Operation Manual

26 NetWare MultiProtocol Router for ISDN 3.1 Installation and ISDN Configuration Guide
ings or by avoiding critical situtations, configuration errors, unde-
sired or too frequent use of B channels by functions that disable a B
channel for any physical action.
♦♦ Features clearing down the physical connection on the B
channel
Inactivity Timeout and Self-Learning Inactivity Timeout clear down
a B channel and are features that optimize ISDN generally for inter-
networking. In other words, they are indispensable for using ISDN
in a cost-efficient way. Another timer, the Disconnect Timeout, plays
a more specialized role, but is also described in this category.
The Inactivity Timeout functions exclusively clear down the physical
B channel, so that no further charges accrue until the B channel is set
up again physically. But it does not "touch" the logical ISDN B
channel connection. This means that everything that has been negoti-
ated once during an initial set-up of a B channel with the remote site
over an ISDN interface for this connection remains active, and the
interface itself is logically reserved for this connection. For remote
node access, however, the interface reservation can be disabled to
allow more than one remote node access to a single interface. The
negotiated connection parameters nevertheless remain valid until
the Disconnect Timeout expires.
The Disconnect Timeout can also clear down a physical connection,
depending on how it is configured in relation to the Inactivity
Timeout, but its main purpose and function is to clear down the
logical ISDN connection on the B channel. This means that every-
thing that has been negotiated once during an initial set-up of a B
channel with the remote site over an ISDN interface for this connec-
tion is deactivated and the interface itself is logically released and
available for any following dial-up operation to negotiate and set up
a connection. Since it releases an ISDN interface, the Disconnect
Timeout is one of the functions that can be used if an interface is not
to be used to maintain a classic WAN link to a remote site, but is to
be used dynamically to negotiate and set up different connections to
remote sites.
♦♦ Features preventing set-up of a physically idle B channel
For this purpose, the NetWare MultiProtocol Router for ISDN 3.1
provides a number of filter and spoofing mechanisms. They prevent
data packets addressed to a remote site from causing an idle B
channel to be set up in order to transmit the packets over ISDN.
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