Multicast echo removal

• US 6,542,503 B1
• Filed: 03/16/1999
• Issued: 04/01/2003
• Est. Priority Date: 03/16/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Xu, Xi, Lou, Shuxian, Zhang, Shujin
• Primary Examiner(s): VANDERPUYE, KENNETH N
• Application Number:
  US09/268,868
• Time in Patent Office: 1,477 Days
• Field of Search: 370/390, 370/401, 370/432, 370/312
• US Class Current: 370/390
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 49/201 Multicast operation; Broadcast operation
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches

Abstract

An apparatus is provided which processes upstream multicast packets and downstream multicast packets in a manner such as to avoid the problem of multicast echo which is generated from a host gateway. For upstream multicast packets, a method is provided which includes: extracting the source network address from the upstream multicast packet; storing said source network address in a table corresponding to the destination host gateway of the packet; and forwarding the upstream multicast packet to the destination network address. For downstream multicast packets, a method is provided which includes: accessing a table corresponding to the host gateway from which the packet was sent; determining if said source network address of the multicast packet is identical to an entry in said table; discarding the multicast packet if said source network address is identical to an entry in said table; and forwarding the multicast packet to said destination network address if said source network address is not identical to an entry in said table. This eliminates any downstream multicast packets which originated from one of the hosts coupled to the apparatus, and thus prevents multicast echo problems from occurring.

Claims

1. A method for processing a multicast packet, the multicast packet having a source network address and a destination network address, the method comprising:

determining if the multicast packet is an upstream packet or downstream packet;

extracting the source network address from the multicast packet if the multicast packet is an upstream multicast packet;

storing the source network address of the multicast packet in a table having a list of network addresses if the multicast packet is an upstream multicast packet;

forwarding the multicast packet to the destination network address if the multicast packet is an upstream multicast packet;

accessing said table if the multicast packet is a downstream multicast packet;

determining if the source network address of the multicast packet is identical to an entry in said table if the multicast packet is a downstream multicast packet;

discarding the multicast packet if the multicast packet is a downstream multicast packet and if the source network address is identical to an entry in said table; and

forwarding the multicast packet to said destination network address if the multicast packet is a downstream multicast packet and if the source network address is not identical to an entry in said table.

2. The method of claim 1, wherein said table is a hash table.

3. The method of claim 1, wherein said accessing includes:

taking information regarding the port on which the multicast packet arrived; and

using said information to determine from which host gateway the multicast packet arrived.

4. A method for processing a multicast packet, the multicast packet having a source network address and a destination network address, the method comprising:

determining if the multicast packet is an upstream or downstream packet;

extracting the source network address from the multicast packet if the multicast packet is an upstream multicast packet;

storing the source network address in a table corresponding to the destination host gateway of the upstream multicast packet if the multicast packet is an upstream multicast packet;

forwarding the multicast packet to the destination network address if the multicast packet is an upstream multicast packet;

accessing a table corresponding to a host gateway from which the multicast packet was sent if the multicast packet is a downstream multicast packet, wherein said table includes a list of network addresses;

determining if the source network address of the multicast packet is identical to an entry in said table corresponding to a host gateway from which the multicast packet was sent if the multicast packet is a downstream multicast packet;

discarding said multicast packet if the multicast packet is a downstream multicast packet and if said source network address is identical to an entry in said table corresponding to a host gateway from which the multicast packet was sent; and

forwarding the multicast packet to the destination address if the multicast packet is a downstream multicast packet and if the source network address is not identical to an entry in said table corresponding to a host gateway from which the multicast packet was sent.

5. The method of claim 4, wherein said table corresponding to a host gateway from which the multicast packet was sent is a hash table.

6. The method of claim 4, wherein said accessing includes:

taking information regarding the port on which the multicast packet arrived; and

using said information to determine from which host gateway the multicast packet arrived.

