Patent ID: 7693092

Claim:
A multicast tree monitoring method for searching for transmission routes of multicast frames by a network monitoring device in an IP network comprised of a transmission terminal which transmits multicast frames, a plurality of receiving terminals which receive said multicast frames, and a plurality of routers arranged on tree-shaped multicast frame transmission routes from said transmission terminal to said plurality of receiving terminals, said multicast tree monitoring method in an IP network comprising: (a) having said network monitoring device instruct said transmission terminal to transmit monitoring test packets differentiated from said normally transmitted multicast frames, (b) having said transmission terminal transmit said test packets toward said routers in accordance with said instruction, (c) having each of said routers receiving said transmitted test packets and passing them through generate pass status information of said test packets, and (d) having said network monitoring device judge transmission directions of said test packets on said IP network based on said pass status information collected from said routers and specify said tree-shaped transmission routes by the result of this judgment, wherein said monitoring test packets are selected from any one of (i) packets having a data length that is usually not adopted as said multicast frames, (ii) packets which have an unused source IP address or unused destination multicast IP address, and (iii) packets set with an effective time period TTL (Time To Live) of the packets of from 1 up to a predesignated N, and wherein a predetermined certain number of said test packets are continuously transmitted.