EFFICIENT NETWORK MULTICAST SWITCHING APPARATUS AND METHODS

• US 20020186694A1
• Filed: 10/07/1998
• Published: 12/12/2002
• Est. Priority Date: 10/07/1998
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: EDSALL, THOMAS J., MAHAJAN, UMESH, KLOTH, RAYMOND, MELLACHERUVU, RAMANA
• Granted Patent: US 6,785,274 B2
• Time in Patent Office: Days
• US Class Current: 370/390
• CPC Class Codes: H04L 12/4641 Virtual LANs, VLANs, e.g. virtual private networks [VPN] LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272
• CPC Class Codes: H04L 12/467 Arrangements for supporting untagged frames, e.g. port-based VLANs

Abstract

Efficient switched network multicasting techniques are provided. Incoming multicast packets are processed by a central forwarding engine (CFE) in a network switch to generate forwarding indices used to make forwarding decisions for the packets based upon whether the packets are special multicast control packets or data packets. Forwarding of the special multicast control packets is determined by the switch'"'"'s network management processor (NMP), while data packets are forwarded based upon conventional bridge forwarding techniques.

Claims

1. A network multicasting method using at least one switch, said method comprising:

receiving at said switch a first multicast control message for removing an endstation from a multicast group specified in said message;

generating at said switch a second multicast control message in response to receipt of said first message by said switch, said second message being for querying as to endstation subscription status in said multicast group;

transmitting from a port of said switch that is associated with said endstation said second message; and

if said switch fails to receive via said port, within a predetermined time period, a third multicast control message indicating endstation subscription to said multicast group, preventing transmission via said port of a further multicast message associated with said multicast group.

2. A method according to claim 1, wherein said method further comprises, if the port via which the multicast message is prevented from being transmitted is the last port of said switch via which transmission of a multicast data message was permitted and is also not associated with a router, transmitting via at least one router-associated port of said s switch said first message.

3. A method according to claim 1, further comprising:

receiving at said switch a first request to subscribe a respective endstation to said multicast group; and

only transmitting, during a predetermined time period, a single proxy subscription request specifying said multicast group even if other requests to subscribe to said group are received by said switch.

4. A network multicasting method using at least one switch having a plurality of ports, said method comprising:

receiving at said switch at least one message;

determining at said switch whether said at least one message is of a predetermined class of multicast control messages, based upon network and data link layer information contained in said at least one message; and

determining forwarding of said at least one message from said switch based upon whether said at least one message is determined at said switch to be of said class of control messages.

5. A method according to claim 4, wherein the step of determining whether said at least one message is of said class of control messages comprises:

examining a header of said at least one message to determine, based upon a message type specified in a network layer header, whether said at least one message is an IGMP protocol message;

determining whether a data link layer destination address matches one of a plurality of predetermined data link layer addresses; and

if said at least one message is determined to be an IGMP protocol message and said data link layer destination address is determined not to match one of said predetermined addresses, determining that said at least one message is to be forwarded as one of said class of control messages.

6. A method according to claim 5, further comprising:

if said at least one message is determined to be an IGMP protocol message and said data link layer destination address is determined to match one of said predetermined addresses, determining that said at least one message is not to be forwarded as one of said class of control messages.

7. A method according to claim 4, wherein said data link layer information includes a media access control (MAC) group destination address.

8. A method according to claim 4, wherein said network layer information includes Internet Protocol (IP) message type.

9. A network multicasting method for use with at least one switch, said method comprising:

initializing said switch to process multicast messages in accordance with a first mode of operation of said switch associated with a first multicast protocol;

receiving at said switch at least one multicast message that is in accordance with a second multicast protocol different from said first protocol;

in response to receipt at said switch of said at least one multicast message, processing other multicast messages received by said switch in accordance with a second mode of operation of said switch that is different from said first mode of operation; and

if after starting to process said other multicast messages according to said second mode of operation a predetermined time period elapses wherein said switch does not receive an additional multicast message that is in accordance with said second protocol, resuming processing of received multicast messages by said switch in accordance with said first mode of operation.

10. A switch, comprising:

a central forwarding engine (CFE) for making a forwarding decision for at least one message received by said switch, said decision being one of permitting said decision to be made by a network management processor of said switch and forwarding said message from at least one port of said switch selected based upon information in a bridge forwarding table of said switch, said CFE making said forwarding decision based upon whether said at least one message is an Internet Group Management Protocol (IGMP) message and comparison of a media access control (MAC) group destination address in said at least one message with one of a plurality of predetermined MAC addresses.

11. A switch according to claim 10, wherein said predetermined addresses are within a range of MAC addresses between 01-00-5E-00-00-01 and 01-00-5E-00-00-FF, excluding MAC address 01-00-5E-00-00-02.