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ICNRG                                                           M. Mosko
Internet-Draft                                                   C. Wood
Intended status: Experimental                                 PARC, Inc.
Expires: October 8, 2016                                   April 6, 2016


                          The CCNx URI Scheme
                   draft-mosko-icnrg-ccnxurischeme-01

Abstract

   This document defines an RFC3986 URI compliant identifier called a
   Labeled Segment URI in which name segments carry a label.  This
   allows differentiation between unrelated resources with similar
   identifiers.  This document also specifies the CCNx URI scheme,
   called "ccnx:," which conforms to the labeled segment encoding rules
   presented here.  The CCNx URI scheme applies specific labels to each
   name segment of a URI to disambiguate between resources with similar
   names.  This document defines a specific set of segment labels with
   label semantics.

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 October 8, 2016.

Copyright Notice

   Copyright (c) 2016 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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  URI path segment grammar for label=value pairs . . . . . . . .  5
     2.1.  Labeled Segments . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  URI comparison . . . . . . . . . . . . . . . . . . . . . .  7
   3.  Application to CCNx Names  . . . . . . . . . . . . . . . . . .  9
     3.1.  The ccnx Scheme  . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  URI Representation . . . . . . . . . . . . . . . . . . . .  9
       3.2.1.  Examples . . . . . . . . . . . . . . . . . . . . . . . 11
     3.3.  ccnx: URI comparison . . . . . . . . . . . . . . . . . . . 11
   4.  IRI Considerations . . . . . . . . . . . . . . . . . . . . . . 13
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18

























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1.  Introduction

   A Labeled Segment is an URI [RFC3986] compliant convention that
   allows an application or protocol to embed labels in name segments,
   thus disambiguating the resource identified by the path.  Labeled
   Segment URIs also allow for query and fragment components to follow
   the Labeled Segment form.

   Some protocols may wish to disambiguate name segments between
   different identifier spaces, such as "version" and "page".  Other
   protocols may wish to use a type system such as "/str=parc/int=7" and
   "/str=parc/str=7".  Labeled Segment URIs provide an unambiguous and
   flexible representation in systems that allow resources with
   otherwise similar names.

   It is not sufficient to leave the determination of type to
   application-specific conventions.  In a networked system with
   multiple applications accessing resources generated by other
   applications, there needs to be a set of common conventions.  For
   example, if one application uses a base 64 encoding of a frame
   number, e.g. base64(0xbdea), and another uses "ver=" to represent a
   document version, there is an ambiguity because base64(0xbdea) is the
   string "ver=".

   Labeled Segments defines "ls-segment" as "label[:param]=value", where
   the value only contains unreserved, percent-encoded, or certain sub-
   delim characters.  In the previous example, one application would say
   "/frame=%BD%EA" and the other would say "/ver=".

   In this document, we use URI [RFC3986] terminology, therefore a URI
   and CCNx Name are both composed of a URI path, which is a collection
   of name segments.  We do not use the term "name component" as was
   common in old CCNx.  In this document, the word "segment" alone means
   "name segment."

   URIs conforming to the CCNx URI scheme carry a label for each name
   segment.  The contents of each name segment must conform to the label
   semantics.  Example segment types are "Binary Segment", "Name", and
   "KeyId".

   We use Labeled Segment URIs as the canonical, human-readable
   representation.  There is an unambiguous, one-to-one correspondence
   between an absolute LS-URI path and a Labeled Name.  Relative URI
   representations are removed during encoding, so no relative name ends
   up in wire format.  Some labels are URIs that are IRI [RFC3987]
   compatible.

   Labeled Names shall be used everywhere a Name is used in CCNx, such



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   as in the Name of an Interest or Content Object.  They are also used
   in Links, KeyLocators, or any other place requiring a name.  When
   encoded for the wire, a binary representation is used, depending on
   the specific wire format codec, which is outside the scope of this
   document.

   This document specifies:

   o  the ccnx scheme.

   o  a canonical URI representation.

   Formal grammars use the ABNF [RFC5234] notation.

   TODO: We have not adopted Requirements Language yet.

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 RFC 2119 [RFC2119].






























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2.  URI path segment grammar for label=value pairs

2.1.  Labeled Segments

   This section describes the formal grammar for Labeled Segments using
   ABNF [RFC5234] notation.  We do not impose restrictions on the length
   of labels or values.  The semantics of values are URI scheme
   specific, here we only describe the meta-structure of Labeled
   Segments.  We begin by reviewing some definitions from [RFC3986] that
   define an absolute path URI.

