High-speed packet-switched communications system with end-to-end flow control and retransmission

Claim 2

A packet switched communications system comprising a plurality of terminals and a plurality of switching nodes for serving said terminals and a plurality of transmission links interconnecting said terminals and said switching nodes, each of said terminals being capable of returning an acknowledgment to a source terminal when a packet is correctly received therefrom, transmitting a series of packets without receiving said acknowledgment and retransmitting to a destination terminal a packet which has not been correctly received, each of said switching nodes comprising: means for detecting the degree of congestion of traffic in a buffer which receives packets from an adjacent one of said switching nodes or terminals and transmitting a traffic control signal instructing a cessation of transmission of packets when the detected degree of congestion exceeds a predetermined level; and means responsive to said traffic control signal for halting the transmission of a packet which is to be transmitted to said adjacent switching node or terminal.

Claim 3

A packet-switched communications system as claimed in claim 1, wherein each of said switching nodes comprises means responsive to said traffic control signal for allowing a packet to be discarded out of a second buffer from which the packet is to be transmitted to said adjacent switching node or terminal when said second buffer is overfilled.

Claim 4

A packet switched communications system as or 2 claimed in claim 1/ wherein each of said terminals is capable of effecting a determination of whether or not a packet to be exchanged between said source and destination terminals is required to be retransmitted and effecting an ommission of the retransmission of a packet which has not been correctly received when it is determined that the packet is not required to be retransmitted.

Claim 5

A packet switched communications system comprising a plurality of terminals and a plurality of switching nodes for serving said terminals and a plurality of transmission links interconnecting said terminals and said switching nodes, said packet switched communications system being of a virtual circuit type in which a logical channel is permanently established through said transmission links between source and destination terminals in response to a control packet of a multipacket message to allow message packets of the multipacket message to follow the established channel, each of said terminals being capable of retransmitting a packet to a destination terminal which is not correctly received by the destination terminal, wherein each of said switching nodes comprises: means for detecting the degree of congestion of traffic in a buffer which receives packets from an adjacent one of said switching nodes or terminals and transmitting a traffic control signal indicating the cessation of transmission of packets when the detected degree of congestion exceeds a predetermined value; means responsive to said traffic control signal for halting the transmission of a packet which is to be transmitted to said adjacent switching node or terminal; means for detecting when said traffic control signal is present for a predetermined time interval and generating a timeout signal; means responsive to said timeout signal for preventing the establishment of a logical channel to said adjacent switching node; means for determining the logical channel established between said adjacent switching node and said destination terminal and identifying the source terminal in accordance with the determined logical channel and preventing the transmission of packets from said source terminal; and means for reestablishing a'logical channel through an alternate transmission link to said destination terminal.

Claim 6

A packet switched communications system comprising a plurality of terminals and a plurality of switching nodes for serving said terminals and a plurality of transmission links interconnecting said terminals and said switching nodes, said packet switched communications system being of a virtual circuit type in which a logical channel is permanently established through said transmission links between source and destination terminals in response to a control packet of a multipacket message to allow message packets of the multipacket message to follow the established channel, each of said terminals being capable of retransmitting a packet to a destination terminal which is not correctly received by the destination terminal, wherein each of said switching nodes comprises: means for detecting the degree of congestion of traffic in a buffer which receives packets from an adjacent one of said switching nodes or terminals and transmitting a traffic control signal indicating the cessation of transmission of packets when the detected degree of congestion exceeds a predetermined value; means responsive to said traffic control signal for halting the transmission of a packet which is to be transmitted to said adjacent switching node or terminal; means for detecting when said traffic control signal is present for a predetermined time interval and generating a timeout signal; means responsive to said timeout signal for preventing the establishment of a logical channel to said adjacent switching node; means for determining the logical channel established between said adjacent switching node and said destination terminal and identifying the source terminal in accordance with the determined logical channel and preventing the transmission of packets from said source terminal; and means for reestablishing a'logical channel through an alternate transmission link to said destination terminal.

