Transmission Control Protocol/Internet Protocol (TCP/IP) is a network communication protocol in which a sender transmits a packet to a receiver, sets a timer in association with the transmission, and waits until a timeout for the receiver's acknowledgement. If the acknowledgement is not received before the timeout, or if an acknowledgement is received but indicates error, the sender retransmits the packet to the receiver.
End-to-end paths between sender and receiver in TCP/IP communications can be a sequence of links, and any of these links can drop packets. Regardless of where the drop occurs though, retransmission in an end-to-end TCP/IP communication can consume bandwidth in every link, from the sender to the receiver.
High packet drop can be exhibited, in some network applications, in the last link or loop to the receiver, or “last mile.” There can be various reasons. For example, channel conditions can be degraded due to weather, radio interference, and other time-varying phenomena. In addition, upgrading to reduce packet loss in the last mile can be costly.