   URI           = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
   hier-part     = "//" authority path-abempty
                   / path-absolute
                   / <other path types>
   path-absolute = "/" [ segment-nz *( "/" segment ) ]
   segment       = *pchar
   segment-nz    = 1*pchar
   pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
   query         = *( pchar / "/" / "?" )
   fragment      = *( pchar / "/" / "?" )
   pct-encoded   = "%" HEXDIG HEXDIG
   unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
   reserved      = gen-delims / sub-delims
   gen-delims    = ":" / "/" / "?" / "#" / "[" / "]" / "@"
   sub-delims    = "!" / "$" / "&" / "'" / "(" / ")"
                       / "*" / "+" / "," / ";" / "="

   Labeled Segments defines a new segment type that provides unambiguous
   representation of a segment's label and its value.  We define the
   top-level LS-URI as the same form as a URI, wherein each part
   conforms to the Label Segment grammar, which is a subset of the URI
   grammar.


















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   LS-URI           = scheme ":" ls-hier-part ["?" ls-query]
                      ["#" fragment]
   ls-hier-part     = ["//" authority] ls-path-absolute
   ls-path-absolute = "/" [ first-segment *( "/" ls-segment ) ]
   first-segment    = ls-segment-nz
   ls-segment       = lpv-segment / v-segment
   lpv-segment      = label [":" param] "=" *s-value-nz
   v-segment        = *s-value-nz
   ls-segment-nz    = lpv-segment-nz / v-segment-nz
   lpv-segment-nz   = label [":" param] "=" s-value-nz
   v-segment-nz     = s-value-nz
   label            = alpha-t / num-t
   param            = alpha-t / num-t
   s-value-nz       = 1*(s-pchar)

   ls-query         = *1 ( lpv-component / v-component
                           *( "&" (lpv-component / v-component) ) )
   lpv-component    = label [":" param] "=" q-value
   v-component      = q-value
   q-value          = *(q-pchar)

   alpha-t          = ALPHA *(ALPHA / DIGIT)
   num-t            = dec-t / hex-t
   dec-t            = 1*(DIGIT)
   hex-t            = "0x" 1*(HEXDIG)
   ls-pchar         =  unreserved / pct-encoded / ls-sub-delims
   s-pchar          = ls-pchar / ":" / "@" / "&"
   q-pchar          = ls-pchar / ":" / "@" / "/"
   ls-sub-delims    = "!" / "$" / "'" / "(" / ")"
                          / "*" / "+" / "," / ";"

   A Labeled Segment URI (LS-URI) contains a scheme that uses Labeled
   Segments, an optional authority, a labeled segment absolute path (ls-
   path-aboslute), an optional labeled segment query (ls-query), and a
   fragment.  The authority is URI scheme specific and the fragment is
   independent of the URI scheme.

   the ls-path-aboslute is a first-segment followed by zero or more "/"
   ls-segment.  The first-segment may be empty or a non-zero ls-segment
   (ls-segment-nz).  If it is empty, it corresponds to a 0-lenght name
   which typically is a default route.  It is distinct from a 1-segment
   name with no value (which is not allowed).  The first-segment MUST
   either be empty (the 0-lenght name) or MUST have a value.  If the
   first-segment is an ls-segment-nz, then it will have a value.

   An ls-segment may (lpv-segment) or may not (v-segment) have a label.
   A particular LS-URI scheme MUST define how unlabeled segments are
   processed, and MAY disallow them.  A v-segment is an implied type.



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   Once the implied type is resolved, it functions like an lpv-segment.

   An lpv-segment has a label, optional parameter, and optional value
   (s-value-nz).  An empty value is a 0-length name segment with a
   defined type.  This is distinct from a 0-length first-segment, which
   has neither type nor value.

   lpv-segment values come from the s-pchar set, which excludes the "="
   equal sign.  This means that the only equal sign in a name segment
   must be the delimiter between the label:param and the value.  Within
   the value, an equal sign must be percent encoded.

   lpv-segment labels and values may be alpha-numeric identifiers or
   numbers (decimal or hexadecimal).  For example, one scheme may define
   the labels "name", "version", and "frame".  A version may be of types
   "date" or "serial", meaning that the version is either a date or a
   monotonic serial number.  Some examples of resulting LS-URIs are:
   "/name=parc/name=csl/version:date=20130930" or "/name=alice_smith/
   version:serial=299".  The parameters may also indicate an instance of
   a label, such as "/name=books/year:1=1920/year:3=1940", where there
   are scheme or application semantics associated with "year:1" and
   "year:3".

   lpv-segment labels and parameters may also be numbers.  For example,
   a protocol with a binary and URI representation may not have pre-
   defined all possible labels.  In such cases, it could render unknown
   labels as their binary value, such as "/name=marc/x2003=green".

