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ICNRG                                                           M. Mosko
Internet-Draft                                                  I. Solis
Intended status: Experimental                                 PARC, Inc.
Expires: July 14, 2016                                  January 11, 2016


                      CCNx Messages in TLV Format
                    draft-irtf-icnrg-ccnxmessages-01

Abstract

   This document specifies the encoding of CCNx messages using a TLV
   Packet specification.  CCNx messages follow the CCNx Semantics
   specification.  This document defines the TLV types used by each
   message element and the encoding of each value.

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 July 14, 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
   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.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Type-Length-Value (TLV) Packets  . . . . . . . . . . . . . . .  6
     3.1.  Overall packet format  . . . . . . . . . . . . . . . . . .  6
     3.2.  Fixed Headers  . . . . . . . . . . . . . . . . . . . . . .  7
       3.2.1.  Interest Fixed Header  . . . . . . . . . . . . . . . .  9
         3.2.1.1.  Interest HopLimit  . . . . . . . . . . . . . . . .  9
       3.2.2.  Content Object Fixed Header  . . . . . . . . . . . . .  9
       3.2.3.  InterestReturn Fixed Header  . . . . . . . . . . . . . 10
         3.2.3.1.  InterestReturn HopLimit  . . . . . . . . . . . . . 10
         3.2.3.2.  InterestReturn Flags . . . . . . . . . . . . . . . 10
         3.2.3.3.  Return Code  . . . . . . . . . . . . . . . . . . . 10
     3.3.  Global Formats . . . . . . . . . . . . . . . . . . . . . . 11
       3.3.1.  Pad  . . . . . . . . . . . . . . . . . . . . . . . . . 11
       3.3.2.  Organization Specific TLVs . . . . . . . . . . . . . . 12
       3.3.3.  Hash Format  . . . . . . . . . . . . . . . . . . . . . 12
       3.3.4.  Link . . . . . . . . . . . . . . . . . . . . . . . . . 13
     3.4.  Hop-by-hop TLV headers . . . . . . . . . . . . . . . . . . 13
       3.4.1.  Interest Lifetime  . . . . . . . . . . . . . . . . . . 14
       3.4.2.  Recommended Cache Time . . . . . . . . . . . . . . . . 14
       3.4.3.  Message Hash . . . . . . . . . . . . . . . . . . . . . 15
     3.5.  Top-Level Types  . . . . . . . . . . . . . . . . . . . . . 16
     3.6.  CCNx Message . . . . . . . . . . . . . . . . . . . . . . . 17
       3.6.1.  Name . . . . . . . . . . . . . . . . . . . . . . . . . 17
         3.6.1.1.  Name Segments  . . . . . . . . . . . . . . . . . . 19
         3.6.1.2.  Interest Payload ID  . . . . . . . . . . . . . . . 19
       3.6.2.  Message TLVs . . . . . . . . . . . . . . . . . . . . . 20
         3.6.2.1.  Interest Message TLVs  . . . . . . . . . . . . . . 20
         3.6.2.2.  Content Object Message TLVs  . . . . . . . . . . . 21
       3.6.3.  Payload  . . . . . . . . . . . . . . . . . . . . . . . 23
       3.6.4.  Validation . . . . . . . . . . . . . . . . . . . . . . 24
         3.6.4.1.  Validation Algorithm . . . . . . . . . . . . . . . 24
         3.6.4.2.  Validation Payload . . . . . . . . . . . . . . . . 30
   4.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 32
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 33
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 34
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 34
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36








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1.  Introduction

   This document specifies a Type-Length-Value (TLV) packet format and
   the TLV type and value encodings for the CCNx network protocol as
   specified in [CCNSemantics].  This draft describes the mandatory and
   common optional fields of Interests and Content Objects.  Several
   additional protocols specified in their own documents are in use that
   extend this specification.

   A full description of the semantics of CCNx messages, providing an
   encoding-free description of CCNx messages and message elements, may
   be found in [CCNSemantics]

   This document specifies:

   o  The TLV packet format.

   o  The overall packet format for CCNx messages.

   o  The TLV types used by CCNx messages.

   o  The encoding of values for each type.

   o  Top level types that exist at the outermost containment.

   o  Interest TLVs that exist within Interest containment.

   o  Content Object TLVs that exist within Content Object containment.

   This document is supplemented by this document:

   o  Message semantics: see [CCNSemantics] for the protocol operation
      regarding Interest and Content Object, including the Interest
      Return protocol.

   o  URI notation: see [LCI] for the LCI URI notation.

   In the final draft, the type values will be assigned to be compact.
   All type values are relative to their parent containers.  It is
   possible for a TLV to redefine a type value defined by its parent.
   For example, each level of a nested TLV structure might define a
   "type = 1" with a completely different meaning.

   Packets are represented as 32-bit wide words using ASCII art.  Due to
   the nested levels of TLV encoding and the presence of optional fields
   and variable sizes, there is no concise way to represent all
   possibilities.  We use the convention that ASCII art fields enclosed
   by vertical bars "|" represent exact bit widths.  Fields with a



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   forward slash "/" are variable bit widths, which we typically pad out
   to word alignment for picture readability.

   TODO -- we have not adopted the 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.  Definitions

   o  HSVLI: Hierarchically structured variable length identifier, also
      called a Name.  It is an ordered list of path segments, which may
      be variable length octet strings.  In human-readable form, it is
      represented in URI format as lci:/path/part.  There is no host or
      query string.

   o  Name: see HSVLI

   o  Interest: A message requesting a Content Object with a matching
      Name and other optional selectors to choose from multiple objects
      with the same Name.  Any Content Object with a Name and optional
      selectors that matches the Name and optional selectors of the
      Interest is said to satisfy the Interest.

   o  Content Object: A data object sent in response to an Interest
      request.  It has an HSVLI Name and a content payload that are
      bound together via cryptographic means.
































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3.  Type-Length-Value (TLV) Packets

   We use 16-bit Type and 16-bit Length fields to encode TLV based
   packets.  This provides 64K different possible types and value field
   lengths of up to 64KiB.  With 64K possible types, there should be
   sufficient space for basic protocol types, while also allowing ample
   room for experimentation, application use, and growth.

