Constrained Resource Identifiers
draft-ietf-core-href-01
CoRE Working Group K. Hartke
Internet-Draft Ericsson
Intended status: Standards Track November 4, 2019
Expires: May 7, 2020
Constrained Resource Identifiers
draft-ietf-core-href-01
Abstract
Constrained Resource Identifiers (CoRIs) are an alternate
serialization of Uniform Resource Identifiers (URIs) that encodes the
URI components in Concise Binary Object Representation (CBOR) instead
of a string of characters. This simplifies parsing, reference
resolution, and comparison of URIs in environments with severe
limitations on processing power, code size, and memory size.
Status of This Memo
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This Internet-Draft will expire on May 7, 2020.
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Internet-Draft Constrained Resource Identifiers November 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Options . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Option Sequences . . . . . . . . . . . . . . . . . . . . 4
3. CBOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Python . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Reference Resolution . . . . . . . . . . . . . . . . . . 9
4.2. URI Recomposition . . . . . . . . . . . . . . . . . . . . 10
4.3. CoAP Encoding . . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . 15
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
Uniform Resource Identifier (URI) references [RFC3986] are the
standard way to link to resources in hypertext formats such as HTML
[W3C.REC-html52-20171214] or the HTTP "Link" header field [RFC8288].
A URI reference is either a URI or a relative reference that must be
resolved against a base URI.
URI references are strings of characters chosen from the repertoire
of US-ASCII characters. The individual components of a URI reference
are delimited by a number of reserved characters, which necessitates
the use of percent-encoding when these reserved characters are used
in a non-delimiting function. One component can also contain special
dot-segments that affect how the component is to be interpreted. The
resolution of URI references involves parsing the character string
into its components, combining those components with the components
of a base URI, merging path components, removing dot-segments, and
recomposing the result back into a character string.
Overall, the proper processing of URIs is quite complicated. This
can be a problem in particular in constrained environments [RFC7228],
where devices often have severe code size limitations. As a result,
many implementations in these environments choose to support only an
ad-hoc, informally-specified, bug-ridden, non-interoperable subset of
half of the URI standard.
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