Reliable multicast transmissions using forward error correction and automatic retransmission requests

Multicasting over a network allows a sender to distribute data to multiple receivers. The sender simply sends the data in question to a pre-determined multicast address, and all receivers interested in this data can listen for it. Multicasting is based on an unreliable transport. A data packet sent by the sender may or may not reach an interested receiver and packets received may be out of order. For some type applications, such as audio or video multicasting, this may be acceptable. However, for other type of applications, such as file distribution and monitoring, the loss of data is unacceptable. There are many ways to deal with providing reliable delivery of data in a multicasting environment. The simplest technique is for each receiver to send ACKs or NACKs to the sender regarding each packet it received or do not receive, causing the sender to retransmit any loss packets. Unfortunately, if there is large pool of receivers, these ACK/NACKs can easily overwhelm the sender causing a feedback implosion at the sender. We proposed a multicasting system based on a class of forward error correction (FEC) codes called Reed-Solomon codes to provide redundancy which may allow the receiver to re-construct lost packets based on received packets. In the event that the receiver does not have enough packets to re-construct lost packets, the receiver will ask the sender for some additional packets in order to re-construct all the source packets. This paper describes a design and implementation of a system that provides reliable multicasting based on forward error correction and automatic retransmission requests.