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Versions: 00 draft-ietf-homenet-hncp

Network Working Group                                        M. Stenberg
Internet-Draft
Intended status: Standards Track                                S. Barth
Expires: August 09, 2014
                                                       February 05, 2014


                    Home Networking Control Protocol
                     draft-stenberg-homenet-hncp-00

Abstract

   This document describes the HomeNet Control Protocol (HNCP), a
   minimalist state synchronization protocol for Homenet routers.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on August 09, 2014.

Copyright Notice

   Copyright (c) 2014 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
   2.  Requirements language . . . . . . . . . . . . . . . . . . . .   3
   3.  Data model  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Trickle-Driven Status Updates . . . . . . . . . . . . . .   4
     4.2.  Protocol Messages . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  Network State Update (NetState) . . . . . . . . . . .   5
       4.2.2.  Network State Request, (NetState-Req) . . . . . . . .   5
       4.2.3.  Node Data Request (Node-Req)  . . . . . . . . . . . .   6
       4.2.4.  Network and Node State Reply (NetNode-Reply)  . . . .   6
     4.3.  HNCP Protocol Message Processing  . . . . . . . . . . . .   6
     4.4.  Adding and Removing Neighbors . . . . . . . . . . . . . .   8
     4.5.  Purging Unreachable Nodes . . . . . . . . . . . . . . . .   8
   5.  Type-Length-Value objects . . . . . . . . . . . . . . . . . .   8
     5.1.  Request TLVs (for use within unicast requests)  . . . . .   9
       5.1.1.  Request Network State TLV . . . . . . . . . . . . . .   9
       5.1.2.  Request Node Data TLV . . . . . . . . . . . . . . . .   9
     5.2.  Data TLVs (for use in both multi- and unicast data) . . .  10
       5.2.1.  Node Link TLV . . . . . . . . . . . . . . . . . . . .  10
       5.2.2.  Network State TLV . . . . . . . . . . . . . . . . . .  10
       5.2.3.  Node State TLV  . . . . . . . . . . . . . . . . . . .  10
       5.2.4.  Node Data TLV . . . . . . . . . . . . . . . . . . . .  11
       5.2.5.  Node Public Key TLV (within
               Node Data TLV)  . . . . . . . . . . . . . . . . . . .  11
       5.2.6.  Neighbor TLV (within Node Data TLV) . . . . . . . . .  12
     5.3.  Custom TLV (within/without Node Data TLV) . . . . . . . .  12
     5.4.  Authentication TLVs . . . . . . . . . . . . . . . . . . .  13
       5.4.1.  Certificate-related TLVs  . . . . . . . . . . . . . .  13
       5.4.2.  Signature TLV . . . . . . . . . . . . . . . . . . . .  13
   6.  Border Discovery and Prefix Assignment  . . . . . . . . . . .  13
   7.  DNS-based Service Discovery . . . . . . . . . . . . . . . . .  17
     7.1.  DNS Delegated Zone TLV  . . . . . . . . . . . . . . . . .  18
     7.2.  Domain Name TLV . . . . . . . . . . . . . . . . . . . . .  18
     7.3.  Router Name TLV . . . . . . . . . . . . . . . . . . . . .  18
   8.  Routing support . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Protocol Requirements . . . . . . . . . . . . . . . . . .  18
     8.2.  Announcement  . . . . . . . . . . . . . . . . . . . . . .  19
     8.3.  Protocol Selection  . . . . . . . . . . . . . . . . . . .  20
     8.4.  Fallback Mechanism  . . . . . . . . . . . . . . . . . . .  20
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     11.1.  Normative references . . . . . . . . . . . . . . . . . .  23
     11.2.  Informative references . . . . . . . . . . . . . . . . .  23
   Appendix A.  Some Outstanding Issues  . . . . . . . . . . . . . .  25
   Appendix B.  Some Obvious Questions and Answers . . . . . . . . .  25



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   Appendix C.  Draft source . . . . . . . . . . . . . . . . . . . .  26
   Appendix D.  Acknowledgements . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   HNCP is designed to synchronize state across a Homenet (or other
   small site) in order to facilitate automated configuration within the
   site, integration with trusted bootstrapping
   [I-D.behringer-homenet-trust-bootstrap] and default perimeter
   detection [I-D.kline-homenet-default-perimeter], automatic IP prefix
   distribution [I-D.pfister-homenet-prefix-assignment], and service
   discovery across multiple links within the homenet as defined in
   [I-D.stenberg-homenet-dnssd-hybrid-proxy-network-zeroconf].

   HNCP is designed to provide enough information for a routing protocol
   to operate without homenet-specific extensions.  In homenet
   environments where multiple IPv6 prefixes are present, routing based
   on source and destination address is necessary
   [I-D.troan-homenet-sadr].  Routing protocol requirements for source
   and destination routing are described in section 3 of
   [I-D.baker-rtgwg-src-dst-routing-use-cases].

