TCP, Transmission Control Protocol

The most commonly-used protocol in the IP stack, hence the tendency to call it "TCP/IP"

Provides bidirectional, sequenced, reliable delivery of data between endpoints

It does this by adding quite a bit more information to the packet header:

• source and destination port numbers (like UDP)
• sequence and acknowledgement numbers
• window size (for regulating data flow)
• flags to signal packet type and usage

A TCP connection is uniquely identified by the tuple

(source IP, source port, destination IP, destination port)

All packets whose components make the same tuple belong to the same connection

Internally, the system has to keep and track lot more state about a TCP connection, including the sequence numbers and round-trip-time statistics on connections

TCP header (addition to IP header):

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