Tunneling on demand: A lightweight approach for IP fast rerouting against multi-link failures

Multi-link failures in the Internet may incur heavy packet loss and degrade the network performance. Existing approaches have been proposed to address this issue by enabling routing protections. However, the effectiveness and efficiency issues of these approaches are not well addressed. In particular, it has not been answered that whether label-free routing can provide full protection against arbitrary multi-link failures in any networks. We propose a model for interface-specific-routing (ISR) which can be seen as a general label-free routing. We present that there exist some networks in which no ISR can be constructed to protect the routing against any k-link failures (k ≥ 2). To improve the protection effectiveness with little overhead in such cases, we propose a tunneling on demand (TOD) approach in this paper. With our approach, most failures can be covered by ISR, and tunneling is activated only when failures cannot be detoured around by ISR. We develop algorithms to compute ISR properly so as to minimize the number of activated tunnels, and compute the protection tunnels if necessary. We prove that TOD can protect routing against any single-link failures and dual-link failures. We evaluate TOD by simulations with real world topologies. The results show that TOD can achieve a protection ratio higher than 98% with small tunneling overhead for multi-link failures, better than existing tunnel-free approach whose protection ratio is 85% to 95%.