CoAP Implementation Guidance
draft-ietf-lwig-coap-04
|
| Document |
Type |
|
Active Internet-Draft (lwig WG)
|
|
Last updated |
|
2017-03-13
|
|
Replaces |
|
draft-kovatsch-lwig-coap
|
|
Stream |
|
IETF
|
|
Intended RFC status |
|
(None)
|
|
Formats |
|
plain text
pdf
html
bibtex
|
| Stream |
WG state
|
|
WG Document
|
|
Document shepherd |
|
No shepherd assigned
|
| IESG |
IESG state |
|
I-D Exists
|
|
Consensus Boilerplate |
|
Unknown
|
|
Telechat date |
|
|
|
Responsible AD |
|
(None)
|
|
Send notices to |
|
(None)
|
LWIG Working Group M. Kovatsch
Internet-Draft ETH Zurich
Intended status: Informational O. Bergmann
Expires: September 14, 2017 C. Bormann, Ed.
Universitaet Bremen TZI
March 13, 2017
CoAP Implementation Guidance
draft-ietf-lwig-coap-04
Abstract
The Constrained Application Protocol (CoAP) is designed for resource-
constrained nodes and networks such as sensor nodes in a low-power
lossy network (LLN). Yet to implement this Internet protocol on
Class 1 devices (as per RFC 7228, ~ 10 KiB of RAM and ~ 100 KiB of
ROM) also lightweight implementation techniques are necessary. This
document provides lessons learned from implementing CoAP for tiny,
battery-operated networked embedded systems. In particular, it
provides guidance on correct implementation of the CoAP specification
RFC 7252, memory optimizations, and customized protocol parameters.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 14, 2017.
Copyright Notice
Copyright (c) 2017 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
(http://trustee.ietf.org/license-info) in effect on the date of
Kovatsch, et al. Expires September 14, 2017 [Page 1]
Internet-Draft CoAP Implementation Guidance March 2017
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Implementation . . . . . . . . . . . . . . . . . . . 4
2.1. Client/Server Model . . . . . . . . . . . . . . . . . . . 4
2.2. Message Processing . . . . . . . . . . . . . . . . . . . 5
2.2.1. On-the-fly Processing . . . . . . . . . . . . . . . . 5
2.2.2. Internal Data Structure . . . . . . . . . . . . . . . 6
2.3. Message ID Usage . . . . . . . . . . . . . . . . . . . . 6
2.3.1. Duplicate Rejection . . . . . . . . . . . . . . . . . 6
2.3.2. MID Namespaces . . . . . . . . . . . . . . . . . . . 7
2.3.3. Relaxation on the Server . . . . . . . . . . . . . . 8
2.3.4. Relaxation on the Client . . . . . . . . . . . . . . 9
2.4. Token Usage . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.1. Tokens for Observe . . . . . . . . . . . . . . . . . 10
2.4.2. Tokens for Blockwise Transfers . . . . . . . . . . . 11
2.5. Transmission States . . . . . . . . . . . . . . . . . . . 11
2.5.1. Request/Response Layer . . . . . . . . . . . . . . . 12
2.5.2. Message Layer . . . . . . . . . . . . . . . . . . . . 13
2.6. Out-of-band Information . . . . . . . . . . . . . . . . . 14
2.7. Programming Model . . . . . . . . . . . . . . . . . . . . 15
2.7.1. Client . . . . . . . . . . . . . . . . . . . . . . . 15
2.7.2. Server . . . . . . . . . . . . . . . . . . . . . . . 16
3. Optimizations . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1. Message Buffers . . . . . . . . . . . . . . . . . . . . . 17
3.2. Retransmissions . . . . . . . . . . . . . . . . . . . . . 17
3.3. Observable Resources . . . . . . . . . . . . . . . . . . 18
3.4. Blockwise Transfers . . . . . . . . . . . . . . . . . . . 19
3.5. Deduplication with Sequential MIDs . . . . . . . . . . . 19
4. Alternative Configurations . . . . . . . . . . . . . . . . . 22
4.1. Transmission Parameters . . . . . . . . . . . . . . . . . 22
Show full document text