Yasushi Wakahara

An acyclic expansion algorithm for fast protocol validation

For the development of communications software composed of many modules, protocol validation is considered essential to detect errors in the interactions among the modules. Protocol validation techniques previously proposed have required validation time that is too long for many actual protocols. The authors propose a novel fast protocol validation technique to overcome this drawback. The proposed technique is to construct the minimum acyclic form of state transitions in individual processes of the protocol, and to detect protocol errors such as system deadlocks and channel overflows fast. The authors also present a protocol validation system based on the technique to confirm its feasibility and show validation results for some actual protocols. As a result, the protocol validation system is expected to improve productivity in the development and maintenance of communications software. >

Component-based protocol synthesis

Protocol synthesis is a very important technology for efficiently designing correct protocol specifications. One powerful means of protocol synthesis is the completion of protocol specifications which, based on a partial specification of functionally incomplete protocol, automatically generates the insufficient part. In contrast to such protocol synthesis, this paper proposes a method for completing protocol specifications with two processes by modeling the protocol by a finite-state machine and combining fundamental components of correct protocol. Compared to conventional method, the protocol synthesis method proposed in this paper has the following merits: (1)protocols containing looping receive-transition sequences can be generated; and (2)redundant send-transition sequences can be eliminated. Because of these merits, it is possible to synthesize protocols used in actual communication systems, for example, the X.25 call setup/clearing protocol.

Distributed collection of message exchange sequences in each process for efficient recovery from protocol errors

In t h e f a u l t t o l e r a n c e design of t h e communication system, one of t h e important techniques is t h e p ro toco l e r r o r recovery which recovers t h e normal s ta te from t h e abnormal s ta te due t o t h e p ro toco l e r r o r s gene ra t ed i n t h e ope ra t ion of t h e communication software. The p ro toco l e r r o r recovery technique proposed up t o now has t h e fol lowing problems: (1) messages are l o s t i n t h e recovery process; and (2) a long recovery t i m e is required from t h e e r r o r gene ra t ion t o t h e normal s ta te .