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Technical Reference for ZyXEL omni.net series
8-9
X.75 Bundled Call
A bundle connection is initiated at the calling site by sending two consecutive SETUP messages to the
network. The two SETUP messages are all the same except for the Call Reference values.
[AT&Jn] can be used for bundle configuration as follows:
AT Command Description
AT&J0
Disables B-channel bundling.
AT&J1
Enables B-channel bundling in answer mode only.
AT&J2
Enables B-channel bundling in call mode only.
AT&J3
Enables B-channel bundling in both call and answer modes.
If channel bundling is enabled, the [ATDIs] command will generate two consecutive SETUP messages to
invoke bundle initiation.
For Northern Telecom ISDN, each BRI destination phone number can only be called once in any time. In order
to use two B channels for aggregation, we must place two calls with different phone numbers. The following
command can be used for this purpose:
& ATDI[phone_number_1]+[phone_number_2]
If the called site receives two consecutive SETUP messages with the same Calling Party Number and Bearer
Capability then it is deemed as a bundle request. The two data calls are established following normal call
control procedures. That is, the network treats them as two independent calls.
The omni.net uses X.75 Multiple Link Protocol or 'cFos' channel bundling protocol to coordinate the two
B-channels. The former would need an overhead of two octets for each packet. The success of bundle
connection initiation is indicated by the connect message reported to DTE as follows:
& CONNECT 460800 / X.75M 128K / V42b
If a B-channel is unavailable at either site then the bundle initiation will fall back to single channel connection. In
this case the connect message may be as follows:
& CONNECT 460800 / X.75 64000 / V42b
Table 50. X.75 Bundled Call