SCHC: Generic Framework for Static Context Header Compression and Fragmentation
RFC 8724
Internet Engineering Task Force (IETF) A. Minaburo
Request for Comments: 8724 Acklio
Category: Standards Track L. Toutain
ISSN: 2070-1721 IMT Atlantique
C. Gomez
Universitat Politecnica de Catalunya
D. Barthel
Orange Labs
JC. Zuniga
SIGFOX
April 2020
SCHC: Generic Framework for Static Context Header Compression and
Fragmentation
Abstract
This document defines the Static Context Header Compression and
fragmentation (SCHC) framework, which provides both a header
compression mechanism and an optional fragmentation mechanism. SCHC
has been designed with Low-Power Wide Area Networks (LPWANs) in mind.
SCHC compression is based on a common static context stored both in
the LPWAN device and in the network infrastructure side. This
document defines a generic header compression mechanism and its
application to compress IPv6/UDP headers.
This document also specifies an optional fragmentation and reassembly
mechanism. It can be used to support the IPv6 MTU requirement over
the LPWAN technologies. Fragmentation is needed for IPv6 datagrams
that, after SCHC compression or when such compression was not
possible, still exceed the Layer 2 maximum payload size.
The SCHC header compression and fragmentation mechanisms are
independent of the specific LPWAN technology over which they are
used. This document defines generic functionalities and offers
flexibility with regard to parameter settings and mechanism choices.
This document standardizes the exchange over the LPWAN between two
SCHC entities. Settings and choices specific to a technology or a
product are expected to be grouped into profiles, which are specified
in other documents. Data models for the context and profiles are out
of scope.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8724.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
2. Requirements Notation
3. LPWAN Architecture
4. Terminology
5. SCHC Overview
5.1. SCHC Packet Format
5.2. Functional Mapping
6. RuleID
7. Compression/Decompression
7.1. SCHC C/D Rules
7.2. Packet Processing
7.3. Matching Operators
7.4. Compression/Decompression Actions (CDA)
7.4.1. Processing Fixed-Length Fields
7.4.2. Processing Variable-Length Fields
7.4.3. Not-Sent CDA
7.4.4. Value-Sent CDA
7.4.5. Mapping-Sent CDA
7.4.6. LSB CDA
7.4.7. DevIID, AppIID CDA
7.4.8. Compute-*
8. Fragmentation/Reassembly
8.1. Overview
8.2. SCHC F/R Protocol Elements
8.2.1. Messages
8.2.2. Tiles, Windows, Bitmaps, Timers, Counters
8.2.3. Integrity Checking
8.2.4. Header Fields
8.3. SCHC F/R Message Formats
8.3.1. SCHC Fragment Format
8.3.2. SCHC ACK Format
8.3.3. SCHC ACK REQ Format
8.3.4. SCHC Sender-Abort Format
8.3.5. SCHC Receiver-Abort Format
8.4. SCHC F/R Modes
8.4.1. No-ACK Mode
8.4.2. ACK-Always Mode
8.4.3. ACK-on-Error Mode
9. Padding Management
10. SCHC Compression for IPv6 and UDP Headers
10.1. IPv6 Version Field
10.2. IPv6 Traffic Class Field
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