Method and apparatus for transparent intermediate system based filtering on a LAN of multicast packets

• US 5,999,530 A
• Filed: 12/06/1996
• Issued: 12/07/1999
• Est. Priority Date: 10/12/1995
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Backes, Floyd, Jung, Cyndi, LeMaire, Thomas
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): RAO, SEEMA SRINIVAS
• Application Number:
  US08/761,574
• Time in Patent Office: 1,096 Days
• Field of Search: 370/401, 370/402, 370/390, 370/410, 370/432, 370/910, 370/911, 370/389, 370/360, 370/362, 370/363, 370/469, 370/400, 370/403, 370/404, 370/431, 370/486, 370/463, 370/487 , 370/489, 370/490, 370/492, 370/501, 370/502, 370/449, 348/16, 395/309, 340/825.52, 340/825.53
• US Class Current: 370/390
• CPC Class Codes: H04L 12/1836 with heterogeneous network architecture
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 12/1877 Measures taken prior to transmission
• CPC Class Codes: H04L 12/1886 with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains
• CPC Class Codes: H04L 12/4604 LAN interconnection over a backbone network, e.g. Internet, Frame Relay
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: Y10S 370/911 Bridge, e.g. brouter, bus extender

Abstract

A bridge (62) capable of reducing unwanted WAN multicast packet traffic in a LAN and an associated method and an associated LAN is disclosed. The bridge examines the contents of WAN multicast query and report packets and WAN multicast router-to-router discovery packets and includes this information in its filtering database (88). The bridge designates ports on which query packets or MRRDPs are received as router ports. When there is no WAN router generating multicast query packets into the LAN, the bridge simulates the behavior of a WAN router and generates WAN multicast query packets so as to cause report packet generation by end systems. A timeout interval for undesignating router ports and a method for determining an appropriate timeout for a port is disclosed.

Claims

1. A method in a LAN intermediate system (IS) for reducing transmission of undesired WAN multicast packets, wherein said LAN comprises a plurality of end systems, packets having an address, and a plurality of LAN intermediate systems capable of transparently forwarding or filtering packets, said ISs having a plurality of ports for connecting to network segments, comprising:

designating any port on which a multicast router-to-router discovery packet (MRRDP) is received as a router port;

receiving requests from said end systems to receive WAN multicast packets;

storing identifiers for ports on which said requests are received along with multicast addresses specified in said requests;

forwarding said requests out of only those ports designated as router ports;

examining every WAN multicast data packet received to determine the packet'"'"'s multicast destination address;

forwarding said WAN multicast data packets out of only those ports on which either a request for said multicast packet'"'"'s destination address was received or those ports designated as router ports; and

if no multicast router-to-router discovery packet (MRRDP) is received, designating a port upon which a multicast query is received as a router port.

2. The method according to claim 1 further comprising:

if no MRRDP is received, designating a port upon which a most recent multicast query is received as a router port.

3. The method according to claim 1 further comprising:

generating at an IS a WAN multicast query packet when no multicast router-to-router discovery packet (MRRDP) are received on any ports and forwarding said WAN multicast query packets out of all ports on said IS.

4. The method according to claim 3 further comprising:

examining at said IS the source address of WAN multicast queries received on one of said IS'"'"'s ports;

comparing said received source address to said IS'"'"'s source address; and

based on said comparing either suppressing or else continuing to generate at said IS WAN multicast queries.

5. The method according to claim 4 wherein said comparing compares WAN source addresses.

6. The method according to claim 4 wherein said comparing compares a received WAN source address to a WAN source address assigned to said IS.

7. The method according to claim 3 wherein reception of an MRRDP causes ports designated as router ports based on receipt of a query packet to become designated non-router ports.

8. The method according to claim 3 wherein reception of an MRRDP causes the IS to cease generating any query packets until a timer elapses.

9. The method according to claim 1 wherein there is specified a plurality of time out intervals wherein if a query packet or MRRDP is not received at a port designated a router port during a designated timeout interval the port is redesignated as a non-router port.

10. The method according to claim 1 wherein said LAN ISs are devices that generally forward LAN unicast packets without examining the WAN addresses of said packets.

11. The method according to claim 1 wherein said LAN ISs are modified to be able to quickly examine WAN routing information in said packets.

12. The method according to claim 1 wherein said LAN ISs forward packets transparently to said end systems without modifying the contents or header of said packets.

13. The method according to claim 1 wherein said end systems communicate with a plurality of routers using protocols in a TCP/IP protocol suite.

14. The method according to claim 1 wherein at least one of said LAN ISs meet specifications set forth in IEEE 802.1d.

15. The method according to claim 1 wherein a plurality of said end systems and said ISs communicate using an Ethernet protocol.

16. A method in a LAN intermediate system (IS) for reducing transmission of undesired WAN multicast packets, wherein said LAN comprises a plurality of end systems, packets having an address, and a plurality of LAN intermediate systems capable of transparently forwarding or filtering packets, said ISs having a plurality of ports for connecting to network segments, comprising:

designating any port on which a multicast router-to-router discovery packet (MRRDP) is received as a router port;

receiving requests from said end systems to receive WAN multicast packets;

storing identifiers for ports on which said requests are received along with multicast addresses specified in said requests;

forwarding said requests out of only those ports designated as router ports;

examining every WAN multicast data packet received to determine the packet'"'"'s multicast destination address;

forwarding said WAN multicast data packets out of only those ports on which either a request for said multicast packet'"'"'s destination address was received or those ports designated as router ports;

specifying a plurality of time out intervals wherein if a query packet or MRRDP is not received at a port designated a router port during a designated timeout interval the port is redesignated as a non-router port;

sampling at a router port the frequency with which query packets or MRRDPs are received; and

setting said time out intervals for different types of packets to be several times the sampled frequency.