   Specifically, the TLV types in the range 0x1000 - 0x1FFF are reserved
   for experimental use.  These type values are reserved in all TLV
   container contexts.In the event that more space is needed, either for
   types or for length, a new version of the protocol would be needed.

   +---------------+--------+------------------+-----------------------+
   |      Type     | Abbrev |       Name       | Description           |
   +---------------+--------+------------------+-----------------------+
   |     %x0FFF    |  T_ORG |  Vendor Specific | Information specific  |
   |               |        |    Information   | to a vendor           |
   |               |        |  (Section 3.3.2) | implementation (see   |
   |               |        |                  | below).               |
   |               |        |                  |                       |
   | %x1000-%x1FFF |   n/a  |   Experimental   | Experimental use.     |
   +---------------+--------+------------------+-----------------------+

                        Table 1: Reserved TLV Types


                        1                   2
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |              Type             |            Length             |
   +---------------+---------------+---------------+---------------+

   The Length field contains the length of the Value field in octets.
   It does not include the length of the Type and Length fields.  A zero
   length TLV is permissible.

   TLV structures are nestable, allowing the Value field of one TLV
   structure to contain additional TLV structures.  The enclosing TLV
   structure is called the container of the enclosed TLV.

   Type values are context-dependent.  Within a TLV container, one may
   re-use previous type values for new context-dependent purposes.

3.1.  Overall packet format

   Each packet includes the 8 byte fixed header described below,
   followed by a set of TLV fields.  These fields are optional hop-by-



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   hop headers and the Packet Payload.

                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |    Version    |  PacketType   |         PacketLength          |
   +---------------+---------------+---------------+---------------+
   |           PacketType specific fields          | HeaderLength  |
   +---------------+---------------+---------------+---------------+
   / Optional Hop-by-hop header TLVs                               /
   +---------------+---------------+---------------+---------------+
   / PacketPayload TLVs                                            /
   +---------------+---------------+---------------+---------------+

   The packet payload is a TLV encoding of the CCNx message, followed by
   optional Validation TLVs.

                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   | CCNx Message TLV                                              /
   +---------------+---------------+---------------+---------------+
   / Optional CCNx ValidationAlgorithm TLV                         /
   +---------------+---------------+---------------+---------------+
   / Optional CCNx ValidationPayload TLV (ValidationAlg required)  /
   +---------------+---------------+---------------+---------------+

   This document describes the Version "1" TLV encoding.

   After discarding the fixed and hop-by-hop headers the remaining
   PacketPayload should be a valid protocol message.  Therefore, the
   PacketPayload always begins with a 4 byte TLV defining the protocol
   message (whether it is an Interest, Content Object, or other message
   type) and its total length.  The embedding of a self-sufficient
   protocol data unit inside the fixed and hop-by-hop headers allows a
   network stack to discard the headers and operate only on the embedded
   message.

   The range of bytes protected by the Validation includes the CCNx
   Message and the ValidationAlgorithm.

   The ContentObjectHash begins with the CCNx Message and ends at the
   tail of the packet.

3.2.  Fixed Headers

   CCNx messages begin with an 8 byte fixed header (non-TLV format).
   The HeaderLength field represents the combined length of the Fixed



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   and Hop-by-hop headers.  The PacketLength field represents the entire
   Packet length.

   A specific PacketType may assign meaning to the reserved bytes.

   The PacketPayload of a CCNx packet is the protocol message itself.
   The Content Object Hash is computed over the PacketPayload only,
   excluding the fixed and hop-by-hop headers as those might change from
   hop to hop.  Signed information or Similarity Hashes should not
   include any of the fixed or hop-by-hop headers.  The PacketPayload
   should be self-sufficient in the event that the fixed and hop-by-hop
   headers are removed.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |    Version    |  PacketType   |         PacketLength          |
   +---------------+---------------+---------------+---------------+
   |           PacketType specific fields          | HeaderLength  |
   +---------------+---------------+---------------+---------------+

   o  Version: defines the version of the packet.

   o  HeaderLength: The length of the fixed header (8 bytes) and hop-by-
      hop headers.  The minimum value is "8".

   o  PacketType: describes forwarder actions to take on the packet.

   o  PacketLength: Total octets of packet including all headers (fixed
      header plus hop-by-hop headers) and protocol message.

   o  PacketType Specific Fields: specific PacketTypes define the use of
      these bits.

   The PacketType field indicates how the forwarder should process the
   packet.  A Request Packet (Interest) has PacketType 0, a Response
   (Content Object) has PacketType 1, and an InterestReturn Packet has
   PacketType 2.

   HeaderLength is the number of octets from the start of the packet
   (Version) to the end of the hop-by-hop headers.  PacketLength is the
   number of octets from the start of the packet to the end of the
   packet.

   The PacketType specific fields are reserved bits whose use depends on
   the PacketType.  They are used for network-level signaling.





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3.2.1.  Interest Fixed Header

   If the PacketType in the Fixed Header is "0", it indicates that the
   PacketPayload should be processed as an Interest message.  For this
   type of packet, the Fixed Header includes a field for a HopLimit as
   well as Reserved and Flags fields.  The Reserved field must be set to
   0 in an Interest - this field will be set to a return code in the
   case of an Interest Return.  There are currently no Flags defined, so
   this field must also be set to 0.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |    Version    |       0       |         PacketLength          |
   +---------------+---------------+---------------+---------------+
   |   HopLimit    |   Reserved    |     Flags     | HeaderLength  |
   +---------------+---------------+---------------+---------------+

3.2.1.1.  Interest HopLimit

   For an Interest message, the HopLimit is a counter that is
   decremented with each hop.  It limits the distance an Interest may
   travel on the network.  The node originating the Interest may put in
   any value - up to the maximum of 255.  Each node that receives an
   Interest with a HopLimit decrements the value upon reception.  If the
   value is 0 after the decrement, the Interest cannot be forwarded off
   the node.

   It is an error to receive an Interest with a 0 hop-limit from a
   remote node.