   A GPLv2-licensed implementation of the HNCP protocol is currently
   under development at https://github.com/sbyx/hnetd/ [1].  Comments
   and/or pull requests are welcome.

   An earlier implementation using many of the same principles,
   algorithms and data structures built within OSPFv3 is available at
   http://www.homewrt.org/doku.php?id=downloads [2].

2.  Requirements language

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

3.  Data model

   The data model of the HNCP protocol is simple: Every participating
   node has (and also knows for every other participating node):

      A unique node identifier.  It may be a public key, unique hardware
      ID, or some other unique blob of binary data which HNCP can run a
      hash upon to obtain a node identifer that is very likely unique
      among the set of routers in the Homenet.





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      A set of Type-Length-Value (TLV) data it wants to share with other
      routers.  The set of TLVs have a well-defined order based on
      ascending binary content that is used to quickly identify changes
      in the set as they occur.

      Latest update sequence number.  A four octet number that is
      incremented anytime TLV data changes are detected.

      Relative time, in milliseconds, since last publishing of the
      current TLV data set.

   If HNCP security is enabled, each node will have a public/private key
   pair defined.  The private key is used to create signatures for
   messages and node state updates and never sent across the network by
   HNCP.  The public key is used to verify signatures of messages and
   node state updates.

4.  Operation

   HNCP is designed to run on UDP port IANA-UDP-PORT, using both link-
   local scoped IPv6 unicast and link-local scoped IPv6 multicast
   messages to address IANA-MULTICAST-ADDRESS for transport.  The
   protocol consists of Trickle [RFC6206] driven multicast status
   messages to indicate changes in shared TLV data, and unicast state
   synchronization message exchanges when the Trickle state is found to
   be inconsistent.

4.1.  Trickle-Driven Status Updates

   Each node MUST send link-local multicast NetState Messages
   (Section 4.2.1) each time the Trickle algorithm [RFC6206] indicates
   they should on each link the protocol is active on.  When the locally
   stored network state hash changes (either by a local node event that
   affects the TLV data, or upon receipt of more recent data from
   another node), all Trickle instances MUST be reset.  Trickle state
   MUST be maintained separately for each link.

   Trickle algorithm has 3 parameters; Imin, Imax and k. Imin and Imax
   represent minimum and maximum values for I, which is the time
   interval during which at least k Trickle updates must be seen on a
   link to prevent local state transmission.  Bounds for recommended
   Trickle values are described below.

      k=1 SHOULD be used, as given the timer reset on data updates,
      retransmissions should handle packet loss.

      Imax MUST be at least one minute.




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      Imin MUST be at least 200 milliseconds (earliest transmissions may
      occur at Imin/2 = 100 milliseconds given minimum values as per the
      Trickle algorithm).

4.2.  Protocol Messages

   Protocol messages are encoded as purely as a sequence of TLV objects
   (Section 5).  This section describes which set of TLVs MUST or MAY be
   present in a given message.

   In order to facilitate fast comparing of local state with that in a
   received message update, all TLVs in every encoding scope (either
   root level, within the message itself, or within a container TLV)
   MUST be placed in ascending order based on the binary comparison of
   both TLV header and value.  By design, the TLVs which MUST be present
   have the lowest available type values, ensuring they will naturally
   occur at the start of the Protocol Message, resembling a fixed format
   preamble.

4.2.1.  Network State Update (NetState)

   This Message SHOULD be sent as a multicast message.

   The following TLVs MUST be present at the start of the message:

      Node Link TLV (Section 5.2.1).

      Network State TLV (Section 5.2.2).

   The NetState Message MAY contain Node State TLV(s) (Section 5.2.3).
   If so, either all Node State TLVs are included (referred to as a
   "long" NetState Message), or none are included (refered to as a
   "short" NetState Message).  The NetState Message MUST NOT contain
   only a portion of Node State TLVs as this could cause problems with
   the Protocol Message Processing (Section 4.3) algorithm.  Finally, if
   the long version of the NetState message would exceed the minimum
   IPv6 MTU when sent, the short version of the NetState message MUST be
   used instead.

   If HNCP security is enabled, authentication TLVs (Section 5.4) MUST
   be present.

4.2.2.  Network State Request, (NetState-Req)

   This Message MUST be sent as a unicast message.

   The following TLVs MUST be present at the start of the message:




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      Node Link TLV (Section 5.2.1).

      Request Network State TLV (Section 5.1.1).

   If HNCP security is enabled, authentication TLVs (Section 5.4) MUST
   be present.

4.2.3.  Node Data Request (Node-Req)

   This Message MUST be sent as a unicast message.

   MUST be present:

      Node Link TLV (Section 5.2.1).

      one or more Request Node Data TLVs (Section 5.1.2).

   If HNCP security is enabled, authentication TLVs (Section 5.4) MUST
   be present.

4.2.4.  Network and Node State Reply (NetNode-Reply)

   This Message MUST be sent as a unicast message.

