Packet forwarding apparatus

A packet forwarding apparatus for controlling packet forwarding in conjunction with at least one functional extension apparatus, the packet forwarding apparatus comprising:

• a plurality of network interfaces each composed of an ingress line interface and an egress line interface;
• a plurality of ingress packet processing units provided in association with the ingress line interfaces to convert ingress packets received from the ingress line interfaces to internal packets each having an internal header including an identifier of the corresponding ingress line interface and a next-hop identifier and send out the internal packets;
• a plurality of egress packet processing units provided in association with the egress line interfaces;
• and
• an internal packet forwarding unit for forwarding the output each of the internal packets Output from each of the ingress packet processing units to one of the egress packet processing units specified by the next-hop identifier included in the internal header thereof, wherein
• one of the network interfaces has been designated as an extension interface connected to the functional extension apparatus,
• each of the ingress packet processing units provided in association with the network interfaces other than the extension interface has a function of adding the internal header including the next-hop identifier indicating the extension interface to one of the ingress packets which matches a pre-specified header condition and a function of sending out the ingress packet having the internal header as one of the internal packets to the internal packet forwarding unit,
• one of the egress packet processing units which is provided in association with the extension interface adds an external network header including an address of the extension apparatus as a destination address to the internal packet received from the internal packet forwarding unit and sends out the internal packet having the external network header as an egress packet to a corresponding egress line interface, and
• one of the ingress packet processing units which is provided in association with the extension interface eliminates the external network header from a packet which is received from the corresponding ingress line interface and has been processed in the extension apparatus:
• and sends out the resultant packet as one of the internal packets to the internal packet forwarding unit.