3.2.2.  Content Object Fixed Header

   If the PacketType in the Fixed Header is "1", it indicates that the
   PacketPayload should be processed as a Content Object message.  A
   Content Object defines a Flags field, however there are currently no
   flags defined, so the Flags field must be set to 0.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |    Version    |       1       |         PacketLength          |
   +---------------+---------------+---------------+---------------+
   |            Reserved           |     Flags     | HeaderLength  |
   +---------------+---------------+---------------+---------------+






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3.2.3.  InterestReturn Fixed Header

   If the PacketType in the Fixed Header is "2", it indicates that the
   PacketPayload should be processed as a returned Interest message.
   The only difference between this InterestReturn message and the
   original Interest is that the PacketType is changed to "2" and a
   ReturnCode is is put into the Reserved octet.  All other fields are
   unchanged.  The purpose of this encoding is to prevent packet length
   changes so no additional bytes are needed to return an Interest to
   the previous hop.  See [CCNSemantics] for a protocol description of
   this packet type.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |    Version    |       2       |         PacketLength          |
   +---------------+---------------+---------------+---------------+
   |   HopLimit    |  ReturnCode   |     Flags     | HeaderLength  |
   +---------------+---------------+---------------+---------------+

3.2.3.1.  InterestReturn HopLimit

   This is the original Interest's HopLimit, as received.  It is the
   value before being decremented at the current node.

3.2.3.2.  InterestReturn Flags

   These are the original Flags as set in the Interest.

3.2.3.3.  Return Code

   The numeric value assigned to the return types is defined below.
   This value is set by the node creating the Interest Return.

   A return code of "0" is not allowed, as it indicates that the
   returning system did not modify the Return Code field.















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           +-------+------------------------------------------+
           | Value | Return Type                              |
           +-------+------------------------------------------+
           |   1   | No Route                                 |
           |       |                                          |
           |   2   | Hop Limit Exceeded                       |
           |       |                                          |
           |   3   | No Resources                             |
           |       |                                          |
           |   4   | Path Error                               |
           |       |                                          |
           |   5   | Prohibited                               |
           |       |                                          |
           |   6   | Congested                                |
           |       |                                          |
           |   7   | MTU too large                            |
           |       |                                          |
           |   8   | Unsupported ContentObjectHashRestriction |
           |       |                                          |
           |   9   | Malformed Interest                       |
           +-------+------------------------------------------+

                           Table 2: Return Codes

3.3.  Global Formats

   This section defines global formats that may be nested within other
   TLVs.

3.3.1.  Pad

   The pad type may be used by protocols that prefer word-aligned data.
   The size of the word may be defined by the protocol.  Padding 4-byte
   words, for example, would use a 1-byte, 2-byte, and 3-byte Length.
   Padding 8-byte words would use a (0, 1, 2, 3, 5, 6, 7)-byte Length.

   A pad may be inserted after any TLV except within a Name TLV.  In the
   remainder of this document, we will not show optional pad TLVs.

                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |             T_PAD             |             Length            |
   +---------------+---------------+---------------+---------------+
   /                 variable length pad MUST be zeros             /
   +---------------+---------------+---------------+---------------+





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3.3.2.  Organization Specific TLVs

   Organizations may request proprietary TLV types in the Hop-By-Hop
   headers section or other TLV containers.  The organization then has
   control of the contents of the Value, which may be its own binary
   field or an encapsulated set of TLVs.  The inner TLVs, because we use
   a context-dependent TLV scheme, may be fully defined by the
   organization.

   Organization specific TLVs MUST use the T_ORG type.  The Length field
   is the length of the organization specific information plus 3.  The
   Value begins with the 3 byte organization number derived from the
   last three digits of the IANA Private Enterprise Numbers
   [EpriseNumbers], followed by the organization specific information.

                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |             T_ORG             |     Length (3+value length)   |
   +---------------+---------------+---------------+---------------+
   |   PEN[0]      |    PEN[1]     |     PEN[2]    |               /
   +---------------+---------------+---------------+               +
   /                  Vendor Specific Value                        /
   +---------------+---------------+---------------+---------------+

3.3.3.  Hash Format

   Hash values are used in several fields throughout a packet.  This TLV
   encoding is commonly embedded inside those fields to specify the
   specific hash function used and it's value.  Note that the reserved
   TLV types (%x1000 - %x1FFF) are also reserved here for user-defined
   experimental functions.

   The LENGTH field of the hash value MUST be less than or equal to the
   hash function length.  If the LENGTH is less than the full length, it
   is taken as the left LENGTH bytes of the hash function output.  Only
   the specified truncations are allowed.

   This nested format is used because it allows binary comparison of
   hash values for certain fields without a router needing to understand
   a new hash function.  For example, the KeyIdRestriction is bit-wise
   compared between an Interest's KeyIdResrcition field and a
   ContentObject's KeyId field.  This format means the outer field
   values do not change with differing hash functions so a router can
   still identify those fields and do a binary comparison of the hash
   TLV without need to understand the specific hash used.  An
   alternative approach, such as using T_KEYID_SHA512-256, would require
   each router keep an up-to-date parser and supporting user-defined



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   hash fucntions here would explode the parsing state-space.

            +-----------------+-----------+------------------+
            |       Type      |   Abbrev  | Lengths (octets) |
            +-----------------+-----------+------------------+
            |      %x0001     | T_SHA-256 |        32        |
            |                 |           |                  |
            |      %x0002     | T_SHA-512 |      64, 32      |
            |                 |           |                  |
            | %x1000 - %x1FFF |    n/a    |        any       |
            +-----------------+-----------+------------------+

                       Table 3: CCNx Hash Functions


                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |             T_FOO             |              36               |
   +---------------+---------------+---------------+---------------+
   |           T_SHA512            |               32              |
   +---------------+---------------+---------------+---------------+
   /                        32-byte hash value                     /
   +---------------+---------------+---------------+---------------+

                     Example nesting inside type T_FOO

3.3.4.  Link

   A Link is the tuple: {CCNx Name, KeyId, ContentObjectHash}.  It is a
   general encoding that is used in both the payload of a Content Object
   with PayloadType = "Link" and in the KeyName field in a KeyLocator.

