Network Router User Manual

7 LAPB and X.25 configuration
Nortel Secure Router 8000 Series
Configuration -WAN Access
7-28 Nortel Networks Inc. Issue 5.3 (
30 March 2009)
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Configuring SVC maximum idle time
Specify a time period. If SVC is idle within this period (no packet interaction), the X.25
automatically clears the SVC to avoid unnecessary expenses. This SVC is re-establishes
before the data packet is sent next time. The activation of these characteristics does not
affect data transmission.
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Configuring the maximum number of SVCs associated with the same address mapping
You can specify the maximum number of VCs to be set up on the same address mapping.
The X.25 can establish a maximum of 8 VCs on one address mapping.
In case of large traffic and low wire speed, you can increase this parameter to reduce data
loss.
By default, one address mapping is associated with only one VC.
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Configuring the pre-acknowledgment of packets
According to the X.25 protocol, the receiving party sends an acknowledgment only after
the receiving window is full (the number of received packets equals the value of
window-size input-window-size).
In some X.25 networks, however, the delays may be long, resulting in low efficiency in
the sending and receiving of data. Therefore, X.25 allows a value to be specified. Each
time the number of received packets reaches the value, the acknowledgment is sent to the
peer, thus improving the receiving and sending efficiency. The value, called a
"receive-threshold", ranges from 1 to 127. If it is set to 1, every packet is acknowledged.
If it is set to window-size input-window-size, the acknowledgment is sent only after the
receiving window is full.
In applications requiring a high response speed, this function is especially important.
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Configuring X.25 user facility
The X.25 protocol defines various user facility options. The user can choose and
configure them. You modify these configurations in the following manner:
− Modifying the configuration on the basis of an X.25 interface using the x25
call-facility..... command: The configuration is effective in every call originating
from this X.25 interface.
− Modifying the configuration on the basis of the address mapping by using the x25
map...... command: The configuration is effective only in the calls originating from
this address mapping.
The x25 pvc command also supports two options:
− window-size: indicates the window size of the PVC.
− packet-size: indicates the maximum packet length of the PVC.
If you do not select these two options in the x25 pvc command, the set PVC chooses the
default value of the X.25 interface.
Use the x25 roa-list command in the system view to configure the parameter name that
is also the ROA ID list.
For example:
[Nortel] x25 roa-list list1 12 34 567
Then list1 can be cited in the serial interface view.
[Nortel-Serial0/0/0] x25 call-facility roa-list list1
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Configuring the sending queue length of VC
The sending and receiving queue lengths of the VC can be specified for the X.25 of the
SR8000 to adapt to different network environments.