DCB BROADCAST POLLING FRAD BPF-2 BU, Руководство пользователя

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1 . DESCRIPTION
The BPF-BU is a special version of the BPF that provides for dial
and/or leased line backup for the frame relay network. Used at the
remote site only, the BPF-BU is the same hardware as standard BPF.
However, the ports are used in a different manner. To implement the
automatic backup functions the async ports are used as follows:
BPF-2 BU BPF-6 / 14 BU
Ports 1 & 2: RTU Ports 1-6 & 9-16: RTU
Port 3: Dial backup Port 7: Dial backup
Port 4: Dedicated link backup Port 8: Dedicated link backup
The BPF-BU receives data from the host on a regular basis, either
user data or a keep alive packet from the host BPF. To keep the
remote BPF-BU from going to the backup mode in the absence of user
data, the host BPF sends out a keep alive signal to the BPF-BU if
there has been no user data for 30 seconds. The keep alive does not
interfere with user data. The host BPF must have firmware version
1.7 or higher to insure the unit has the keep alive and can be used
with the remote BPF-BU units.
If the data or keep alive fails for 40 seconds, the remote BPF-BU
begins the backup process. The BPF-BU first attempts a connection
through the Leased Line port if port RTS is asserted. If RTS is not
asserted, the BPF-BU tries the Dialup port by sending an “AT” and
looking for an “OK” response. If an “OK” is returned, the BPF-BU
sends the command ATDS=0. This tells the modem to dial the
number stored in phone number register 0. The user must program
the remote modem to dial the appropriate phone number of a host
end modem. If a number cannot be stored in the modem, the number
to dial can be stored in the BPF-BU using the CBN command (see
Section 5).
The BPF-BU will continue to cycle through the backup choices, trying
to establish a connection, until a connection is made or until the
frame relay composite link is re-established. Once the Leased Line or
Dial modem backup link is established, the BPF-BU channels data
from the backup port to the RTU ports. Data from the RTU ports is
channeled back to the host via whichever port is active. The RTU
ports that are backed up in this manner can vary from a single port to
all RTU ports. If no ports are selected, the backup process will not be
performed. The backup link is dropped when the frame relay link is
re-established.