Homenet Working Group M. Stenberg Internet-Draft Intended status: Standards Track S. Barth Expires: April 30, 2015 October 27, 2014 Home Networking Control Protocol draft-ietf-homenet-hncp-02 Abstract This document describes the Home Networking 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 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 April 30, 2015. 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. Stenberg & Barth Expires April 30, 2015 [Page 1] Internet-Draft Home Networking Control Protocol October 2014 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 . . . . . . . . . . . . . . . . . . . . 4 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) . . . . . . . . . . . . 5 4.2.4. Network and Node State Reply (NetNode-Reply) . . . . 6 4.3. HNCP Protocol Message Processing . . . . . . . . . . . . 6 4.4. Adding and Removing Neighbors . . . . . . . . . . . . . . 7 4.5. Purging Unreachable Nodes . . . . . . . . . . . . . . . . 8 5. Type-Length-Value objects . . . . . . . . . . . . . . . . . . 8 5.1. Request TLVs (for use within unicast requests) . . . . . 8 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) . . . 9 5.2.1. Node Link TLV . . . . . . . . . . . . . . . . . . . . 9 5.2.2. Network State TLV . . . . . . . . . . . . . . . . . . 9 5.2.3. Node State TLV . . . . . . . . . . . . . . . . . . . 10 5.2.4. Node Data TLV . . . . . . . . . . . . . . . . . . . . 11 5.2.5. Neighbor TLV (within Node Data TLV) . . . . . . . . . 11 5.3. Custom TLV (within/without Node Data TLV) . . . . . . . . 11 5.4. Version TLV (within Node Data TLV) . . . . . . . . . . . 12 6. Border Discovery and Prefix Assignment . . . . . . . . . . . 12 7. DNS-based Service Discovery . . . . . . . . . . . . . . . . . 17 7.1. DNS Delegated Zone TLV . . . . . . . . . . . . . . . . . 17 7.2. Domain Name TLV . . . . . . . . . . . . . . . . . . . . . 18 7.3. Router Name TLV . . . . . . . . . . . . . . . . . . . . . 18 8. Routing support . . . . . . . . . . . . . . . . . . . . . . . 18 8.1. Protocol Requirements . . . . . . . . . . . . . . . . . . 18 8.2. Announcement . . . . . . . . . . . . . . . . . . . . . . 18 8.3. Protocol Selection . . . . . . . . . . . . . . . . . . . 19 8.4. Fallback Mechanism . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 21 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 11.1. Normative references . . . . . . . . . . . . . . . . . . 22 11.2. Informative references . . . . . . . . . . . . . . . . . 23 11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Appendix A. Some Outstanding Issues . . . . . . . . . . . . . . 24 Appendix B. Some Obvious Questions and Answers . . . . . . . . . 24 Appendix C. Changelog . . . . . . . . . . . . . . . . . . . . . 25 Appendix D. Draft source . . . . . . . . . . . . . . . . . . . . 26 Appendix E. Acknowledgements . . . . . . . . . . . . . . . . . . 26 Stenberg & Barth Expires April 30, 2015 [Page 2] Internet-Draft Home Networking Control Protocol October 2014 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 1. Introduction HNCP is designed to synchronize state across a homenet (or other small site) in order to facilitate automated configuration within the site. The design supports border discovery, IP prefix distribution [I-D.ietf-homenet-prefix-assignment], and service discovery across multiple links[I-D.stenberg-homenet-dnssd-hybrid-proxy-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/ and the binaries are available in the routing feed of OpenWrt [2] trunk release. Some information how to get started with it is available at [3]. Comments and/or pull requests are welcome. 2. 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]. 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 identifier that is very likely unique among the set of routers in the homenet. 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 32 bit number that is incremented anytime TLV data changes are detected. Stenberg & Barth Expires April 30, 2015 [Page 3] Internet-Draft Home Networking Control Protocol October 2014 Relative time, in milliseconds, since last publishing of the current TLV data set. It is also 32 bit number on the wire. 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. 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 Stenberg & Barth Expires April 30, 2015 [Page 4] Internet-Draft Home Networking Control Protocol October 2014 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 (referred 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. 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: Node Link TLV (Section 5.2.1). Request Network State TLV (Section 5.1.1). 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). Stenberg & Barth Expires April 30, 2015 [Page 5] Internet-Draft Home Networking Control Protocol October 2014 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). 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 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), potentially incorrect (local update number is same and the hash of node data TLV differs) 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. Stenberg & Barth Expires April 30, 2015 [Page 6] Internet-Draft Home Networking Control Protocol October 2014 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, different node data TLV hash, or we lack the node data altogether), and 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 there is no global guarantee of unique node identifier, a new node identifier SHOULD be generated and node data republished accordingly. 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 5.2.5) 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 no layer 2 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). Stenberg & Barth Expires April 30, 2015 [Page 7] Internet-Draft Home Networking Control Protocol October 2014 4.5. Purging Unreachable Nodes When node data has changed, the neighbor graph SHOULD be traversed for each node following the bidirectional neighbor relationships. These are identified by looking for neighbor TLVs on both nodes, that have the remote node's identifier hash as h(neighbor node identifier), and local and neighbor link identifiers swapped. After the traverse, unreachable nodes SHOULD be purged after some grace period. During the grace period, the unreachable nodes MUST NOT be used for calculation of network state hash, or even be provided to any applications that need to use the whole TLV graph. 