# Reliable transmission of [[Transmission Control Protocol (TCP)|TCP]] messages [[Transmission Control Protocol (TCP)|TCP]] uses sequence numbers with acknowledgements to increase the reliability of messages. If a message was corrupted or not received it will resend that [[Segment|segment]]. ![[Automatic Repeat Request (ARQ)]] The most basic implementation of [[Automatic Repeat Request (ARQ)|ARQ]] stops and waits to check if the message was received. ![[Stop and wait ARQ]] In [[Transmission Control Protocol (TCP)|TCP]] the acknowledgement header is set to be the next sequence number the receiver is waiting to get. There are different ways you can handle unacknowledged messages. ![[Go back N]] ![[Fast retransmit]]