Spanning tree support in a high performance network device

• US 6,081,512 A
• Filed: 06/30/1997
• Issued: 06/27/2000
• Est. Priority Date: 06/30/1997
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Muller, Shimon, Hendel, Ariel
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): Qureshi, Afsar M.
• Application Number:
  US08/885,001
• Time in Patent Office: 1,093 Days
• Field of Search: 370/254, 370/255, 370/256, 370/400, 370/351, 370/389, 370/401, 370/236, 370/216, 370/217, 370/248, 370/390, 370/432, 714/2, 714/3, 714/4
• US Class Current: 370/256
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/245 Link aggregation, e.g. trunking
• CPC Class Codes: H04L 45/48 Routing tree calculation
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A method and apparatus for providing spanning tree support are provided. According to one aspect of the present invention, a network device includes two or more ports that are part of a trunk. One of the two or more ports are selected for participation in a loop-free topology discovery protocol. Then, the loop-free topology discovery protocol is executed for the selected port. If the loop-free topology discovery protocol indicates the selected port is to be blocked, then all of the ports of the trunk are blocked. According to another aspect of the present invention, a set of states for association with each port of a network device is provided. The set of states includes a "blocked" state in which both learning and forwarding are inhibited, a "learn only" state in which learning is permitted and forwarding remains inhibited, and a "non-blocked" state in which both learning and forwarding are permitted. Responsive to an indication from a loop-free topology discovery protocol that a port of the network device is to be unblocked, a state associated with the first port is set to the "learn only" state for a predetermined amount of time. Then, after the predetermined amount of time, the state associated with the first port is set to the "non-blocked" state.

Claims

1. A method of configuring a blocked port to receive configuration messages, the method comprising the steps of:

providing an input interface address register in each of a plurality of ports for filtering packets destined to addresses that do not match an address contained therein;

executing a loop-free topology discovery protocol for a first port of the plurality of ports; and

if the loop-free topology discovery protocol indicates the first port is to be blocked, then writing a multicast address associated with configuration messages into the input interface address register of the first port, whereby the first port will subsequently accept configuration messages while filtering all other packets.

2. The method of claim 1, wherein the configuration messages comprise bridge protocol data units (BPDUs).

3. The method of claim 1, wherein the input interface address register comprises a media access control (MAC) address register.

4. The method of claim 1, wherein the loop-free topology discovery protocol comprises the Spanning Tree Protocol.

5. A method of forwarding configuration messages onto a network over a blocked port, the method comprising the steps of:

a central processing unit (CPU) generating a configuration message and a corresponding set of control information, the corresponding set of control information including a directed mode flag indicating that packet header matching is to be avoided and indicating that the configuration message is to be transferred to a specified output port;

the CPU transferring the configuration message and the corresponding set of control information to a network device for transmission,

based upon the directed mode flag, a CPU interface forwarding the configuration message to the specified output port, the specified output port having previously been blocked by a loop-free topology discovery protocol; and

the specified output port transmitting the configuration message onto the network.

6. The method of claim 5, wherein the configuration messages comprise bridge protocol data units (BPDUs).

7. The method of claim 5, wherein the input interface address register comprises a media access control (MAC) address register.

8. The method of claim 5, wherein the loop-free topology discovery protocol comprises the Spanning Tree Protocol.

9. A method comprising the steps of:

selecting one port of a plurality of ports associated with a trunk to participate in a loop-free topology discovery protocol;

the loop-free topology discovery protocol employing configuration messages;

executing the loop-free topology discovery protocol for the selected port; and

if the loop-free topology discovery protocol indicates the selected port is to be blocked, then causing each of the plurality of port associated with the trunk to subsequently accept configuration messages while filtering all other packet traffic other than configuration messages by writing a multicast address associated with configuration messages into input interface address registers associated with the plurality of ports, each of the input interface address registers configured to filter packets specifying a destination address other than that contained in the input interface address register.

10. The method of claim 9, wherein the configuration messages comprise bridge protocol data units (BPDUs).

11. The method of claim 9, wherein the input interface address register comprises a media access control (MAC) address register.

12. The method of claim 9, wherein the loop-free topology discovery protocol comprises the Spanning Tree Protocol.

13. A network device comprising:

a plurality ports capable of being logically combined into one or more trunks;

an input interface address register associated with each of the plurality of ports; and

a processor communicatively coupled to the input interface address registers, the processor configured to

select one port per trunk to participate in a loop-free topology discovery protocol, the loop-free topology discovery protocol employing configuration messages,

execute the loop-free topology discovery protocol for the selected port, and

if the loop-free topology discovery protocol indicates the selected port is to be blocked, then configuring each port associated with the trunk to subsequently accept configuration messages while filtering all other packet traffic other than configuration messages by writing a multicast address associated with configuration messages into input interface address registers associated with each port, the input interface address registers each configured to filter packets specifying a destination address other than that contained therein.

14. The method of claim 13, wherein the configuration messages comprise bridge protocol data units (BPDUs).

15. The method of claim 13, wherein the input interface address register comprises a media access control (MAC) address register.

16. The method of claim 13, wherein the loop-free topology discovery protocol comprises the Spanning Tree Protocol.