Reliable multicast transport protocol

• US 20090006641A1
• Filed: 06/28/2007
• Published: 01/01/2009
• Est. Priority Date: 06/28/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Gemmell, David James, Yaqoob, Asad
• Granted Patent: US 8,612,617 B2
• Time in Patent Office: Days
• US Class Current: 709/231
• CPC Class Codes: H04L 12/1868 Measures taken after transmission, e.g. acknowledgments
• CPC Class Codes: H04L 12/1886 with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains
• CPC Class Codes: H04L 12/1895 for short real-time information, e.g. alarms, notifications, alerts, updates

Abstract

A semi-reliable multicast transport protocol uses multiple channels for communication between a server and multiple client devices. A join channel allows the sever to negotiate with client devices to join and exit a transmission session. A communication channel allows the server to communicate with client devices about a status of the transmission session. A polling channel initiated by a content transfer protocol, which runs on top of the transport protocol, transmits polling queries received from the content transfer protocol, receives client device responses to the polling queries, and passes the client device responses to the content transfer protocol. A data channel transmits data to client devices over a network.

Claims

1. A semi-reliable multicast transport protocol for use in a computer system comprising

a join channel for negotiating with client devices to join and exit a transmission session;

a query channel for communicating with client devices about a status of the transmission session;

a polling channel initiated by a content transfer protocol that transmits polling queries received from the content transfer protocol, receives client device responses to the polling queries, and passes the client device responses to the content transfer protocol; and

a data channel for transmitting data to client devices.

2. The protocol of claim 1 further comprising an acknowledgement message generated by a single representative client device in response to receipt of data packets, wherein the acknowledgement message includes a cumulative identification of all data packets received up to present by the single representative client device.

3. The protocol of claim 1 further comprising

a source path message providing current protocol values;

an acknowledgement message generated by a single representative client device in response to receipt of the source path message; and

a delay period implemented upon generation of the source path message to provide a window of time to transmit the acknowledgement message.

4. The protocol of claim 1 further comprising

a round trip time query of client devices;

and

a selection criteria for a single representative client device as a sender of acknowledgement messages based upon a longest response time from one of the client devices to the round trip time query.

5. The protocol of claim 1 further comprising a buffer window that provides data packets for retransmission in response to negative acknowledgement messages received during a period and prevents resending of data packets in response to negative acknowledgement messages received after expiration of the period.

6. The protocol of claim 1 further comprising a buffer criteria that provides data packets for retransmission in response to negative acknowledgement messages requesting missing data packets originally transmitted after a cut-off time and prevents resending of data packets in response to negative acknowledgement messages requesting data packets sent before the cut-off time.

7. The protocol of claim 1 further comprising

a negative acknowledgement message used by client devices to indicate that packets of data were not received in a transmission cycle;

and

a random back-off period calculated for each client device to delay the negative acknowledgement message of each client device in a staggered fashion to reduce possible congestion in transmission of multiple negative acknowledgement messages.

8. The protocol of claim 7 further comprising a negative acknowledgement confirmation message that triggers cancellation of the negative acknowledgement message in one or more client devices if the negative acknowledgement confirmation message indicates receipt of an earlier negative acknowledgement message directed to a same data packet not received by the one or more client devices.

9. The protocol of claim 1 further comprising a cancellation trigger for a negative acknowledgement message in one or more client devices if repair data is received by the one or more client devices that corresponds to a same original data packet not received by the one or more client devices before the negative acknowledgement message is transmitted.

10. The protocol of claim 1 further comprising

a negative acknowledgement suppression scheme that suppresses immediate negative acknowledgement messages from all client devices except a single representative client device;

a negative acknowledgement confirmation message that includes a data loss report from the single representative client device; and

a negative acknowledgement suppression waiver for a particular client device that allows the particular client device to send an immediate negative acknowledgement message when, upon comparison of a local loss rate by the particular client device with the data loss report, a finding is that the local rate is worse than the data loss report.

11. The protocol of claim 10, wherein a selection of the single representative client device is updated to be the particular client device with the worse local loss rate.

12. A reliable multicast transmission system comprising

a transport protocol layer further comprising

a join channel for negotiating with client devices to join and exit a multicast transmission session;

a query channel for communicating with client devices about a status of the multicast transmission session;

a polling channel that transmits polling queries and client device responses to the polling queries; and

a data channel for transmitting a data file to client devices; and

a content transfer protocol layer further comprising

a data management function that identifies the data file for the multicast transmission session and provides the data file to the transport protocol layer in a form suitable for transmission; and

a polling management function that generates the polling queries to monitor reliability of data transmissions by the transport protocol layer, passes the polling queries to the transport protocol layer for transmission to the client devices, and receives responses to the polling queries by the client devices from the transport protocol layer.

13. The system of claim 12, wherein the polling queries ask the client devices for a number of blocks of the data file being transmitted that the client devices have yet to receive.

14. The system of claim 13, wherein the data management function further provides non-sequential access to blocks of the data file to provide only blocks of the data file that the client devices have yet to receive.

15. The system of claim 13, wherein the data management function further removes duplicate block requests to create a single list of blocks to access for transmission.

16. The system of claim 15, wherein when removing duplicate block requests, the data management function begins with blocks requested by an oldest-joining client device and then merges only blocks requested by other client devices that joined the transmission session within a set time period of the oldest-joining client device.

17. The system of claim 12, wherein the data management function guarantees integrity of the data file during the transmission session.

18. A method in a computer system for providing reliable multicast transmissions comprising

negotiating with client devices to join and exit a transmission session;

communicating a query to client devices requesting a status of the transmission session;

receiving a polling query initiated by a content transfer protocol;

transmitting the polling query to the client devices;

receiving responses to the polling query from the client devices;

passing responses to the polling query to the content transfer protocol; and

transmitting a data file to the client devices.

19. The method of claim 18 further comprising providing non-sequential access to blocks of the data file to provide only blocks of the data file that the client devices have yet to receive.

20. A computer-readable medium having computer-executable instructions for performing a computer process implementing the operations of claim 18.