Computers often communicate over a network using asymmetrical communications protocols. For example, in the Asymmetrical Digital Subscriber Line (ADSL) protocol, the downstream bandwidth is typically larger than the upstream bandwidth. As a result, the downstream transmission rate, or the rate at which information is communicated from another network element to the subscriber, is typically higher than the upstream transmission rate, or the rate at which information is transferred from the subscriber to another network element.
Network elements may communicate with one another by transferring packets of information over the network. A source network element packetizes information into one or more packets and then communicates the packets over the network toward a destination network element. Depending on the transmission protocol used, the destination network element may send acknowledgment messages to the source network element indicating that the destination network element successfully received the information packets. The Transmission Control Protocol (TCP) is one example of a protocol that supports the transfer of acknowledgment messages.
Subscribers to network services typically execute multiple applications at the customer premises, and each of those applications may use a transmission protocol that supports acknowledgment messages. Applications downloading information from other network elements may need to send acknowledgment messages to the sending network element to confirm the proper receipt of information. The sending network element may delay communicating additional information to the subscriber until it receives the acknowledgment messages. At the same time, the same application or another application executed at the subscriber's premises may seek to upload other information to a network element. Transmission of this information can temporarily delay communication of the acknowledgment messages, resulting in a delay in the receipt of information downloaded from the network element awaiting those acknowledgment messages. For example, in both the upstream and the downstream directions, the information packets and the acknowledgment messages may become interleaved. In the upstream direction, the subscriber typically transmits one information packet, one acknowledgment message, one information packet, one acknowledgment message, and so on. In the downstream direction, the subscriber typically receives one information packet, one acknowledgment message, one information packet, one acknowledgment message, and so on. The interleaving of the information packets and the acknowledgment messages can delay the transmission of the acknowledgment messages where the upstream bandwidth is saturated with information packets. The subscriber's delay in sending the acknowledgment messages can result in the network element receiving those acknowledgment messages at a slower rate, which causes that network element to transmit information to the subscriber at a slower rate. As a result, the transmission rates in the upstream and downstream directions typically equalize. The actual downstream transmission rate achieved by the subscriber is usually at or near the slower upstream transmission rate. The subscriber is unable to take advantage of the higher transmission rate in the downstream direction.