Halle 06114 Germany cyrus@openwrt.org

Internet Homenet Working Group IPv6 Homenet DNCP HNCP This document describes an incremental approach towards deploying HNCP and routing protocols in home networks. Its aim is to provide a minimal, forward-compatible transitional extension to HNCP to promote testing, deployment and adoption of homenet technology while the IGP decision and standardization process is not yet finalized.

While it is expected that the average number of routers and their hardware and software capabilities in a typical home network will grow over time, this trend has historically been gradual. Thus it can be expected that in the near future there will most likely be not more than a handful of routers in a home and their capabilities for operating in a fully-routed mode are limited. It is also hard to predict which types of other networks the homenet technology will be used in and what attributes these networks will have (e.g. number of routers, links, link-types, topologies, suitable methods for detecting link-layer status and deriving metric). Furthermore the standardization of autoconfiguring and source-dest-routing capable protocols is not expected to be finalized soon and there is currently a shortage of widely testable or deployable implementations fulfilling these criteria. These issues and a general lack of consensus over an all-purpose routing protocol support a transitional forward-compatible extension to HNCP implementations in order to advance homenet progress and to promote adoption. This draft describes a solution sufficient for small networks allowing gradual adoption of homenet principles into existing networks while ensuring an easy transition to a future standardized version.

Each homenet router runs an incremental connectivity algorithm at all times on each network interface it is running HNCP on and can optionally additionally run one or more routing protocols. A router running a routing protocol alongside the incremental connectivity algorithm must strictly prefer all routes of the routing protocol over all routes generated by the incremental connectivity algorithm, except for those having destinations not already known to the routing protocol but that lie within one of the designated prefixes of the homenet (i.e. prefixes assigned by a homenet router that does not speak the respective routing protocol). In case of routers running more than one routing protocol alongside the incremental connectivity algorithm, all such routers in the homenet ensure that in doing so they do not cause routing loops, e.g. by agreeing upon a network-wide order in which routes of the protocols are considered.

This algorithm is designed to provide connectivity in small home networks that would not benefit from exploiting link characteristics or metrics. It is intentionally kept simple to require no additional TLV-information by reusing existing topology and address assignment information provided by HNCP and only requires minimal implementation overhead. Each homenet router traverses the HNCP neighbor graph using a breadth-first search starting with its own node's immediate neighbors. Neighbors of a node are traversed in ascending order of their node identifier. During traversal the router determines the path to each other router (R), the next-hop neighbor N(R) and the number of hops to it D(R). The router then creates routes based on the following rules: Create a route To From Via Metric For each Prefix (A) in an Assigned Prefix TLV of any Router (R) A any N(R) D(R) For each IPv6 prefix (P) in a Delegated Prefix TLV of any Router (R) ::/0 P N(R) D(R) For the first Router (R) traversed that announces an IPv4 Delegated Prefix TLV 0.0.0.0/0 any N(R) D(R) This process is repeated every time the router detects a change in the neighbor graph or prefix assignment information in the network.

The mechanism described in this document is based on HNCP, thus security considerations for this document are already covered by .

This document has no actions for IANA.

Thanks to Pierre Pfister and Markus Stenberg for comments and suggestions.