   MUST be present:

      Node Link TLV (Section 5.2.1).

      Network State TLV (Section 5.2.2) and Node State TLV
      (Section 5.2.3) for every known node by the sender, or

      one or more combinations of Node State and Node Data TLVs
      (Section 5.2.4).

   If HNCP security is enabled, authentication TLVs (Section 5.4) MUST
   be present.

4.3.  HNCP Protocol Message Processing

   The majority of status updates among known nodes are handled via the
   Trickle-Driven updates (Section 4.1).  This section describes
   processing of messages as received, along with associated actions or
   responses.

   HNCP is designed to operate between directly connected neighbors on a
   shared link using link-local IPv6 addresses.  If the source address
   of a received HNCP packet is not an IPv6 link-local unicast address,
   the packet SHOULD be dropped.  Similarly, if the destination address



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   is not IPv6 link-local unicast or IPv6 link-local multicast address,
   packet SHOULD be dropped.

   Upon receipt of:

      NetState Message (Section 4.2.1): If the network state hash within
      the message matches the hash of the locally stored network state,
      consider Trickle state as consistent with no further processing
      required.  If the hashes do not match, consider Trickle state as
      inconsistent.  In this case, if the message is "short" (contains
      zero Node State TLVs), reply with a NetState-Req Message
      (Section 4.2.2).  If the message was in long format (contained all
      Node State TLVs), reply with NodeState-Req (Section 4.2.3) for any
      nodes for which local information is outdated (local update number
      is lower than that within the message) or missing.  Note that if
      local information is more recent than that of the neighbor, there
      is no need to send a message.

      NetState-Req (Section 4.2.2): Provide requested data in a NetNode-
      Reply Message containing Network State TLV and all Node State
      TLVs.

      NodeState-Req (Section 4.2.3): Provide requested data in a
      NetNode-Reply containing Node State and Node Data TLVs.

      State-Reply (Section 4.2.4): If the message contains Node State
      TLVs that are more recent than local state (higher update number
      or we lack the node data altogether), if the message also contains
      corresponding Node Data TLVs, update local state and reset
      Trickle.  If the message is lacking Node Data TLVs for some Node
      State TLVs which are more recent than local state, reply with a
      NodeState-Req (Section 4.2.3) for the corresponding nodes.

   Each node is responsible for publishing a valid set of data TLVs.
   When there is a change in a node's set of data TLVs, the update
   number MUST be incremented accordingly.

   If a message containing Node State TLVs (Section 5.2.3) is received
   via unicast or multicast with the node's own node identifier and a
   higher update number than current local value, or the same update
   number and different hash, there is an error somewhere.  A
   recommended default way to handle this is to attempt to assert local
   state by increasing the local update number to a value higher than
   that received and republish node data using the same node identifier.
   If this happens more than 3 times in 60 seconds and the local node
   identifier is not globally unique, there may be more than one router
   with the same node identifier on the network.  If HNCP security is
   not enabled, a new node identifier SHOULD be generated and node data



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   republished accordingly.  If HNCP security is enabled, this is event
   is highly unlikely to occur as collision of identifier hashes for
   public keys is highly unlikely.

   In all cases, if node data for any node changes, all Trickle
   instances MUST be considered inconsistent (I=Imin + timer reset).

4.4.  Adding and Removing Neighbors

   Whenever multicast message or unicast reply is received on a link
   from another node, the node should be added as Neighbor TLV
   (Section 5.2.6) for current node.  If nothing (for example - no
   router advertisements, no HNCP traffic) is received from that
   neighbor in Imax seconds and the neighbor is not in neighbor
   discovery cache (and L2 indication of presence is available), at
   least 3 attempts to ping it with request network state message
   (Section 4.2.2) SHOULD be sent with increasing timeouts (e.g. 1, 2, 4
   seconds).  If even after suitable period after the last message
   nothing is received, the Neighbor TLV MUST be removed so that there
   are no dangling neighbors.  As an alternative, if there is a layer 2
   unreachability notification of some sort available for either whole
   link or for individual neighbor, it MAY be used to immediately
   trigger removal of corresponding Neighbor TLV(s).

4.5.  Purging Unreachable Nodes

   Nodes should be purged when unreachable.  When node data has changed,
   the neighbor graph SHOULD be traversed for each node following the
   Neighbor TLVs, purging nodes that were found entirely unreachable
   (not traversed).

5.  Type-Length-Value objects

   Every TLV is encoded as 2 octet type, followed by 2 octet length (of
   the whole TLV, including header; 4 means no value whatsoever), and
   then the value itself (if any).  The actual length of TLV MUST be
   always divisible by 4; if the length of the value is not, zeroed
   padding bytes MUST be inserted at the end of TLV.  The padding bytes
   MUST NOT be included in the length field.












