Multipart Content-Format Encoding for CoAP
draft-fossati-core-multipart-ct-02

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Last updated 2013-10-11
Replaced by draft-ietf-core-multipart-ct
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Internet Engineering Task Force                               T. Fossati
Internet-Draft                                                 KoanLogic
Intended status: Standards Track                        October 11, 2013
Expires: April 14, 2014

               Multipart Content-Format Encoding for CoAP
                   draft-fossati-core-multipart-ct-02

Abstract

   This memo defines Multipart, an "anonymous" Content-Format that can
   be used to combine several different media types into a single CoAP
   message-body with minimal framing overhead.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on April 14, 2014.

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   Copyright (c) 2013 IETF Trust and the persons identified as the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Multipart Content-Format Encoding . . . . . . . . . . . . . .   2
   3.  Length Encoding . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Small . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Medium  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Large . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   This memo defines Multipart, an "anonymous" Content-Format that can
   be used to combine several different media types into a single CoAP
   message-body with minimal framing overhead.

   This simple and pretty efficient binary framing mechanism can be
   employed as an alternative to fully fledged marshalling mechanisms
   (e.g. JSON [RFC4627]), to create application specific formats which
   build on already existing types by assigning to them individual
   semantics.

   Applications using the Multipart Content-Format are supposed to
   define the internal structure of the Multipart representation, as
   well as registering its outermost type -- typically one in range
   10000-64999.

   Specific sub-types in a Multipart container are always found at the
   same fixed position corresponding to their implicit name.  Thus, the
   way to allow for optional parts, is to carry them as zero-length
   values for their respective types.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Multipart Content-Format Encoding

   Multipart encoding uses multiple adjacent frames each of which
   represents a single media.  Every frame can be broken down into three

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   logical pieces: the type of the framed media (T), its length in bytes
   (L), and the media payload itself (V) as depicted in the following
   figure.

   ,------------------ Multipart ------------------.
   +------+------+------+     +------+------+------+
   | T[1] | L[1] | V[1] | ... | T[n] | L[n] | V[n] |
   +------+------+------+     +------+------+------+
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