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Block-Wise Transfers in the Constrained Application Protocol (CoAP) (RFC7959)

IP.com Disclosure Number: IPCOM000247357D
Original Publication Date: 2016-Aug-01
Included in the Prior Art Database: 2016-Aug-27
Document File: 74 page(s) / 87K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

C. Bormann: AUTHOR [+3]

Abstract

The work on Constrained RESTful Environments (CoRE) aims at realizing the Representational State Transfer (REST) architecture in a suitable form for the most constrained nodes (such as microcontrollers with limited RAM and ROM [RFC7228]) and networks (such as IPv6 over Low- Power Wireless Personal Area Networks (6LoWPANs) [RFC4944]) [RFC7252]. The CoAP protocol is intended to provide RESTful [REST] services not unlike HTTP [RFC7230], while reducing the complexity of implementation as well as the size of packets exchanged in order to make these services useful in a highly constrained network of highly constrained nodes.

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Internet Engineering Task Force (IETF)                        C. Bormann Request for Comments: 7959                       Universitaet Bremen TZI Updates: 7252                                             Z. Shelby, Ed. Category: Standards Track                                            ARM ISSN: 2070-1721                                              August 2016

   Block-Wise Transfers in the Constrained Application Protocol (CoAP)

Abstract

   The Constrained Application Protocol (CoAP) is a RESTful transfer    protocol for constrained nodes and networks.  Basic CoAP messages    work well for small payloads from sensors and actuators; however,    applications will need to transfer larger payloads occasionally --    for instance, for firmware updates.  In contrast to HTTP, where TCP    does the grunt work of segmenting and resequencing, CoAP is based on    datagram transports such as UDP or Datagram Transport Layer Security    (DTLS).  These transports only offer fragmentation, which is even    more problematic in constrained nodes and networks, limiting the    maximum size of resource representations that can practically be    transferred.

   Instead of relying on IP fragmentation, this specification extends    basic CoAP with a pair of "Block" options for transferring multiple    blocks of information from a resource representation in multiple    request-response pairs.  In many important cases, the Block options    enable a server to be truly stateless: the server can handle each    block transfer separately, with no need for a connection setup or    other server-side memory of previous block transfers.  Essentially,    the Block options provide a minimal way to transfer larger    representations in a block-wise fashion.

   A CoAP implementation that does not support these options generally    is limited in the size of the representations that can be exchanged,    so there is an expectation that the Block options will be widely used    in CoAP implementations.  Therefore, this specification updates    RFC 7252.

Bormann & Shelby             Standards Track                    [Page 1]
 RFC 7959               Block-Wise Transfer in CoAP           August 2016

 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 docu...