Apparatus for multicast forwarding in a virtual local area network environment

• US 20020191628A1
• Filed: 06/12/2001
• Published: 12/19/2002
• Est. Priority Date: 06/12/2001
• Status: Active Grant

• Current Assignee: Acuere Technologies Corporation
• Original Assignee: Actue Communications Corporation
• Inventors: Liu, Kuang-Chih, Lee, Fang-Yong
• Granted Patent: US 6,947,419 B2
• Time in Patent Office: Days
• US Class Current: 370/428
• 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 12/4641 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

Abstract

An apparatus distributing multicast messages with a multicast address among the ports of a network device on the basis of, inter alia, virtual local area network (VLAN) associations among the ports. One or more VLANs within the network device are assigned to the multicast address. The apparatus comprises a lookup engine, a forwarding engine coupled to the lookup engine, and a plurality of translation engines. The lookup engine needs to map the multicast address to a unique index value assigned to the multicast address and a bit string representing the group of multicast destination ports only once. The forwarding engine distributes the multicast messages and the unique index value to the group of multicast destination ports of the network device in accordance with the bit string. The translation engines are associated with each port of the network device respectively. Each translation engine independently performs a VLAN identifier (VID) translation in parallel on each port of the network device from the unique index value, the destination port and a VID-select index.

Claims

1. An apparatus for distributing multicast messages associated with a multicast address among ports of a network device on the basis of a virtual local area network (VLAN), one or more VLANs within the network device are assigned to the multicast address, each VLAN having a multicast destination subset which includes one or more destination ports assigned from the ports of the network device, the apparatus comprising:

a means for generating a group of multicast destination ports by collectively combining every multicast destination subset within all of the VLANs assigned to the multicast address on the network device; and

a plurality of translation engines respectively associated with each port of the network device, each translation engine independently performing a VLAN identifier (VID) translation in parallel on each port which belongs to the group of multicast destination ports;

wherein the group of multicast destination ports are all of the destination ports assigned to the multicast address on the network device.

2. The apparatus as claimed in claim 1, the apparatus further comprises:

a lookup engine for mapping the multicast address to a unique index value assigned to the multicast address and a bit string representing the group of multicast destination ports;

a forwarding engine coupled to the lookup engine, the forwarding engine distributing the unique index value and the multicast messages to the group of multicast destination ports of the network device in accordance with the bit string;

3. The apparatus as claimed in claim 2, wherein each translation engine associated with each port translates the VID from the unique index value and a VID-select index.

4. The apparatus as claimed in claim 2, wherein the lookup engine comprises an address lookup table having a plurality of entries each of which comprises the multicast address, the unique index value, and the bit string.

5. The apparatus as claimed in claim 2, wherein the bit string functions as a port mask, wherein each bit of the port mask corresponds to a specific port of the network device, and wherein the multicast messages are forwarded to the group of destination ports of the network device in accordance with the port mask.

6. The apparatus as claimed in claim 2, wherein each translation engine comprises:

a VID tag list corresponding to each port of the network device; and

a VID-select table containing a plurality of VID-select bitmap each of which corresponds to the unique index value, wherein each VID-select bitmap functions as a selection mask for the corresponding port, wherein each active bit of the selection mask is indicative of the VID-select index for each port of the network device, and wherein the VID-select index selects the corresponding VID associated with the multicast address from the VID tag list.

7. The apparatus as claimed in claim 6, wherein every VID-select index is respectively fetched from the VID-select bitmap corresponding to the unique index value on each port of the network device.

8. The apparatus as claimed in claim 2, wherein the lookup engine further comprises means for performing link aggregation complied with the 802.3ad standard.

9. A method of distributing multicast messages associated with a multicast address among ports of a network device on the basis of virtual local area network (VLAN), one or more VLANs within the network device are assigned to the multicast address, each VLAN having a multicast destination subset which consists of one or more destination ports assigned from the ports of the network device, the method comprising the steps of:

A. providing a group of multicast destination ports, a unique index value, one or more VID-select indices assigned to each destination port, and a plurality of VLAN identifier (VID) tag lists respectively associated with each port of the network device;

B. looking up the group of multicast destination ports and the unique index value assigned to the multicast address in an address lookup table;

C. forwarding the multicast messages to the group of multicast destination ports of the network device; and

D. translating one or more VLAN identifiers (VIDs) on each port in parallel and independently from the unique index value, one or more VID-select indices and the VID tag list corresponding to each port of the network device;

wherein the group of multicast destination ports are all of the destination ports assigned to the multicast address on the network device;

wherein the unique index value is assigned to the multicast address;

wherein the VID-select indices are associated with the unique index value.

10. The method as claimed in claim 9, wherein the step A comprises the steps of:

A1. generating the group of multicast destination ports assigned to the multicast address by collectively combining every multicast destination subset within all of the VLANs assigned to the multicast address on the network device;

A2. storing the group of multicast destination ports, the unique index value, and the multicast address in one of a plurality of entries of the address lookup table, wherein the group of multicast destination ports are stored in a bit string of the entry; and

A3. storing the VID-select indices in one of a plurality of VID-select bitmap of a VID-select bitmap table.

11. The method as claimed in claim 10, wherein the steps A1˜

A3 are performed in response to the Internet Group Management Protocol (IGMP) service request.

12. The method as claimed in claim 10, wherein the step D comprises the steps of:

D1. selecting the VID-select bitmap corresponding to the unique index value from the VID-select bitmap table;

D2. fetching one of the VID-select indices from the VID-select bitmap independently on each port of the network device;

D3. fetching the VID associated with the multicast address independently on each port of the network device, according to the VID-select index from step D2 and the VID tag list corresponding to each port;

D4. repeating step D2 and D3 until each port of the network device examines all of bits of the VID-select bitmap.

13. The method as claimed in claim 9 further comprising the step of:

E. tagging the related VID on the outgoing multicast messages independently on every destination port of the network device.

14. The method as claimed in claim 9, wherein the step B further comprises the step of performing link aggregation complied with the 802.3ad standard.