Cross-layer failure restoration of IP multicast with applications to IPTV

Recent applications such as broadcast TV distribution over an IP network require that stringent QoS constraints, such as low latency and loss be met. Streaming content in IPTV is typically delivered to distribution points on an IP backbone using IP multicast, in particular Protocol Independent Multicast (PIM). Local restoration from link failures using MPLS or layer-2 Fast Reroute (FRR) is a proven technique to achieve rapid failure restoration. Link-based FRR creates a pseudo-wire or tunnel in parallel to the IP adjacencies; thus, single link failures are transparent to the Interior Gateway Protocol (IGP) such as OSPF. Although one may choose the back-up path’s IGP link weights appropriately to avoid traffic overlap during any single physical link failure, multiple failures may still cause packet loss because of (a) congestion resulting from overlap of an active FRR path with the multicast tree, (b) congestion resulting from overlap of two active FRR paths, or (c) a hit resulting from an OSPF reconvergence after the failure of a link in an active FRR path. We present a cross-layer restoration approach that combines both FRR-based restoration for single link failures and “hitless” (i.e., without loss) PIM tree reconfiguration algorithms to prevent traffic overlap when multiple failures occur. We demonstrate the efficacy of our schemes through simulations. The average recovery time on double failures can be reduced from more than 10s to only approximately 100 ms with our enhancements.