Network device with multicast forwarding data

• US 6,539,022 B1
• Filed: 04/26/1999
• Issued: 03/25/2003
• Est. Priority Date: 04/25/1995
• Status: Expired due to Term

• Current Assignee: Enterasys Networks Incorporated (Extreme Networks, Inc.)
• Original Assignee: Enterasys Networks Incorporated (Extreme Networks, Inc.)
• Inventors: Virgile, Kenneth
• Primary Examiner(s): Yao, Kwang Bin
• Application Number:
  US09/299,970
• Time in Patent Office: 1,429 Days
• Field of Search: 370/254, 370/235, 370/389, 370/390, 370/392, 370/395.2, 370/395.3, 370/395.31, 370/401, 370/428, 370/429, 370/432, 370/463, 709/249, 709/250
• US Class Current: 370/401
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 12/1886 with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains

Abstract

A system and method are disclosed for routing multicast packets in a subnetwork so as to conserve bandwidth in at least some of the network segments or collision domains of the subnetwork. In particular, multicast packets are only retransmitted in the network segments that are on a path to a host that is a member of the multicast group of hosts to which the multicast packet is destined.

Claims

1. A network bridge for reducing multicast communications in a network, the network bridge including at least two I/O interfaces to each receive and transmit data packets and also including multicast forwarding data, the device comprising:

means for determining, by examining data in a first portion of a first packet received at the network bridge, whether the first packet is a multicast control packet destined for a device other than the network bridge;

means for identifying a multicast group from the first packet when the first packet is a multicast control packet destined for a device other than the network bridge; and

means for updating the multicast forwarding data according to the identified multicast group and the data in the first portion of the first packet.

2. The network bridge as recited in claim 1, further comprising:

means for identifying the I/O interface on which the first packet arrived,

wherein the updating means include means for cross-referencing the identified I/O interface to the identified multicast group in the multicast forwarding data.

3. The network bridge as recited in claim 1, further comprising:

means for identifying a source of the first data packet,

wherein the updating means include means for cross-referencing the identified source to the identified multicast group in the multicast forwarding data.

4. The network bridge as recited in claim 1, further comprising:

means for identifying the I/O interface on which the first packet arrived; and

means for identifying a source of the packet,

wherein the updating means include means for cross-referencing the identified multicast group with the identified source and the identified I/O interface in the multicast forwarding data.

5. The network bridge as recited in claim 1, further comprising:

means for determining, when the first packet is not a control packet, whether the first packet is a message packet having a multicast group as a destination address; and

means for identifying, when the first packet is determined to be a multicast message packet, the destination multicast group;

the destination multicast group identifying means further comprising;

means for retrieving first data from the multicast forwarding data according to the identified destination multicast group, the retrieved first data including at least one cross-referenced I/O interface; and

means for sending the multicast message packet out each at least one cross-referenced I/O interface in the first data other than the identified I/O interface.

6. A method of reducing multicast communications in a network, the network including a network device having multicast communications forwarding data and at least two I/O interfaces to each receive and transmit data packets, the method comprising:

determining an I/O interface on which a first packet arrived;

determining, by examining data in a first portion of the first packet, whether the first packet is a multicast control packet addressed to a device other than the network device;

when the first packet is determined to be a multicast control packet addressed to a device other than the network device;

determining a multicast group from the first portion of the multicast control packet; and

updating the multicast forwarding data as a function of data in the first portion of the multicast control packet.

7. The method as recited in claim 6, wherein the step of updating the multicast forwarding data comprises:

cross-referencing the identified multicast group with the determined I/O interface.

8. The method as recited in claim 6, wherein the step of updating the multicast forwarding data comprises:

updating the multicast forwarding data by removing any cross-reference between the identified multicast group and the identified I/O interface.

9. The method as recited in claim 8, further including a step of:

updating the multicast forwarding data for the identified destination multicast group by deleting any cross-referenced I/O interface that is not connected to a device that is a member of the identified multicast group.

10. The method as recited in claim 6, wherein:

when the first packet is not a multicast control packet;

determining whether the first packet is a message packet having a multicast group as a destination; and

when the first packet is determined to be a multicast message packet;

identifying a destination multicast group from the multicast message packet;

retrieving first data from the multicast forwarding data according to the identified destination multicast group, the retrieved first data including at least one cross-referenced I/O interface; and

sending the multicast message packet out each at least one cross-referenced I/O interface in the retrieved first data other than the identified I/O interface.

11. The method as recited in claim 10, further comprising a step of:

when there is no data associated with the identified destination multicast group in the multicast forwarding data, transmitting the multicast message packet out all I/O interfaces other than the identified I/O interface.

12. The method as recited in claim 6, wherein the control packet is defined according to an Internet Group Management Protocol (IGMP) standard.

13. The method as recited in claim 12, wherein the multicast control packet is one of:

a host membership query packet;

a host membership report packet;

a join host group packet; and

a leave host group packet.

14. A method of reducing multicast communications in a network, the network including a network bridge, the network bridge having at least two I/O interfaces to each receive and transmit data packets and the network bridge including multicast forwarding data, the method including:

(a) determining, by examining data in a first portion of a first packet received at the network bridge, whether the first packet is a multicast control packet destined for a device other than the network bridge; and

when the first packet has been determined to be a multicast control packet destined for a device other than the network bridge;

(b) identifying a multicast group from the data in the first portion of the first packet; and

(c) updating the multicast forwarding data according to the data in the first portion of the first packet.

15. The method as recited in claim 14, further comprising:

identifying the one I/O interface on which the first packet arrived;

wherein, step (c) includes a step of updating the multicast forwarding data so as to cross-reference the identified I/O interface with the identified multicast group.

16. The method as recited in claim 14, further comprising:

identifying a source of the first packet;

wherein, step (c) includes a step of updating the multicast forwarding table so as to cross-reference the identified source to the identified multicast group.

17. The method as recited in claim 14, further comprising:

identifying the one I/O interface on which the first packet arrived; and

identifying a source of the first packet;

wherein, step (c) includes a step of updating the multicast forwarding data so as to cross-reference the identified multicast group with the identified I/O interface and the identified source.

18. The method as recited in claim 14, wherein:

when the first packet is not a multicast control packet;

determining whether the first packet is a message packet having a multicast group as a destination; and

when the first packet is determined to be a multicast message packet;

identifying a destination multicast group from the multicast message packet;

retrieving first data from the multicast forwarding data according to the identified destination multicast group, the retrieved first data including at least one cross-referenced I/O interface; and

sending the multicast message packet out each at least one cross-referenced I/O interface in the first data other than the identified I/O interface.

19. The method of claim 14, wherein the network includes at least one host and at least one router that exchange multicast control packets to maintain multicast routing information, and wherein the first packet is a multicast control packet destined for a host or a router.

20. A method of conserving bandwidth in a communications network by reducing transmission of unneeded multicast messages, the method comprising:

monitoring, at a first location, multicast control packets destined for a location other than the first location;

from each monitored multicast control packet, identifying a multicast group, a source of the monitored multicast control packet and an interface on which the monitored multicast control packet arrived;

maintaining an association of the identified multicast group with the identified interface; and

for any multicast message received at the first location and destined for the identified multicast group, transmitting the received multicast message on any interface associated with the multicast group identified in the multicast message.