Basics Of Computer Networking: Communication Protocols
This blog post was last updated on May 31, 2024
It was originally published on September 15, 2022
In our previous blog post on computer networking basics, we talked about how the Internet and the World Wide Web are not controlled or regulated by anyone. In such a largely unregulated digital environment,
how is universal information exchange made possible,
how are liabilities and vulnerabilities limited, and
how does authentication work?
In simple terms, how are devices connected to a network of networks able to communicate with each other?
Unlike in your kitchen where water streams down the faucet as soon as you open it, in a computer network, data cannot freely flow all the time. Meaningful data flow can occur among networked devices only if transmitted data is sequenced and synchronized in great detail. And this is where communications protocols play a pivotal role.
In this blog post, we will discuss communication protocols, their different types, and the role they play in computer networking.
What Is A Communication Protocol?
Communication protocols are sets of formal rules that describe how digital messages must be formatted. They are vital in networking and telecommunication systems because they bring uniformity in the sending and receiving of digital messages. Therefore, communication protocols are necessary for the exchange of messages in or between computing systems.
Before networked devices can share information, they need to agree on various aspects of communication. And the communication protocols define these rules that govern data transmission. The communication protocols are usually constructed based on the Open System Interconnect (OSI) model (which we cover briefly in the following section) with the communication functions divided into protocol layers.
Communication protocols are implemented in hardware and software and usually cover authentication, error detection, correction, and signaling. Additionally, communication protocols may describe the syntax, semantics, and synchronization of the communications. The following are common properties that the protocols include:
Packet size
Transmission speed
Error detection and correction
Synchronization techniques
Address mapping and formatting
Routing information
Acknowledgment processes
Flow control
Before we dive further into communication protocols, we need to understand the basics of the OSI model. So, let’s take a quick look at it.
The OSI Model
The Open Systems Interconnection (OSI) model is a conceptual framework that enables computer systems to communicate with each other. It is a universal standard for networking that standardizes the internal structure and technology for communication functions in both computer systems and telecommunications.
The OSI model divides the communication process into seven distinct layers, each stacked sequentially. Each layer performs a specific function and interacts with the layers directly above and below it, ensuring smooth and efficient communication.
The seven layers of the OSI model are:
Layer 1: Physical layer
Layer 2: Data link layer
Layer 3: Network layer
Layer 4: Transport layer
Layer 5: Session layer
Layer 6: Presentation layer
Layer 7: Application layer
For example, the Internet Protocol (IP), which is responsible for routing data by indicating the source and destination of data packets, enables communication between different networks, making it a network layer (Layer 3) protocol.
Another example is the Transmission Control Protocol (TCP), which ensures the reliable transport of data packets across networks. Since it manages the smooth delivery of data, TCP is classified as a transport layer (Layer 4) protocol.
How Do Communication Protocols Work?
Network protocols work by taking large processes or data and breaking them down into small bits units called packets or frames. This occurs at every level of the network as conceptualized in the OSI model. Each packet or frame is made up of a header- containing information about the source, destination, sequence number, protocol type, and other parameters, and a payload- containing the main data or message. The header information enables the network devices and systems to interpret, process, and route the packet or frame to the destination.
When data is sent, a bit of information is added by each layer, starting from the application layer and moving down to the physical layer. When the data reaches the physical layer, the data is transmitted over a physical or wireless medium, such as a cable, a radio wave, or an optical fiber to the receiving device.
For example, say you start with application data. It is first passed down to the next layer, i.e. the transport layer, where a TCP header containing the source and destination port numbers, sequence numbers, etc. are added. The data then moves to the network layer, where the IP header, which contains the source and destination IP addresses, is added. Then it is passed to the data link layer, where a header, as well as a trailer, are added. The header contains the source and destination MAC addresses and the trailer contains some error-checking information that the destination device can use to ensure that the data has been received correctly. After that, the data is sent to the physical layer, which physically transmits the data to the destination.