17. A method in a LAN intermediate system (IS) for reducing transmission of undesired WAN multicast packets, wherein said LAN comprises a plurality of end systems, packets having an address, and a plurality of LAN intermediate systems capable of transparently forwarding or filtering packets, said ISs having a plurality of ports for connecting to network segments, comprising:

designating any port on which a multicast router-to-router discovery packet (MRRDP) is received as a router port;

receiving requests from said end systems to receive WAN multicast packets;

storing identifiers for ports on which said requests are received along with multicast addresses specified in said requests;

forwarding said requests out of only those ports designated as router ports;

examining every WAN multicast data packet received to determine the packet'"'"'s multicast destination address; and

forwarding said WAN multicast data packets out of only those ports on which either a request for said multicast packet'"'"'s destination address was received or those ports designated as router ports;

wherein said WAN multicast queries and said WAN multicast packets are encapsulated into LAN group packets, said LAN group packets having a LAN multicast address which is algorithmically translatable with said WAN multicast address and wherein said IS detects, stores, and examines said LAN multicast addresses.

18. A local area network comprising;

a plurality of end systems, each with a connection to a network segment wherein said end systems are capable of transmitting on said segment a multicast report packet, said multicast report packet comprising a requested multicast address from which said end system wishes to receive data; and

a plurality of bridges, each bridge having connections to at least two network segments, at least one of said bridges capable of detecting multicast report packets transmitted on said network segments and capable of storing an identifier of said requested multicast address along with an identifier of said segment, said at least one bridge forwarding received multicast packets only to those segments on which a multicast report packet requesting those multicast packets was received wherein said bridges are further capable of determining a frequency of received query packets on a router port and setting a timeout interval to be several times said frequency and wherein said bridges will designate a router port a non-router port when a query packet is not received during a timeout interval.

19. The local area network according to claim 18 wherein said bridges are further capable of detecting multicast query packets received on a port and designating that port a router port.

20. A method for reducing transmission of undesired layer 3 WAN multicast packets within a LAN, wherein said LAN comprises a plurality of end systems capable of transmitting and receiving layer 2 LAN packets, said packets having at least a LAN source address and a LAN destination address, and a plurality of layer 2 LAN intermediate systems (ISs) capable of transparently forwarding packets at layer 2, said ISs having a plurality of ports for connecting to network segments, comprising:

detecting at at least one of said ISs, encapsulated layer 3 WAN multicast queries to said end systems and MRRDPs by examining the contents of all layer 2 group packets and recording at said IS an identifier for each port on which said WAN multicast queries or MRRDPs are received designating those ports as router ports;

receiving at said IS layer 3 requests from said end systems to receive WAN multicast packets, said request being directed by said end system to a destination address other than the destination address of said IS and examining the layer 3 contents of said requests;

storing at said IS in a layer 2 filtering table, identifiers for ports on which said requests are received along with the layer 2 group address specified in said requests;

forwarding said requests out of only those ports on said IS designated as router ports; and

filtering at said IS every LAN group addressed data packet based on said layer 2 filtering table and thereby forwarding said WAN multicast data packets out of only those ports on which either a request for said multicast packet'"'"'s destination address or a query was received; and

generating at an IS a layer 3 WAN multicast query packet when no ports connected to said IS are designated as router ports and forwarding said WAN multicast query packets out of all ports on said IS.

21. The method according to claim 20 further comprising:

examining at said IS the source address of WAN multicast queries received on one of said IS'"'"'s ports;

comparing said received source address to said IS'"'"'s source address; and

based on said comparing either designating said port a router port or else continuing to generate at said IS WAN multicast queries.

22. The method according to claim 20 wherein said end systems communicate with a plurality of routers connecting said LAN to a WAN using a layer 3 protocol, said routers and said end systems exchanging control information, said control information including said WAN multicast queries and said requests.

23. A method in a LAN intermediate system (IS) for reducing transmission of undesired WAN multicast packets, wherein said LAN comprises a plurality of end systems, packets having an address and a plurality of LAN intermediate systems capable of transparently forwarding or filtering packets said ISs having a plurality of ports for connecting to network segments comprising:

designating any port on which a multicast router-to-router discovery packet (MRRDP) is received as a router port;

receiving requests from said end systems to receive WAN multicast packets;

storing identifiers for ports on which said requests are received along with multicast addresses specified in said requests;

forwarding said requests out of only those ports designated as router ports;

examining every WAN multicast data packet received to determine the packet'"'"'s multicast destination address; and

forwarding said WAN multicast data packets out of only those ports on which either a request for said multicast packet'"'"'s destination address was received or those ports designated as router ports;

wherein said IS upon startup enters two phases of startup operation, a multicast router discovery phase and a group discovery phase.