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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Value                             |
   |                     (variable # of bytes)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Encoding of type=123 (0x7b) TLV with value 'x' (120 = 0x78): 007B
   0005 7800 0000

   Notation:

      .. = octet string concatenation operation

      H(x) = MD5 hash of x

      H-64(x) = H(x) truncated by taking just first 64 bits of the
      result.

5.1.  Request TLVs (for use within unicast requests)

5.1.1.  Request Network State TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type: REQ-NETWORK-STATE (2)  |           Length: 4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5.1.2.  Request Node Data TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type: REQ-NODE-DATA (3)    |          Length: 20           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       H(node identifier)                      |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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5.2.  Data TLVs (for use in both multi- and unicast data)

5.2.1.  Node Link TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type: NODE-LINK (1)      |          Length: 24           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       H(node identifier)                      |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Link-Identifier                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5.2.2.  Network State TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type: NETWORK-STATE (4)    |          Length: 20           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |          H(H(node data TLV 1) .. H(node data TLV N))          |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The Node Data TLVs are ordered for hashing by octet comparison of the
   corresponding node identifier hashes in ascending order.

5.2.3.  Node State TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type: NODE-STATE (5)     |          Length: 44           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       H(node identifier)                      |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Update Sequence Number                     |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Milliseconds since Origination                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        H(node data TLV)                       |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The whole network should have roughly the same idea about the time
   since origination, i.e. even the originating router should increment
   the time whenever it needs to send a new Node State TLV regarding
   itself without changing the corresponding Node Data TLV.  This age
   value is not included within the Node Data TLV, however, as that is
   immutable and potentially signed by the originating node at the time
   of origination.

5.2.4.  Node Data TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type: NODE-DATA (6)      |        Length: >= 24          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       H(node identifier)                      |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Update Sequence Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Nested TLVs containing node information            |


   The Node Public Key TLV (Section 5.2.5) SHOULD be always included if
   signatures are ever used.

   If signatures are in use, the Node Data TLV SHOULD also contain the
   originator's own Signature TLV (Section 5.4.2).

5.2.5.  Node Public Key TLV (within Node Data TLV)

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type: PUBLIC-KEY (7)      |          Length: >= 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   |               Public Key (raw node identifier)                |


   Public key data for the node.  Only relevant if signatures are used.
   Can be used to verify that H(node identifier) equals public key, and
   that the Signature TLVs are signed by appropriate public keys.

5.2.6.  Neighbor TLV (within Node Data TLV)

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Type: NEIGHBOR (8)      |          Length: 28           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                  H(neighbor node identifier)                  |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Neighbor Link Identifier                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Local Link Identifier                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This TLV indicates that the node in question vouches that the
   specified neighbor is reachable by it on the local link id given.
   This reachability may be unidirectional (if no unicast exchanges have
   been performed with the neighbor).  The presence of this TLV at least
   guarantees that the node publishing it has received traffic from the
   neighbor recently.  For guaranteed bidirectional reachability,
   existence of both nodes' matching Neighbor TLVs should be checked.

5.3.  Custom TLV (within/without Node Data TLV)

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type: CUSTOM-DATA (9)     |         Length: >= 12         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            H-64(URI)                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Opaque Data                          |


   This TLV can be used to contain anything; the URI used should be
   under control of the author of that specification.  For example:



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   V=H-64('http://example.com/author/json-for-hncp') .. '{"cool": "json
   extension!"}'

   or

   V=H-64('mailto:author@example.com') .. '{"cool": "json extension!"}'

5.4.  Authentication TLVs

5.4.1.  Certificate-related TLVs

   TBD; should be probably some sort of certificate ID to be used in a
   lookup at most, as raw certificates will overflow easily IPv6 minimum
   MTU.

5.4.2.  Signature TLV

   TLV with T=0xFFFF, V=(TBD) public key algorithm based signature of
   all TLVs within current scope as well as the parent TLV header, if
   any.  The assumed signature key is private key matching the public
   key of the the originator of node link TLV (if signature TLV is
   within main body of message), or that of the originator of the node
   data TLV (if signature TLV is within Node Data TLV)..

6.  Border Discovery and Prefix Assignment

   Using Default Border Definition [I-D.kline-homenet-default-perimeter]
   as a basis, this section defines border discovery algorithm specifics
   derived from the edge router interactions described in the Basic
   Requirements for IPv6 Customer Edge Routers [RFC7084].  The algorithm
   is designed to work for both IPv4 and IPv6 (single or dual-stack).

   In order to avoid conflicts between border discovery and homenet
   routers running DHCP [RFC2131] or DHCPv6-PD [RFC3633] servers each
   router MUST implement the following mechanism based on The User Class
   Option for DHCP [RFC3004] or its DHCPv6 counterpart [RFC3315]
   respectively into its DHCP and DHCPv6-logic:

      A homenet router running a DHCP-client on a homenet-interface MUST
      include a DHCP User-Class consisting of the ASCII-String
      "HOMENET".

