Network Protocols

Network Protocols

Learning Objectives

Show understanding of why a protocol is essential for communication between computers Show understanding of how protocol implementation can be viewed as a stack, where each layer has its own functionality. Show understanding of the TCP/IP protocol suite Show understanding of protocols (HTTP, FTP, POP3, IMAP, SMTP, BitTorrent) and their purposes

Protocol Key Terms

What is a Protocol?

Before one computer can communicate with another, there must be a set of agreed rules in place that manage how the communication is to take place. These rules are known collectively as a protocol. To illustrate the need for rules when two or more objects communicate, we will look at some rules used when humans talk to each other. For example, we:

• use sound to send messages
• use a common language that we both understand
• listen when the other person is talking, so we can hear them speak
• speak at a rate that allows us to clearly transmit words and receive them
• have ways of checking that the other person has heard what we have said.

Network Protocols

Similarly to human communication, computers use rules, and these form the protocols that are used for computer communication. Protocols need to specify several aspects of communication, for example:

• the communication medium to be used, such as wired or wireless
• the transmission type, such as duplex or simplex
• whether the handshake is hardware or software in nature
• the method of error checking to be used
• the bit rate
• the character set that will be used.

Common Protocols

The protocols allow messages to be transmitted in a structured, specific manner, so that the receiving device is able to process the data sent from the sending device. Protocols therefore make sure that communication between any two devices is successful. Different communication protocols exist to specify rules for different types of communication, for example:

• Hyper Text Transfer Protocol (HTTP) – handles transmission of data to and from a website
• Simple Mail Transfer Protocol (SMTP) – handles email transmission
• File Transfer Protocol (FTP) – handles transmission of files across a network
• TCP/IP – handles communication over the internet.

The OSI Model

Many types of computer – for example, personal computers, laptops, servers, tablets and smartphones – exist, and they are made by many different manufacturers. As a result, it is important to have standards in place that designers and equipment manufacturers can follow to make sure their products can communicate with others’. The Open Systems Interconnection model (OSI model) was introduced to form standards for computer communication. The model takes the various elements of communication and conceptually separates them into layers. Each layer can be treated individually, and is independent from the others. Each layer contains different protocols and handles a different part of the transmission.

The OSI Model

The OSI model

The layers are numbered and sit one above each other, and can therefore be thought of as a stack. The output from one layer provides the input for the next. Each layer interacts only with the layer directly above it and/or below it, and at the bottom of the stack, the Physical Layer transmits data between the source and destination devices

TCP/IP

Watch the video, then answer the questions on the following slides

Task

Answer these questions on a doc, and upload in Canvas for feedback: Describe the purpose of a protocol stack. Compare the OSI model with the TCP/IP model:

• How many layers does each have?

• Which layers from the OSI model are combined in TCP/IP?

• Why is the TCP/IP model more widely used in real-world networking?

For each layer of the TCP/IP model, explain the purpose, and common protocols used. Choose three application layer protocols (e.g. HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, DHCP). For each one:

• State what the acronym stands for.

• Explain its purpose.

• Give a real-world example of when it is used.