System and method for distributing multicasts in virtual local area networks

• US 6,839,348 B2
• Filed: 04/30/1999
• Issued: 01/04/2005
• Est. Priority Date: 04/30/1999
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Tang, Cheng, Naik, Chickayya G.
• Primary Examiner(s): Rao, Seema S.
• Assistant Examiner(s): ABELSON, RONALD B
• Application Number:
  US09/303,296
• Publication Number:
  US 20030165140A1
• Time in Patent Office: 2,076 Days
• Field of Search: 370/401, 370/389, 370/392, 370/400, 370/402, 370403-406, 370/390, 370/351, 370412-418, 370/432
• US Class Current: 370/390
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 12/4645 Details on frame tagging routing of packets H04L45/00; support for virtual LAN H04L49/354
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04L 45/16 Multipoint routing

Abstract

The invention relates to a system and method for efficiently distributing multicast messages within computer networks configured to have one or more virtual local area network (VLAN) domains. A multicast network device (MND), having a plurality of interfaces, includes a multicast controller for efficiently distributing multicast messages among subscribing entities associated with various VLAN domains. The multicast controller, which is in communicating relationship with the interfaces, includes a VLAN assignment engine for assigning responsibility for the VLAN domains to the extent there are multiple MNDs. The multicast controller also accesses a multicast tag source to establish a plurality of novel VLAN tags for efficiently distributing multicast messages, including a sub-regional Multicast VLAN Identifier (MVLAN-ID) that encompasses all of the VLAN domains for which the respective MND is responsible, and one or more color-limited MVLAN-IDs that encompass all of the VLAN domains for which the MND is responsible except for one. The multicast controller then tags multicast messages with its sub-regional or a color-limited MVLAN-ID depending on whether the message is considered internal or external by the respective MND. The tagged messages are then forwarded for distribution to the subscribers associated with the various VLAN domains.

Claims

1. A multicast network device (MND) having a plurality of interfaces for forwarding messages within a computer network, the computer network having at least one region that includes a plurality of virtual local area network (VLAN) domains and to which the MND is directly-coupled, the MND comprising:

a multicast controller for efficiently distributing multicast messages to subscribing entities associated with one or more of the VLAN domains, wherein the multicast controller is configured to;

establish a sub-regional Multicast VLAN Identifier (MVLAN-ID) that encompasses a set of the VLAN domains, and one or more color-limited MVLAN-IDs that encompass all but one of the VLAN domains within the set,

append the sub-regional MVLAN-ID to multicast messages received either from outside of the VLAN region or from a VLAN domain not included with the set of VLAN domains,

append a selected color-limited MVLAN-ID to multicast messages that are received from within the VLAN region, and are associated with a VLAN domain included within the set of VLAN domains, and

establish an inter-router VLAN (IRL) designation for use in communicating with one or more neighboring MNDs.

2. The MND of claim 1 further comprising a VLAN assignment engine that is configured to select zero, one or more VLAN domains for inclusion within the set of VLAN domains.

3. The MND of claim 2 further comprising a multicast VLAN control message generator that is configured to generate and transmit one or more advertisement messages for associating the sub-regional MVLAN-ID with the set of VLAN domains, and for associating the color-limited MVLAN-IDs with the respective VLAN domains.

4. The MND of claim 3 further comprising a plurality of interfaces a number of which may be associated with the VLAN domains of the directly-connected region, wherein the multicast controller is further configured to:

perform a reverse path forwarding (RPF) check on a received multicast message based upon the interface on which the multicast message was received; and

provided that the multicast message was received on an interface associated with a VLAN domain, determine whether the interface is associated with a VLAN domain included within the set so as to determine whether to append the sub-regional MVLAN-ID or a color-limited MVLAN-ID.

5. The MND of claim 4 further comprising a VLAN tag source coupled to the multicast controller such that the multicast controller may obtain a corresponding VLAN designation from the tag source for use in establishing the sub-regional MVLAN-ID and the color-limited MVLAN-IDs.

6. The MND of claim 5 further comprising a multicast routing table coupled to the multicast controller, the multicast routing table having a corresponding route entry for each multicast group address for which the MND has received a subscription request, each route entry including a list of outgoing interfaces containing the interfaces on which the respective subscription requests were received.

