Message Based Redundancy Approach using Totem Protocol for Telecom Applications and Protocol Stacks

High availability in telecom system is achieved by having redundant setups of both hardware and software. Software level redundancy requires process context to be replicated across the redundant setup, so that other processes can take off from where the failed process left off. Several common ways of achieving the context replication is mentioned in various literatures and also presented in this paper mentioning their trade-offs. However, these approaches do not fare well when there are frequent context updates, which is typically the case of telecom and protocol stacks. This paper proposes an alternate approach for achieving context replication indirectly, specially suited for telecom stacks, by replicating the incoming and outgoing messages at a stack level across the redundant setup. As only the messages arriving at the stack are replicated, the overhead incurred by exchanging information whenever a context change takes place, is avoided resulting in superior performance.