Abstract—The configuration and management of security policies
in enterprise networks becoming hard due to complex policy
constraints of the organizations and dynamic changes in the
network topologies. Typically, the organizational security policy
is defined as a collection of rules for allowing/denying service
accesses between various network zones. Implementation of the
policy is realized in a distributed fashion through appropriate
sets of access control rules (ACL) in the interface switches
(Layer-3 routers) of the network. The verification of the ACL
implementations with respect to the security policy is a major
technical challenge to the network administrators. This is due
to organizational complex security needs and presence of inconsistent
hidden service access paths in the network which may in
turn violate one or more policy rules implicitly. The problem
becomes more complex due to changes in network topologies.
In any point of time, the failure of the network interfaces(links)
may change the network topology as a result alternative routing
paths can be formed. Hence, the existing security implementation
(distribution of ACL rules) may not conform to the policy. In this
paper, a Fault Analysis module has been proposed over a formal
verification framework which as a whole can derive a correct
ACL implementation with respect to a given policy specification
and can ensure that the correct implementation is fault tolerant
to certain number of link failures. The basis of the fault analysis
module is representing the network topology and the existing
ACL implementation as a graph based network access model.
Index Terms—LAN, Network Security, Access Control List
(ACL), SAT based verification