ISO IEC 7776-1995 PDF

Full title and description

ISO/IEC 7776:1995 — Information technology — Telecommunications and information exchange between systems — High-level data link control procedures — Description of the X.25 LAPB-compatible DTE data link procedures. Defines an application of HDLC procedures to describe the structure, elements and operation of a DTE implementing the X.25 LAPB-compatible data‑link procedures (DTE↔DCE and DTE↔DTE, duplex links, synchronous or start/stop transmission).

Abstract

This International Standard (edition 2, July 1995) cancels and replaces the 1986 edition and specifies the frame structure, procedural elements and detailed behaviour for DTEs using the LAPB-compatible X.25 data‑link procedures. An Amendment (1996) adds the modulo 32 768 option and the multi‑selective reject option.

General information

• Status: Published (International Standard; reviewed and confirmed following review).
• Publication date: July 1995 (Edition 2).
• Publisher: ISO/IEC (joint publication by the International Organization for Standardization and the International Electrotechnical Commission).
• ICS / categories: 35.100.20 (Telecommunications and information exchange between systems).
• Edition / version: Edition 2 (1995). Amendment: ISO/IEC 7776:1995/Amd 1:1996.
• Number of pages: 39 pages (main document); Amendment 1 (1996) — 28 pages.

Scope

Specifies an application of relevant HDLC standards to define the DTE data‑link procedures compatible with X.25 LAPB. The standard covers frame formats, control fields, error handling and recovery procedures, selective reject options, multilink behaviour examples and conformance provisioning for implementations operating over duplex links using synchronous or asynchronous (start/stop) transmission. The 1996 amendment incorporates the multi‑selective reject option and a modulo 32 768 sequence numbering option.

Key topics and requirements

• Definition of frame structure and control field usage for LAPB‑compatible operation.
• Elements of procedures: link establishment, data transfer, acknowledgement, retransmission and recovery.
• Multilink procedure (MLP) and examples of multi‑link use.
• Conformance requirements and PICS (Protocol Implementation Conformance Statement) proforma for implementers.
• Amendment options: multi‑selective reject (option 3.3) and modulo 32 768 numbering (option 10.2).

Typical use and users

Used by implementers of legacy and specialized packet‑switching equipment, telecom protocol engineers, test and conformance laboratories, and standards committees working with X.25/LAPB and HDLC‑based links. It is primarily relevant where interoperation with X.25 LAPB‑compatible DTEs or DCEs is required or where precise, standards‑level data‑link behaviour must be specified or tested.

Related standards

Associated HDLC/X.25 and related standards include ISO/IEC 3309 (frame structure), ISO/IEC 4335 (elements of procedures), ISO/IEC 7809 (consolidation/options for HDLC procedures), and other X.25 family and HDLC documents. The 1996 amendment draws options from ISO/IEC 7809:1993. ISO/IEC JTC 1/SC 6 is the responsible technical committee.

Keywords

HDLC, LAPB, X.25, DTE, DCE, data link control, frame structure, selective reject, modulo 32768, multilink, PICS, conformance.

FAQ

Q: What is this standard?

A: An international standard that specifies high‑level data‑link control procedures for DTEs compatible with the X.25 LAPB protocol (ISO/IEC 7776:1995, Edition 2).

Q: What does it cover?

A: It covers frame formats, control and sequence numbering, link setup and release, error detection and recovery, selective reject options and conformance provisions for implementations operating over duplex links (synchronous or start/stop). The 1996 amendment adds the multi‑selective reject option and modulo 32 768 numbering.

Q: Who typically uses it?

A: Telecommunications protocol implementers, network equipment vendors maintaining X.25/LAPB compatibility, test houses and standards developers concerned with HDLC and X.25 data‑link behaviour.

Q: Is it current or superseded?

A: ISO/IEC 7776:1995 (Edition 2) replaced the 1986 edition. The 1995 edition was issued with an amendment in 1996 and — according to the ISO catalogue entry — was reviewed and confirmed (remained current at last review). Users should check the ISO catalogue for any later revisions or withdrawal notices before relying on it for new product development.

Q: Is it part of a series?

A: Yes — it is part of the HDLC/X.25 family of standards developed under ISO/IEC JTC 1/SC 6 and relates to other HDLC procedural documents and X.25 specifications (see ISO/IEC 3309, 4335, 7809, etc.).

Q: What are the key keywords?

A: HDLC; LAPB; X.25; data link; DTE; DCE; selective reject; modulo 32768; multilink; conformance.