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ISDN Connection Management
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Combination
A combination of the Address Connect and Auto-Call options may be configured when a semi-permanent
connection is required to one remote site and a dynamic connection is required to multiple sites. A dynamic
connection indicates that the remote site for the second ISDN call will change depending upon what destination
IP address is required for the connection. One ISDN B-channel is configured to have an Auto-Call ISDN
number and the other B-channel may be used for the Address Connect functions.
555-1000
555-8000
The ISDN connection is made
using the
to the appropriate remote network
according to the entries in the
Address Connect table.
secondB-channel
This ISDN connection is made
using the
upon initial power-up and is
maintained according to the
Auto-Call parameters.
first B-channel
Network B
Network X
Network H
Network A
555-2000
ISDN Network
Remote Network
Network B
Network C
Network D
Network E
Network F
Network G
Network H
555-2000
555-3000
555-4000
555-5000
555-6000
555-7000
555-8000
ISDN Number
Networks C through G
Figure 2 - 3 Auto-Call & Address Connect WAN Topology
Connection Process
When a LAN client requests a session with a LAN server, the client will initiate the session by sending a session
connection request to the server. If the server is located on a remote LAN, the session connection request must be
sent to that remote LAN before the server can process the session connection request and reply to it. Any of the call
establishment processes may be used to establish the ISDN call between the routers in order to establish a LAN
session between the local and remote LANs.
Once the client-server session has been established, keepalive or status packets are generated by either or both ends
of the session. The keepalive packets are used to verify the status of the device at the opposite end of the session.
When Connection Management is enabled, LAN sessions that are established across the ISDN calls are monitored
and maintained in a table. The session table may contain up to 256 entries for each supported session type, with the
router filtering all traffic for any sessions over the 256 limit of the table. The 257th and greater LAN sessions will not
be allowed by the router.
While an ISDN call is up and connected, all traffic within the sessions will be transferred to the partner router across
the ISDN call.