Codec with network congestion detection and automatic fallback: methods, systems & program products

A computer readable medium storing program instructions, executable on a computer system, for detecting congestion and automatically adjusting bandwidth of a codec in a packet network, the computer system when executing the instructions performs the following steps, comprising:

• establishing a session between end points in a network, each including a codec;
• negotiating a commonly-agreed to codec type between the codecs using ITU-T H.323 protocol;
• periodically generating a “heartbeat” indication as control packets where absence of a control packet is an indication of network congestion where each end point uses the absence of any control packets as an indication of congestion;
• incrementing an error counter when a missing packet is detected;
• comparing the current error count against a slowdown threshold after a selected time interval;
• and
• determining whether or not the codec is already operating at the lowest rate permitted, otherwise re-negotiating packet rate to select a lower bit rate codec to reduce network congestion, if and only if the current error count is larger than a slowdown threshold value.

A method for detecting congestion and automatically adjusting bandwidth of a codec in a packet network, comprising the steps of:

• establishing a session between end points in a network, each including a codec;
• processing session content to produce an encoded or compressed representation of that content, and processing compressed representations of session content to produce replicas of original session content;
• negotiating a commonly-agreed to codec type between the codecs using a session control protocol;
• generating a “heartbeat” indication as control packets where absence of control packets is an indication of network congestion;
• determining the absence of any packets in the session packet flow;
• incrementing an error counter when a missing packet is detected;
• determining whether or not to check the error counter against pre-defined thresholds after a selected time interval;
• comparing the current error count against a slowdown threshold;
• determining whether or not the codec is already operating at the lowest rate permitted otherwise re-negotiating packet rate to select a lower bit rate codec to reduce network congestion, if and only if a current error count is smaller than a slowdown threshold value after the comparing step;
• comparing the error count against a speedup threshold thus determining whether or not the codec is already operating at the highest bit rate permitted, otherwise re-negotiating the packet rate flow to select a higher bit rate codec corresponding to higher session quality, if and only if a current error count is smaller than a speedup threshold value;
• and
• delaying the response of the codec to resumed flow of congestion control packets to minimize thrashing between two codec types for better tracking of long-term trends of network congestion.

A computer readable medium, storing program instructions executable on a computer system, for detecting congestion and automatically adjusting bandwidth of a codec in a packet network, the computer system when executing the instructions performs the following steps comprising:

• establishing a session between end points in a network, each including a codec;
• negotiating a commonly-agreed to codec type between the codecs using ITU-T H.323 protocol;
• generating a “heartbeat” indication as control packets where absence of a control packet is an indication of network congestion;
• determining the absence of any packets in the packet flow;
• incrementing an error counter when a missing packet is detected;
• comparing the current error count against a slowdown threshold after a selected time interval;
• determining whether or not the codec is already operating at the lowest rate permitted, otherwise re-negotiating packet rate to select a lower bit rate codec to reduce network congestion.
• comparing the error count against a speedup threshold determining whether or not the codec is already operating at the highest bit rate permitted, otherwise re-negotiating the packet rate flow to select a higher bit rate codec corresponding to higher session quality, and
• delaying the response of the codec to resumed flow of congestion control packets to minimize thrashing between two codec types for better tracking of long-term trends of network congestion, if and only if the current error count is larger than a slowdown threshold value.