      A homenet router running a DHCP-server on a homenet-interface MUST
      ignore or reject DHCP-Requests containing a DHCP User-Class
      consisting of the ASCII-String "HOMENET".

   An interface MUST be considered external if at least one of the
   following conditions is satisfied:



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   1.  The interface has a fixed category classifying it as external.

   2.  A delegated prefix could be acquired by running a DHCPv6-client
       on the interface.

   3.  An IPv4-address could be acquired by running a DHCP-client on the
       interface.

   4.  HNCP security is enabled and there are routers on the interface
       which could not be authenticated.

   Each router MUST continuously scan each active interface that does
   not have a fixed category in order to dynamically reclassify it if
   necessary.  The router therefore runs an appropriately configured
   DHCP and DHCPv6-client as long as the interface is active including
   states where it considers the interface to be internal.  The router
   SHOULD wait for a reasonable time period (5 seconds as a possible
   default) in which the DHCP-clients can acquire a lease before
   treating a newly activated or previously external interface as
   internal.  Once it treats a certain interface as internal it MUST
   start forwarding traffic with appropriate source addresses between
   its internal interfaces and allow internal traffic to reach external
   networks.  Once a router detects an interface to be external it MUST
   stop any previously enabled internal forwarding.  In addition it
   SHOULD announce the acquired information for use in the homenet as
   described in later sections of this draft if the interface appears to
   be connected to an external network.

   To distribute an external connection in the homenet an edge router
   announces one or more delegated prefixes and associated
   DHCP(v6)-encoded auxiliary information like recursive DNS-servers.
   Each external connection is announced using one container-TLV as
   follows:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type: EXTERNAL-CONNECTION (41)|          Length: > 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Nested TLVs                          |











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   Auxiliary connectivity information is encoded as a stream of
   DHCPv6-attributes or DHCP-attributes placed inside a TLV of type
   EXTERNAL-CONNECTION or DELEGATED-PREFIX (for IPv6 prefix-specific
   information).  There MUST NOT be more than one instance of this TLV
   inside a container and the order of the DHCP(v6)-attributes contained
   within it MUST be preserved as long as the information contained does
   not change.  The TLVs are encoded as follows:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type: DHCPV6-DATA (45)     |          Length: > 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    DHCPv6 attribute stream                    |


   and

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type: DHCP-DATA (44)      |          Length: > 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      DHCP attribute stream                    |


   Each delegated prefix is encoded using one TLV inside an EXTERNAL-
   CONNECTION TLV.  For external IPv4 connections the prefix is encoded
   in the form of an IPv4-mapped address [RFC4291] and is usually from a
   private address range [RFC1597].  The related TLV is defined as
   follows.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type: DELEGATED-PREFIX (42)  |         Length: >= 13         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Valid until (milliseconds)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Preferred until (milliseconds)                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Prefix Length |                                               |
   +-+-+-+-+-+-+-+-+        Prefix Address [+ nested TLVs]         +
   |                                                               |







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      Valid until is the time in milliseconds the delegated prefix is
      valid.  The value is relative to the point in time the TLV is
      first announced.

      Preferred until is the time in milliseconds the delegated prefix
      is preferred.  The value is relative to the point in time the TLV
      is first announced.

      Prefix length specifies the number of significant bits in the
      prefix.

      Prefix address is of variable length and contains the significant
      bits of the prefix padded with zeroes up to the next byte
      boundary.

      Nested TLVs might contain prefix-specific information like
      DHCPv6-options.

   In order for routers to use the distributed information, prefixes and
   addresses have to be assigned to the interior links of the homenet.
   A router MUST therefore implement the algorithm defined in Prefix and
   Address Assignment in a Home Network
   [I-D.pfister-homenet-prefix-assignment].  In order to announce the
   assigned prefixes the following TLVs are defined.

   Each assigned prefix is given to an interior link and is encoded
   using one TLVs.  Assigned IPv4 prefixes are stored as mapped
   IPv4-addresses.  The TLV is defined as follows:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type: ASSIGNED-PREFIX (43)   |          Length: >= 9         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Link Identifier                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  R. |A| Pref. | Prefix Length |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+         Prefix Address        +
   |                                                               |


      Link Identifier is the local HNCP identifier of the link the
      prefix is assigned to.

      R. is reserved for future additions and MUST be set to 0 when
      creating TLVs and ignored when parsing them.





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      A is the authoritative flag which indicates that an assigment is
      enforced and ignores usual collision detection rules.

      Pref. describes the preference of the assignment and can be used
      to differentiate the importance of a given assignment over others.

      Prefix length specifies the number of significant bits in the
      prefix.

      Prefix address is of variable length and contains the significant
      bits of the prefix padded with zeroes up to the next byte
      boundary.