7. The MND of claim 1 wherein the multicast controller is further configured, in response to receiving a Protocol Independent Multicast (PIM) Join request from a neighboring MND for a given multicast group address, to add the IRL designation to the outgoing interface list for the route entry that corresponds to the given multicast group address.

8. The MND of claim 7 wherein the multicast controller is further configured to append the IRL designation to multicast messages that match a route entry having the IRL designation in the outgoing interface list.

11. The MND of claim 1 further comprising a VLAN assignment engine that is configured to select one or more VLAN domains for inclusion within the set of VLAN domains.

12. The MND of claim 1 further comprising a multicast routing table coupled to the multicast controller, the multicast routing table having one or more route entries for each multicast group address for which the MND has received a subscription request, each route entry specifying the outgoing interfaces on which the respective subscription requests were received.

9. A computer readable medium containing executable program instructions for efficiently distributing multicast messages within a computer network having at least one region that includes a plurality of virtual local area network (VLAN) domains, the executable program instructions comprising program instructions for:

establishing a sub-regional Multicast VLAN Identifier (MVLAN-ID) that encompasses a set of the VLAN domains;

establishing one or more color-limited MVLAN-IDs that encompass all but one of the VLAN domains within the set;

establishing an inter-router VLAN (IRL) designation for use in communicating with one or more neighboring MNDs;

in response to receiving a multicast message, determining whether or not the multicast message was received from a VLAN domain included within the set;

appending the sub-regional MVLAN-ID to the multicast messages provided that it was not received from a VLAN domain included within the set; and

appending a color-limited MVLAN-ID to the multicast message provided that it was received from a VLAN domain included within the set.

10. A method for distributing multicast messages within a computer network having a plurality of virtual local area network (VLAN) domains, the method comprising the steps of:

establishing a sub-regional Multicast VLAN Identifier (MVLAN-ID) that encompasses a set of the VLAN domains;

establishing one or more color-limited MVLAN-IDs, each color-limited MVLAN-ID encompassing all but one of the VLAN domains within the set,

establishing an inter-router VLAN (IRL) designation for use in communicating with one or more neighboring MNDs;

appending the sub-regional MVLAN-ID to multicast messages received either from outside of the VLAN region or from a VLAN domain not included with the set of VLAN domains, and

appending a selected color-limited MVLAN-ID to multicast messages that are received from within the VLAN region, and are associated with a VLAN domain included within the set of VLAN domains.

13. The method of claim 10 wherein the color-limited MVLAN-ID that is appended to the multicast message corresponds to the color-limited MVLAN-ID that does not encompass the VLAN domain associated with the received multicast message.

14. The method of claim 10 wherein the received multicast message has a source address and a multicast group destination address, the method further comprising the steps of:

providing a multicast routing table having, for each of a plurality of source address and multicast destination address pairs, a matching outgoing interface list;

performing a lookup on the multicast routing table using the source address and the multicast group destination address of the received multicast message as indices to identify the matching outgoing interface list; and

forwarding the received multicast message from each of the outgoing interfaces from the matching list other than the interface on which the multicast message was received.

15. The method of claim 14 further comprising the steps of:

in response to receiving at a first interface a Join message specifying a multicast destination address, updating the outgoing interface list corresponding to the specified multicast destination address by including the first interface.

16. The method of claim 14 wherein the routing table has an entry for a wildcard source address and a first multicast group destination address pair, the method further comprising the steps of:

in response to receiving a multicast message specifying the first multicast group destination address and a first source address, creating a new entry in the multicast routing table having the first source address and the first multicast group destination address; and

copying the outgoing interface list from the routing table entry for the wildcard source address into the new entry created for the first source address.

17. The method of claim 10 further comprising the steps of:

providing a block of available VLAN designations;

selecting from the block of available VLAN designations a first VLAN designation for association with the sub-regional MVLAN-ID; and

selected from the block of available VLAN designations a separate VLAN designation for association with each of the color limited MVLAN-IDs.

18. The method of claim 17 further comprising the step of issuing a plurality of advertisement messages, the advertisement messages configured to associate the first VLAN designation with each VLAN domain within the set of VLAN domains encompassed by the sub-regional MVLAN-ID with which the first VLAN designation is associated.