Method and system for measuring reception characteristics in a multicast data distribution group

• US 6,693,907 B1
• Filed: 04/11/2000
• Issued: 02/17/2004
• Est. Priority Date: 04/11/2000
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Chiu, Dah Ming, Hanna, Stephen R., Provino, Joseph E., Kadansky, Miriam C., Wesley, Joseph S.
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): NG, CHRISTINE Y
• Application Number:
  US09/546,946
• Time in Patent Office: 1,407 Days
• Field of Search: 370/252, 370/253, 370/256, 370/390, 370/394, 370/400, 370/408, 370/473
• US Class Current: 370/390
• CPC Class Codes: H04L 12/185 with management of multicast group membership
• CPC Class Codes: H04L 12/1854 with non-centralised forwarding system, e.g. chaincast
• CPC Class Codes: H04L 12/1868 Measures taken after transmission, e.g. acknowledgments
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/15 in relation to multipoint traffic arrangements for broadcast or multicast in data networks H04L12/18
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/27 Evaluation or update of window size, e.g. using information derived from acknowledged [ACK] packets

Abstract

A method and system for accurately measuring the reception characteristics of receivers in a multicast data distribution group having a sending node and a plurality of receivers. The multicast group is organized as a repair tree in which selected nodes of the multicast group comprise repair nodes for downstream receivers. Multicast data packets transmitted by the repair nodes include a retransmission count field in addition to the multicast packet header information, a session identifier, a packet sequence number and payload data. The retransmission count provides an indication of the number of times the respective packet has been retransmitted in response to a repair request. The receivers include an original packet counter and a retransmission count counter for each multicast session. Each receiver increments the original packet counter upon receipt of a packet that has not been previously received. Each receiver adds the value contained in the retransmission count field of a received packet to the retransmission count counter upon receipt of a retransmitted multicast packet that corresponds to a packet identified as a missing packet by the respective receiver. The data in the actual packet count counter and the retransmission count counter is employed to generate a loss metric at each receiver that provides a measure of the reception characteristic of the respective receiver for the particular multicast session.

Claims

1. A method of operation at a receiver in a multicast data distribution group, said method comprising:

receiving at said receiver a plurality of multicast data packets of a multicast session, wherein each one of said packets includes a retransmission count within a retransmission count field, said retransmission count being indicative of the number of times the respective packet has been retransmitted;

in response to receipt of each one of said plurality of multicast data packets adding to a retransmission counter said retransmission count contained within the respective retransmission count field to produce a retransmission counter value in the event the respective received packet is a retransmitted packet and the respective received packet is identified within the receiver as a missing packet; and

generating a loss value indicative of a reception characteristic of said receiver as a function of said retransmission counter value.

2. The method of claim 1 wherein said method further includes the step of incrementing an original packet counter to produce an original packet counter value in response to receipt of each received packet that is first received as a result of a packet transmission from a sending node or as a result of a packet retransmission from a repair head and wherein said generating step comprises the step of generating said loss value as a function of said retransmission counter value and said original packet counter value.

3. The method of claim 2 wherein said step of generating said loss value comprises the step of dividing said retransmission counter value by said original packet counter value.

4. The method of claim 2 wherein said step of generating said loss value comprises the step of adding to said retransmission counter value a value corresponding to the number of missing packets within a predetermined loss measurement interval to obtain a loss numerator, and dividing said loss numerator by a predetermined number equal to a number of packets comprising said predetermined loss measurement interval.

5. The method of claim 1 further comprising the step of dissociating said receiver from said multicast data distribution group in the event said loss value exceeds a specified threshold value.

6. The method of claim 1 further comprising the step of transmitting from said receiver a message indicative of congestion at said receiver in the event said loss value exceeds a specified threshold value.