   In some cases (e.g. IPv4) the set of addresses is very limited and
   stateless mechanisms are not really suitable for address assignment.
   Therefore HNCP can manage router address in these cases by itself.
   Each router assigning an address to one of its interfaces announces
   one TLV of the following kind:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type: ROUTER-ADDRESS (46)   |           Length: 20          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Router Address                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Router Address is the address assigned to one of the router
      interfaces.

7.  DNS-based Service Discovery

   Service discovery is generally limited to a local link.
   [I-D.stenberg-homenet-dnssd-hybrid-proxy-network-zeroconf]  defines a
   mechanism to automatically extended DNS-based service discovery
   across multiple links within the home automatically.  Of the three
   TLVs, the DNS Delegated Zone TLV MUST be supported, and the remaining
   two SHOULD be.









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7.1.  DNS Delegated Zone TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type: DNS-DELEGATED-ZONE (50) |        Length: >= 21          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                            Address                            |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Reserved  |S|B|                                               |
   +-+-+-+-+-+-+-+-+  Zone (DNS label sequence - variable length)  |
   |                                                               |


7.2.  Domain Name TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type: DOMAIN-NAME (51)     |         Length: >= 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Domain (DNS label sequence - variable length)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


7.3.  Router Name TLV

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type: ROUTER-NAME (52)     |         Length: >= 4          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Name (not null-terminated - variable length)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


8.  Routing support

8.1.  Protocol Requirements

   In order to be advertised for use within the Homenet, a routing
   protocol MUST:

      Comply with Requirements and Use Cases for Source/Destination
      Routing [I-D.baker-rtgwg-src-dst-routing-use-cases].



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      Be configured with suitable defaults or have an autoconfiguration
      mechanism (e.g. [I-D.acee-ospf-ospfv3-autoconfig]) such that it
      will run in a Homenet without requiring specific configuration
      from the Home user.

   A router MUST NOT announce that it supports a certain routing
   protocol if its implementation of the routing protocol does not meet
   these requirements, e.g. it does not implement extensions that are
   necessary for compliance.

8.2.  Announcement

   Each router SHOULD announce all routing protocols that it is capable
   of supporting in the Homenet.  It SHOULD assign a preference value
   for each protocol that indicates its desire to use said protocol over
   other protocols it supports and SHOULD make these values
   configurable.

   Each router includes one HNCP TLV of type ROUTING-PROTOCOL for every
   such routing protocol.  This TLV is defined as follows:

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type: ROUTING-PROTOCOL (60)  |           Length: 6           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Protocol ID  |   Preference  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Protocol ID is one of:

         0 = reserved

         1 = Babel (dual-stack)

         2 = OSPFv3 (dual-stack)

         3 = IS-IS (dual-stack)

         4 = RIP (dual-stack)

      Preference is a value from 0 to 255.  If a router is neutral about
      a routing protocol it SHOULD use the value 128, otherwise a lower
      value indicating lower preference or a higher value indicating
      higher preference respectively.





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8.3.  Protocol Selection

   When HNCP detects that a router has joined or left the Homenet it
   MUST examine all advertised routing protocols and preference values
   from all routers in the Homenet in order to find the one routing
   protocol which:

   1.  Is understood by all routers in the homenet

   2.  Has the highest preference value among all routers (calculated as
       sum of preference values)

   3.  Has the highest protocol ID among those with the highest
       preference

   If the router protocol selection results in the need to change from
   one routing protocol to another on the homenet, the router MUST stop
   the previously running protocol, remove associated routes, and start
   the new protocol in a graceful manner.  If there is no common routing
   protocol available among all Homenet routers, routers MUST utilize
   the Fallback Mechanism (Section 8.4).

8.4.  Fallback Mechanism

   In cases where there is no commonly supported routing protocol
   available the following fallback algorithm is run to setup routing
   and preserve interoperability among the homenet.  While not intended
   to replace a routing protocol, this mechanism provides a valid - but
   not necessarily optimal - routing topology.  This algorithm uses the
   node and neighbor state already synchronized by HNCP, and therefore
   does not require any additional protocol message exchange.

   1.  Interpret the neighbour information received via HNCP as a graph
       of connected routers.

   2.  Use breadth-first traversal to determine the next-hop and hop-
       count in the path to each router in the homenet:

          Start the traversal with the immediate neighbours of the
          router running the algorithm.

          Always visit the immediate neighbours of a router in ascending
          order of their router ID.

          Never visit a router more often than once.

   3.  For each delegated prefix P of any router R in the homenet:
       Create a default route via the next-hop for R acquired in #2.



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       Each such route MUST be source-restricted to only apply to
       traffic with a source address within P and its metric MUST
       reflect the hop-count to R.

   4.  For each assigned prefix A of a router R: Create a route to A via
       the next-hop for R acquired in #2.  Each such route MUST NOT be
       source-restricted.

   5.  For the first router R visited in the traversal annuncing an
       IPv4-uplink: Create a default IPv4-route via the next-hop for R
       acquired in #2.

