6lo Working Group A. Minaburo
Internet-Draft Acklio
Intended status: Standards Track L. Toutain
Expires: May 7, 2020 Institut MINES TELECOM; IMT Atlantique
November 04, 2019

Comparison of 6lo and SCHC
draft-toutain-6lo-6lo-and-schc-00

Abstract

6lo and 6lowpan have standardized a stateless IPv6 and UDP compression method for mesh networks. SCHC proposes a generic compression mechanism that can be applied to any protocol stack. The lpwan working group is focusing on star topologies for IPv6, UDP and CoAP header compression and fragmentation.

This document summarizes the differences between 6lo and SCHC and possible combination of SCHC and 6lo.

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Table of Contents

1. Introduction

6lo and 6lowpan have standardized a stateless IPv6 and UDP compression method for mesh networks. SCHC proposes a generic compression mechanism that can be applied to any protocol stack. The lpwan working group is focusing on star topologies for IPv6, UDP and CoAP header compression and fragmentation.

This document summarizes the differences between 6lo and SCHC and possible combination of SCHC and 6lo.

2. Comparison

2.1. Stateless compression.

Both compression protocols are stateless regarding the compression/decompression process. Each packet is compressed and decompressed independently of the others and no information is stored during compression or decompression.

The SCHC name comes from the fact that it is a generic mechanism and the context tells how to compress a specific packet.

2.2. Meshed vs Star

6lo is defined for meshed network therefore all the node must be able to manipulate any 6lo packet.

SCHC is defined for star network and compression is done at both ends. SCHC offers the possibility to have different compression scheme for each branch of the star. This scheme is described though a context.

If SCHC had to be used in a mesh network, all the intermediary nodes will have to know the rules used in the network.

2.3. Alignment

6lo preserves alignment on bye boundary when sending header fields. SCHC is bit oriented and padding can be added when the packet is sent.

3. Uniform vs specific compression rules.

6lo focuses mainly on IPv6 header and predefine a compression scheme known by all the nodes in a 6lo network.

SCHC defines a generic compression mechanism based on fields. A field is an abstract notion. A field has several properties:

The rule contains some functions:

3.1. Bitmap vs Rule ID

6lo defines a dispatch indicating the nature of the 6lo packet and for IPHC defines a bitmap to indicates the nature of the header compression.

SCHC uses a rule ID to identify the nature of the SCHC packet. Rule ID have a variable length, most frequent rules may use shorter values. The rule ID space is split between compression and decompression rules. The rule ID refers to a context which contains the nature of the rule and associated parameters.

In a sense the combination dispatch and bitmap for compression are equivalent to the rule ID, the main difference is that the rules are implicit in 6lo and the same rules are shared by all the node and explicit in SCHC. Context synchronization is needed between both ends.

3.2. Fragmentation

SCHC implement a fragmentation mechanisms dedicaded to LPWAN networks. 3 modes exists:

4. Applicability of SCHC in a 6lo network.

To apply SCHC in a 6lo meshed network, the following requirements are needed:

5. Normative References

[I-D.ietf-lpwan-ipv6-static-context-hc] Minaburo, A., Toutain, L., Gomez, C., Barthel, D. and J. Zuniga, "Static Context Header Compression (SCHC) and fragmentation for LPWAN, application to UDP/IPv6", Internet-Draft draft-ietf-lpwan-ipv6-static-context-hc-22, October 2019.
[rfc2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.

Authors' Addresses

Ana Minaburo Acklio 1137A avenue des Champs Blancs 35510 Cesson-Sevigne Cedex, France EMail: ana@ackl.io
Laurent Toutain Institut MINES TELECOM; IMT Atlantique 2 rue de la Chataigneraie CS 17607 35576 Cesson-Sevigne Cedex, France EMail: Laurent.Toutain@imt-atlantique.fr