Patent ID: 7106751

Claim:
A linking apparatus which is connected to first and second networks of different line protocols for communication lines, and performs a packet relay between said first and second networks, comprising: a first port connected to said first network for receiving a first packet from said first network, said first packet including two kinds of packets such that one kind of packet includes a first header of a line protocol of a higher layer than said line protocols of said first and second networks, a second header of the protocol of said first network, packet identification information and user data, the other kind of packet includes said second header, said packet identification information and said user data, but does not include said first header, the latter packet that includes no first header is a packet of a plurality of packets divided from one packet, said packet identification information being information having a same value for the packets divided from a same packet so as to provide information for determining whether packets are divided from a same packet or not; a second port connected to said second network for sending a second packet to said second network; a receiving section connected to said first port, said receiving section including a memory section storing at least one first header with being associated with packet identification information, determining whether said first packet includes the first header, and when the first header is included, storing in said memory section said packet identification information and first header of said first packet with said packet identification information and first header being associated with each other and outputting said first packet, and when the first header is not included, reading out from said memory section a first header, which is stored with being associated with a packet identification information having a same value as for the packet identification information included in said first packet, among the first headers stored in said memory section to output said first packet to which said read-out first header is added; and a sending section connected to said second port and said receiving section, said sending section receiving said first packet output from said receiving section, converting said first packet to said second packet, and outputting said second packet to said second port, said sending section adding a third header of the line protocol of said second network to said second packet based on the first header added to said first packet.