A mechanized proof of loop freedom of the (untimed) AODV routing protocol

TL;DR

This paper presents a formal mechanized proof of the loop freedom property of the AODV routing protocol using Isabelle/HOL, enabling automated verification and analysis of protocol improvements.

Contribution

It introduces a novel compositional approach for mechanizing network invariants and applies it to verify AODV's loop freedom in a theorem prover.

Findings

Mechanized proof confirms loop freedom of AODV

Automated re-verification of protocol improvements

Identification of invalid proof steps in modifications

Abstract

The Ad hoc On-demand Distance Vector (AODV) routing protocol allows the nodes in a Mobile Ad hoc Network (MANET) or a Wireless Mesh Network (WMN) to know where to forward data packets. Such a protocol is 'loop free' if it never leads to routing decisions that forward packets in circles. This paper describes the mechanization of an existing pen-and-paper proof of loop freedom of AODV in the interactive theorem prover Isabelle/HOL. The mechanization relies on a novel compositional approach for lifting invariants to networks of nodes. We exploit the mechanization to analyse several improvements of AODV and show that Isabelle/HOL can re-establish most proof obligations automatically and identify exactly the steps that are no longer valid.