ACC HDLC/LAP-B (ABM) User's Guide

Chapter 1 13
Overview
Product Features
Product Featur es
This software provides Level 2 interface operation within the BAC class
of procedures recommended by ITU-T (C CITT). As described in the
standards cited below, BAC (Balanced operation Asynchronous balanced
mode Class) applies to point-to-point configurations involving two
combined stations on a logical data link. Unlike primary/secondary
stations, these may have an equal (balanced) stake in the responsibility
for data link management.
NOTE For Level 2 interface operation within the unbalanced class of p rocedures
(UNC, for Unbalanced operation Normal response mode Class),
Hewlett-Packard provides a separate ACC accessory product: The HDLC
NRM Protocol product. (The HDLC NRM Protocol accessory includes an
SDLC loop mode option.)
The LAP-B (ABM) protocol is defined in ISO standards 3309, 4335, and
6256 as follows:
• Standard 3309 pertaining to ‘Data communications - High level data
link control procedures - Frame structure’;
• Standard 4335 pertaining to ‘Data communications - High level data
link control procedures - Elements of procedures’, and
• Standard 6256 pertaining to ‘Data communications - HDLC balanced
class of procedures’.
All were drawn up by ISO/TC 97, Computers and information processing.