Packet Forwarding In A Network

A step to which a method of providing routing information on a packet codes routing information from a sauce node to one or more destination nodes in compact expression of a set member ship, It has a step which puts the compact expression of a set in a header of a packet which should transmit to one or more [above] destination nodes from the sauce node. The compact expression can be obtained by generating expression of d sets of an identifier, generating a candidate of d compact expressions of a set member ship from d expressions of the identifier, and choosing one of candidates of the compact expression of a set member ship. The selection may be performed by basing whether probability that a candidate of which compact expression will return false positivity is the lowest.