Ethernet units adapted for loop configuration and method of operating same

• US 6,999,452 B1
• Filed: 02/23/2000
• Issued: 02/14/2006
• Est. Priority Date: 12/16/1999
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Moran, Paul J, Drummond-Murray, Justin A
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): HO, CHUONG T
• Application Number:
  US09/511,118
• Time in Patent Office: 2,183 Days
• Field of Search: 370/387, 370/388, 370/396, 370/400, 370/392, 370/403, 370/401, 370/402, 370/389, 370/360, 370/223, 370/224, 370/249, 370/358, 370/404, 370/405, 370/406, 370/452, 370/460, 370/386, 370/395.32, 370/428, 709/238
• US Class Current: 370/389
• CPC Class Codes: H04L 12/42 Loop networks
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/354 for supporting virtual local area networks [VLAN]

Abstract

A packet-switched network system comprises a multiplicity of multi-port network units each of which has first and second ports and other ports and transmission links coupling the first and second ports of said unit in a closed ring. The first and second ports and transmission links support duplex transmission of Ethernet data packets. Each unit transmits from said first and second ports packets including selected information enabling on reception of a packet at any of the units a determination of a number of hops from unit to unit around said ring said packet has made. Each unit has a forwarding database and in response to the said selected information controls the transmission of said packets in two directions around said ring, and each unit causes discard of packets which have according to said selected information circumnavigated the ring.

Claims

1. A packet-switched network system comprising

a multiplicity of multi-port network units each of which has first and second ports and other ports;

and

transmission links coupling the first and second ports of said units in a closed ring, said first and second ports and said transmission links supporting duplex transmission of data packets;

wherein each unit transmits from said first and second ports packets including selected information enabling on reception of a packet at any of the units a determination of a number of hops from unit to unit around said ring said packet has made, each unit has a forwarding database and in response to the said selected information controls the transmission of said packets in two directions around said ring, and each unit causes discard of packets which have according to said selected information circumnavigated the ring; and

wherein each unit includes means responsive to said selected information (i) to determine the number of hops from unit to unit around the ring a received packet has made;

(ii) when the number is less than half the total number of hops around the ring, to learn a source address of the packet as that one of the said first and second ports at which the packet was received;

(iii) when the number is greater than half the total number of hops around the ring, to learn a source address for the packet as that one of the first and second ports other than that at which the packet was received; and

(iv) when the number is equal to the total number of hops around the ring, to cause discard of the packet.

2. A network unit comprising a multiplicity of ports including first and second ports for connection of said unit in a closed ring with other network units, said first and second ports supporting duplex transmission of data packets, said unit being operative:

(a) to transmit from and receive at said first and second ports Ethernet packets including selected information enabling on reception of a packet at any of the units a determination of a number of hops from unit to unit around said ring said packet has made;

(b) in response to the said selected information to control the transmission of said packets in two directions around said ring; and

(c) to cause discard of packets which have according to said selected information circumnavigated the ring;

wherein each unit includes means responsive to said selected information;

(i) to determine the number of hops from unit to unit around the ring a received packet has made;

(ii) when said number of hops is less than half the total number of hops around the ring, to learn a source address of the packet as that one of the said first and second ports at which the packet was received;

(iii) when the said number of hops is greater than half the total number of hops around the ring, to learn a source address for the packet as that one of the first and second ports other than that at which the packet was received; and

(iv) when the said number of hops is equal to the total number of hops around the ring, to cause discard of the packet.

3. A method of operating a packet-switched network system comprising a multiplicity of multi-port network units each of which has first and second ports and other ports and transmission links coupling the first and second ports of the units in a closed ring, said first and second ports and said transmission links supporting duplex transmission of data packets, the method comprising:

transmitting from said first and second ports of each unit Ethernet packets including selected information enabling on reception of a packet at any of the units a determination of a number of hops from unit to unit around said ring said packet has made;

controlling in response to the said selected information the transmission of said packets in two directions around said ring; and

discarding packets which have according to said selected information circumnavigated the ring;

wherein said method includes;

(i) determining the number of hops from unit to unit around the ring a received packet has made;

(ii) when the number is less than half the total number of hops around the ring, learning the source address of the received packet as that one of the said first and second ports at which the packet was received;

(iii) when the number is greater than half the total number of hops around the ring, learning a source address for the received packet as that one of the first and second ports other than that at which the packet was received; and

(iv) when the number is equal to the total number of hops around the ring, causing discard of the received packet.