7. Apparatus for generating a value indicative of the data loss rate of a receiver in a multicast data distribution group, said apparatus comprising:

receive logic for receiving a plurality of data packets of a multicast session, wherein each one of said packets includes a retransmission count value within a retransmission count field, said retransmission count value being indicative of the number of times the respective packet has been retransmitted;

first counter control logic for incrementing a first counter in response to receipt of each one of said plurality of data packets that is an originally received data packet;

said first counter control logic further operative to increment said first counter in response to receipt of each one of said plurality of data packets that is a retransmitted packet and identified as a missing packet;

second counter control logic, said second counter control logic operative in response to receipt of each one of said plurality of received packets that is a retransmitted packet and identified as a missing packet for adding to a second counter the retransmission count value contained within the respective retransmission count field; and

a loss value generator, said loss value generator operative to generate a loss value indicative of a reception characteristic of said receiver as a function said first and second counters.

8. A method for generating a loss value in receivers of a multicast data distribution group, said method comprising:

maintaining at a repair head within said data distribution group, a table containing an identification of a plurality of multicast packets within a multicast session and an associated retransmission count value indicative of the number of times the respective packet identified within said table has been retransmitted by said repair head;

receiving at said repair head a plurality of requests to retransmit specified ones of said multicast packets identified within said table;

in response to receipt at said repair head of each of said plurality of requests to retransmit said specified multicast packets, incrementing the respective retransmission count value, inserting the incremented retransmission count value associated with the respective specified packet into the respective specified packet and transmitting said specified packet for receipt by receivers of a repair group within said multicast data distribution group;

in response to receipt of at least some of said multicast packets at each one of said receivers of said repair group, adding to a value contained in a retransmission counter said retransmission count contained within the respective received packet to generate a first value in the event the respective received packet is a retransmitted packet and the packet is identified within the respective receiver as a missing packet; and

generating a loss value indicative of a reception characteristic of said respective receiver, wherein said loss value is a function of said first value.

9. The method of claim 8 further including the step of:

transmitting a plurality of original multicast data packets from a sending node within said multicast data distribution group for receipt by said receivers of said multicast data distribution group; and

in a first incrementing step, incrementing a value contained in an original packet counter at one of said receivers to generate a second value in the event the respective received packet at said one of said receivers is an originally received packet; and

in a second incrementing step, incrementing said second value contained in said original packet counter in the event the respective received packet is a retransmitted packet and the packet is identified within the receiver as a missing packet.

10. The method of claim 9 wherein said first incrementing step further includes the step of determining the respective received packet to be an originally received packet in the event said retransmission count field within the respective packet contains a predetermined value.

11. The method of claim 10 wherein said predetermined value equals zero.

12. The method of claim 9 wherein each of said plurality of receivers maintains an identification of received and missing packets and said first incrementing step further includes the step of determining the respective received packet to be an originally received packet in the event said respective received packet is not identified as one of said received or missing packets.

13. The method of claim 9 wherein said generating step comprises the step of generating said loss value as a function of said first and second values.

14. The method of claim 12 wherein said generating step comprises the step of dividing said first value by said second value.

15. The method of claim 12 wherein said generating step includes the step of adding a number corresponding to the number of packets identified as missing packets to said first value to provide an estimated retransmission count and dividing said estimated retransmission count by a predetermined number associated with the number of packets within a predetermined measurement interval.

16. A system for generating a loss value in receivers of a multicast data distribution group, said system comprising:

a repair head within said data distribution group, said repair head operative to maintain a table containing an identification of a plurality of multicast packets within a multicast session and an associated retransmission count value indicative of the number of times the respective packet identified within said table has been retransmitted by said repair head;

a repair group including said repair head and a plurality of receivers, said repair head being operative to receive repair requests from said receivers within said repair group and, in response to said requests, said repair head operative to increment the respective retransmission count value associated with the at least one selected packet, to insert the incremented retransmission count value associated with the at least one selected packet into each of the respective at least one selected packet and to the respective at least one selected packet for receipt by said plurality of receivers within said repair group;

said at least one of said plurality of receivers of said repair group being operative in response to receipt of said multicast packets from said repair head to add to a value contained in a retransmission counter said retransmission count contained within the respective received packet to generate a retransmission counter value in the event the respective received packet is a retransmitted packet and the packet is identified within the respective receiver as a missing packet, and to generate a loss value indicative of a reception characteristic of said at least one of said other receivers as a function of said retransmission counter value.