                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+-------------------------------+
   / Mandatory CCNx Name                                           /
   +---------------+---------------+-------------------------------+
   / Optional KeyIdRestriction                                     /
   +---------------------------------------------------------------+
   / Optional ContentObjectHashRestriction                         /
   +---------------------------------------------------------------+

3.4.  Hop-by-hop TLV headers

   Hop-by-hop TLV headers are unordered and no meaning should be
   attached to their ordering.  Four hop-by-hop headers are described in
   this document:



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   +--------+-------------+-----------------+--------------------------+
   |  Type  |    Abbrev   |       Name      | Description              |
   +--------+-------------+-----------------+--------------------------+
   | %x0001 |  T_INTLIFE  |     Interest    | The time an Interest     |
   |        |             |     Lifetime    | should stay pending at   |
   |        |             | (Section 3.4.1) | an intermediate node.    |
   |        |             |                 |                          |
   | %x0002 | T_CACHETIME |   Recommended   | The Recommended Cache    |
   |        |             |    Cache Time   | Time for Content         |
   |        |             | (Section 3.4.2) | Objects.                 |
   |        |             |                 |                          |
   | %x0003 |  T_MSGHASH  |   Message Hash  | The hash of the CCNx     |
   |        |             | (Section 3.4.3) | Message to end of packet |
   |        |             |                 | using Section 3.3.3      |
   |        |             |                 | format.                  |
   +--------+-------------+-----------------+--------------------------+

                     Table 4: Hop-by-hop Header Types

   Additional hop-by-hop headers are defined in higher level
   specifications such as the fragmentation specification.

3.4.1.  Interest Lifetime

   The Interest Lifetime is the time that an Interest should stay
   pending at an intermediate node.  It is expressed in milliseconds as
   an unsigned, network byte order integer.

   A value of 0 (encoded as 1 byte %x00) indicates the Interest does not
   elicit a Content Object response.  It should still be forwarded, but
   no reply is expected.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |          T_INTLIFE            |             Length            |
   +---------------+---------------+---------------+---------------+
   /                                                               /
   /                      Lifetime (length octets)                 /
   /                                                               /
   +---------------+---------------+---------------+---------------+

3.4.2.  Recommended Cache Time

   The Recommended Cache Time (RCT) is a measure of the useful lifetime
   of a Content Object as assigned by a content producer or upstream
   node.  It serves as a guideline to the Content Store cache in
   determining how long to keep the Content Object.  It is a



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   recommendation only and may be ignored by the cache.  This is in
   contrast to the ExpiryTime (described in Section 3.6.2.2.2)which
   takes precedence over the RCT and must be obeyed.

   Because the Recommended Cache Time is an optional hop-by-hop header
   and not a part of the signed message, a content producer may re-issue
   a previously signed Content Object with an updated RCT without
   needing to re-sign the message.  There is little ill effect from an
   attacker changing the RCT as the RCT serves as a guideline only.

   The Recommended Cache Time (a millisecond timestamp) is a network
   byte ordered unsigned integer of the number of milliseconds since the
   epoch in UTC of when the payload expires.  It is a 64-bit field.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |         T_CACHETIME           |               8               |
   +---------------+---------------+---------------+---------------+
   /                                                               /
   /                    Recommended Cache Time                     /
   /                                                               /
   +---------------+---------------+---------------+---------------+

3.4.3.  Message Hash

   Within a trusted domain, an operator may calculate the message hash
   at a border device and insert that value into the hop-by-hop headers
   of a message.  An egress device should remove the value.  This
   permits intermediate devices within that trusted domain to match
   against a ContentObjectHashRestriction without calculating it at
   every hop.

   The message hash is a cryptographic hash from the start of the CCNx
   Message to the end of the packet.  It is used to match against the
   ContentObjectHashRestriction (Section 3.6.2.1.2).  The Message Hash
   may be of longer length than an Interest's restriction, in which case
   the device should use the left bytes of the Message Hash to check
   against the Interest's value.

   The Message Hash may only carry one hash type and there may only be
   one Message Hash header.

   The Message Hash header is unprotected, so this header is only of
   practical use within a trusted domain, such as an operator's
   autonomous system.





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                       1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |          T_MSGHASH            |         (length + 4)          |
   +---------------+---------------+---------------+---------------+
   |         (hash type)           |            length             |
   +---------------+---------------+---------------+---------------+
   /                           hash value                          /
   +---------------+---------------+---------------+---------------+

                            Message Hash Header

3.5.  Top-Level Types

   The top-level TLV types listed below exist at the outermost level of
   a CCNx protocol message.

   +-------+----------------------+-------------------+----------------+
   |  Type |        Abbrev        |        Name       | Description    |
   +-------+----------------------+-------------------+----------------+
   | %x000 |      T_INTEREST      |      Interest     | An Interest    |
   | 1     |                      |   (Section 3.6)   | MessageType.   |
   |       |                      |                   |                |
   | %x000 |       T_OBJECT       |   Content Object  | A Content      |
   | 2     |                      |   (Section 3.6)   | Object         |
   |       |                      |                   | MessageType    |
   |       |                      |                   |                |
   | %x000 |   T_VALIDATION_ALG   |     Validation    | The method of  |
   | 3     |                      |     Algorithm     | message        |
   |       |                      | (Section 3.6.4.1) | verification   |
   |       |                      |                   | such as        |
   |       |                      |                   | Message        |
   |       |                      |                   | Integrity      |
   |       |                      |                   | Check (MIC), a |
   |       |                      |                   | Message        |
   |       |                      |                   | Authentication |
   |       |                      |                   | Code (MAC), or |
   |       |                      |                   | a              |
   |       |                      |                   | cryptographic  |
   |       |                      |                   | signature.     |
   |       |                      |                   |                |
   | %x000 | T_VALIDATION_PAYLOAD |     Validation    | The validation |
   | 4     |                      |      Payload      | output, such   |
   |       |                      | (Section 3.6.4.2) | as the CRC32C  |
   |       |                      |                   | code or the    |
   |       |                      |                   | RSA signature. |
   +-------+----------------------+-------------------+----------------+




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                       Table 5: CCNx Top Level Types

