Wuxu Peng

Data flow analysis of communicating finite state machines

Let ( F’l, Pz, . . . . Pm) be a network of n finite state machines, communicating with each other asynchronously using typed messages over unbounded FIFO channels, In this paper we present a data flow approach to analyzing these communicating machines for nonprogress properties (deadlock and unspecified reception). We set up flow equations to compute the set of pending messages in the queues at any given state of such a network, The central technical contribution of this paper is an algorithm to compute approximations to solutions for the ensuing equations We then show how these approximate solutions can be used to check that interactions between the processes are free of nonprogress errors. We conclude with a number of example protocols that our algorithm certifies to be free of nonprog-ess errors. Included in the examples is a specification of X25 call establishment/clear protocol,

A practical spanning tree based MANET routing algorithm

We present a new and practical spanning tree based routing algorithm for mobile ad hoc networks (MANET). The algorithm, named LCMRMGCS, extends and significantly enhances the LCMRMG MANET routing algorithm previously proposed in W. Peng et al., (2003). Hosts in a LCMRMGCS MANET form non-overlapping trees. Our simulation results show that LCMRMGCS consistently outperforms LCMRMG in both maintenance cost and delivery ratio.

Distributed wavelength assignment protocols with priority for WDM all-optical networks

We propose a new concept for wavelength assignment in WDM all-optical networks-priority-based wavelength assignment. Our priority scheme is protocol-independent and can be easily integrated into any distributed wavelength assignment protocol. The proposed priority scheme has been integrated with the SIR (source initiated reservation) protocol. A new simulation software based on the well-known YACSIM simulation package was developed to show that the extended SIR protocol can improve the efficiency and throughput of WDM optical networks by five to ten percent. The proposed priority scheme should also be applicable to wide-area wavelength routed networks.

Dynamic key management for secure routing in LCMRMG MANET

We present a secure key management scheme for the locality caching multi-root multi-generation (LCMRMG) MANET routing algorithm (W. Peng et al., 2003). The proposed scheme is fully distributed, flexible in secure share distribution, and scalable well to large MANET. The scheme takes advantage of the multi-root nature of LCMRMG and successfully integrates public key, certification and threshold technologies. Our simulation has proven that the proposed scheme is indeed secure, robust, efficient, and scalable

A NEW TYPE OF PUSHDOWN AUTOMATA ON INFINITE TREES

In this paper we consider pushdown automata on infinite trees with empty stack as the accepting condition (ω-EPDTA). We provide the following regarding ω-EPDTA: (a) its relationship to other Pushdown automata on infinite trees, (b) a Kleene-Closure theorem and (c) a single exponential time algorithm for checking emptiness. We demonstrate the usefulness of ω-EPDTA through two example applications: defining the temporal uniform inevitability property and specifying a context-free process with unbounded state space, both of which cannot be defined and/or specified by the classical finite state automata on infinite trees. We also discuss the relevance of the results presented here to model-checking.

Dynamic key management for secure routing in MANET

A secure key management scheme for the locality caching multi-root multi-generation (LCMRMG) MANET routing algorithm is proposed. The scheme takes advantage of the multi-root nature of LCMRMG and successfully integrates public key, certification and threshold technologies. The scheme is hierarchical and fully distributed. The key management operations are flexible in secure share distribution and scalable well to large MANET. Extensive simulations have shown that the scheme is secure, robust, efficient, and scalable. Copyright

Locality caching multiroot multigeneration routing algorithm in mobile ad hoc networks

A locality caching multiroot multigeneration (LCMRMG) routing algorithm for mobile ad hoc networks (MANET). The LCMRMG algorithm extends and significantly enhances a previously proposed single-root MANET routing algorithm. Hosts in a LCMRMG MANET cache the locality of network traffic routing through them. Based on the cached locality statistics, a host can calculate the estimated reduction of network traffic if it becomes a new root router and can elect to do so if the reduction exceeds a predefined threshold value.

A modular methodology to verify communication protocols

State explosion has been a major problem for verifying communication protocols and distributed algorithms. In this paper we analyze the sources that cause the state explosion problem and propose a modular approach to verifying communication protocols based on networks of communicating finite state machines (CFSMs). Our proposed method is innovative and its time and space complexity is independent of the number of processes in a system. The new methodology can significantly reduce the time and space needed to verify a number of interesting logical properties, as evidenced by our implementations.

Reachability and reverse reachability analysis of CFSMs

Reachability analysis and the recently proposed reverse reachability analysis are two important verification techniques for communicating finite state machines (CFSM). The issue of the relative efficiency of reachability analysis and reverse reachability analysis is still unsettled. In this paper, we first propose a new theory of reachability and reverse reachability analysis. Based on the new theory, we discuss and analyse the suitability of these two reachability analysis methods. We then present a reachability evaluator which, given any network of CFSMs, will try to estimate the sizes of the reachable and reverse reachable state spaces by taking snapshots of the reachability and reverse reachability spaces. The core of the evaluator is the notion of random state generation with seed states, which extends the idea of random state exploration proposed in [1]. Results from example applications have shown that the evaluator provides an excellent guidance in choosing the better of the two methods.

On reachability and reverse reachability analysis of communicating finite state machines

Reachability analysis and reverse reachability analysis are two important verification techniques for communicating finite state machines (CFSMs). The issue of the relative efficiency of reachability analysis and reverse reachability analysis is still unsettled. We first propose a new theory of reachability and reverse reachability analysis. Based on the new theory we discuss and analyze the suitability of these two reachability analysis methods. We then present a reachability evaluator, which, given any network of CFSMs, will try to estimate the sizes of the reachable and reverse reachable state spaces by taking snapshots of the reachability and reverse reachability spaces. The core of the evaluator is the notion of random state generation with seed states, which extends the idea of random state exploration proposed by West (1986). Results from example applications have shown that the evaluator provides guidance in choosing the better of the two methods.