[1] In the context of computer networks, the signal is typically a data packet.
End-to-end delay is the length of time it takes for a signal to travel in one direction and is often approximated as half the RTT.
RTT is a measure of the amount of time taken for an entire message to be sent to a destination and for a reply to be sent back to the sender.
Such long fat networks require a special protocol design.
close to 1 makes the weighted average immune to changes that last a short time (e.g., a single segment that encounters long delay).
close to 0 makes the weighted average respond to changes in delay very quickly.