   The ls-query component is a non-hierarchical set of components
   separated by "&".  Each ls-query component is either a lpv-component
   or a v-component, similar to segments.  They are based on q-value,
   which uses q-pchar that excludes "&", but includes "/".  This allows
   an LS-URI scheme to use type query parameters.

   Labeled Segments allow for dot-segments "." and ".." in a v-segment.
   They operate as normal.  A single dot "." refers to the current
   hierarchy level and may be elided when the URI is resolved.  Double
   dot ".." segments pop off the previous non-dot segment.  An lpv-
   segment with a value of "." or ".." is not a dot-segment.  It means
   that the value of the given label is "." or "..".  For example
   /a=parc/b=csl/.. is equivalent to "/a=parc/b=csl", but the LS-URI
   "/a=parc/b=csl/c=.." does not contain a dot-segment.

2.2.  URI comparison

   An LS-URI scheme MUST specify the normalization rules to be used,
   following the methods of Section 6 [RFC3986].  At minimum, an LS-URI
   scheme SHOULD do the following:



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   o  Normalize unrestricted percent-encodings to the unrestricted form.

   o  Normalize num-t to either dec-t or hex-t.

   o  If the scheme allows for value-only segments or query components
      and interprets them as a default type, they should be normalized
      to having the type specified.

   o  If the scheme allows for undefined labels and represents them, for
      example, as num-t, then it should normalize all labels to their
      corresponding num-t.  If "name", for example, is known to be %x50
      in a binary encoding of the URI, then all labels should be
      compared using their numeric value.






































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3.  Application to CCNx Names

3.1.  The ccnx Scheme

   This section describes the CCNx URI scheme "ccnx:" for Labeled Names.
   A Labeled Name assigns a semantic type or label to each segment of
   the hierarchical content Name.

   Unless otherwise specified, a name segment is an arbitrary sequence
   of octets.

   Several name segment labels are binary unsigned integers.  These are
   always encoded as variable length sequences of 1 or more octets in
   network byte order using the shortest representation (i.e. no leading
   %x00).  The value of "0" is encoded as the single byte of "%x00".  A
   zero-length sequence must be interpreted as "not present."

   The CCNx Name segment types are:

   o  Name Segment: A generic name segment that includes arbitrary
      octets.

   o  Application Type N: An application may use application-specific
      parameters, numbered as integers, where N is from 0 to a system-
      specific maximum, not less than 255.  These are represented as
      "App:1=value", for example.

   It is common for an information centric networking protocol, such as
   CCNx or NDN, to use a binary on-the-wire representation for messages.
   Such protocols, if they use the ccnx: scheme, must have an
   appropriate codec that unambiguously represents Labeled Content
   Information in the chosen wire format.  Relative dot-segments should
   not occur in the wire format, they should be resolved before
   encoding.

3.2.  URI Representation

   Typed Names use a standard RFC 3986 representation following the LS-
   URI convention.  A name segment consists of any "unreserved"
   characters plus percent-encoded characters.  Reserved characters must
   be percent encoded.

   Within an absolute path, each segment consists of an "ls-segment"
   (c.f.  LS-URI).  A labeled segment is a type and a name component
   value, with a URI representation of "type=value".  The "type="
   portion may be omitted if it is type Name.

   Some name types take a parameter, such as the Application types.



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   They are represented as "A:nnn=value", where the "nnn" is the
   application type number and value is the name component.

   A CCNx URI MUST NOT include an Authority, Query, or Fragment.  It is
   an error to include them.

   Dot-segments (relative name components) are resolved when the URI is
   converted to a Typed Name.  The "." dot-segment is removed.  The ".."
   dot-segment is removed along with the previous non-dot-segment.

