BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the problem of the prior art;
FIG. 2 shows the summary of the present invention;
FIG. 3 shows an example of the network configuration adopting the present invention;
FIG. 4 shows an example of the functional configuration of a contents sever;
FIG. 5 shows an example of the functional configuration of the cache server;
FIG. 6 shows a contents delivery network for showing an example of the operation of the present invention;
FIG. 7 shows an example of the operation of switching the connection destination of a two-order lower cache server to another cache server, due to the load increase of the highest-order cache server;
FIG. 8 shows an example of information included in a connection destination switch request message;
FIG. 9 shows an example of information included in a connection destination switch response message;
FIG. 10 shows an example of information included in a switch destination notice message;
FIG. 11 shows an example of information included in a switch destination response message;
FIG. 12 shows an example of information included in a connection request message;
FIG. 13 shows an example of information included in a connection response message;
FIG. 14 shows an example of the operation of switching the connection destination of a two-layer lower cache server to another two-layer lower cache server, due to the load increase of the highest-order cache server;
FIG. 15 shows an example of information included in a connection destination retrieval request message;
FIG. 16 shows an example of information included in a connection destination retrieval response message;
FIG. 17 shows another example of the operation of switching the connection destination of a two-layer lower cache server to another two-layer lower cache server, due to the load increase of the highest-order cache server;
FIG. 18 shows an example of the operation of switching the connection destination of a two-layer lower cache server to a contents sever, due to the load increase of the highest-order cache server;
FIG. 19 shows an example of the operation in the case where the connection is switched, due to the decrease of overlapped cache contents between a parent cache server and a child cache server;
FIG. 20 shows an example of the operation in the case where a request for switching a connection to a cache server in which overlapped contents to cache is large is received from a contents sever;
FIG. 21 shows an example of the connection destination switching operation in the case where the amount of contents requested by a child cache server relatively increases and the child cache server is directly connected to a contents sever;
FIG. 22 shows an example of the connection destination switching operation in the case where the amount of contents requested by a child cache server relatively increases and the connection of the child cache server is switched to another cache server;
FIG. 23 shows an example of the operation in the case where a failure occurs in a parent cache server and the connection destination of the cache server is modified;
FIG. 24 shows an example of the operation of switching the connection destination of the highest-order cache server to another cache server;
FIG. 25 shows an example of the operation of modifying cache update under the lead of a cache server to cache update under the lead of a contents sever;
FIG. 26 shows an example of the operation of modifying cache update under the lead of a contents sever to cache update under the lead of a cache server;
FIG. 27 shows an example of the operation of a cache server at the time of receiving a connection destination retrieval request;
FIG. 28 shows an example of the operation of a cache server at the time of receiving a connection switch request;
FIG. 29 shows an example of the operation of a cache server at the time of receiving a connection switch response;
FIG. 30 shows an example of the operation of the parent cache server at the time of receiving a switch destination cache server notice;
FIG. 31 shows an example of the operation of a child cache server at the time of receiving a switch destination cache server notice;
FIG. 32 shows an example of the operation of a cache server at the time of receiving a switch destination cache server notice response;
FIG. 33 shows an example of the operation of a cache server at the time of receiving a connect request;
FIG. 34 shows an example of the operation of a cache server at the time of receiving a connect response;
FIG. 35 shows an example of the operation of a cache server of transmitting a child cache server connection switch request to a higher-order server at the time of heavy load;
FIG. 36 shows an example of the operation of a cache server of transmitting a connection switch request to a child cache server at the time of heavy load;
FIG. 37 shows an example of the operation of a contents sever in the case where a connection destination is switched due to the load status of the contents server;
FIG. 38 shows an example of the operation of a contents sever at the time of receiving a connection destination retrieval request;
FIG. 39 shows an example of the operation of a contents sever at the time of receiving a connection destination switch request;
FIG. 40 shows an example of the operation of a contents sever at the time of receiving a connect request;
FIG. 41 shows an example of the operation of a contents sever at the time of receiving a connection destination retrieval response;
FIG. 42 shows an example of the operation of a contents sever at the time of receiving a connection destination switch response;
FIG. 43 shows the hardware configurations of a contents sever and cache server of the present invention; and
FIG. 44 shows how to load the connection destination server switching control program of the present invention onto a computer.