There is an ongoing explosion of interactive Internet

applications.

By nature, these applications require responsive client-server data exchange

and lossless, in-order delivery.

In previous work, we have shown that a hybrid FEC-ARQ protocol which

combines sending original data packets with forward error correction (FEC)

packets is effective in reducing the latency caused by retransmissions

of lost packets.

However, the prior scheme only sends FEC packets when there are no

original packets pending transmission.

In this paper, we further expand the investigation of the

hybrid FEC-ARQ protocol

and show that sometimes, the transmission latency can be further reduced by

preempting original data packets with FEC packets.

We have formulated the decision of whether to send

new original data packets, FEC packets, or resend original data packets

as a transmission policy.

An optimal transmission policy is selected to minimize the

delay experienced by the application subject to a constraint on

the amount of waste.

By using this optimal policy,

we significantly improve the delay performance over

straightforward FEC schemes while controlling the amount of waste due to FEC.

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