Packet congestion control method and packet switching equipment

A packet switching system operable to inform transmission sources of an occurrence of packet congestion to make said transmission sources reduce the transmission rate of packets, comprising:

• a plurality of pairs of lines, each pair consisting of one input line and one output line;
• a plurality of line interfaces respectively disposed for each of said pairs of input and output lines;
• switch means for operating to switch packets between said line interfaces;
• means for detecting a packet congestion state in association with each output line in said switch means;
• and
• means for adding congestion information to a packet to be outputted through said switch means to an output line for which a congestion is detected by said detecting means;
• each line interface including means operative when a packet having congestion information is received for producing a congestion notice packet to be delivered to a transmission source of the packet;
• said congestion notice packet being delivered to said transmission source via said switch means and one of said output lines associated with said transmission source, whereby the number of input packets flowing into the congested output line is reduced after said transmission source has received said congestion notice packet.

A packet switching system operable to inform transmission sources of an occurrence of packet congestion to make said transmission sources reduce the transmission rate of packets, comprising:

• a plurality of pairs of lines, each pair consisting of one input line and one output line;
• a plurality of line interfaces each provided for a respective one of said pairs of input and output lines;
• switch means for operating to switch packets between said line interfaces;
• and
• means for detecting packet congestion occurring in association with each of said output lines in said switch means;
• each of said line interfaces including means responsive to a control signal from said congestion detecting means for returning to the output line thereof a congestion notice packet created by adding a congestion indicator to an input packet from the input line thereof.

A packet congestion control method in a packet switching system including switch means accommodating a plurality of pairs of input and output lines respectively connected to a communication equipment or to another packet switching system such that packets inputted from either one of said input lines are temporarily stored in a buffer memory so as to thereafter output the packet to one of said output lines associated with a destination communication equipment of the packet, means for monitoring a congestion state of packets in the switch means for each of said output lines and means for generating congestion control packets, comprising:

• a step of storing in said buffer memory a packet inputted from any one of said input lines in association with an output line onto which the packet is to be outputted;
• a step of monitoring by said monitoring means, for each of said output lines, the number of packets existing in the buffer memory to be outputted to each output line to generate a state signal indicating whether or not there occurs packet congestion;
• a step of reading ut a packet to be outputted to one of said output lines from the buffer memory in an order of the output lines so as to transmit the read out packet to said one output line;
• a step of producing, when the state signal indicates an occurrence of congestion or cease of a congestion on either one of the output lines, a congestion control packet including a congestion state indictor by said generating means in response to the reception of the packet to be outputted to the output line to return the congestion control packet to an output line paired with the input line of the packet;
• and
• a step of forcing the communication equipment having received the congestion control packet to change a transmission rate of subsequent packets depending on a content of the congestion state indicator included in the congestion control packet, whereby the number of new input packets to be sent to the congested output line is reduced for a while by said communication equipment until said communication equipment is informed of the cease of the congestion by another congestion control packet issued by said generation means.