Central Site Remote Access Switch 245
C
ONFIGURING
A
LTERNATE
A
CCESSES
X.25 Accesses
4.
Enter the X.121 address of the local DTE (the CyberSWITCH).
5.
Select the data rate for the line.
6.
Enter a list of bearers (a channel map). For PRI lines, the range of channels is from 1 to 24. For
BRI lines, the range of channels is from 1 to 2. Separate bearer channels by commas, and/or list
a range by using a dash (-).
LAPB C
ONFIGURATION
I
NFORMATION
1.
Enter the LAPB sequence number range to use, regular, or extended. Extended sequence
numbering allows for frames to be assigned sequence numbers from 0-127 (modulo 128), as
opposed to 0-7 (modulo 8).
2.
Enter the duration of Timer T1, which is the maximum time to wait for responses to pending
commands.
3.
Enter the duration of Timer T3, which is used to signal that an excessively long idle time is
occurring on the link. LAPB requires that Timer T3 be greater than Timer T1.
4.
Enter the maximum number of frame re-transmissions that can be performed (this is
commonly known as “N2”).
5.
Enter the maximum number of frames that the transmitting station may have outstanding at
any given time (this is commonly known as “K”). The range for this parameter will be 1-7 if the
Modulo 8 sequence numbers are being used for LAPB, or 1-127 if Modulo 128 sequence
numbers are being used.
X.25 C
ONFIGURATION
I
NFORMATION
1.
Configure the X.25 Logical Channel Assignments. This requires entering the maximum
number of PVCs and SVCs to be supported. For X.25 over B-channel, a total of 48 virtual
circuits are supported; over D-channel 8 virtual circuits are supported. Therefore, the total
number of PVCs and SVCs combined cannot exceed the maximum number of VCs.
a.
Enter the maximum number of PVCs to support.
b.
Enter the maximum number of SVCs to support.
2.
Configure the X.25 Timers.
a.
Enter the duration of Timer T20.
This timer designates the time limit in which a restart confirmation must be returned by the
DCE (the PPSN) after a restart request has been issued by the DTE (the CyberSWITCH).
b.
Enter the duration of Timer T21.
This timer designates the time limit in which a call connected response must be returned
by the DCE (the PPSN) after a call request has been issued by the DTE (the CyberSWITCH).
c.
Enter the duration of Timer T22.
This timer designates the time limit in which a reset confirmation must be returned by the
DCE (the PPSN) after a reset request has been issued by the DTE (the CyberSWITCH).
d. Enter the duration of Timer T23.
This timer designates the time limit in which a clear confirmation must be returned by the
DCE (the PPSN) after a clear request has been issued by the DTE (the CyberSWITCH).