3.6.  CCNx Message

   This is the format for the CCNx protocol message itself.  The CCNx
   message is the portion of the packet between the hop-by-hop headers
   and the Validation TLVs.  The figure below is an expansion of the
   "CCNx Message TLV" depicted in the beginning of Section 3.  The CCNx
   message begins with MessageType and runs through the optional
   Payload.  The same general format is used for both Interest and
   Content Object messages which are differentiated by the MessageType
   field.  The first enclosed TLV of a CCNx Message is always the Name
   TLV.  This is followed by an optional Message TLVs and an optional
   Payload TLV.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |         MessageType           |         MessageLength         |
   +---------------+---------------+---------------+---------------+
   | Name TLV       (Type = T_NAME)                                |
   +---------------+---------------+---------------+---------------+
   / Optional Message TLVs   (Various Types)                       /
   +---------------+---------------+---------------+---------------+
   / Optional Payload TLV  (Type = T_PAYLOAD)                      /
   +---------------+---------------+---------------+---------------+


   +--------+-----------+-----------------+----------------------------+
   |  Type  |   Abbrev  |       Name      | Description                |
   +--------+-----------+-----------------+----------------------------+
   | %x0000 |   T_NAME  |       Name      | The CCNx Name requested in |
   |        |           | (Section 3.6.1) | an Interest or published   |
   |        |           |                 | in a Content Object.       |
   |        |           |                 |                            |
   | %x0001 | T_PAYLOAD |     Payload     | The message payload.       |
   |        |           | (Section 3.6.3) |                            |
   +--------+-----------+-----------------+----------------------------+

                        Table 6: CCNx Message Types

3.6.1.  Name

   A Name is a TLV encoded sequence of segments.  The table below lists
   the type values appropriate for these Name segments.  A Name MUST NOT
   include PAD TLVs.

   As described in CCNx Semantics [CCNSemantics], using the LCI [LCI]



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   notation, a T_NAME with 0 length corresponds to lci:/ (the default
   route) and is distinct from a name with one zero length segment, such
   as lci:/NAME=.  In the TLV encoding, lci:/ corresponds to T_NAME with
   0 length, while lci:/NAME= corresponds to T_NAME with 4 length and
   T_NAMESEGMENT with 0 length.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |            T_NAME             |            Length             |
   +---------------+---------------+---------------+---------------+
   / Name segment TLVs                                             /
   +---------------+---------------+---------------+---------------+

   +--------+---------------+-------------------+----------------------+
   |  Type  | Symbolic Name |        Name       | Description          |
   +--------+---------------+-------------------+----------------------+
   | %x0001 | T_NAMESEGMENT |    Name segment   | A generic name       |
   |        |               | (Section 3.6.1.1) | Segment.             |
   |        |               |                   |                      |
   | %x0002 |     T_IPID    |  Interest Payload | An identifier that   |
   |        |               |         ID        | represents the       |
   |        |               | (Section 3.6.1.2) | Interest Payload     |
   |        |               |                   | field.  As an        |
   |        |               |                   | example, the Payload |
   |        |               |                   | ID might be a hash   |
   |        |               |                   | of the Interest      |
   |        |               |                   | Payload.  This       |
   |        |               |                   | provides a way to    |
   |        |               |                   | differentiate        |
   |        |               |                   | between Interests    |
   |        |               |                   | based on their       |
   |        |               |                   | payloads without     |
   |        |               |                   | having to parse all  |
   |        |               |                   | the bytes of the     |
   |        |               |                   | payload itself;      |
   |        |               |                   | instead using only   |
   |        |               |                   | this Payload ID Name |
   |        |               |                   | segment              |
   |        |               |                   |                      |
   | %x1000 |   T_APP:00 -  |    Application    | Application-specific |
   |    -   |   T_APP:4096  |     Components    | payload in a name    |
   | %x1FFF |               | (Section 3.6.1.1) | segment.  An         |
   |        |               |                   | application may      |
   |        |               |                   | apply its own        |
   |        |               |                   | semantics to the     |
   |        |               |                   | 4096 reserved types. |
   +--------+---------------+-------------------+----------------------+



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                         Table 7: CCNx Name Types

3.6.1.1.  Name Segments

   Special application payload name segments are in the range %x1000 -
   %1FFF.  These have application semantics applied to them.  A good
   convention is to put the application's identity in the name prior to
   using these name segments.

   For example, a name like "lci:/foo/bar/yo" would be encoded as:

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |            (T_NAME)           |           %x14 (20)           |
   +---------------+---------------+---------------+---------------+
   |        (T_NAME_SEGMENT)       |           %x03 (3)            |
   +---------------+---------------+---------------+---------------+
   |       f                o               o      |(T_NAME_SEGMENT)
   +---------------+---------------+---------------+---------------+
   |               |            %x03 (3)           |       b       |
   +---------------+---------------+---------------+---------------+
   |      a                r       |           (T_NAME_SEGMENT)   |
   +---------------+---------------+---------------+---------------+
   |           %x02 (2)            |        y      |       o       |
   +---------------+---------------+---------------+---------------+

3.6.1.2.  Interest Payload ID

   The InterestPayloadID is a name segment created by the origin of an
   Interest to represent the Interest Payload.  This allows the proper
   multiplexing of Interests based on their name if they have different
   payloads.  A common representation is to use a hash of the Interest
   Payload as the InterestPayloadID.

   As part of the TLV 'value', the InterestPayloadID contains a one
   identifier of method used to create the InterestPayloadID followed by
   a variable length octet string.  An implementation is not required to
   implement any of the methods to receive an Interest; the
   InterestPayloadID may be treated only as an opaque octet string for
   purposes of multiplexing Interests with different payloads.  Only a
   device creating an InterestPayloadID name segment or a device
   verifying such a segment need to implement the algorithms.

   It uses the Section 3.3.3 encoding of hash values.

   In normal operations, we recommend displaying the InterestPayloadID
   as an opaque octet string in an LCI scheme, as this is the common



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   denominator for implementation parsing.

   The InterestPayloadID, even if it is a hash, should not convey any
   security context.  If a system requires confirmation that a specific
   entity created the InterestPayload, it should use a cryptographic
   signature on the Interest via the ValidationAlgorithm and
   ValidationPayload or use its own methods inside the Interest Payload.

3.6.2.  Message TLVs

   Each message type (Interest or Content Object) is associated with a
   set of optional Message TLVs.  Additional specification documents may
   extend the types associated with each.

