Anyone working on a network should have a solid understanding of the protocols that traverse the network. Although there are hundreds of protocols, this chapter focused on the functions of the transport layer of the OSI model, specifically the two predominant protocols, TCP and UDP.

We evaluated TCP, a connection-oriented protocol. You now understand that, in order to achieve reliability, TCP sequences and acknowledges every octet. We saw that, in addition to transporting data, TCP monitors the transmission and provides not only flow control, but congestion control as well. So that you grasped how TCP is so effective in providing reliable data transport, we took a closer look at the header, along with the eight control flags. 

Along with TCP, we looked at the other transport layer protocol, UDP, which ensures fast transportation of time-sensitive data and protocols such as DHCP and DNS. We discovered the four-field UDP header, which provides enough information to deliver data with no additional overhead.

Now that you have a solid understanding of TCP, the next step is to gain a better understanding of how TCP establishes and tears down a connection in more detail. In the next chapter, we will step through the process of starting a TCP conversation and examine the TCP three-way handshake and resultant socket creation. We will look at the packet exchange and have a closer look at the TCP options. Finally, we'll study how TCP ends data transmission by exchanging FIN packets.