Enterasys Networks CSX7000, CSX5500, CSX6000 manual Lapb Configuration Elements

USER’S GUIDE

BEARER CHANNELS

A list of bearers (a channel map) that will be used on the line associated with this X.25 access. 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 CONFIGURATION ELEMENTS

Link Access Protocol-Balanced (LAPB), is a data link layer protocol that is used in X.25 connections. LAPB is based on the HDLC protocol.

Note: If you are unsure of any of these values, use the default values where provided.

LAPB SEQUENCE NUMBER RANGE

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). Using modulo 128, the DTEs can send up to 127 frames without receiving an acknowledgment. Using modulo 8, the DTEs can send up to 7 frames without receiving an acknowledgment. The default value is modulo 8.

TIMER T1

This timer defines the maximum time to wait for responses to pending commands. The range for the T1 timer is 1 to 10 seconds. The default value is 1 second.

TIMER T3

This timer signals that an excessively long idle time is occurring on the link. LAPB requires that Timer T3 be greater than Timer T1. The range for the T3 timer is 2 to 20 seconds. The default value is 10 seconds.

MAXIMUM NUMBER OF FRAME RETRANSMISSIONS

This is the maximum number of frame retransmissions that can be performed (commonly known as “N2”). If this maximum is exceeded, the link is considered out of order. The range for the maximum number of frame retransmissions is 1 to 5 retransmissions. The default value is 3 retransmissions.

MAXIMUM NUMBER OF OUTSTANDING FRAMES

Enter the maximum number of frames that the transmitting station may have outstanding at any given time (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. The range for the maximum number of outstanding frames is 1 to 7 frames. The default value is seven frames.

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