Method and apparatus for dynamically selecting timer durations
A data communication system dynamically selects timer durations to ensure delivery of data at a desired bit rate. A source or proxy source transmits data, such as streaming media, to a destination according to a dynamic bit rate timer, where the timer regulates the transmission frequency and/or the packet size of the data being transmitted. The timer dynamically adapts the transmission frequency or packet size according to the relative positioning of data pointers in a buffer and effectively changes the rate of data delivery. In this way, data may be delivered at the desired average bit rate to the destination despite network capacity fluctuations.
1. A network switch for transmitting streaming data to a plurality of destinations, each of the destinations having a separate streaming connection to the network switch, the network switch comprising:
a receiver to receive a unicast stream at a desired rate;
a circular buffer having a first threshold and a second threshold to buffer the unicast stream and to split the unicast stream into multiple unicast streams;
a timer to determine a transmission rate based in part on a desired rate, an average bit rate for each connection, and a maximum segment size (MSS) for each connection, the transmission rate regulating transmission of the multiple unicast streams to multiple client destinations;
a stream-processing module in communication with the timer and the buffer, the stream-processing module to
generate a data pointer to a next segment of streaming data in the buffer for each of the destinations,
monitor utilization of the buffer relative to the first and second thresholds for each connection, and
send timing signals to the timer; and
wherein the timer further to increase the transmission rate for a particular connection if buffer utilization for that connection falls below the first threshold, and to reduce the transmission rate for a particular connection if buffer utilization for that connection exceeds the second threshold.
2. The network switch of claim 1 , wherein the timer dynamically determines the transmission rate according to the relative positioning of data pointers to streaming data in the circular buffer.
3. The network switch of claim 2 , wherein the stream-processing module updates the relative position of data pointers associated with each destination after a transmission event.
4. The network switch of claim 1 , wherein the timer adjusts the transmission rate of streaming data to the destination midstream based in part upon usage of the buffer by each destination.
5. A method comprising:
receiving from a source a unicast stream at a Streaming Media Accelerator (SMA) enabled switch at a desired rate;
buffering the unicast stream at the SMA enabled switch with a circular buffer having a first threshold and a second threshold;
splitting the unicast stream at the SMA enabled switch into multiple unicast streams;
transmitting the multiple unicast streams to multiple client destinations at a transmit rate upon receipt of timer events, each client destination having a separate connection with the SMA enabled switch and wherein the transmit rate is determined based at least in part on the desired rate, an average bit rate for each connection, and a Maximum Segment Size (MSS) for each connection;
monitoring utilization of the circular buffer relative to the first and second thresholds for each connection;
upon recognizing that buffer utilization falls below the first threshold for a particular connection, increasing the transmit rate for that connection; and
upon recognizing that buffer utilization exceeds the second threshold, reducing the transmit rate for that connection.
6. The method of claim 5 , wherein a timer event is an expiration of a timer interval.
7. The method of claim 5 , wherein a timer event is reception of an acknowledgment packet from the client destination.
8. The method of claim 5 , wherein increasing the transmit rate comprises multiplying the transmit rate by a timer multiplier.
9. The method of claim 5 , wherein data is received from the source via a packet switched connection.
10. The method of claim 5 , wherein the connection is a TCP/IP connection.
11. The method of claim 5 , wherein the source is a server.
12. The method of claim 5 , wherein the source is a network switch.
13. The method of claim 5 , wherein the destination is a client computer.
14. The method of claim 5 , wherein the unicast stream is streaming media.