Packet communication system with QoS control function

1. A packet communication device for transmitting a packet, said packet having header information including address information, a port information, and a DS (Differentiated Services) value, comprising:

a plurality of input lines;

a plurality of output lines;

a switching unit connected to said input lines and said output lines, said switching unit outputting said packet from an input line of said plurality of input lines to an output line of said plurality of output lines; and

a control unit for switching a mode to apply to the packet among a first mode and a second mode based on the header information,

said first mode being a mode that decides priority of the packet by the DS value,

said second mode being a mode that decides priority of the packet by at least one of the address information and the port information, and decides to write the DS value, by at least one of the address information and the port information.

2. The packet communication device according to claim 1 , wherein

said control unit comprises a table indicating which mode to apply to each of the input lines of the first mode and the second mode, and

said control unit decides the mode to be applied to the packet according to the table.

3. The packet communication device according to claim 1 , wherein the packet is an IP (Internet Protocol) packet and the address information is a source IP address.

4. The packet communication device according to claim 1 , wherein the packet is an IP (Internet Protocol) packet and the application information is a TCP (Transmission Control Protocol) port number.

5. The packet communication device according to claim 1 , wherein the first mode or the second mode is set in each of the input lines.

6. A QoS (Quality of Service) control method for a packet communication device, an inputted packet having header information including address information, port information, and DS (Differentiated Services) value comprising:

a mode selecting step for selecting one of a first mode and a second mode;

wherein said first mode comprises a step of deciding priority of the inputted packet by DS value;

said second mode comprises a step of deciding priority of the packet by at least one of the address information and the port information and a step of deciding to write the DS value, by at least one of the address information and the port information.

7. The QoS (Quality of Service) control method according to claim 6 , wherein said first mode comprises a first step for making a decision about a coincidence between header information of the inputted packet and a flow condition and a second step for executing QoS control based on a data corresponding to the flow condition.

8. The QoS (Quality of Service) control method according to claim 6 , wherein said mode selecting step includes the step of making a selection for each packet based on the port number to which said packet is related.

9. The QoS (Quality of Service) control method according to claim 6 , wherein the packet is an IP (Internet Protocol) packet and the address information is a source IP address.

10. The QoS (Quality of Service) control method according to claim 6 , wherein the packet is an IP (Internet Protocol) packet and the application information is a TCP (Transmission Control Protocol) port number.

11. The QoS (Quality of Service) control method according to claim 6 , wherein

the packet communication device comprises a plurality of input lines, and

the first mode or the second mode is selected for each of the plurality of input lines.