Reliable Delivery of Multi-Cast Conferencing Data

Abstract

Conferencing data is reliably delivered to computer systems participating in a hierarchically arranged multi-cast conferencing session. When a child computer system does not receive a multi-cast packet (e.g., an IP multi-cast packet), the child computer system sends a negative acknowledgment to a parent computer system. In response, the parent computer system re-transmits conferencing data that was contained in the multi-cast packet to the child computer system. Conferencing data can be re-transmitted to the child computer system via uni-cast (e.g., TCP). Accordingly, conferencing data that is not received or that is damaged via multi-cast can be repaired via uni-cast. Computer systems can join an existing multi-cast conference session without having to communicate with the root computer system. The root computer system adjusts a multi-cast send rate to compensate for changed network conditions.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims benefit to U.S. patent application Ser. No. 10 / 436,613 filed on May 13, 2003.BACKGROUND OF THE INVENTION [0002] 1. The Field of the Invention [0003] The present invention relates to network communication technology, and more specifically, to reliable delivery of multi-cast conferencing data. [0004] 2. Background and Relevant Art [0005] Computer networks have enhanced our ability to communicate and access information by allowing one computer or device (hereinafter both referred to as a “computing system”) to communicate over a network with another computing system using electronic messages. When transferring an electronic message between computing systems, the electronic message will often pass through a protocol stack that performs operations on the data within the electronic message (e.g., packetizing, routing, flow control). The Open System Interconnect (“OSI”) model is an example of a networking framework for i...

AI Technical Summary

Benefits of technology

[0014] On the other hand, when the parent computer system is not the root computer system, the parent computer system can identify a uni-cast mechanism. Thus, conferencing data can be re-transmitted to a child computer system via uni-cast when it is indicated that a multi-cast packet is not received. Accordingly, embodiments of the present invention can more reliably deliver conferencing data through recovery via connection-oriented protocols, while still realizing potential bandwidth savings and reduced latency associated with multi-cast protocols. Further, embodiments of the present invention allow both multi-cast capable computer systems and computers that are not multi-cast enabled to participate in the same conferencing session. Multi-cast capable computer systems can participate in the conferencing session via multi-cast and computers that are not multi-cast enabled can participate in the conferencing session via uni-cast.

[0015] In some embodiments, a parent computer system invites a child computer system to join an existing multi-cast conference session. The parent computer system access a multi-cast address for the multi-cast conference session and transmits a multi-cast invite message, including at least the multi-cast address, to the child computer system. In response to the multi-cast invite, the child computer system sends a multi-cast status message indicating to the parent computer system the capability to receive multi-cast packets. In response to the multi-cast status message, the parent computer system sends a next multi-cast sequence number to the child computer system. The next multi-cast sequence number indicates the multi-cast sequence number that is to be associated with the next multi-cast packet received at the child computer system. Accordingly, the child computer system can dynamically join an existing multi-cast conference session without significantly impacting other computer systems already participating in the existing multi-cast conference session.

[0016] From time to time, a root computer system can adjust a current send rate for multi-cast packets. When the root computer system's immediate child computer systems acknowledge reception of a sequence of multi-cast packets within a specified period of time, a current send rate can be increased. On the other hand, when the immediate child computer systems do not acknowledge reception of a sequence of multi-cast packets within a specified period of time (e.g., as a result of network congestion or latency), the send rate of multi-cast packets can be decreased. Accordingly, a root computer system can adjust a send rate to compensate for changes in the transmission characteristics (e.g., available bandwidth and latency) of networks used to deliver multi-cast packets.

Problems solved by technology

Maintenance and transfer of state information consumes computing system resources (e.g., system memory), consumes network bandwidth, and potentially increases network latency.

In an electronic conference with a number of intermediate and leaf computing systems the bandwidth consumed by transferred state information can be relatively large.

However, since multi-cast protocols are typically not connection-oriented, multi-cast protocols do not provide any reliable messaging features (e.g., end-to-end error recovery, resequencing, flow control, etc).

Thus, when multi-cast data is lost or damaged there is little, if anything, that can be done to recover the lost or damaged data.

This is unfortunate, since lost or damaged conferencing data can significantly reduce the usefulness of an electronic conference.

Further, since multi-cast conferencing data is transmitted to every computer system, lost or damaged multi-cast conferencing data can potentially affect every intermediate and leaf computing system participating in the electronic conference.

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