   6.  For each assigned IPv4-prefix A of a router R: Create an
       IPv4-route to A via the next-hop for R acquired in #2.

9.  Security Considerations

   General security issues for Home Networks are discussed at length in
   [I-D.ietf-homenet-arch].  The protocols used to setup IP in home
   networks today have very little security enabled within the control
   protocol itself.  For example, DHCP has defined [RFC3118] to
   authenticate DHCP messages, but this is very rarely implemented in
   large or small networks.  Further, while PPP can provide secure
   authentication of both sides of a point to point link, it is most
   often deployed with one-way authentication of the subscriber to the
   ISP, not the ISP to the subscriber.  HNCP aims to make security as
   easy as possible for the implementer by including built-in
   capabilities for authentication of node data being exchanged as well
   as the protocol messages themselves, but it is ultimately up to the
   shipping system to take advantage of the protocol constructs defined.

   HNCP is designed to integrate with trusted bootstrapping
   [I-D.behringer-homenet-trust-bootstrap] including the ability to
   authenticate messages between nodes.  This authentication can be used
   to securely define a border as well as protect against malicious
   attacks and spoofing attempts from inside or outside the border.

   HNCP itself sends messages as (possibly authenticated) clear text
   which is as secure, or insecure, as the security of the link below as
   discussed in [I-D.kline-homenet-default-perimeter].  When no unique
   public key is available, a hardware fingerprint or equivalent to
   identify routers must be available for use by HNCP.

   As HNCP messages are sent over UDP/IP, IPsec may be used for
   confidentiality or additional message authenitation.  However, this
   requires manually keyed IPsec per-port granularity for port IANA-UDP-
   PORT UDP traffic.  Also, a pre-shared key has to be utilized in this
   case given IKE cannot be used with multicast traffic.



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   If no router can be trusted and additional guarantees about source of
   node status updates is necessary, real public and private keys should
   be used to create signatures and verify them in HNCP on both on per-
   node data TLVs as well as across the entire HNCP message.  In this
   mode, care must be taken in rate limiting verification of invalid
   packets, as otherwise denial of service may occur due to exhaustion
   of computation resources.

   As a performance optimization, instead of providing signatures for
   actual node data and the protocol messages themselves, it is also
   possible to provide signatures just for protocol messages.  While
   this means it is no longer possible to verify the original source of
   the node data itself, as long as the set of routers is trusted (i.e.,
   no router in the set has itself been hacked to provide malicious node
   data) then one can assume the node data is trusted because the router
   is trusted and the data arrived in a protected protocol message.

10.  IANA Considerations

   IANA should set up a registry (policy TBD) for HNCP TLV types, with
   following initial contents:

   0: Reserved (should not happen on wire)

   1: Node link

   2: Request network state

   3: Request node data

   4: Network state

   5: Node state

   6: Node data

   7: Node public key

   8: Neighbor

   9: Custom

   41: External connection

   42: Delegated prefix

   43: Assigned prefix




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   44: DHCP-data

   45: DHCPv6-data

   46: Router-address

   50: DNS Delegated Zone

   51: Domain name

   52: Node name

   60: Routing protocol

   65535: Signature

   HNCP will also require allocation of a UDP port number IANA-UDP-PORT,
   as well as IPv6 link-local multicast address IANA-MULTICAST-ADDRESS.

11.  References

11.1.  Normative references

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC6206]  Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
              "The Trickle Algorithm", RFC 6206, March 2011.

   [I-D.pfister-homenet-prefix-assignment]
              Pfister, P., Arkko, J., and B. Paterson, "Prefix and
              Address Assignment in a Home Network", draft-pfister-
              homenet-prefix-assignment-00 (work in progress), January
              2014.

   [I-D.stenberg-homenet-dnssd-hybrid-proxy-network-zeroconf]
              Stenberg, M., "Auto-Configuration of a Network of Hybrid
              Unicast/Multicast DNS-Based Service Discovery Proxy Nodes
              ", draft-pfister-homenet-prefix-assignment-00 (work in
              progress), January 2014.

11.2.  Informative references

   [RFC7084]  Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
              Requirements for IPv6 Customer Edge Routers", RFC 7084,
              November 2013.





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   [RFC3004]  Stump, G., Droms, R., Gu, Y., Vyaghrapuri, R., Demirtjis,
              A., Beser, B., and J. Privat, "The User Class Option for
              DHCP", RFC 3004, November 2000.

   [RFC3118]  Droms, R. and W. Arbaugh, "Authentication for DHCP
              Messages", RFC 3118, June 2001.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
              2131, March 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC1597]  Rekhter, Y., Moskowitz, R., Karrenberg, D., and G. de
              Groot, "Address Allocation for Private Internets", RFC
              1597, March 1994.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [I-D.ietf-homenet-arch]
              Chown, T., Arkko, J., Brandt, A., Troan, O., and J. Weil,
              "IPv6 Home Networking Architecture Principles", draft-
              ietf-homenet-arch-11 (work in progress), October 2013.

