RFC 935 (rfc935) - Page 1 of 13


Reliable link layer protocols



Alternative Format: Original Text Document



Network Working Group                                        J. Robinson
Request for Comments: 935                                            BBN
                                                            January 1985

                     RELIABLE LINK LAYER PROTOCOLS


Status of This Memo

   This RFC discusses protocols proposed recently in RFCs 914 and 916,
   and suggests a proposed protocol that could meet the same needs
   addressed in those memos.  The stated need is reliable communication
   between two programs over a full-duplex, point-to-point communication
   link, and in particular the RFCs address the need for such
   communication over an asynchronous link at relatively low speeds.
   The suggested protocol uses the methods of existing national and
   international data link layer standards.  This RFC suggests a
   proposed protocol for the ARPA-Internet community, and requests
   discussion and suggestions for improvements.  Distribution of this
   memo is unlimited.

Introduction

   This RFC is motivated by recent RFCs 914 and 916, which propose new
   standards for protocols that transfer serial data reliably over
   asynchronous communication lines.  In this note, I summarize
   widely-used standards that have been in existence for some time that
   might be appropriate for this environment.  I hope that the existing
   standards will be found to meet the needs the new proposals seek to
   address.

   In both the US and international standards areas, there are two major
   categories of serial data communication standards for the link layer.
   These categories are character-oriented and bit-oriented.  The first
   is the older class; it is standardized in the US standard ANSI
   X3.28-1976 (which superseded the original version of 1971), and in
   the ISO standards IS 1745, IS 2111, IS 2628 and IS 2629.  Although
   frequently used in synchronous environments, wherein the name binary
   synchronous (or bisynch) is used, these standards use the term "basic
   mode" to describe their procedures.  The latter class is standardized
   in the US standard ADCCP (Advanced Data Communication Control
   Procedures), ANSI X3.66- 1979, and in the ISO standard HDLC
   (High-level Data Link Control procedures), in IS 3309, IS 4335 and IS
   7809.

   Other international standards, draft standards and vendor standards
   follow the ADCCP/HDLC procedures.  Among these are SDLC (IBM), X.25
   LAPB (CCITT), IEEE 802.2/ISO 8802.2 LLC (LAN Logical Link Control)
   and ISDN LAPD (CCITT).  Many vendors have built equipment which meets




Robinson