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), 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. 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) Stenberg & Barth Expires April 30, 2015 [Page 8] Internet-Draft Home Networking Control Protocol October 2014 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) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 Stenberg & Barth Expires April 30, 2015 [Page 9] Internet-Draft Home Networking Control Protocol October 2014 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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. Stenberg & Barth Expires April 30, 2015 [Page 10] Internet-Draft Home Networking Control Protocol October 2014 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 | 5.2.5. 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) Stenberg & Barth Expires April 30, 2015 [Page 11] Internet-Draft Home Networking Control Protocol October 2014 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: 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. Version 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: VERSION (10) | Length: >= 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | User-agent | This TLV indicates which version of HNCP TLV binary structures is in use by this particular node. All TLVs within node data from nodes that do not publish version TLV, or with different Version value than locally supported one MUST be ignored (but forwarded). The user- agent is an optional human-readable UTF-8 string that can describe e.g. current HNCP implementation version. This draft describes Version=1 TLVs. 6. Border Discovery and Prefix Assignment This section defines border discovery algorithm 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 Stenberg & Barth Expires April 30, 2015 [Page 12] Internet-Draft Home Networking Control Protocol October 2014 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". The border discovery auto-detection algorithm works as follows, with evaluation stopping at first match: 1. If a fixed category is set for an interface, it MUST be used. 2. Any of the following conditions indicate an interface MUST be considered external: 1. A delegated prefix could be acquired by running a DHCPv6-client on the interface. 2. An IPv4-address could be acquired by running a DHCP-client on the interface. 3. As default fallback, interface MUST be considered internal. A router MUST allow setting a category of either auto-detected, internal or external for each interface which is suitable for both internal and external connections. In addition the following specializations of the internal category are defined to modify the local router behavior: Leaf category: This declares an interface used by clients only. A router SHOULD implement this category and MUST NOT send nor accept HNCP messages on these interfaces. Guest category: This declares an interface used by untrusted clients only. In addition to the restrictions of the leaf category, clients connected to these interfaces MUST NOT be able to reach devices inside the home network by default and instead SHOULD only be able to reach the internet. This category SHOULD be also supported. Ad-hoc category: This declares an interface to be in ad-hoc mode. This indicates to HNCP applications such as prefix assignment that Stenberg & Barth Expires April 30, 2015 [Page 13] Internet-Draft Home Networking Control Protocol October 2014 links on this interface are potentially non-transitive. This category MAY be implemented. Hybrid category: This allows the router to still accepts external connections but does not do border discovery. It is assumed that the link is under control of a legacy, trustworthy non-HNCP router, still within the same home network. Detection of this category automatically in addition to manual configuration is out of scope for this document. This category MAY be implemented. A homenet router SHOULD provide basic connectivity to legacy CERs [RFC7084] connected to internal interfaces in order to allow coexistence with existing devices. 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 | 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 Stenberg & Barth Expires April 30, 2015 [Page 14] Internet-Draft Home Networking Control Protocol October 2014 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 [RFC1918]. 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] + | | 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. Stenberg & Barth Expires April 30, 2015 [Page 15] Internet-Draft Home Networking Control Protocol October 2014 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.ietf-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. A is the authoritative flag which indicates that an assignment 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. Stenberg & Barth Expires April 30, 2015 [Page 16] Internet-Draft Home Networking Control Protocol October 2014 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: 24 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Router Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Link Identifier is the local HNCP identifier of the link the address is assigned to. 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-zeroconf] defines a mechanism to automatically extended DNS-based service discovery across multiple links within the home automatically. Following TLVs MAY be used to provide transport for that specification. 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) | | | Stenberg & Barth Expires April 30, 2015 [Page 17] Internet-Draft Home Networking Control Protocol October 2014 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]. Be configured with suitable defaults or have an auto-configuration 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 MUST announce at least one protocol or the fallback mechanism to be considered for protocol selection and MAY omit announcing the fallback mechanism if it announces at least one other routing protocol. It SHOULD assign a preference value for each protocol that indicates its desire to use said protocol over Stenberg & Barth Expires April 30, 2015 [Page 18] Internet-Draft Home Networking Control Protocol October 2014 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 = Fallback (explicit announcement) 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. 