MX-2100/2104
Installation and Operation Manual
Chapter 1 General Information
Application Considerations
1-29
MX-2100
MX-2100
Modem
Modem
Modem
Modem
Modem
Modem
KCL
KCL
I/
O
M
od
ule
s
I/
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M
od
ule
s
KML A
KML B
KML A
KML B
Active Link
Switched
Data
Network
Switched
Backup Link
Figure 1-17. Typical Switched Backup Configuration
Since usually the data rate supported by dial-up modems does not exceed
19.2 kbps, the backup link can also be configured for operation at 9.6 or
19.2 kbps. This means that in case of a main link failure, only a fraction of the
normal traffic (carried by the channels defined by the system administrator as
having high priority) can still be transmitted.
When a failure occurs on the main link, a MX-2100 activates the DTR line in the
backup link interface connector. The dial-up modem connected to this link dials a
preprogrammed number, to set up a call to the other MX-2100. After the called
destination answers, the traffic is switched to the backup link (if the call cannot be
established within a predetermined interval, the attempt is aborted).
When the primary link returns to normal operation, the dial-up modem hangs up
and thus disconnects the backup link.
Switched Backup Using ISDN Lines
This mode is supported when a KML.10 module is connected to a switched ISDN
line. In this case, higher data rates are available for the backup link:
64 kbps (use of one B channel) and 128 kbps (use of both B channels).
shows a typical switched backup application.
MX-2100 offers a proprietary algorithm, which enables using both B channels to
obtain the 128 kbps rate even when differential delay is present. However, the use
of a proprietary algorithm means that KML.10 modules must be installed at both
ends of the link. This proprietary algorithm, based on the BONDING mode 1
protocol defined by the Bandwidth-on-Demand Inter-operability Group
(BONDING), enables the KML.10 modules to combine the bandwidth of the two
B channels while correcting for differential delays of up to 512 ms between the
two channels. This delay is sufficient to enable using links which pass through up
to two satellite hops.