Sughrue, Mion, Zinn, Macpeak & Seas
Routing system capable of effectively processing routing information
 In a routing system having a plurality of external input ports and a plurality of external output ports, a switch network having a plurality of internal input ports and a plurality of internal output ports, an input section between the external input ports and the internal input ports, an output section between the internal output ports and the external output ports, and a control section connected to the switch network and the input section, an input port number which may be assigned to each of the external input ports is arranged in a routing information field of a transmission path signal by an input port number setter included in the input section. The input port number is memorized in a discarded cell memory of the control section together with an internal output port number which is assigned to the internal output ports and which is derived from a routing table along with a header. On occurrence of a discarded cell, the cause of discard can be analyzed by the use of the input port number and the header. When a plurality of external input cells are multiplexed into a multiplexed input cell sequence, the input port number may be replaced by the internal output port number in the control section to effectively utilize the routing information field. 
NEC Corporation
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Hiroshi Takayuki Takatoshi
Yamashita Kobayashi Kurano