Systematic Testing of Multicast Routing Protocols: Analysis of Forward and Backward Search Techniques

TL;DR

This paper introduces new systematic, automated testing algorithms for multicast routing protocols that reduce complexity and improve topology synthesis by employing forward and backward search techniques based on FSM models.

Contribution

It presents two novel algorithms leveraging domain knowledge and search strategies to automate and enhance the testing of multipoint protocols, addressing the state space explosion problem.

Findings

Reduced complexity from exponential to polynomial for multicast routing over LANs

Successfully applied algorithms to verify correctness of PIM protocol

Proposed extension to study end-to-end multipoint protocols

Abstract

In this paper, we present a new methodology for developing systematic and automatic test generation algorithms for multipoint protocols. These algorithms attempt to synthesize network topologies and sequences of events that stress the protocol's correctness or performance. This problem can be viewed as a domain-specific search problem that suffers from the state space explosion problem. One goal of this work is to circumvent the state space explosion problem utilizing knowledge of network and fault modeling, and multipoint protocols. The two approaches investigated in this study are based on forward and backward search techniques. We use an extended finite state machine (FSM) model of the protocol. The first algorithm uses forward search to perform reduced reachability analysis. Using domain-specific information for multicast routing over LANs, the algorithm complexity is reduced from exponential to polynomial in the number of routers. This approach, however, does not fully automate topology synthesis. The second algorithm, the fault-oriented test generation, uses backward search for topology synthesis and uses backtracking to generate event sequences instead of searching forward from initial states. Using these algorithms, we have conducted studies for correctness of the multicast routing protocol PIM. We propose to extend these algorithms to study end-to-end multipoint protocols using a virtual LAN that represents delays of the underlying multicast distribution tree.