Apparatus, design method, and recording medium

A design method in a system for content delivery, wherein content is delivered using cache servers distributed among a plurality of nodes in a network, comprising:

• receiving a request from a user terminal connected to the network for a content delivery item, and in response to the received request, the method includes
• receiving, as input parameter values, at least a parameter related to the network and an estimated amount of demand for delivery requests generated by users for content, a group of cache servers which keep possession of the content delivery item at a given time, and a group of candidate paths from the cache servers to the user terminal;
• designing, based on the received input parameter values, a selection probability that a cache server is selected as a delivery server for content delivery or a selection probability that a delivery route is selected, using model predictive control, wherein the model predictive control uses an objective function for reducing the number of excessive delivery requests, each of which is a delivery request generated by a user for a content item and then rejected, and said delivery route is a combination of the delivery server and a delivery path on which the content is delivered by the delivery server;
• outputting the designed selection probability of the cache server or the selection probability of the delivery route, wherein the selection probability minimizes a frequency with which the request for the user terminal is rejected because of exceeding a capacity of a cache server;
• and
• causing delivery of the requested content delivery item to the user terminal based on the outputted selection probability of the cache server or the selection probability of the delivery route.

A non-transitory computer-readable storage medium storing instructions, wherein content is delivered using cache servers distributed among a plurality of nodes in a network, the instructions, when executed by processing circuitry, causing the processing circuitry to perform a method comprising:

• receiving a request from a user terminal connected to the network for a content delivery item, and in response to the received request, the method includes
• receive, as input parameter values, at least a parameter related to the network and an estimated amount of demand for delivery requests generated by users for content, a group of cache servers which keep possession of the content delivery item at a given time, and a group of candidate paths from the cache servers to the user terminal;
• design, based on the input parameter values, a selection probability that a cache server is selected as a delivery server for content delivery or a selection probability that a delivery route is selected, using model predictive control, wherein the model predictive control uses an objective function for reducing the number of excessive delivery requests, each of which is a delivery request generated by a user for a content item and then rejected, and said delivery route is a combination of the delivery server and a delivery path on which the content is delivered by the delivery server;
• outputting the designed selection probability of the cache server or the selection probability of the delivery route, wherein the selection probability minimizes a frequency with which the request for the user terminal is rejected because of exceeding a capacity of a cache server, and
• causing delivery of the requested content delivery item to the user terminal based on the outputted selection probability of the cache server or the selection probability of the delivery route.