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Summary: Verifying Network Protocol Implementations by
Symbolic Refinement Checking
Rajeev Alur and BowYaw Wang
Department of Computer and Information Science
University of Pennsylvania
[alur,bywang] @ cis.upenn.edu
www.cis.upenn.edu/~[alur,bywang]
Abstract. We consider the problem of establishing consistency of code
implementing a network protocol with respect to the documentation as
a standard RFC. The problem is formulated as a refinement checking
between two models, the implementation extracted from code and the
specification extracted from RFC. After simplifications based on assume
guarantee reasoning, and automatic construction of witness modules to
deal with the hidden specification state, the refinement checking prob
lem reduces to checking transition invariants. The methodology is illus
trated on two casestudies involving popular network protocols, namely,
PPP (pointtopoint protocol for establishing connections remotely) and
DHCP (dynamichostconfigurationprotocol for configuration manage
ment in mobile networks). We also present a symbolic implementation
of a reduction scheme based on compressing internal transitions in a hi
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