Deniz, Dervish Zihni; (1991) Dynamic channel management in packet mode usage of circuit switched ISDN. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis investigates the problem of Dynamic Channel Management in an access node to a multiple channel transmission facility using packet mode communications over circuit switched connections. The Integrated Services Digital Network provides a multichannel facility to users at its user-network interface. It is at this interface that the Dynamic Channel Management is applied. Bandwidth Allocation and Dynamic Bandwidth Management are two important aspects of Channel Management. The work covers four major sections; an extensive definition of the problem area and its relationship to associated problems; design of a Dynamic Channel Management Architecture for Connectionless mode data communications over circuit switched ISDN; study of problems in Superchannel formation in ISDN and extension of this model to cover different channel types; and the performance of several heuristic Channel Management Policies using a simulation model of the architecture. The original contributions of this work are five-fold. First, Channel Management is identified as a cmcial issue in the ISDN user-network interface for the support of user and network performance requirements. This problem is more acute in the case of Connectionless mode of operations over user channels. Second, it is shown that effective Dynamic Channel Management can be achieved using a flexible architecture. A design where a common software interface for both data paths and signalling control is developed and is shown to be suitable for dynamic control. Third, the ISDN D-channel protocol facilities for Superchannel formation and dynamic variation of charmel bandwidth are shown to be inadequate. Modifications and additions to the existing D-channel protocols specified in the CCITT Recommendation Q.931 are proposed. A novel protocol for superchannel identification operating over the user-user signalling facility in ISDN is designed. Fourth, 4 heuristic Channel Management Policies based on multilevel hysteresis threshold control of channel capacity with switching delays, are proposed and their performances compared using simulation models. It is shown that multi-level hysteresis control policies result in critical behaviour for values of arrival rates corresponding to the minimum channel capacity allowed. Fifth, a new taxonomy for the classification of service rate control doctrines based on threshold principle is introduced. Different service rate control doctrines are compared and two modified multi-level hysteresis threshold control policies are proposed. It is found that bi-level control policies result in smooth response curves in comparison with the multi-level counterparts. It is also shown by way of an example that the multi-level policies are advantageous over bilevel counterparts under certain conditions. Practical implications of both types of policies are also discussed.

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