Method and system for intelligently forwarding multicast packets

• US 20030079040A1
• Filed: 10/19/2001
• Published: 04/24/2003
• Est. Priority Date: 10/19/2001
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Foundry Networks Incorporated (Broadcom, Inc.)
• Inventors: Chen, Lee, Ferguson, Earl, Jain, Nitin, Zhu, Min
• Granted Patent: US 7,389,359 B2
• Time in Patent Office: Days
• US Class Current: 709/238
• CPC Class Codes: H04L 12/1886 with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains

Abstract

A routing system utilizes a layer 2 switch interconnecting several routers to intelligently forward multicast packets throughout an internet exchange carrying multicast content. The layer 2 switch performs protocol snooping to extract a lookup key that is based on network layer protocol information. The lookup key is uniquely formulated to support either shared or explicit source distribution trees. The lookup key is used to query a forwarding memory that returns an outgoing port index. The outgoing port index points to one or more outgoing ports that are eligible to receive the multicast packet. The outgoing ports are also connected to the neighboring device(s) that are designated to receive the multicast packet. The routing system also supports real time maintenance and updating of the forwarding memory based on the periodic exchange of control messages. The routing system is configured to support PIM routers operating in PIM SM or PIM SSM modes. However, the routing system can also support other multicast protocols and/or standards.

Claims

1. In an internet exchange carrying multicast content, a method for intelligently forwarding a content packet received at a layer 2 switch, the method comprising the steps of:

receiving the content packet at the layer 2 switch;

determining whether a multicast indicator is present in a destination address included in the content packet; and

if said multicast indicator is present, then

querying a forwarding memory based on a lookup key,

determining an outgoing port for the content packet based on the result of said querying of said forwarding memory, and

forwarding the content packet to said outgoing port for subsequent delivery to a destination device.

2. The method of claim 1, further comprising the step of:

deriving a destination MAC address from the content packet, wherein said destination MAC address serves as said lookup key to query said forwarding memory.

3. The method of claim 2, further comprising the step of:

querying a forwarding table within said forwarding memory based on said lookup key, wherein said forwarding table comprises at least one outgoing port index corresponding to one or more destination MAC addresses.

4. The method of claim 1, further comprising the step of:

extracting a source address, a destination address, a protocol type, and an incoming port from the content packet to derive an explicit source lookup key, wherein said explicit source lookup key serves as said lookup key to query said forwarding memory.

5. The method of claim 4, further comprising the step of:

querying a session table within said forwarding memory based on said lookup key, wherein said session table comprises one or more session entries, each session entry comprising a source address, a destination address, protocol type, an incoming port, and an outgoing port index.

6. The method of claim 1, further comprising the step of:

creating a new entry in said forwarding memory if the result of said querying of said forwarding memory returns no match for said lookup key, wherein said new entry includes a cross-reference to said outgoing port for subsequent queries.

7. The method of claim 6, further comprising the step of:

processing a neighbor list to determine said outgoing port from a destination address indicated in the content packet in response to the result.

8. The method of claim 1, further comprising the steps of:

returning an outgoing port index as the result of said querying of said forwarding memory; and

querying an outgoing port lookup table to determine said outgoing port.

9. The method of claim 8, further comprising the step of:

receiving a control packet at the layer 2 switch, wherein said control packet includes at least one of a join set and a prune set for a multicast group.

10. The method of claim 9, further comprising the step of:

modifying at least one of said forwarding memory and said outgoing port lookup table in response to said control packet.

11. A layer 2 switch for intelligently forwarding a content packet carrying multicast content, comprising:

means for determining whether a multicast indicator is present in a destination address included in the content packet;

means for querying a forwarding memory based on a lookup key;

means for determining an outgoing port for the content packet based on the result of said querying of said forwarding memory; and

means for forwarding the content packet to said outgoing port for subsequent delivery to a destination device.