   [I-D.troan-homenet-sadr]
              Troan, O. and L. Colitti, "IPv6 Multihoming with Source
              Address Dependent Routing (SADR)", draft-troan-homenet-
              sadr-01 (work in progress), September 2013.

   [I-D.behringer-homenet-trust-bootstrap]
              Behringer, M., Pritikin, M., and S. Bjarnason,
              "Bootstrapping Trust on a Homenet", draft-behringer-
              homenet-trust-bootstrap-00 (work in progress), October
              2012.

   [I-D.baker-rtgwg-src-dst-routing-use-cases]
              Baker, F., "Requirements and Use Cases for Source/
              Destination Routing", draft-baker-rtgwg-src-dst-routing-
              use-cases-00 (work in progress), August 2013.

   [I-D.kline-homenet-default-perimeter]




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              Kline, E., "Default Border Definition", draft-kline-
              homenet-default-perimeter-00 (work in progress), March
              2013.

   [I-D.arkko-homenet-prefix-assignment]
              Arkko, J., Lindem, A., and B. Paterson, "Prefix Assignment
              in a Home Network", draft-arkko-homenet-prefix-
              assignment-04 (work in progress), May 2013.

   [I-D.stenberg-homenet-dnssdext-hybrid-proxy-ospf]
              Stenberg, M., "Hybrid Unicast/Multicast DNS-Based Service
              Discovery Auto-Configuration Using OSPFv3", draft-
              stenberg-homenet-dnssdext-hybrid-proxy-ospf-00 (work in
              progress), June 2013.

   [I-D.acee-ospf-ospfv3-autoconfig]
              Lindem, A. and J. Arkko, "OSPFv3 Auto-Configuration",
              draft-acee-ospf-ospfv3-autoconfig-03 (work in progress),
              July 2012.

Appendix A.  Some Outstanding Issues

   Should we use MD5 hashes, or EUI-64 node identifier to identify
   nodes?

   Is there a case for non-link-local unicast?  Currently explicitly
   stating this is link-local only protocol.

   Consider if using Trickle with k=1 really pays off, as we need to do
   reachability checks if L2 doesn't provide them periodically in any
   case.  Using Trickle with k=inf would remove the need for unicast
   reachability checks, but at cost of extra multicast traffic.  On the
   other hand, N*(N-1)/2 unicast reachability checks when lot of routers
   share a link is not appealing either.

   Should we use something else than MD5 as hash?  It IS somewhat
   insecure; however signature stuff (TBD) should rely on it mainly for
   security in any case, and MD5 is used in a non-security role.

Appendix B.  Some Obvious Questions and Answers

   Q: Why not use TCP?

   A: It doesn't address the node discovery problem.  It also leads to
   N*(N-1)/2 connections when N nodes share a link, which is awkward.

   Q: Why effectively build a link state routing protocol without
   routing?



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   A: It felt like a good idea at the time.  It does not require
   periodic flooding except for very minimal Trickle-based per-link
   state maintenance (potentially also neighbor reachability checks if
   so desired).

   Q: Why not multicast-only?

   A: It would require defining application level fragmentation scheme.
   Hopefully the data amounts used will stay small so we just trust
   unicast UDP to handle 'big enough' packets to contain single node's
   TLV data.  On some link layers unicast is also much more reliable
   than multicast, especially for large packets.

   Q: Why so long IDs?  Why real hash even in insecure mode?

   A: Scalability of protocol isn't really affected by using real
   (=cryptographic) hash function.

   Q: Why trust IPv6 fragmentation in unicast case?  Why not do L7
   fragmentation?

   A: Because it will be there for a while at least.  And while PMTU et
   al may be problems on open internet, in a home network environment
   UDP fragmentation should NOT be broken in the foreseeable future.

   Q: Should there be nested container syntax that is actually self-
   describing? (i.e. type flag that indicates container, no body except
   sub-TLVs?)

   A: Not for now, but perhaps valid design.. TBD.

   Q: Why not doing (performance thing X, Y or Z)?

   A: This is designed mostly to be minimal (only timers Trickle ones;
   everything triggered by Trickle-driven messages or local state
   changes).  However, feel free to suggest better (even more minimal)
   design which works.

Appendix C.  Draft source

   As usual, this draft is available at https://github.com/fingon/ietf-
   drafts/ [3] in source format (with nice Makefile too).  Feel free to
   send comments and/or pull requests if and when you have changes to
   it!

Appendix D.  Acknowledgements





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Internet-Draft      Home Networking Control Protocol       February 2014


   Thanks to Ole Troan, Pierre Pfister, Mark Baugher, Mark Townsley and
   Juliusz Chroboczek for their contributions to the draft.

Authors' Addresses

   Markus Stenberg
   Helsinki  00930
   Finland

   Email: markus.stenberg@iki.fi


   Steven Barth

   Email: cyrus@openwrt.org




































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