3.6.2.1.  Interest Message TLVs

   There are two Message TLVs currently associated with an Interest
   message: the KeyIdRestriction selector and the ContentObjectHashRestr
   selector are used to narrow the universe of acceptable Content
   Objects that would satisfy the Interest.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |         MessageType           |         MessageLength         |
   +---------------+---------------+---------------+---------------+
   | Name TLV                                                      |
   +---------------+---------------+---------------+---------------+
   / Optional KeyIdRestriction TLV                                 /
   +---------------------------------------------------------------+
   / Optional ContentObjectHashRestriction TLV                     /
   +---------------------------------------------------------------+

   +-------+--------------+----------------------------+---------------+
   |  Type |    Abbrev    |            Name            | Description   |
   +-------+--------------+----------------------------+---------------+
   | %x000 | T_KEYIDRESTR |      KeyIdRestriction      | A             |
   | 2     |              |     (Section 3.6.2.1.1)    | Section 3.3.3 |
   |       |              |                            | representatio |
   |       |              |                            | nof the KeyId |
   |       |              |                            |               |










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   | %x000 | T_OBJHASHRES | ContentObjectHashRestricti | A             |
   | 3     | T      R     | o   n (Section 3.6.2.1.2)  | Section 3.3.3 |
   |       |              |                            | representatio |
   |       |              |                            | nof the hash  |
   |       |              |                            |  of the       |
   |       |              |                            |  specific     |
   |       |              |                            |  Content      |
   |       |              |                            |  Object that  |
   |       |              |                            |  would satisf |
   |       |              |                            | ythe Interest |
   |       |              |                            | .             |
   +-------+--------------+----------------------------+---------------+

                 Table 8: CCNx Interest Message TLV Types

3.6.2.1.1.  KeyIdRestriction

   An Interest may include a KeyIdRestriction selector.  This ensures
   that only Content Objects with matching KeyIds will satisfy the
   Interest.  See Section 3.6.4.1.4.1 for the format of a KeyId.

3.6.2.1.2.  ContentObjectHashRestriction

   An Interest may also contain a ContentObjectHashRestriction selector.
   This is the hash of the Content Object - the self-certifying name
   restriction that must be verified in the network, if an Interest
   carried this restriction.  It is calculated from the beginning of the
   CCNx Message to the end of the packet.  The LENGTH must be from one
   of the allowed values for that hash (see Section 3.3.3).

   The ContentObjectHashRestriction SHOULD use at least 32 bytes of hash
   length.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |        T_OBJHASHRESTR         |            LENGTH+4           |
   +---------------+---------------+---------------+---------------+
   |          <hash type>          |             LENGTH            |
   +---------------+---------------+---------------+---------------+
   /                     LENGTH octets of hash                     /
   +---------------+---------------+---------------+---------------+

3.6.2.2.  Content Object Message TLVs

   The following message TLVs are currently defined for Content Objects:
   PayloadType (optional) and ExpiryTime (optional).




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                         1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |         MessageType           |         MessageLength         |
   +---------------+---------------+---------------+---------------+
   | Name TLV                                                      |
   +---------------+---------------+---------------+---------------+
   / Optional PayloadType TLV                                      /
   +---------------------------------------------------------------+
   / Optional ExpiryTime TLV                                       /
   +---------------------------------------------------------------+


   +--------+-------------+---------------------+----------------------+
   |  Type  |    Abbrev   |         Name        | Description          |
   +--------+-------------+---------------------+----------------------+
   | %x0005 | T_PAYLDTYPE |     PayloadType     | Indicates the type   |
   |        |             | (Section 3.6.2.2.1) | of Payload contents. |
   |        |             |                     |                      |
   | %x0006 |   T_EXPIRY  |      ExpiryTime     | The time at which    |
   |        |             | (Section 3.6.2.2.2) | the Payload expires, |
   |        |             |                     | as expressed in the  |
   |        |             |                     | number of            |
   |        |             |                     | milliseconds since   |
   |        |             |                     | the epoch in UTC.    |
   |        |             |                     | If missing, Content  |
   |        |             |                     | Object may be used   |
   |        |             |                     | as long as desired.  |
   +--------+-------------+---------------------+----------------------+

              Table 9: CCNx Content Object Message TLV Types

3.6.2.2.1.  PayloadType

   The PayloadType is a network byte order integer representing the
   general type of the Payload TLV.

   o  0: Data (possibly encrypted)

   o  1: Key

   o  2: Link

   o  3: Manifest

   The Data type indicate that the Payload of the ContentObject is
   opaque application bytes.  The Key type indicates that the Payload is
   a DER encoded public key.  The Link type indicates that the Payload



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   is a Link (Section 3.3.4).  If this field is missing, a "Data" type
   is assumed.  A Manifest type indicates that the Payload is a Manifest
   (format TBD).

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |            T_PAYLDTYPE        |            Length             |
   +---------------+---------------+---------------+---------------+
   |  PayloadType  /
   +---------------+

3.6.2.2.2.  ExpiryTime

   The ExpiryTime is the time at which the Payload expires, as expressed
   by a timestamp containing the number of milliseconds since the epoch
   in UTC.  It is a network byte order unsigned integer in a 64-bit
   field.  A cache or end system should not respond with a Content
   Object past its ExpiryTime.  Routers forwarding a Content Object do
   not need to check the ExpiryTime.  If the ExpiryTime field is
   missing, the Content Object has no expressed expiration and a cache
   or end system may use the Content Object for as long as desired.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |           T_EXPIRY            |               8               |
   +---------------+---------------+---------------+---------------+
   /                          ExpiryTime                           /
   /                                                               /
   +---------------+---------------+---------------+---------------+

3.6.3.  Payload

   The Payload TLV contains the content of the packet.  It is
   permissible to have a "0" length.  If a packet does not have any
   payload, this field may be omitted, rather than carrying a "0"
   length.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |           T_PAYLOAD           |            Length             |
   +---------------+---------------+---------------+---------------+
   /                        Payload Contents                       /
   +---------------+---------------+---------------+---------------+





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3.6.4.  Validation

   Both Interests and Content Objects have the option to include
   information about how to validate the CCNx message.  This information
   is contained in two TLVs: the ValidationAlgorithm TLV and the
   ValidationPayload TLV.  The ValidationAlgorithm TLV specifies the
   mechanism to be used to verify the CCNx message.  Examples include
   verification with a Message Integrity Check (MIC), a Message
   Authentication Code (MAC), or a cryptographic signature.  The
   ValidationPayload TLV contains the validation output, such as the
   CRC32C code or the RSA signature.