8.3. Protocol Selection When HNCP detects that a device has joined or left the homenet it MUST examine all advertised routing protocols and preference values from all devices announcing at least one ROUTING-PROTOCOL-TLV 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 Stenberg & Barth Expires April 30, 2015 [Page 19] Internet-Draft Home Networking Control Protocol October 2014 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 neighbor 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: 1. Start the traversal with the immediate neighbors of the router running the algorithm. 2. Always visit the immediate neighbors of a router in ascending order of their router ID. 3. 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. 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 announcing 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. Stenberg & Barth Expires April 30, 2015 [Page 20] Internet-Draft Home Networking Control Protocol October 2014 9. Security Considerations General security issues for home networks are discussed at length in [RFC7368]. The protocols used to set up IP in home networks today have rarely 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 itself sends messages as clear text which is as secure, or insecure, as the security of the link it runs on. As HNCP messages are sent over IPv6 UDP, IPsec may be used for confidentiality or message authentication. This requires manually keyed IPsec per-port granularity for port IANA-UDP-PORT UDP traffic, and a pre-shared key has to be utilized in this case given IKE cannot be used with multicast traffic. This seems acceptable, though, as most routing protocols also operate based on pre-shared keys, and the homenet architecture draft explicitly allows their use for securing them[RFC7368]. Other traffic security mechanisms are out of scope for this specification. There is ongoing work [I-D.barth-homenet-hncp-security-trust] to define a mechanism that can be used with HNCP and be more user-friendly than pre-shared keys. 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: (unused - was node public key, but never implemented) 8: Neighbor Stenberg & Barth Expires April 30, 2015 [Page 21] Internet-Draft Home Networking Control Protocol October 2014 9: Custom 10: Version 41: External connection 42: Delegated prefix 43: Assigned prefix 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.ietf-homenet-prefix-assignment] Pfister, P., Paterson, B., and J. Arkko, "Prefix and Address Assignment in a Home Network", draft-ietf-homenet- prefix-assignment-01 (work in progress), October 2014. Stenberg & Barth Expires April 30, 2015 [Page 22] Internet-Draft Home Networking Control Protocol October 2014 [I-D.stenberg-homenet-dnssd-hybrid-proxy-zeroconf] Stenberg, M., "Auto-Configuration of a Network of Hybrid Unicast/Multicast DNS-Based Service Discovery Proxy Nodes", draft-stenberg-homenet-dnssd-hybrid-proxy- zeroconf-01 (work in progress), June 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. [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. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC7368] Chown, T., Arkko, J., Brandt, A., Troan, O., and J. Weil, "IPv6 Home Networking Architecture Principles", RFC 7368, October 2014. [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. Stenberg & Barth Expires April 30, 2015 [Page 23] Internet-Draft Home Networking Control Protocol October 2014 [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-01 (work in progress), October 2014. [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. [I-D.barth-homenet-hncp-security-trust] Barth, S., "HNCP - Security and Trust Management", draft- barth-homenet-hncp-security-trust-01 (work in progress), October 2014. 11.3. URIs [2] http://www.openwrt.org [3] http://www.homewrt.org/doku.php?id=run-conf 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 layer 2 does not 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. Valid and preferred are now 32 bit millisecond and you cannot even represent a month in them; is this enough? Or should we switch to 32 bit seconds (or 64 bit milliseconds)? Appendix B. Some Obvious Questions and Answers Q: Why not use TCP? A: It does not 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 not multicast-only? Stenberg & Barth Expires April 30, 2015 [Page 24] Internet-Draft Home Networking Control Protocol October 2014 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. Also on wireless, multicast is much more power expensive than unicast. Q: Why so long IDs? A: Scalability of protocol is not 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. Changelog draft-ietf-homenet-hncp-02: Removed any built-in security. Relying on IPsec. Reorganized interface categories, added requirements languages, made manual border configuration a MUST-support. Redesigned routing protocol election to consider non-router devices. draft-ietf-homenet-hncp-01: Added (MAY) guest, ad-hoc, hybrid categories for interfaces. Removed old hnetv2 reference, and now pointing just to OpenWrt + github. Fixed synchronization algorithm to spread also same update number, but different data hash case. Made purge step require bidirectional connectivity between nodes when traversing the graph. Edited few other things to be hopefully slightly clearer without changing their meaning. Stenberg & Barth Expires April 30, 2015 [Page 25] Internet-Draft Home Networking Control Protocol October 2014 draft-ietf-homenet-hncp-00: Added version TLV to allow for TLV content changes pre-RFC without changing IDs. Added link id to assigned address TLV. Appendix D. Draft source As usual, this draft is available at https://github.com/fingon/ietf- drafts/ 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 E. Acknowledgements Thanks to Ole Troan, Pierre Pfister, Mark Baugher, Mark Townsley and Juliusz Chroboczek for their contributions to the draft. Thanks to Eric Kline for the original border discovery work. Authors' Addresses Markus Stenberg Helsinki 00930 Finland Email: markus.stenberg@iki.fi Steven Barth Email: cyrus@openwrt.org Stenberg & Barth Expires April 30, 2015 [Page 26]