:
■
Fast call setup times, typically taking less than one second for national
calls.
■
Greater bandwidth with multiple channels.
The basic rate service, often referred to as ISDN 2, carries two 64 Kbps
(possibly 56
Kbps i
n USA) user channels, called B channels and one
16 Kbps control channel called the D channel. The line service is
presented into the customers premises through a standard RJ45 socket.
The PRI Bridge/Router module is designed to operate with Primary Rate
ISDN services provided to the AccessBuilder 7000 through the PRI
Interface M
odule and supports up to eight 64
Kbps (
possibly 56
Kbps i
n
USA) user channels.
A significant aspect of the ISDN service is that it can be provided over
the same wiring that was installed for the original telephone service.
Therefore, ISDN can be made available relatively cheaply almost
anywhere that previously had access to the analog system
. T
he cost of