PPP in HDLC-like Framing
RFC 1662
| Document | Type |
RFC - Internet Standard
(July 1994; Errata)
Obsoletes RFC 1549
Also known as STD 51
|
|
|---|---|---|---|
| Author | William Simpson | ||
| Last updated | 2020-01-21 | ||
| Stream | Internent Engineering Task Force (IETF) | ||
| Formats | plain text html pdf htmlized (tools) htmlized with errata bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 1662 (Internet Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group W. Simpson, Editor
Request for Comments: 1662 Daydreamer
STD: 51 July 1994
Obsoletes: 1549
Category: Standards Track
PPP in HDLC-like Framing
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
The Point-to-Point Protocol (PPP) [1] provides a standard method for
transporting multi-protocol datagrams over point-to-point links.
This document describes the use of HDLC-like framing for PPP
encapsulated packets.
Table of Contents
1. Introduction .......................................... 1
1.1 Specification of Requirements ................... 2
1.2 Terminology ..................................... 2
2. Physical Layer Requirements ........................... 3
3. The Data Link Layer ................................... 4
3.1 Frame Format .................................... 5
3.2 Modification of the Basic Frame ................. 7
4. Octet-stuffed framing ................................. 8
4.1 Flag Sequence ................................... 8
4.2 Transparency .................................... 8
4.3 Invalid Frames .................................. 9
4.4 Time Fill ....................................... 9
4.4.1 Octet-synchronous ............................... 9
4.4.2 Asynchronous .................................... 9
4.5 Transmission Considerations ..................... 10
4.5.1 Octet-synchronous ............................... 10
4.5.2 Asynchronous .................................... 10
Simpson [Page i]
RFC 1662 HDLC-like Framing July 1994
5. Bit-stuffed framing ................................... 11
5.1 Flag Sequence ................................... 11
5.2 Transparency .................................... 11
5.3 Invalid Frames .................................. 11
5.4 Time Fill ....................................... 11
5.5 Transmission Considerations ..................... 12
6. Asynchronous to Synchronous Conversion ................ 13
7. Additional LCP Configuration Options .................. 14
7.1 Async-Control-Character-Map (ACCM) .............. 14
APPENDICES ................................................... 17
A. Recommended LCP Options ............................... 17
B. Automatic Recognition of PPP Frames ................... 17
C. Fast Frame Check Sequence (FCS) Implementation ........ 18
C.1 FCS table generator ............................. 18
C.2 16-bit FCS Computation Method ................... 19
C.3 32-bit FCS Computation Method ................... 21
SECURITY CONSIDERATIONS ...................................... 24
REFERENCES ................................................... 24
ACKNOWLEDGEMENTS ............................................. 25
CHAIR'S ADDRESS .............................................. 25
EDITOR'S ADDRESS ............................................. 25
1. Introduction
This specification provides for framing over both bit-oriented and
octet-oriented synchronous links, and asynchronous links with 8 bits
of data and no parity. These links MUST be full-duplex, but MAY be
either dedicated or circuit-switched.
An escape mechanism is specified to allow control data such as
XON/XOFF to be transmitted transparently over the link, and to remove
spurious control data which may be injected into the link by
intervening hardware and software.
Some protocols expect error free transmission, and either provide
error detection only on a conditional basis, or do not provide it at
all. PPP uses the HDLC Frame Check Sequence for error detection.
This is commonly available in hardware implementations, and a
software implementation is provided.
Simpson [Page 1]
RFC 1662 HDLC-like Framing July 1994
1.1. Specification of Requirements
In this document, several words are used to signify the requirements
of the specification. These words are often capitalized.
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