   An Interest would most likely only use a MIC type of validation - a
   crc, checksum, or digest.

3.6.4.1.  Validation Algorithm

   The ValidationAlgorithm is a set of nested TLVs containing all of the
   information needed to verify the message.  The outermost container
   has type = T_VALIDATION_ALG.  The first nested TLV defines the
   specific type of validation to be performed on the message.  The type
   is identified with the "ValidationType" as shown in the figure below
   and elaborated in the table below.  Nested within that container are
   the TLVs for any ValidationType dependent data, for example a Key Id,
   Key Locator etc.

   Complete examples of several types may be found in Section 3.6.4.1.5

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |       T_VALIDATION_ALG        |      ValidationAlgLength      |
   +---------------+---------------+---------------+---------------+
   |        ValidationType         |            Length             |
   +---------------+---------------+---------------+---------------+
   / ValidationType dependent data                                 /
   +---------------+---------------+---------------+---------------+














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   +--------+---------------+---------------------+--------------------+
   |  Type  |     Abbrev    |         Name        | Description        |
   +--------+---------------+---------------------+--------------------+
   | %x0002 |    T_CRC32C   |        CRC32C       | Castagnoli CRC32   |
   |        |               | (Section 3.6.4.1.1) | (iSCSI, ext4,      |
   |        |               |                     | etc.), with normal |
   |        |               |                     | form polynomial    |
   |        |               |                     | 0x1EDC6F41.        |
   |        |               |                     |                    |
   | %x0004 | T_HMAC-SHA256 |     HMAC-SHA256     | HMAC (RFC 2104)    |
   |        |               | (Section 3.6.4.1.2) | using SHA256 hash. |
   |        |               |                     |                    |
   | %x0005 |   T_VMAC-128  |       VMAC-128      | VMAC with 128bit   |
   |        |               | (Section 3.6.4.1.2) | tags [VMAC]        |
   |        |               |                     |                    |
   | %x0006 |  T_RSA-SHA256 |      RSA-SHA256     | RSA public key     |
   |        |               | (Section 3.6.4.1.3) | signature using    |
   |        |               |                     | SHA256 digest.     |
   |        |               |                     |                    |
   | %x0007 | EC-SECP-256K1 |      SECP-256K1     | Elliptic Curve     |
   |        |               | (Section 3.6.4.1.3) | signature with     |
   |        |               |                     | SECP-256K1         |
   |        |               |                     | parameters (see    |
   |        |               |                     | [ECC]).            |
   |        |               |                     |                    |
   | %x0008 | EC-SECP-384R1 |      SECP-384R1     | Elliptic Curve     |
   |        |               | (Section 3.6.4.1.3) | signature with     |
   |        |               |                     | SECP-384R1         |
   |        |               |                     | parameters (see    |
   |        |               |                     | [ECC]).            |
   +--------+---------------+---------------------+--------------------+

                      Table 10: CCNx Validation Types

3.6.4.1.1.  Message Integrity Checks

   MICs do not require additional data in order to perform the
   verification.  An example is CRC32C that has a "0" length value.

3.6.4.1.2.  Message Authentication Checks

   MACs are useful for communication between two trusting parties who
   have already shared private keys.  Examples include an RSA signature
   of a SHA256 digest or others.  They rely on a KeyId.  Some MACs might
   use more than a KeyId, but those would be defined in the future.






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3.6.4.1.3.  Signature

   Signature type Validators specify a digest mechanism and a signing
   algorithm to verify the message.  Examples include RSA signature og a
   SHA256 digest, an Elliptic Curve signature with SECP-256K1
   parameters, etc.  These Validators require a KeyId and a mechanism
   for locating the publishers public key (a KeyLocator) - optionally a
   PublicKey or Certificate or KeyName.

3.6.4.1.4.  Validation Dependent Data

   Different Validation Algorithms require access to different pieces of
   data contained in the ValidationAlgorithm TLV.  As described above,
   Key Ids, Key Locators, Public Keys, Certificates, Links and Key Names
   all play a role in different Validation Algorithms.

   Following is a table of CCNx ValidationType dependent data types:

   +--------+-------------+-----------------------+--------------------+
   |  Type  |    Abbrev   |          Name         | Description        |
   +--------+-------------+-----------------------+--------------------+
   | %x0009 |   T_KEYID   |      SignerKeyId      | An identifier of   |
   |        |             | (Section 3.6.4.1.4.1) | the shared secret  |
   |        |             |                       | or public key      |
   |        |             |                       | associated with a  |
   |        |             |                       | MAC or Signature.  |
   |        |             |                       |                    |
   | %x000B | T_PUBLICKEY |       Public Key      | DER encoded public |
   |        |             | (Section 3.6.4.1.4.2) | key.               |
   |        |             |                       |                    |
   | %x000C |    T_CERT   |      Certificate      | DER encoded X509   |
   |        |             | (Section 3.6.4.1.4.3) | certificate.       |
   |        |             |                       |                    |
   | %x000E |  T_KEYNAME  |        KeyName        | A CCNx Link        |
   |        |             | (Section 3.6.4.1.4.4) | object.            |
   |        |             |                       |                    |
   | %x000F |  T_SIGTIME  |     SignatureTime     | A millsecond       |
   |        |             | (Section 3.6.4.1.4.5) | timestamp          |
   |        |             |                       | indicating the     |
   |        |             |                       | time when the      |
   |        |             |                       | signature was      |
   |        |             |                       | created.           |
   +--------+-------------+-----------------------+--------------------+

              Table 11: CCNx Validation Dependent Data Types






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3.6.4.1.4.1.  KeyId

   The KeyId is the publisher key identifier.  It is similar to a
   Subject Key Identifier from X509 [RFC 5280, Section 4.2.1.2].  It
   should be derived from the key used to sign, such as from the SHA-256
   hash of the key.  It applies to both public/private key systems and
   to symmetric key systems.

