Isdn-Backup Connections - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

Configuring Backup WAN Connections
Backing Up Primary WAN Connections
3-6
Analog modems provide comparatively little bandwidth. (The ProCurve
Secure Router analog module provides between 300 bps and 33.6 kbps.) When
analog modems are incorporated into WAN routers, they are designed only to
provide redundancy for other WAN lines, not to furnish a long-term WAN
connection.

ISDN-Backup Connections

ISDN is a dial-up WAN connection that supports voice, data, fax, and video
services over standard telephone lines. Unlike analog communications, ISDN
communications are digital.
Public carriers offer two types of ISDN services:
Basic Rate Interface (BRI)
Primary Rate Interface (PRI)
ISDN BRI provides two 64-Kbps bearer (B) channels and one 16 Kbps data (D)
channel. The B channels carry data, and the D channel handles the signaling
and call control for the ISDN line.
PRI ISDN, on the other hand, provides 23 B channels and 1 D channel in North
America and Japan. It provides 30 B channels and 1 D channel in Europe, Asia
(except Japan), Australia, and South America. (When PRI includes 30 B
channels, channel 0 is used to maintain synchronization and is not counted as
either a B or D channel.) The transmission rates for PRI ISDN match the
transmission rates for an E1- or T1-carrier line. In North America and Japan,
PRI ISDN provides 1.544 Mbps. In other areas, PRI ISDN provides 2.048 Mbps.
In an ISDN connection, the B channels are treated independently. They can
be used for simultaneous voice and data; in other words, you can talk on the
phone and surf the Web at the same time. For example, if you have an ISDN
BRI connection, you can use both channels for data transmissions to a remote
network, or you can use each channel to connect to a different remote office.
Because the ProCurve Secure Router supports BRI ISDN for backup connec-
tions, this chapter focuses on BRI ISDN. (The ProCurve Secure Router also
supports BRI ISDN for primary WAN connections. For more information, see
Chapter 8: Configuring Demand Routing for Primary ISDN Modules in the
Basic Management and Configuration Guide.)