ns-3 6LoWPAN Neighbor Discovery

ns-3 is a discrete-event network simulator. Its sixlowpan module compresses IPv6 headers for low-power wireless links such as IEEE 802.15.4, but nodes still run plain RFC 4861 Neighbor Discovery: multicast solicitations for duplicate detection and periodic multicast router advertisements. RFC 6775, updated by RFC 8505, replaces that with a host-driven scheme: a node solicits routers, forms addresses from advertised prefixes and registers each with the border router, which keeps a binding table and rejects duplicates. The agent starts from the commit before ns-3 landed this protocol (merge request !2482). Lifetimes, renewals and departures run over hours of simulated time, and plain nodes must still behave as before.

The agent adds 6LoWPAN Neighbor Discovery to the sixlowpan module for host and border router roles on a single mesh-under link. Helper methods install both roles and set advertised prefixes and contexts, a protocol object carries lifetime attributes and trace sources, and a binding table prints in a fixed format. Message formats and processing follow RFC 6775 and RFC 8505, with RFC 4861 and RFC 4862 for what they leave unchanged. Route-over routing, multihop duplicate detection and backbone routers are out of scope; where the RFCs leave a choice open, the agent decides and documents it. Only committed work is graded.

The offline sandbox (4 CPUs, 8 GB, 4 hours) holds an ns-3-dev checkout with its real history at commit 0740177d, configured and built with the needed modules, tests and examples. The scenario driver and its cases are held out.

The committed tree is rebuilt from a clean checkout, and every test suite passing at the start must still pass. 224 seeded simulations in seven families cover bootstrapping, multiple prefixes, renewal, departure, duplicate addresses, router solicitation and combined scenarios. Registration results, binding tables, neighbor caches, addresses, routers and exchanged messages are compared with the upstream implementation at checkpoints whose outcome is deterministic. A wire family checks messages against RFC rules such as hop limit 255 and no multicast solicitations. Each of the eight families must reach 90%.