7. An apparatus for processing a multicast packet, the multicast packet having a source network address and a destination network address, the apparatus including:

a multicast packet determiner;

a table;

a source network address extractor coupled to said multicast packet determiner if the multicast packet is an upstream multicast packet;

a source network address storer coupled to said table and coupled to said source network address extractor if the multicast packet is an upstream multicast packet;

a multicast packet forwarder coupled to said source network address storer if the multicast packet is an upstream multicast packet;

a table accessor coupled to said table if the multicast packet is a downstream multicast packet, wherein said table includes a list of network addresses;

a source network address comparator coupled to said table accessor if the multicast packet is a downstream multicast packet;

a multicast packet discarder coupled to said source network address comparator if the multicast packet is a downstream multicast packet and if said source network address is identical to an entry in said table; and

a multicast packet forwarder coupled to said source network address comparator if the multicast packet is a downstream multicast packet and if said source network address is not identical to an entry in said table.

8. The apparatus of claim 7, wherein said table is a hash table.

9. The apparatus of claim 7, wherein said table accessor includes:

an information accessor; and

a host gateway determiner couped to said information accessor.

10. An apparatus for processing a multicast packet, the multicast packet having a source network address and a destination network address, the apparatus including:

a multicast packet determiner;

one or more tables, each of said table corresponding to a different host gateway;

a source network address extractor coupled to said multicast packet determiner if the multicast packet is an upstream multicast packet;

a source network address storer coupled to said tables and coupled to said source network address extractor if the multicast packet is an upstream multicast packet;

a multicast packet forwarder coupled to said source network address storer if the multicast packet is an upstream multicast packet;

a table accessor coupled to said tables if the multicast packet is a downstream multicast packet, wherein said tables include a list of network addresses;

a source network address comparator coupled to said table accessor if the multicast packet is a downstream multicast packet;

a multicast packet discarder coupled to said source network address comparator if if the multicast packet is a downstream multicast packet and if said source network address is identical to an entry in the one of said one or more tables corresponding to the host gateway from which the downstream multicast packet was sent; and

a multicast packet forwarder coupled to said source network address comparator if the multicast packet is a downstream multicast packet and if said source network address is not identical to an entry in said table.

11. The apparatus of claim 10, wherein said table is a hash table.

12. The apparatus of claim 10, wherein said table accessor includes:

an information accessor; and

a host gateway determiner couped to said information accessor.

13. A program storage device read able by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for processing a multicast packet, the multicast packet having a source network address and a destination network address, said method comprising:

determining if the multicast packet is an upstream or downstream packet,

extracting the source network address from the multicast packet if the multicast packet is an upstream multicast packet;

storing the source network address of the multicast packet in a table if the multicast packet is an upstream multicast packet;

forwarding the multicast packet to the destination network address if the multicast packet is an upstream multicast packet;

accessing a table corresponding to a host gateway from which the multicast packet was sent if the multicast packet is a downstream multicast packet, wherein said table includes a list of network addresses;

determining if the source network address of the multicast packet is identical to an entry in said table if the multicast packet downstream multicast packet;

discarding said multicast packet if the multicast packet is a downstream multicast packet and if said source network address is identical to an entry in said table; and

forwarding the multicast packet to said destination network address if the multicast packet is a downstream multicast packet and if said source network address is not identical to an entry in said table.

14. The program storage device of claim 13, wherein said table is a hash table.

15. The program storage device of claim 13, wherein said accessing includes:

taking information regarding the port on which the multicast packet arrived; and

using said information to determine from which host gateway the multicast packet arrived.

16. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for processing a multicast packet, the multicast packet having a source network address and a destination network address, said method comprising:

determining if the multicast packet is an upstream or downstream packet;

extracting the source network address from the multicast packet if the multicast packet is an upstream multicast packet;

storing said source network address in a table corresponding to the destination host gateway of the upstream multicast packet if the multicast packet is an upstream multicast packet;

forwarding the multicast packet to the destination network address if the multicast packet is an upstream multicast packet;

accessing a table corresponding to a host gateway from which the multicast packet was sent if the multicast packet is a downstream multicast packet, wherein said table includes a list of network addresses;

determining if the source network address of the multicast packet is identical to an entry in said table if the multicast packet is a downstream multicast packet;

discarding said multicast packet if the multicast packet is a downstream multicast packet and if said source network address is identical to an entry in said table; and

forwarding the multicast packet to said destination network address if the multicast packet is a downstream multicast packet and if said source network address is not identical to an entry in said table.

17. The program storage device of claim 16, wherein said table is a hash table.

18. The program storage device of claim 16, wherein said accessing includes:

taking information regarding the port on which the multicast packet arrived; and

using said information to determine from which host gateway the multicast packet arrived.