Chapter 1:
Introduction
1-2
WPIM-S/T User’s Guide
1.1.1 Performance
The capability of the WPIM-S/T is 128 Kbps when both B Channels are
active.
There are several user-configurable timers that control the connect and
disconnect time-outs to provide optimum performance. These are detailed
in
Chapter 3
.
1.2 ISDN
ISDN provides inexpensive switched digital access to remote sites. The
ISDN BRI standard provides for two high-speed 64-Kbps
bearer (B)
channel
s used for voice or data connections and one 16-Kbps signaling
data (D) channel used for call setup, signaling, and other information.
ISDN allows all types of information to be transmitted including voice,
data, fax, and video. Multiple devices can be linked to a single ISDN
connection, each having their own telephone number. Two or more
channels can be combined into a single larger transmission pipe offering
variable transmission speeds.
1.3 ISDN CALL BACK-UP
The ISDN call back-up feature provides a back-up link for a remote site
or branch office when one or more primary WAN interfaces for a frame
relay circuit or a
nailed-up PPP
connection fails. The WPIM-S/T serves
as the backup medium for this primary connection, using the ISDN
interfaces to back-up any primary interfaces that have been configured for
ISDN back-up.
The following are two reasons to use ISDN call back-up:
•
Hardware failure of a nailed-up PPP connection
•
PPP
fails to connect (software problem)
Use call back-up if either of the following conditions exist when using
Frame Relay:
•
DLCI
circuit fails to connect in 12 minutes
•
DLCI goes inactive
