TCP - Transmission Control Protocol

TCP is a utility built on top of IP
TCP was created to solve a problem with IP
- Data over IP is typically sent in multiple packets because each packet is fairly small (2^16 bytes).
- Multiple packets can result in
  - lost or dropped packets and
  - disordered packets
  - thus corrupting the transmitted data
- TCP solves both of these by guaranteeing transmission of packets in an ordered way.
the packet has a header called the TCP header in addition to the IP header.
- TCP header contains information about the ordering of packets, and the number of packets and so on.
TCP needs to establish a connection between source and destination before it transmits the packets, and it does this via a "handshake".
- This connection itself is established using packets where the source informs the destination that it wants to open a connection, and the destination says OK, and then a connection is opened.
- is what happens when a server "listens" at a port - just before it starts to listen there is a handshake, and then the connection is opened (listening starts).
- one sends the other a message that it is about to close the connection, and that ends the connection.

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