Patent ID: 6965573
Filing Date: 2005-11-15
Classification: H04L

Abstract:
1. A network system, comprising: a terminal unit that sends an echo response with a predetermined counter value to the sender of a predetermined echo request; an access server that couples said terminal unit through a communication line and routes data and said echo request to be communicated between said terminal unit and said access server, decrements a count value of the echo request every time repeating the echo request, and, when the count value becomes zero, sends an echo response to the sender of the echo request; one or more routers that are connected to said access server and that routes data and said echo request to be communicated between said terminal unit and said routers, decrements a count value of the echo request every time repeating the echo request, and, when the count value becomes zero, sends an echo response to the sender of the echo request; and an application server that is connected to any one of said routers, said application server comprising, a first echo request sending means that sends a first echo request to said terminal unit, a first echo response receiving means that receives a first echo response in reply to the first echo request from said terminal unit, a first measuring means that measures a first round trip time as a data delay time between said terminal unit and said application server, said first round trip time being an elapsed time from send time of the first echo request until receive time of the first echo response, an estimating means that estimates the number of routers up to said access server from a counter value of the first echo response received by said first echo response receiving means, a second echo request sending means that sends a second echo request with a count value that is set to be the number of routers estimated by said estimating means to said terminal unit, a second echo response receiving means that receives a second echo response in reply to the second echo request, a second measuring means that measures a second round trip time as a data delay time between said access server and said application server, said second round trip time being an elapsed time from send time of the second echo request until receive time of the second echo response, a communication line delay calculating means that calculates a data delay time of said communication line from the first and second round trip times measured by said first and second measuring means, respectively, a communication line bandwidth storing means that stores a bandwidth of said communication line corresponding to the data delay time of said communication line, and a data sending means that sends data to said terminal unit according to the bandwidth of said communication line stored in said communication line bandwidth storing means corresponding to the data delay time calculated by said communication line delay calculating means.