Claim 7

A packet switching system for a packet switched communications network, comprising a plurality of line controllers and a central processor which are connected by a switching network, wherein said switching system handles a multipacket message comprising a control packet and one or more message packets, each of said packets having a logical channel number, comprising: control means for determining a logical channel in response to said control packet and determining the relationship between the route number of an outgoing transmission link through which said logical channel passes and the channel number of said logical channel and sending a routing signal representing the determined relationship through said network to each of said line controllers; and each of said line controllers comprising: a memory; means for writing said routing signal into said memory; means for extracting the logical channel number from said message packet and accessing said memory as a function of the extracted logical channel number to detect the route number of an outgoing transmission link through which said message packet is to be transmitted and the logical channel number of said packet at said outgoing transmission link and processing the message packet by updating the logical channel number of said message packet with the detected logical channel number and by appending the detected route number to said message packet; and means for transferring the processed message packet through said network to one of said line controllers associated with said outgoing transmission link and receiving the message packet transferred through said network.

Claim 8

A packet switching system for a packet switched communications network, comprising a plurality of line controllers and a central processor which are connected by a switching network, wherein said switching system handles a multipacket message comprising a control packet and one or more message packets, each of said packets having a logical channel number, comprising: control means for determining a logical channel in response to said control packet and determining the relationship between the route number of an outgoing transmission link through which said logical channel passes and the channel number of said logical channel and sending a routing signal representing the determined relationship through said network to each of said line controllers; and each of said line controllers comprising: a memory; means for writing said routing signal into said memory; means for extracting the logical channel number from said message packet and accessing said memory as a function of the extracted logical channel number to detect the route number of an outgoing transmission link through which said message packet is to be transmitted and the logical channel number of said packet at said outgoing transmission link and processing the message packet by updating the logical channel number of said message packet with the detected logical channel number and by appending the detected route number to said message packet; and means for transferring the processed message packet through said network to one of said line controllers associated with said outgoing transmission link and receiving the message packet transferred through said network.

Claim 9

A packet switching system as claimed in claim 5, wherein said switching network comprises a control data transfer subnetwork for transferring said routing signal between said control means and said line controllers and a packet transfer subnetwork for transferring the updated message packets between said line controllers.

Claim 10

A packet switching system as claimed in claim 6, wherein said central processor includes said control means.

Claim 11

A packet switching system comprising a plurality of line controllers, a central processor and a switching network interconnecting said line controllers and said central processor, said line controllers being associated with incoming transmission links and outgoing transmission links respectively, wherein: each of said line controllers comprises: means for detecting an overflow traffic in each one of said outgoing transmission links; means for notifying the other line controllers of the detected overflow traffic; an overflow control table for storing data representing said overflow traffic; means for addressing said overflow control table in response to reception of a packet on the associated incoming transmission link; means for tranferring said packet through said switching network to one of said line controllers associated with the outgoing transmission link which is not detected as having an overflow traffic; and means for forcibly discarding said packet when the last-mentioned outgoing transmission link is detected as having an overflow traffic.

Claim 12

A packet switching system comprising a plurality of line controllers, a central processor and a switching network interconnecting said line controllers and said central processor, said line controllers being associated with incoming transmission links and outgoing transmission links respectively, wherein: each of said line controllers comprises: means for detecting an overflow traffic in each one of said outgoing transmission links; means for notifying the other line controllers of the detected overflow traffic; an overflow control table for storing data representing said overflow traffic; means for addressing said overflow control table in response to reception of a packet on the associated incoming transmission link; means for tranferring said packet through said switching network to one of said line controllers associated with the outgoing transmission link which is not detected as having an overflow traffic; and means for forcibly discarding said packet when the last-mentioned outgoing transmission link is detected as having an overflow traffic.

Claim 13

A packet switched communications system having a plurality of switching nodes for serving a plurality of terminals through transmission links, wherein: each of said terminals transmitting a packet of data link layer control protocol including a network layer control protocol to one of said switching nodes; and each of said switching nodes comprising means responsive to the network control protocol of said packet for routing said packet to one of said transmisssion links defined by said network layer control protocol of said packet.

Claim 14

A packet switched communications system having a plurality of switching nodes for serving a plurality of terminals through transmission links, wherein: each of said terminals transmitting a packet of data link layer control protocol including a network layer control protocol to one of said switching nodes; and each of said switching nodes comprising means responsive to the network control protocol of said packet for routing said packet to one of said transmisssion links defined by said network layer control protocol of said packet.

