Packet switch, scheduling device, drop control circuit, multicast control circuit and QoS control device

A scheduling device comprising:

• queues provided in a number equal to a number of QoS classes that can be designated, for registering variable-length packets according to a QoS class;
• means for adding a first value to a corresponding token when a variable-length packet has reached a front of one of the queues;
• means for subtracting a second value from each of tokens of active QoS classes each time when a unit time has passed;
• and
• means for starting the reading of a variable-length packet of which corresponding token is a minimum or 0 among the active QoS classes when a packet can be sent to the output line.

A scheduling device comprising:

• queues provided in a number equal to a number of QoS classes that can be designated, for registering variable-length packets according to a QoS class;
• a counter for counting for each QoS class a number of fixed-length packets composing variable-length packets;
• a priority control section for determining and posting a QoS class of a packet to be output with priority based on a constant packet length, from out of QoS classes that have count values other than 0;
• and
• a variable-length packet managing section for counting the posts from the priority control section for each QoS class, reading out a variable-length packet of the QoS class of which count value has reached a value corresponding to the packet length of the variable-length packet at the front of a corresponding queue, and sending the read variable-length packet to the output line.

A scheduling device comprising:

• queues provided in a number equal to a number of QoS classes that can be designated, for registering variable-length packets according to a QoS class;
• a first counter for counting for each QoS class a number of fixed-length packets composing variable-length packets of the bandwidth guaranteed class and variable-length packets of the minimum bandwidth guaranteed class that have been input within a designated bandwidth;
• a second counter for counting for each QoS class a number of fixed-length packets composing variable-length packets of the best effort class and variable-length packets of the minimum bandwidth guaranteed class that have been input in excess of the designated bandwidth;
• a priority control section for determining and posting a QoS class of a packet to be output with priority based on a constant packet length, from out of QoS classes that have count values other than 0 for the first counter and QoS classes that have count values other than 0 for the second counter;
• and
• a variable-length packet managing section for counting the posts from the priority control section for each QoS class, reading out a variable-length packet of the QoS class of which count value has reached a value corresponding to the packet length of the variable-length packet at a front of a corresponding queue, and sending the read variable-length packet to the output line.

A drop control circuit comprising:

• a calculation circuit for multiplying a difference between a volume of packets stored in a buffer and a threshold value thereof to a packet length of a variable-length packet existing at a front of the buffer, and outputting a result of the multiplication;
• a register;
• an adder circuit for adding a calculation result of the calculation circuit to the register;
• and
• a control circuit for dropping at once a variable-length packet that exists at the front of the buffer when a register value has exceeded a predetermined value, and subtracting from the register a value obtained by multiplying the packet length by the predetermined value.

A drop control circuit comprising:

• a calculation circuit for outputting a difference between a volume of packets stored in a buffer and a threshold value thereof;
• a register;
• an adder circuit for adding a calculation result of the calculation circuit to the register;
• and
• a control circuit for dropping a fixed-length packet that exists at a front of the buffer when a register value has exceeded a predetermined value, and subtracting the predetermined value from the register.

A multicast control circuit comprising:

• a multicast queue for registering an address of a variable-length packet to be multicast-controlled that is stored in a buffer;
• a plurality of output buffer queues provided corresponding to a plurality of output lines;
• an address management table for managing the address of a variable-length packet stored in the buffer;
• and
• control means for storing as many records as there are output destinations into the address management table, each record including the address of the variable-length packet, and for registering addresses of the records in the output buffer queues corresponding to the output destinations, when the address of the variable-length packet to be multicast-controlled has been registered in the multicast queue.

A packet switch for converting an IP packet that has a QoS class into fixed-length packets, for switching the IP packet on the basis of the fixed-length packets, the packet switch comprising:

• means for mapping priority classes of IP packets into simple priority classes of a smaller number than the number of QoS classes that are allocated to the IP packets;
• means for controlling the reading of the fixed-length packets to the switch based on the simple priority classes;
• and
• means for controlling the reading of the fixed-length packets after the switching based on the QoS classes allocated to the IP packets.

A QoS control device comprising:

• a first selector for selecting one QoS class for reading a packet from at least one QoS class that belongs to a high-priority group;
• a second selector for selecting one QoS class for reading a packet from at least one QoS class that belongs to a low-priority group;
• and
• a third selector for selecting one of the high-priority group and the low-priority group, thereby selecting a packet of a QoS class selected by the first or second selector.

A packet switch having a plurality of input lines for receiving packets and a plurality of output lines for sending packets, comprising:

• a plurality of input buffer sections provided corresponding to the plurality of input lines, each input buffer section having queues provided for each of a plurality of output lines and for each of designated QoS classes, and for registering packets from corresponding input lines to corresponding queues according to the output line and a QoS class;
• a scheduler for controlling the reading the packets registered in the queues of the input buffer sections so that two or more packets of the same output line are not read out within a unit time;
• a switch for routing each packet read out to a designated one output line out of the plurality of output lines;
• and
• a plurality of output buffer sections provided corresponding to the plurality of output lines, for controlling the sending of the switched packet to the designated one output line according to a priority based on the QoS class.

A packet switch for converting an IP packet that has a QoS class into fixed-length packets, for switching the IP packet on the basis of the fixed-length packets, the packet switch comprising:

• means for mapping priority classes of IP packets into simple priority classes of a smaller number than the number of QoS classes that are allocated to the IP packets;
• means for controlling the switching of the fixed-length packets based on the simple priority classes;
• and
• means for controlling the sending of the IP packets after switching based on the QoS classes allocated to the IP packets.

A method for switching packets in a packet switch having a plurality of input lines for receiving packets and a plurality of output lines for sending packets, comprising:

• storing packets from the plurality of input lines to a plurality of input buffer sections provided corresponding to the plurality of input lines, each input buffer section having queues provided for each of a plurality of output lines and for each of designated QoS classes, and where packets from corresponding input lines are stored to corresponding queues according to the output line and a QoS class;
• reading the packets stored in the queues of the input buffer sections so that two or more packets of the same output line are not read out within a unit time;
• switching each packet read out to a designated one output line out of the plurality of output lines;
• and
• sending the switched packet to the designated one output line according to a priority based on the QoS class.

A method of scheduling reading of packets belonging to a QoS class to be output from a packet switch, comprising:

• storing packets according to the QoS class of the packet in queues provided in a number equal to a number of different QoS classes that can be designated;
• adding a first value to a corresponding token when a packet has reached a front of one of the queues;
• subtracting a second value from each of tokens of active QoS classes each time when a unit time has passed;
• and
• starting the reading of a packet of which corresponding token is a minimum or 0 among the active QoS classes when a packet can be sent to the output line.

A method of selecting a packet to be switched in a packet switch comprising the steps of:

• mapping a plurality of different QoS classes designated for packets to be switched into a high-priority group and a low-priority group;
• selecting a QoS class of the high-priority group for reading a packet belonging to the selected QoS class of the high-priority group;
• selecting a QoS class of the low-priority group for reading a packet belonging to the selected QoS class of the low-priority group;
• and
• selecting one of the high-priority group and the low-priority group, thereby selecting for reading one of the selected packet belonging the high-priority group and the low-priority group.