Data link interface for packet-switched network

• US 5,781,532 A
• Filed: 08/02/1996
• Issued: 07/14/1998
• Est. Priority Date: 12/23/1993
• Status: Expired due to Term

• Current Assignee: Alcatel Canada Inc. (Nokia Corporation)
• Original Assignee: Newbridge Networks Corporation (Nokia Corporation)
• Inventors: Watt, James
• Primary Examiner(s): NGUYEN, CHAU T
• Application Number:
  US08/666,335
• Time in Patent Office: 711 Days
• Field of Search: 370/230-232, 370/235, 370/236, 370/229, 370/352, 370/252, 370/253, 370/429, 370/417, 370/418, 370/412-416, 370/401, 370/394, 370/468, 370/395, 395/200.02, 395/200.13
• US Class Current: 370/236
• CPC Class Codes: H04L 12/2854 Wide area networks, e.g. public data networks
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/12 Avoiding congestion; Recovering from congestion
• CPC Class Codes: H04L 47/16 in connection oriented networks, e.g. frame relay
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A router for sending and receiving data over a virtual connection in a packet-switched network, such as a frame relay network, includes a device for detecting congestion in received data packets, and a device for adjusting the transmission rate of packets into the network when congestion is detected.

Claims

1. A data link interface for sending and receiving data over a virtual connection on a common link in a packet-switched network, comprising means for detecting congestion in the network, means for enqueing packets for transmission over said virtual connection, means for adjusting the transmission rate in response to the detection of said congestion so as to reduce congestion in the network, means for sorting traffic by conversation between two endpoints and re-ordering packets from different conversations on said common link while maintaining the order of transmission for each conversation in order to achieve fair allocation of bandwidth among different conversations when the detected congestion exceeds a predetermined mild congestion threshold, and means for dropping packets when the detected congestion exceeds a predetermined severe congestion threshold.

2. A data link interface as claimed in claim 1, wherein said detecting means comprises means for detecting congestion notification bits in received data packets.

3. A data link interface as claimed in claim 1, wherein said adjusting means reduces the transmission rate to a predetermined committed information rate in the event of network congestion.

4. A data link interface as claimed in claim 1, wherein said network is a frame relay network.

5. A data link interface as claimed in claim 4, wherein said virtual connection is a permanent virtual connection.

6. A data link interface as claimed in claim 1, characterized in that it further comprises means for computing when a packet in each conversation would normally be transmitted on the basis of packet size assuming each conversation had a dedicated link, said sorting and re-ordering means arranging the order of transmission so that the packets with the earliest start of transmission time are sent first.

7. A router incorporating a frame relay data link interface as claimed in claim 1.

8. A method of reducing congestion over a virtual connection on a common link in a frame relay network, comprising the steps of detecting congestion in the network, adjusting the transmission rate in response to the detection of said congestion so as to reduce congestion in the network, sorting traffic by conversation between two endpoints and re-ordering packets from different conversations on said common link when the detected congestion exceeds a predetermined mild congestion threshold while maintaining the order of transmission for each conversation in order to achieve fair allocation of bandwidth among different conversations, and dropping packets when said detected congestion exceeds a predetermined severe congestion threshold.

9. A method as claimed in claim 8, wherein congestion notification bits are detected in received data packets.

10. A method as claimed in claim 8, wherein the transmission rate is reduced to a predetermined committed information rate in the event of network congestion.

11. A method as claimed in claim 8, characterized in that said virtual connection is a permanent virtual connection.

12. A method as claimed in claim 8, wherein the time when a packet in each conversation would be transmitted is computed on the basis of packet size assuming each conversation had a dedicated link, and the order of transmission is arranged so that the packets with the earliest start of transmission time are sent first.