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198 CHAPTER 16: CONFIGURING LAPB AND X.25
Figure 61 Relations among LAPB, X.25 and X.25 switching
Configure LAPB LAPB configuration includes:
■ Configure the link protocol of the interface to LAPB
■ Configure LAPB protocol parameters
1 Configure the Link Layer Protocol of the Interface to LAPB
Perform the following command in the interface view.
Table 229 Configure the link layer protocol of the interface to LAPB
If not specified, the working mode of LAPB is DTE by default.
2 Configure LAPB Protocol Parameter
a Configure LAPB operating mode (also called modulo)
There are two LAPB modulus: Modulo 8 and Modulo128. Each data frame (I
frame) is numbered by sequence, the number can be any from 0 to modulo
minus 1, and the sequence number is selected periodically within the range of
the modulo.
In the interface view, configure as follows:
Table 230 Configure LAPB frame numbering mode
By default, the LAPB modulus is Modulo 8.
b Configure LAPB parameter K
The parameter K in the LAPB window represents the maximum number of I
frames numbered in sequence that is to be identified by the DTE or DCE in any
specified time.
In the interface view, configure as follows:
Table 231 Configure LAPB window parameter K
By default, k is 7.
c Configure LAPB N1, N2
Inter-network protocol
X.25
switching
X.25
LAPB
Operation Command
Configure the link layer protocol of the interface to
LAPB
link-protocol lapb [ dte |
dce ] [ ip ]
Operation Command
Configure LAPB frame numbering mode (also called
modulo)
lapb modulo { 128 | 8 }
Operation Command
Configure LAPB window parameter K lapb window-size k-value
Restore the default value of LAPB window parameter
K
undo lapb window-size