ABSTRACTS OF ARTICLES OF THE JOURNAL "INFORMATION TECHNOLOGIES".
No. 12. Vol. 24. 2018

DOI: 10.17587/it.24.772-781

V. A. Bogatyrev, D. Sc., Professor, e-mail: vladimir.bogatyrev@gmail.com, S. A. Parshutina, Postgraduate, e-mail: svetlana.parshutina@gmail.com, St. Petersburg National Research University of Information Technologies, Mechanics and Optics

The Analysis of How the Redundancy Degree of Multipath Transmissions Affects the Probability of their Timely Service

The possibility of using redundant processing of delay-sensitive requests to increase the probability of timely faultless service and reduce delays in multipath data transmission systems is investigated. Simulation is used to evaluate the effectiveness of redundant multipath transmissions: the process of sending multiple copies of packets along different paths in a given network, in order to deliver them to one destination node or to one of several service nodes which are ready to execute incoming requests. The models are developed based on the discrete-event approach in AnyLogic 7 Professional simulation environment.
The degree of redundancy defines the number of copies of packages which are distributed among different routes in the network and depends on the sensitivity of these packets to time delays.
In distributed computer systems, the redundant multipath data transmission and the redundant multipath distribution of requests are considered the ways of increasing the efficiency of communication between computational processes which exchange messages that are critical to service delays over the network.
The redundant data transmission means that data packets are cloned and copies of those packets travel along several paths to one destination node. Data are regarded to be transmitted successfully if at least one copy of each packet has been delivered to that node in time, i.e. within a given period of time. The redundant distribution of requests over the network implies that copies of requests are forwarded along several routes to one or more destination nodes, which have been selected out of all possible ones in some way. A request is regarded to be distributed successfully if at least one copy of it has been delivered to all selected nodes within the specified time and those nodes have been ready for serving incoming requests. The effectiveness of redundant multipath transmissions — when the time of delivery of packets is limited — is determined by the probability of timely faultless service.
The existence of the scope of efficiency for the redundant multipath data transmissions and the redundant multipath distribution of requests, with considering their sensitivity to time delays, is shown.
It is found that there exists the optimal degree of redundancy that ensures the maximization of the probability of timely and faultless distribution of the multiplied requests over a given network when those requests are critical to time delays and/ or can be transmitted only once.
It was also discovered that the optimal redundancy degree of multipath transmissions depends on the intensity of the flow of requests and their sensitivity to time delays.
Keywords: redundancy, multipath transmission, distribution of requests, sensitivity to time delays

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