Data stream filtering apparatus & method

• US 20020146026A1
• Filed: 03/27/2002
• Published: 10/10/2002
• Est. Priority Date: 05/14/2001
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Allen, Matthew John, Grant, Michael, Phillips, David, Unitt, Brian
• Granted Patent: US 7,272,137 B2
• Time in Patent Office: Days
• US Class Current: 370/428
• CPC Class Codes: H04L 12/1836 with heterogeneous network architecture
• CPC Class Codes: H04L 12/1886 with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains
• CPC Class Codes: H04L 69/22 Parsing or analysis of headers
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method and apparatus for filtering data packets in a shared-medium or point-to-multipoint communications network. A filter unit is sent a data packet carrying a filter tag value in a packet addressed to the filter unit. The value is stored in the filter unit and subsequently received packets not addressed to the filter unit itself are forwarded only if they carry the stored filter tag. An embodiment of particular interest applies the method to Ethernet frames over a telecommunications access network (including optical or wireless networks), and uses the VLAN tag field to carry the filter tag information.

Claims

1. A method of filtering data packets each comprising an address field and a filter tag field, the method comprising the steps of, at a filtering node:

storing a value of a filter tag field; and

forwarding subsequently received data packets, other than those addressed to the filtering node, responsive to a comparison between values of their respective filter tag fields and the value of the stored filter tag field, regardless of the value of their respective address fields.

2. A method of filtering data packets each comprising an address field and a filter tag field, the method comprising the steps of, at a filtering node:

receiving a first data packet addressed, by means of the address field, to the filtering node;

storing the value of the filter tag field of the first data packet;

forwarding subsequently received data packets, other than those addressed to the filtering node, responsive to a comparison between values of their respective filter tag fields and the value of the filter tag field of the first data packet, regardless of the value of their respective address fields.

3. A method according to claim 2 in which the data packets are Ethernet data packets.

4. A method according to claim 3 in which the filter tag field is a Ethernet VLAN tag field.

5. A method according to claim 2 in which the filter tag field is an MPLS label.

6. A method of filtering a stream of data packets each comprising an address field and a filter tag field, the method comprising the steps of, at a filtering node:

receiving a data packet;

if the address field of the data packet contains the address of the filtering node, storing the value of the filter tag field of the data packet;

if the address field of the data packet does not contain the address of the filtering node, forwarding the data packet responsive to a comparison between the filter tag field of the data packet and a previously stored filter tag value.

15. A communications network comprising:

a headend node having an output port;

a plurality of data packet filters according to claim 6;

a shared downstream medium connecting the output port of the headend node to respective input ports of each of the plurality of data packet filters;

in which data packets output at the output port of the headend node are transmitted over the shared downlink medium to each of the plurality of data packet filters.

7. A data packet filter comprising:

a input port arranged to receive a stream of data packets each comprising an address field and an filter tag field;

an output port arranged to output a stream of data packets each having an address field; and

a processor and store;

the processor being arranged to receive, at the input port, a first data packet addressed, by means of the address field of the packet, to the data packet filter;

to store the value of the filter tag field of the first data packet in the store;

to forward subsequent data packets received at the first port responsive to a comparison between values of their respective filter tag fields and the stored value of the filter tag field, regardless of the value of their respective address fields.

8. A data packet filter according to claim 7 in which the data packets are Ethernet data packets.

9. A data packet filter according to claim 8 in which the filter tag field is a Ethernet VLAN tag field.

10. A data packet filter according to claim 7 in which the filler tag field is an MPLS label.

11. A data packet filter according to claim 7 in which the input port is one of an optical port and a wireless port.

12. A data packet filter as claimed in claim 7, and arranged to add tags to upstream traffic.

13. A data packet filter as claimed in claim 7, and arranged to remove said tags prior to forwarding said packets to a customer.

14. A communications network comprising at least one data packet filter according to claim 7.

16. A communications network according to claim 15 in which the shared downstream medium is one of an optical medium and a wireless medium.

17. A communications network according to claim 15 being a telecommunications access network.

18. A program for a computer in a machine-readable form and comprising:

a first portion arranged to receive and store a value of a filter tag field;

a second portion arranged to forward subsequently received data packets, other than those addressed to the filtering node, responsive to a comparison between values of their respective filter tag fields and the value of the stored filter tag field, regardless of the value of their respective address fields.

19. An application specific integrated circuit comprising:

a first portion arranged to receive and store a value of a filter tag filled;

a second portion arranged to forward subsequently received data packets, other than those addressed to the filtering node, responsive to a comparison between values of their respective filter tag fields and the value of the stored filter tag field, regardless of the value of their respective address fields.

20. A data signal comprising a sequence of packets each provided with a respective virtual local area network (VLAN) tag identifying a customer to whom that packet is directed and whereby the signal may be filtered such that each customer receives only those packets intended for that customer.

21. A method of transmitting data from a head end of a point-to-multipoint network comprising the steps of;

at the head end;

storing an association between destination addresses and filter tag values, each filter tag value being associated with a filter node reachable via the point-to-multipoint network;

receiving data directed to a destination address;

identifying a stored filter tag value associated with the destination address;

forwarding the data over the point-to-multipoint network in at least one data packet comprising the filter tag value.

22. A method according to claim 21 additionally comprising the steps of:

receiving a request to associate a new filter tag value with a filter unit having an address accessible via the network;

updating the association to include a mapping between the address and a new filter tag value;

sending a message over the network, addressed to the address of the filter unit, and containing the new filter tag value.

23. A method according to claim 22 additionally comprising the steps of:

receiving a request to disassociate a filter tag value from a filter unit having an address accessible via the network;

updating the association to omit any mapping between the address and the filter tag value.

24. A head end for a point-to-multipoint network, the head end comprising:

a store arranged for storing an association between destination addresses and filter tag values, each filter tag value being associated with a filter node reachable via the network;

an input port arranged to receive data directed to a destination address;

a processor arranged to identify a stored filter tag value associated with the destination address and to forward the data over the network in at least one data packet comprising the filter tag value.

25. A program for a computer in a medium-readable form having code portions arranged to:

store an association between destination address and filter tag values, each filter tag value being associated with a filter node reachable via the point-to-multipoint network;

receive data directed to a destination address;

identify a stored filter tag value associated with the destination address;

forward the data over the point-to-multipoint network in at least one data packet comprising the filter tag value.