17. A computer program product including a computer readable medium, said computer readable medium having a computer program stored thereon, said computer program for execution in a processor within a receiver of a multicast data distribution group and for use in generating a loss value indicative of the ability of the receiver to receive multicast data packets, said computer program comprising:

program code for receiving a plurality of data packets of a multicast session, wherein each one of said packets includes a retransmission count value within a retransmission count field, said retransmission count value being indicative of the number of times the respective packet has been retransmitted;

program code for incrementing a first counter in response to receipt of each one of said plurality of data packets that is an originally received data packet; and

program code for incrementing said first counter in response to receipt of each one of said plurality of data packets that is a retransmitted packet and identified as a missing packet;

program code responsive to receipt of each one of said plurality of received packets that is a retransmitted packet and identified as a missing packet for adding to a second counter said retransmission count value contained within the respective retransmission count field; and

program code generating a loss value indicative of a reception characteristic of said receiver as a function said first and second counters.

18. A computer data signal, said computer data signal including a computer program for execution in a processor within a receiver of a multicast data distribution group, said computer program operative to generate a loss value indicative of the ability of the receiver to receive multicast data packets, said computer program comprising:

program code for receiving a plurality of data packets of a multicast session, wherein each one of said packets includes a retransmission count value within a retransmission count field, said retransmission count value being indicative of the number of times the respective packet has been retransmitted;

program code for incrementing a first counter in response to receipt of each one of said plurality of data packets that is an originally received data packet; and

program code for incrementing said first counter in response to receipt of each one of said plurality of data packets that is a retransmitted packet and identified as a missing packet;

program code responsive to receipt of each one of said plurality of received packets that is a retransmitted packet and identified as a missing packet for adding to a second counter said retransmission count value contained within the respective retransmission count field; and

program code generating a loss value indicative of a reception characteristic of said receiver as a function said first and second counters.

19. Apparatus for generating a loss value indicative of the ability of the receiver within a multicast data distribution group to receive multicast data packets, said apparatus comprising:

means for receiving a plurality of data packets of a multicast session, wherein each one of said packets includes a retransmission count value within a retransmission count field, said retransmission count value being indicative of the number of times the respective packet has been retransmitted;

means for incrementing a first counter in response to receipt of each one of said plurality of data packets that is an originally received data packet; and

means for incrementing said first counter in response to receipt of each one of said plurality of data packets that is a retransmitted packet and identified as a missing packet;

means responsive to receipt of each one of said plurality of received packets that is a retransmitted packet and identified as a missing packet for adding to a second counter the retransmission count value contained within the respective retransmission count field; and

means for generating a loss value indicative of a reception characteristic of said receiver as a function said first and second counters.

20. A method of operation at a receiver in a multicast data distribution group, said method comprising:

receiving at said receiver a plurality of multicast data packets of a multicast session, wherein each one of said packets includes a retransmission count within a retransmission count field, said retransmission count being indicative of the number of bytes contained in the the respective packet multiplied by the number of times the respective packet has been retransmitted;

in response to receipt of each one of said plurality of multicast data packets adding to a retransmission counter said retransmission count to produce a retransmission counter value in the event the respective received packet is a retransmitted packet and the respective received packet is identified within the receiver as a missing packet; and

generating a loss value indicative of a reception characteristic of said receiver as a function of said retransmission counter value.

21. The method of claim 20 wherein said method further includes the step of adding to an original packet counter a value indicative of the number of bytes contained in each one of said plurality of received packets to produce an original packet counter value in response to receipt of each received packet that is first received as a result of a packet transmission from a sending node or as a result of a packet retransmission from a repair head and wherein said generating step comprises the step of generating said loss value as a function of said retransmission counter value and said original packet counter value.

22. The method of claim 21 wherein said step of generating said loss value comprises the step of dividing said retransmission counter value by said original packet counter value.

23. The method of claim 20 further comprising the step of dissociating said receiver from said multicast data distribution group in the event said loss value exceeds a specified threshold value.

24. The method of claim 20 further comprising the step of transmitting from said receiver a message indicative of congestion at said receiver in the event said loss value exceeds a specified threshold value.