Patent ID: 6259705
Filing Date: 2001-07-10
Classification: H04L

Abstract:
A network load balancing device for use in a system in which data is transferred from a client to a plurality of servers, each capable of performing data processing, over a network, said network load balancing device comprising:a conversion information storage unit to store conversion information representing a correspondence relationship of the client to one of the servers;a distributive relay unit to transfer data sent by the client to one or more of the servers on the basis of the conversion information storage unit;a distribution ratio adjusting unit to adjust the correspondence relationship in the conversion information stored in the conversion information storage unit; anda load measuring unit to measure a load on one of the servers and to notify the distribution ratio adjusting unit of load conditions of one of the servers to thereby allow the distribution ratio adjusting unit to adjust the correspondence relationship in the conversion information stored in the conversion information storage unit;wherein the conversion information storage unit includes a table in which the correspondence relationship of the client to the servers is established and a unit to maintain the correspondence relationship of the client to one of the servers throughout transmission of a sequence of data, the distribution ratio adjusting unit having a unit, when the measurement of the load on each server shows an abnormal value, to judge whether one of the servers is in a stopped state, a unit to compare a connection average time and the number of connections for each of the servers with a connection average time reference value and a number-of connections reference value which are a minimum connection average time and a maximum number of connections for one of the servers, respectively, and judging that one of the servers is over loaded for which the connection average time is sufficiently larger than a corresponding reference value and the number of connections is sufficiently smaller than the corresponding reference value, a management unit to manage a service distribution ratio to one of the servers as numbers allocated to one of the servers, the management unit including a stopped state management unit, in the presence of the servers considered to be in the stopped state, to distribute the allocated number of the servers to the servers which are not in the stopped state at the ratio of the allocated numbers of the servers and an over load management unit decreasing the allocated number of the servers considered to be over loaded and to increase the allocated numbers of the servers which are not over loaded and the over load management unit including a unit decreasing the incremental or decremental value of the allocated numbers of the servers with each adjustment cycle to thereby converge a distribution ratio for said servers, and the load measuring unit includes a unit to periodically measure the connection average time and the number of connections per unit time for each of the servers on the basis of data relayed to it and to notify the distribution ratio adjusting unit of the statuses of the servers.