Communication route presumption technique

A method for presuming a communication route in a first network connecting with second and third networks, comprising:

• identifying a test source address among unused addresses in said second network and a test destination address among unused addresses in said third network, wherein a packet is presumed to be transmitted from said second network to said third network through a plurality of communication routes in said first network;
• causing an output edge router that is an edge router connected to said third network and provided at a boundary of said first network to change settings of an Address Resolution Protocol table of said output edge router so as not to transfer a packet addressed to said test destination address to said third network;
• first obtaining, as a first number of input packets, a value of an input packet counter from each of routers to be monitored on each of said plurality of communication routes;
• generating a test packet including, as a source routing, an address of an input edge router that is an edge router connected to said second network and including, as source and destination addresses, said test source address and said test destination address, and transmitting the generated test packet a predetermined number of times;
• second obtaining, as a second number of input packets, a value of said input packet counter from each of said routers to be monitored;
• calculating a difference between said first number of input packets and said second number of input packets for each of said plurality of communication routes;
• and
• identifying a communication route through which said test packets passed, based on the calculated differences.

A route monitoring apparatus for presuming a communication route in a first network connecting with second and third networks, comprising:

• a storage device;
• an address determination unit to identify a test source address among unused addresses in said second network and a test destination address among unused addresses in said third network, wherein a packet is presumed to be transmitted from said second network to said third network through a plurality of communication routes in said first network;
• a table controller to cause an output edge router that is an edge router connected to said third network and provided at a boundary of said first network to change settings of an Address Resolution Protocol table of said output edge router so as not to transfer a packet addressed to said test destination address to said third network;
• an obtaining unit to obtain, as a first number of input packets, a value of an input packet counter from each of routers to be monitored on each of said plurality of communication routes, and store said first number of input packets into said storage device;
• and
• a test packet transmitter to generate a test packet including, as a source routing, an address of an input edge router that is an edge router connected to said second network and including, as source and destination addresses, said test source address and said test destination address, and to transmit the generated test packet a predetermined number of times, and
• wherein, after said test packet transmitter transmitted the generated test packet, said obtaining unit obtains, as a second number of input packets, a value of said input packet counter from each of said routers to be monitored, and store said second number of input packets into said storage device, and
• said route monitoring apparatus further comprises:
• a communication route identifying unit to calculate a difference between said first number of input packets and said second number of input packets, which are stored in said storage device, for each of said plurality of communication routes, and to identify a communication route through which said test packets passed, based on the calculated differences.