Apparatus and Method for Multicast Data Packet Forwarding

Patent metadata

Field	Value
Publication number	US-2016014018-A1
Application number	US-201514861838-A
Country	US
Kind code	A1
Filing date	Sep 22, 2015
Priority date	Mar 15, 2013
Publication date	Jan 14, 2016
Grant date	—

Abstract

A switching device supports a mixed mode of operation using both layer 2 and layer 3 multicast forwarding tables for multicast forwarding of packets. In the mixed mode of operation the switching device programs multicast forwarding entries in a corresponding layer 2 or layer 3 table depending on a type of protocol to be used for multicast forwarding. The switching device programs multicast forwarding entries in the layer 3 table for multicast packets forwarded using layer 3 routing protocols, and in the layer 2 table for multicast packets forwarded using layer 2 protocols. The switching device converts layer 3 multicast information to layer 2 multicast information before programming multicast forwarding entries in the corresponding layer 2 table.

First claim

1 . In a switching device, a method comprising:
receiving a request to program a multicast entry in a forwarding table for forwarding a data packet to multiple destinations, the forwarding table including a layer 2 table and a layer 3 table, the request associated with a multicast group address and a VLAN ID; identifying a protocol with which the request is associated, the protocol identified from among a plurality of protocols supported in the switching device; programming the multicast entry for the multicast group address associated with the request into the layer 3 table when the identified protocol requires forwarding across VLANs; and otherwise, programming the multicast entry for the multicast group address associated with the request into the layer 2 table.

2 . The method of claim 1 , further comprising:
determining whether the identified protocol with which the request is associated requires forwarding across VLANs based on mapping the identified protocol to a corresponding one of the layer 2 and layer 3 tables.

3 . The method of claim 2 , wherein the mapping is encoded in a cache distribution table that maps each of the plurality of protocols supported in the switching device to the corresponding one of the layer 2 and layer 3 tables.

4 . The method of claim 1 , wherein programming the multicast entry into the layer 3 table includes:
allocating a layer 3 index for insertion into the layer 3 table, the layer 3 index corresponding to the multicast group address; and programming table entries corresponding to the allocated layer 3 index for an egress VLAN and port lists associated with the request.

5 . The method of claim 1 , wherein programming the multicast entry into the layer 2 table includes:
converting the multicast group address associated with the request into a layer 2 multicast group address, the converted layer 2 multicast group address composed of a multicast group MAC address and egress VLAN associated with the request; allocating a layer 2 index for insertion into the layer 2 table, the layer 2 index corresponding to the converted layer 2 multicast group address; and programming egress table entries corresponding to the allocated layer 2 index for ports in port lists associated with the request.

6 . The method of claim 5 , wherein programming the multicast entry into the layer 2 table further includes linking the multicast group address associated with the request with the converted layer 2 multicast group address.

7 . The method of claim 1 , wherein the identified protocol requires forwarding across VLANs when the identified protocol is any one of a PIM, MVR and Private VLAN protocols.

8 . The method of claim 1 , wherein the identified protocol does not require forwarding across VLANs when the identified protocol is a snooping protocol, the snooping protocol including any one of an IGMP and MLD snooping protocol.

9 . The method of claim 1 , wherein the multicast entry is programmed into the layer 2 table as a static entry.

10 . A computer system for Internet Protocol (IP) multicast forwarding, the computer system comprising:
a hardware layer for programming layer 2 and layer 3 multicast tables for hardware forwarding of multicast data packets; protocol modules issuing requests to program entries in the multicast tables for a specified multicast group address and VLAN ID, the protocol modules implementing a plurality of protocols including layer 2 protocols and layer 3 protocols; and a processor in communication with the hardware layer and the protocol modules, wherein the processor is configurable to operate in a mixed mode enabling multicast hardware forwarding using both the layer 2 and layer 3 multicast tables, the processor managing requests to program the multicast entries including: determining whether a protocol associated with a request requires forwarding across VLANs, processing the request to program the layer 3 multicast table after determining that the associated protocol requires forwarding across VLANs, and otherwise, processing the request to program the layer 2 multicast table.

11 . The computer system of claim 10 , wherein managing requests to program the multicast entries includes:
generating a database to support operating in the mixed mode; creating an IP multicast cache node in the database for each IP multicast group address and VLAN ID specified in the requests; storing in the database port lists and egress VLANs for the IP multicast cache node; encoding each IP multicast cache node with a cache mode based on determining whether the protocol associated with a request requires forwarding across VLANs, the cache mode indicating in which of the layer 2 and layer 3 tables the hardware layer should program the multicast entries for the IP multicast group address and VLAN ID specified in the requests; and for each IP multicast cache node in the database encoded with a cache mode indicating the layer 2 table, creating a MAC-VLAN node in the database based on a MAC address representing the IP multicast group address and an egress VLAN.

12 . The computer system of claim 11 , further comprising:
for each IP multicast cache node in the database encoded with a cache mode indicating the layer 2 table, linking the IP multicast cache node to each created MAC-VLAN node.

13 . The computer system of claim 11 , further comprising:
a cache distribution table in which:
protocols requiring forwarding across VLANs are mapped to a layer 3 flag, and
protocols not requiring forwarding across VLANs are mapped to a layer 2 flag; and
wherein encoding each IP multicast cache node with the cache mode based on determining whether the protocol associated with a request requires forwarding across VLANs includes:
matching the protocol associated with the request to one of the protocols in the cache distribution table, and
setting the cache mode to the mapped layer 2 or layer 3 flag corresponding to the matching protocol in the cache distribution table.

14 . The computer system of claim 11 , further comprising:
interfacing with the hardware layer to program the layer 2 and layer 3 multicast tables in accordance with the requests to program the multicast entries, wherein: for each IP multicast cache node in the database that is encoded with a cache mode indicating the layer 3 table, programming the layer 3 table in the hardware layer, including:
allocating a layer 3 index for insertion into the layer 3 table, the layer 3 index corresponding to the IP multicast group address and VLAN ID of the IP multicast cache node, and
programming table entries corresponding to the allocated layer 3 index for the egress VLANs and port lists stored in the database; and
for each IP multicast cache node in the database that is encoded with a cache mode indicating the layer 2 table, programming the layer 2 table in the hardware layer based on the MAC-VLAN node including:
converting the IP multicast group address associated with the request into a layer 2 multicast group address, the layer 2 multicast group address composed of the MAC address and the egress VLAN represented by the MAC-VLAN node;
allocating a layer 2 index for insertion into the layer 2 table, the layer 2 index corresponding to the converted layer 2 multicast group address; and
programming egress table entries corresponding to the allocated layer 2 index for the port lists stored in the database.

15 . The computer system of claim 12 , further comprising:
interfacing with the hardware layer to program the layer 2 multicast tables in accordance with the requests to program the multicast entries,

Assignees

• Extreme Networks Inc

Inventors

• Grosser Donald B
• Neelamegam Vanitha
• Palani Maruthamuthu
• Ramu Balasubramanian
• Selvaraj Kannan

Classifications

• H04L45/16 Primary

  Multipoint routing · CPC title

• H04L12/18

  for broadcast or conference {, e.g. multicast} · CPC title

• H04L12/4641

  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 title

• H04L12/1886

  with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains · CPC title

• H04L12/6418

  Hybrid transport · CPC title