Trust Models and Security Considerations in Multicast Listener Discovery Protocol version 2 (MLDv2)

Multicast listener discovery (MLD) protocols are employed by IPv6 routers and hosts for group management. Routers use MLD to discover the presence of multicast listeners -nodes that wish to receive multicast packets- on their directly attached links, and to discover which multicast addresses are of interest to those neighbouring nodes. Existing MLDv2 protocol specification discusses the effects of on-link forgery of MLD packets but does not provide any protection from on-link attacks. By taking advantage of or abusing MLD messages, bogus devices can cause incorrect multicast records and disruption to multicast or unicast packet delivery. In this paper we identify and analyse the various trust models for MLD protocols, their workings and their interaction with link-layer and multicast proxy devices. We also provide security and threat analysis for each model.