6-36 MAX 6000/3000 Network Configuration Guide
Configuring X.25
Always On/Dynamic ISDN (AO/DI)
Introduction
AO/DI is a networking service that enables you to send and receive data by means of an X.25
connection by way of an ISDN line (or leased-56k line) as well as by means of switched
B-channels. Through its use of X.25 and Bandwidth Allocation Control Protocol (BACP), the
MAX avoids dialup charges and usage of switched B-channels whenever it sends or receives
data by way of the X.25 connection.
In a traditional ISDN environment, data moves across B-channels, and signalling information
moves across the D-channel. Because signalling information uses a small percentage of
available D-channel bandwidth, AO/DI was developed to maximize bandwidth usage while
reducing the necessity that all data travel by way of B-channels. Lucent’s implementation of
AO/DI enables you to configure a nailed X.25 connection by way of serial WAN, nailed
B-channel, or nailed D-channel connections.
Among the functions that can take advantage of AO/DI are the following:
•Transfer of email
•Reception of news broadcasts and other pushed information
•Automated collection of data
For all Lucent units, AO/DI enables you to use X.25 bandwidth up to 9600 bps. If data
transfers require more bandwidth, B-channels are dialed and combined using BACP. Although
MAX units support an X.25 by way of any dedicated or leased connection, the Pipeline units
support X.25 only through a serial WAN connection or nailed D-channel (for AO/DI). Contact
your carrier for more details.
How it works
When you configure AO/DI for a connection, data flows by way of the X25 connection as long
as bandwidth usage is less than the value specified in the Ethernet > Connections > any
Connection profile > Encaps options > X25 Chan Target Util parameter. The MAX dials a
B-channel if the Average Line Utilization (ALU) for the connection stays above the value in
X25 Chan Target Util for the amount of seconds specified in the Ethernet > Connections > Any
Connection profile > Encaps Options > Add Pers parameter. The MAX dials additional
B-channels if the ALU for the connection stays above the value in the Ethernet > Connections
> any Connection profile > Encaps options > Target Util parameter.
When the MAX adds bandwidth on the basis of dynamic bandwidth allocation (DBA), it
brings up a B-channel to transport data and stops sending data on the X.25 call. Because the
9600 bps bandwidth available by way of the X.25 connection is so small when compared to
that available through the B-channel, it is not efficient to continue to transfer data by way of
the nailed D-channel connection simultaneously.
When the device that originated the call (typically at the customer premises) requires an
additional B-channel, it requests a phone number from the MAX. The MAX sends the number
specified in the Ethernet > X.25 > Any X.25 profile > B Ch # parameter. If you do n ot specify a
number in B Ch #, the MAX dials the first active, available B-channel for which you specify
the:
•Net/T1 > Line Config > Line profile > Line m > Ch n # parameter
•Net/E1 > Line Config > Line profile > Line m > Ch n # parameter