Formal Notation for RObust Header Compression (ROHC-FN)
RFC 4997
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RFC - Proposed Standard
(July 2007; No errata)
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2015-10-14
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draft-ietf-rohc-epic-lite
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IETF
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IESG state |
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RFC 4997 (Proposed Standard)
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Consensus Boilerplate |
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Unknown
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Responsible AD |
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Magnus Westerlund
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Network Working Group R. Finking
Request for Comments: 4997 Siemens/Roke Manor Research
Category: Standards Track G. Pelletier
Ericsson
July 2007
Formal Notation for RObust Header Compression (ROHC-FN)
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.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document defines Robust Header Compression - Formal Notation
(ROHC-FN), a formal notation to specify field encodings for
compressed formats when defining new profiles within the ROHC
framework. ROHC-FN offers a library of encoding methods that are
often used in ROHC profiles and can thereby help to simplify future
profile development work.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of ROHC-FN . . . . . . . . . . . . . . . . . . . . . 5
3.1. Scope of the Formal Notation . . . . . . . . . . . . . . . 6
3.2. Fundamentals of the Formal Notation . . . . . . . . . . . 7
3.2.1. Fields and Encodings . . . . . . . . . . . . . . . . . 7
3.2.2. Formats and Encoding Methods . . . . . . . . . . . . . 9
3.3. Example Using IPv4 . . . . . . . . . . . . . . . . . . . . 11
4. Normative Definition of ROHC-FN . . . . . . . . . . . . . . . 13
4.1. Structure of a Specification . . . . . . . . . . . . . . . 13
4.2. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 14
4.3. Constant Definitions . . . . . . . . . . . . . . . . . . . 15
4.4. Fields . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.4.1. Attribute References . . . . . . . . . . . . . . . . . 17
4.4.2. Representation of Field Values . . . . . . . . . . . . 17
Finking & Pelletier Standards Track [Page 1]
RFC 4997 ROHC-FN July 2007
4.5. Grouping of Fields . . . . . . . . . . . . . . . . . . . . 17
4.6. "THIS" . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.7. Expressions . . . . . . . . . . . . . . . . . . . . . . . 19
4.7.1. Integer Literals . . . . . . . . . . . . . . . . . . . 20
4.7.2. Integer Operators . . . . . . . . . . . . . . . . . . 20
4.7.3. Boolean Literals . . . . . . . . . . . . . . . . . . . 20
4.7.4. Boolean Operators . . . . . . . . . . . . . . . . . . 20
4.7.5. Comparison Operators . . . . . . . . . . . . . . . . . 21
4.8. Comments . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.9. "ENFORCE" Statements . . . . . . . . . . . . . . . . . . . 22
4.10. Formal Specification of Field Lengths . . . . . . . . . . 23
4.11. Library of Encoding Methods . . . . . . . . . . . . . . . 24
4.11.1. uncompressed_value . . . . . . . . . . . . . . . . . . 24
4.11.2. compressed_value . . . . . . . . . . . . . . . . . . . 25
4.11.3. irregular . . . . . . . . . . . . . . . . . . . . . . 26
4.11.4. static . . . . . . . . . . . . . . . . . . . . . . . . 27
4.11.5. lsb . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.11.6. crc . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.12. Definition of Encoding Methods . . . . . . . . . . . . . . 29
4.12.1. Structure . . . . . . . . . . . . . . . . . . . . . . 30
4.12.2. Arguments . . . . . . . . . . . . . . . . . . . . . . 37
4.12.3. Multiple Formats . . . . . . . . . . . . . . . . . . . 38
4.13. Profile-Specific Encoding Methods . . . . . . . . . . . . 40
5. Security Considerations . . . . . . . . . . . . . . . . . . . 41
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 41
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 41
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.1. Normative References . . . . . . . . . . . . . . . . . . . 42
8.2. Informative References . . . . . . . . . . . . . . . . . . 42
Appendix A. Formal Syntax of ROHC-FN . . . . . . . . . . . . . . 43
Appendix B. Bit-level Worked Example . . . . . . . . . . . . . . 45
B.1. Example Packet Format . . . . . . . . . . . . . . . . . . 45
B.2. Initial Encoding . . . . . . . . . . . . . . . . . . . . . 46
B.3. Basic Compression . . . . . . . . . . . . . . . . . . . . 47
B.4. Inter-Packet Compression . . . . . . . . . . . . . . . . . 48
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