   The KeyId is represented using the Section 3.3.3.  If a protocol uses
   a non-hash identifier, it should use one of the reserved values (e.g.
   %x1000).

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |            T_KEYID            |            LENGTH+4           |
   +---------------+---------------+---------------+---------------+
   |          <hash type>          |             LENGTH            |
   +---------------+---------------+---------------+---------------+
   /                     LENGTH octets of hash                     /
   +---------------+---------------+---------------+---------------+


3.6.4.1.4.2.  Public Key

   A Public Key is a DER encoded Subject Public Key Info block, as in an
   X509 certificate.

                        1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +---------------+---------------+---------------+---------------+
   |          T_PUBLICKEY          |            Length             |
   +---------------+---------------+---------------+---------------+
   /                Public Key (DER encoded SPKI)                  /
   +---------------+---------------+---------------+---------------+

3.6.4.1.4.3.  Certificate

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |            T_CERT             |            Length             |
   +---------------+---------------+---------------+---------------+
   /                 Certificate (DER encoded X509)                /
   +---------------+---------------+---------------+---------------+






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3.6.4.1.4.4.  KeyName

   A KeyName type KeyLocator is a Link.

   The KeyName digest is the publisher digest of the Content Object
   identified by KeyName.  It may be included on an Interest's digest
   restriction.  A KeyName is a mandatory Name and an optional KeyId.
   The KeyId inside the KeyLocator may be included in an Interest's
   KeyId to retrieve only the specified key.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+-------------------------------+
   |          T_KEYNAME            |            Length             |
   +---------------+---------------+-------------------------------+
   / Link                                                          /
   +---------------------------------------------------------------+

3.6.4.1.4.5.  SignatureTime

   The SignatureTime is a millisecond timestamp indicating the time at
   which a signature was created.  The signer sets this field to the
   current time when creating a signature.  A verifier may use this time
   to determine whether or not the signature was created during the
   validity period of a key, or if it occurred in a reasonable sequence
   with other associated signatures.  The SignatureTime is unrelated to
   any time associated with the actual CCNx Message, which could have
   been created long before the signature.  The default behavior is to
   always include a SignatureTime when creating an authenticated message
   (e.g.  HMAC or RSA).

   SignatureTime is a network byte ordered unsigned integer of the
   number of milliseconds since the epoch in UTC of when the signature
   was created.  It is a fixed 64-bit field.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+-------------------------------+
   |           T_SIGTIME           |               8               |
   +---------------+---------------+-------------------------------+
   /                         SignatureTime                         /
   +---------------------------------------------------------------+

3.6.4.1.5.  Validation Examples

   As an example of a MIC type validation, the encoding for CRC32
   validation would be:




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                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |      T_VALIDATION_ALG         |               4               |
   +---------------+---------------+---------------+---------------+
   |            T_CRC32            |               0               |
   +---------------+---------------+---------------+---------------+

   As an example of a MAC type validation, the encoding for an HMAC
   using a SHA256 hash would be:

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |       T_VALIDATION_ALG        |               40              |
   +---------------+---------------+---------------+---------------+
   |        T_HMAC-SHA256          |               36              |
   +---------------+---------------+---------------+---------------+
   |             T_KEYID           |               32              |
   +---------------+---------------+---------------+---------------+
   /                            KeyId                              /
   /---------------+---------------+-------------------------------+

   As an example of a Signature type validation, the encoding for an RSA
   public key signing using a SHA256 digest and Public Key would be:

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |       T_VALIDATION_ALG        |      44 + Variable Length     |
   +---------------+---------------+---------------+---------------+
   |          T_RSA-SHA256         |      40 + Variable Length     |
   +---------------+---------------+---------------+---------------+
   |             T_KEYID           |               32              |
   +---------------+---------------+---------------+---------------+
   /                            KeyId                              /
   /---------------+---------------+-------------------------------+
   |          T_PUBLICKEY          |   Variable Length (~ 160)     |
   +---------------+---------------+---------------+---------------+
   /                Public Key (DER encoded SPKI)                  /
   +---------------+---------------+---------------+---------------+










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3.6.4.2.  Validation Payload

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+---------------+---------------+---------------+
   |     T_VALIDATION_PAYLOAD      |  ValidationPayloadLength      |
   +---------------+---------------+---------------+---------------+
   / Type-dependent data                                           /
   +---------------+---------------+---------------+---------------+

   The ValidationPayload contains the validation output, such as the
   CRC32C code or the RSA signature.







































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4.  Acknowledgements


















































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5.  IANA Considerations

   TODO: Work with IANA to define the type space for: Top level types,
   Hop-by-hop header types, Name segment types, CCNx messages types,
   Interest message TLV types, Content Object TLV message types,
   Validation types, and Validation dependent data types.

   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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6.  Security Considerations

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















































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7.  References

7.1.  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>.

7.2.  Informative References

   [CCN]      PARC, Inc., "CCNx Open Source", 2007,
              <http://www.CCNx.org>.

   [CCNSemantics]
              Mosko, M. and I. Solis, "CCNx Semantics (Internet draft)",
              2016, <http://tools.ietf.org/html/
              draft-mosko-icnrg-ccnxsemantics-01>.

   [ECC]      Certicom Research, "SEC 2: Recommended Elliptic Curve
              Domain Parameters", 2010,
              <http://www.secg.org/sec2-v2.pdf>.

   [EpriseNumbers]
              IANA, "IANA Private Enterprise Numbers", 2015, <http://
              www.iana.org/assignments/enterprise-numbers/
              enterprise-numbers>.

   [LCI]      Mosko, M., "Labeled Content Information (Internet draft)",
              2015, <http://tools.ietf.org/html/
              draft-mosko-icnrg-ccnxlabeledcontent-01>.

   [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>.

   [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>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.




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   [RFC6920]  Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
              Keranen, A., and P. Hallam-Baker, "Naming Things with
              Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,
              <http://www.rfc-editor.org/info/rfc6920>.

   [VMAC]     Krovertz, T. and W. Dai, "VMAC: Message Authentication
              Code using Universal Hashing", 2007,
              <http://www.fastcrypto.org/vmac/
              draft-krovetz-vmac-01.txt>.










































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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


   Ignacio Solis
   PARC, Inc.
   Palo Alto, California  94304
   USA

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

































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