Communication control unit

A communication control unit comprising:

• a memory device storing a path table corresponding to a path tree used to retrieve a place to which received packet data is transferred, wherein a node constituting said path tree is represented by a split address containing a least significant bit of a valid address of a real address out of each of said split addresses obtained by setting off said real address of said node by each specified bit starting from its high order portion and by a split mask length showing a number of bits of said valid address portion of said real address;
• a path retrieving circuit composed of a retrieval data managing circuit, a next node selecting circuit and a path renewing circuit, wherein said retrieval data managing circuit is operated to produce a split retrieving address composed of two or more stages obtained by setting off said retrieving address showing a destination of received packet data by each said specified bit and, at a same time, to generate a bit string for selection composed of the bit string obtained by displacing the bit string of said split retrieving address by one bit toward a low order portion on said retrieving address, wherein said next node selecting circuit is operated to decide a next node to be retrieved based on the bit having a value being equivalent to a value of a length of high order split mask contained in said bit strings for selection and wherein said path renewing circuit is operated to compare a valid address portion being equivalent to a number of bits represented by the length of said high order split mask contained in split addresses showing said node decided by said next node selecting circuit with the bit string being equivalent to the number of bits represented by the length of said high order split mask contained in split retrieving addresses outputted from said retrieval data managing circuit and if comparison results conform to each other, to hold path information corresponding to said node and to output path information being held at a time of termination of said retrieving as a place to which said received packet data is to be transferred.