Operation Manual

Introduction to NetWare MultiProtocol Router for ISDN 3.1 33
cal B channel (or B channels) is (are) always available for the respec-
tive connection, the same way a leased line or a LAN media is.
♦♦ Initial call set-up
These classic WAN links are set up only once, mostly manually by
using CALLMGR, or, if static routes/services have been configured,
they are set up by a request from the respective network protocol
each time a packet is addressed to a remote destination.
♦♦ Physical clear-down
For control of all underlying physical ISDN connections over the B
channels, you configure the Inactivity Timeout for each destination.
It will clear down B channels physically when no packets are to be
transmitted to a destination. The B channel is always set up again
automatically within 1 to 2 seconds if data is to be transferred. Thus,
this process of underlying connection set-up is completely transpar-
ent to users or applications.
♦♦ ISDN interface stays reserved for the connection
Whereas you configure an Inactivity Timeout in this case, you do not
configure a Disconnect Timeout. Thus, although the Inactivity
Timeout clears down the B channel physically, the ISDN interface,
which has been assigned by the network administrator to handle the
link and treats one or more underlying B channels according to the
configuration for the specific connection, stays logically connected
and reserves underlying B channels for the connection. This means
that, even in times when the B channel is physically idle and could
theoretically be used for any other connection, the ISDN interface
will reject any call set-up request coming from either site of this
interface: If a call set-up request is issued from within the LAN using
another call destination over the same ISDN interface, manually
through CALLMGR or by a data packet for example, the request will
be rejected by this ISDN interface. If a remote site dials in and
addresses this ISDN interface, the call will "reach" the ISDN-Control-
ler this interface belongs to, the physical B channel will be set up to
negotiate connection parameters (whenever a B channel is physically
idle, it is available and will listen to any call-set up request if not
configured differently) and, since the information on which ISDN
interface is addressed is transmitted over the B channel (AVM
Proprietary: by the Destination Subaddress; for PPP over ISDN, this
is different), the ISDN interface will then immediately reject the call
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