Perle Systems P840 - Manual (Page 18)

ISDN Connection Management
18
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.
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Th e IS D N con n ection is m ad e
usin g th e
to th e a p prop ria te re m ote ne tw o rk
accordin g to the e ntries in the
A d dre ss C o n nect ta ble .
secon d B-chan nel
Th is IS D N co nn e ctio n is m a de
usin g th e
up o n in itial p ow e r-u p and is
m aintain e d a ccord ing to the
A u to -C all p ara m eters.
first B-channel
N etw ork B
N etw ork X
N etw ork H
N etw ork A
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IS D N N etw o rk
R em o te N e tw o rk
N etw ork B
N etw ork C
N etw ork D
N etw ork E
N etw ork F
N etw ork G
N etw ork H 55 5 -2 000
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ISD N N um be r
N etw orks C th rou g h 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 P840s 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 P840
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 P840.
While an ISDN call is up and connected, all traffic within the sessions will be transferred to the partner P840 across the
ISDN call.