Claim 15

A packet switched communications system as claimed in claim 9, wherein said routing means comprises: a plurality of line controllers associated respectively to said transmission links, each of said line controllers including means for appending a physical address of said packet at said defined transmission link to said packet, updating the network layer control protocol of said packet with a logical address of said packet at said defined transmission link and sending said updated packet to one of said line controllers corresponding to said defined transmission link; and a switching network for interconnecting said line controllers.

Claim 16

A packet switched communications system as or 10 claimed in claim 9/ wherein each of said switching nodes comprises: means for detecting an overflow of said packets sent in one direction of transmission on a first one of said transmission links and sending an overflow indicating signal in an opposite direction on a second one of said transmission links; and means responsive to said overflow indicating signal for holding said packets in a buffer.

Claim 17

A packet switched communications system as claimed in claim 11, wherein each of said switching nodes further comprises means for relaying said overflow indicating signal to one of said terminals from which said packets have been transmitted.

Claim 18

A packet switched communications system as claimed in anyone of claims 9 to 12, wherein said packet contains a logical address of the packet, and wherein said routing means comprises: a first line controller to which a first one of said transmission links is terminated; a second line controller to which a second one of said transmission links is terminated; a switching network for interconnecting said first and second line controllers; said first line controller including a first memory for storing an address defining said second transmission link and means for updating said packet received from said first transmission link according to said address and routing said updated packet to said second line controller according to said address stored in said first memory; said second line controller including a second memory for storing an address defining said first transmission link and means responsive to said updated packet for routing said packet to said second transmission link; and a central processor responsive to the network layer control protocol of said packet received at said first transmission link for rewriting said first and second memories.

Claim 19

A packet switched communications system as claimed in claim 13, wherein said second line controller includes means for detecting an overflow traffic in said second transmission link and transferring the address stored in said second memory to said first line controller, wherein said first line controller includes means responsive to the transferred address for preventing the packets destined to said second transmission link from being routed to said second line controller.

Claim 20

A packet switching system for serving a plurality of terminals through transmission links, each of said terminals transmitting a packet of data link layer control protocol including a network layer control protocol through a transmission link to said switching system comprising: means responsive to the network control protocol of said packet for routing said packet to one of said transmisssion links defined by said network layer control protocol of said packet, said routing means comprising: a plurality of line controllers associated respectively to said transmission links, each of said line controllers including means for appending an address of said said defined transmission link to said packet and sending said packet with said address to one of said line controllers corresponding to said defined transmission link; and a switching network for interconnecting said line controllers.

Claim 21

A packet switching system for serving a plurality of terminals through transmission links, each of said terminals transmitting a packet of data link layer control protocol including a network layer control protocol through a transmission link to said switching system comprising: means responsive to the network control protocol of said packet for routing said packet to one of said transmisssion links defined by said network layer control protocol of said packet, said routing means comprising: a plurality of line controllers associated respectively to said transmission links, each of said line controllers including means for appending an address of said said defined transmission link to said packet and sending said packet with said address to one of said line controllers corresponding to said defined transmission link; and a switching network for interconnecting said line controllers.

Claim 22

A packet switching system as claimed in claim 15, further comprising: means for detecting an overflow of said packets sent in one direction of transmission on a first one of said transmission links and sending an overflow indicating signal in an opposite direction on a second one of said transmission links; and means responsive to said overflow indicating signal for holding said packets in a buffer.

Claim 23

or 16 17. A packet switching system as claimed in claim 15/, further comprising means for relaying said overflow indicating signal to one of said terminals from which said packets have been transmitted.

Claim 24

18 . A packet switching system as claimed in anyone of claims 15 to 17, wherein said packet contains a logical address of the packet, and wherein first and second ones of said line controllers are associated respectively with first and second ones of said transmission links, wherein: said first line controller includes a first memory for storing an address defining said second transmission link and means for updating said packet received from said first transmission link according to said address and routing said updated packet to said second line controller according to said address stored in said first memory; said second line controller include a second memory for storing an address defining said first transmission link and means responsive to said updated packet for routing said packet to said second transmission link; and a central processor responsive to the network layer control protocol of said packet received at said first transmission link for rewriting said first and second memories.

Claim 25

A packet switching system as claimed in claim 18, wherein said second line controller includes means for detecting an overflow traffic in said second transmission link and transferring the address stored in said second memory to said first line controller, wherein said first line controller includes means responsive to the transferred address for preventing the packets destined to said second transmission link being routed to said second line controller.