   +-------------------+-------------+---------------------------------+
   |        Type       |   Display   |               Name              |
   +-------------------+-------------+---------------------------------+
   |       'Name'      | Hexadecimal |           Name Segment          |
   |                   |             |                                 |
   |       'IPID'      | Hexadecimal |   Interest Payload Identifier   |
   |                   |             |             segment             |
   |                   |             |                                 |
   |     'App:0' -     | Hexadecimal |      Application Component      |
   |     'App:255'     |             |                                 |
   +-------------------+-------------+---------------------------------+

                    Table 1: The CCNx URI Scheme Types




























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3.2.1.  Examples

   A name / is
       ccnx:/ and is a 0-length name.

   A name /Name= is
       ccnx:/Name= and is a 1-segment name of 0-length.

   A name /foo/bar.
      ccnx:/Name=foo/Name=bar
      ccnx:/foo/Name=bar
      ccnx:/foo/bar

   A name /foo/bar with key %xA0.
       ccnx:/Name=foo/Name=bar/App:1=0xA0

   A name /foo/bar with version %xA0 and App:2 value 0x09.
       ccnx:/foo/bar/Version=0xA0/App:2=0x09

   A name /foo/.., where the ".." is a literal name component,
   not a relative dot-segment.
      ccnx:/foo/Name=..

   A name /foo/bar with application type 0 "hello"
   and application type 1 "world".
      ccnx:/Name=foo/Name=bar/App:0=hello/App:1=world

3.3.  ccnx: URI comparison

   While most comparisons are done using a wire format representation of
   a ccnx: URI, some applications may compare the CCNx URI using their
   URI representation.  This section defines the rules for comparing
   ccnx: URIs using the methods of Section 6 [RFC3986]

   Comparing typed name URIs must be done with:

   o  Syntax-based normalization

   o  Case normalization: normalize the representation of percent
      encodings. ccnx: does not use the host portion of the URI, and
      should be ignored if present.

   o  Percent encoding normalization: Percent encodings of unreserved
      characters must be converted to the unreserved character.

   o  Path segment normalization: dot-segments must be resolved first.





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   o  Scheme-based normalization: The authority should be removed and
      the path represented as an absolute path.

   o  Protocol-based normalization: Should not be done.  A trailing
      slash indicates a zero-length terminal name component and
      signifies a different name.

   o  typed-name-segment normalization: All segments should be presented
      with their type, do not elide the "N=" for Name components.

   o  Binary unsigned integer normalization: remove any leading %x00
      from numbers, leaving only the terminal %x00 for "0".

   o  type parameters: they must have their percent encodings
      normalized.  If they are integers, such as for the 'A' type, they
      must not have leading zeros.



































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4.  IRI Considerations

   International Resource Identifiers extend the unreserved character
   set to include characters above U+07F and encode them using percent
   encoding.  This extension is compatible with the ccnx: schema.  It
   applies only to the "value" portion of an ls-segment.

   The canonical name is determined by the URI representation of the
   IRI, after applying the rules of Section 3.1 of [RFC3987] and
   resolving dot-segments.  The canonical name thus includes the URI
   representation of language markers, including the bidirectional
   components.

   The value of a UTF-8 Name segment should be interpreted using IRI
   rules, including bidirectional markers.  They may be displayed using
   localized formats.

   Binary unsigned integer types are not interpreted under IRI rules,
   they are specifically percent encoded numbers.  They may be displayed
   using a localized format.































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5.  Acknowledgements


















































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6.  IANA Considerations

   This memo includes no request to IANA.

   All drafts are required to have an IANA considerations section (see
   Guidelines for Writing an IANA Considerations Section in RFCs
   [RFC5226] for a guide).  If the draft does not require IANA to do
   anything, the section contains an explicit statement that this is the
   case (as above).  If there are no requirements for IANA, the section
   will be removed during conversion into an RFC by the RFC Editor.









































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7.  Security Considerations

   All drafts are required to have a security considerations section.
   See RFC 3552 [RFC3552] for a guide.















































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8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

8.2.  Informative References

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <http://www.rfc-editor.org/info/rfc3552>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
              January 2005, <http://www.rfc-editor.org/info/rfc3987>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
              RFC5234, January 2008,
              <http://www.rfc-editor.org/info/rfc5234>.

















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Authors' Addresses

   Marc Mosko
   PARC, Inc.
   Palo Alto, California  94304
   USA

   Phone: +01 650-812-4405
   Email: marc.mosko@parc.com


   Christopher A. Wood
   PARC, Inc.
   Palo Alto, California  94304
   USA

   Phone: +01 650-812-4421
   Email: christopher.wood@parc.com

































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