This process of sequentially adding data is called encapsulation. At each stage of encapsulation, the data has a different name. In the transport layer, after the relevant information has been added, the data is called a segment. After network layer information is added, it is called a packet. Once the data link information is added, it is called a frame.
After the transmitted data has been received, the receiving device decapsulates the data. The decapsulation occurs in the reverse order, starting from the MAC address in the frame. It is processed further only if the device MAC address matches the destination MAC address in the frame. Then the device checks the IP information of the packet, which will be processed further only if the IP address matches the destination information in the packet. After this, the transport information is read and the application data is sent to the receiving application.
Importance of Communication Protocols
Communication protocols are important because they provide a common way to exchange information across networks, applications, and devices. Without these protocols, there would be no way to ensure data is sent and received accurately.
In addition, communication protocols also provide mechanisms for error detection, correction, encryption, authentication, and quality of service, ensuring the reliability and security of the data transmission.
Last but not least, communication protocols enable interoperability and compatibility, making it possible for different devices and systems that use different hardware, software, and languages to communicate and exchange information. This provides a great benefit for network device users since it significantly mitigates the risks of vendor lock-in or future communications obsolescence.
Who Makes Network Protocols?
Network protocols are based on industry standards created by various networking and information technology organizations. The following is the list of organizations that have defined and published network protocols:
The Institute of Electrical and Electronics Engineers (IEEE)
The Internet Engineering Task Force (IETF)
The International Organization for Standardization (ISO)
The International Telecommunications Union (ITU)
The World Wide Web Consortium (W3C)
Types Of Communication Protocols
Although there are thousands of network protocols, all of them can be classified into the following three:
1. Communication Protocols
As mentioned above communication protocols are sets of rules that facilitate communication between different network devices. These protocols are used for a variety of purposes such as transferring files, automating processes, text-based communications, accessing the Internet, etc.
Common communication protocols include:
Internet Protocol (IP) - makes it possible for devices to send and receive data via the internet.
File Transfer Protocols (FTP) - make it possible to transfer files between a client and a server on a network.
Bluetooth Protocols- allow wireless connection between mobile devices over a short range to form a personal area network (PAN).
Instant Messaging & Chat Protocols - make it possible to send messages across the globe efficiently and securely.
Routing Protocols- make communication between routers and other network devices possible.
Automation Protocols- are used to automate different processes in smart buildings, cloud technology, self-driving vehicles, etc.
2. Network Management Protocols
Network management protocols provide the rules for effectively operating a computer network. These protocols define the policies and procedures for monitoring and managing a network to ensure stable communication and performance.
Network management protocols provide vital information such as host availability, packet loss, the health of the connection, etc. Network operators then use this information to troubleshoot network connectivity issues and improve network performance.
Network management protocols apply to all network devices such as routers, switches, servers, computers, etc., and are responsible for establishing and maintaining stable connections between the network devices. They also help network administrators to identify network errors, evaluate the quality of the network connection, and determine how to fix the network issues.
3. Security Protocols
Security protocols are communication protocols that use cryptographic mechanisms to ensure that the network and the data sent over it are protected from unauthorized users. These protocols define the sequence and formats of digital messages including cryptographic elements exchanged between network devices.
Security protocols are instrumental in providing security services such as confidentiality, authentication, and integrity for data transmitted over the network. To achieve this security protocols fulfill the following functions:
Encryption - that protects the data by ensuring that only authorized entities have access;
Authentication - ensures that the devices on a network are who they claim to be;
Transportation - ensure the security of data while it is transmitted from one network device to another.
What Is Transmission Control Protocol/Internet Protocol (TCP/IP)?
The Transmission Control Protocol/Internet Protocol (TCP/IP) is made up of a suite of non-proprietary protocols used to interconnect devices on the Internet as well as on private networks. The TCP/IP protocol suite defines how applications can create channels of communication over the network. It also governs how digital messages are assembled into packets, addressed, transmitted, routed, and reassembled at the destination.
TCP and IP are the main protocols in this suite or collection of protocols. TCP deals with how applications create communication channels, transmit, and receive messages. While IP deals with addressing and routing the messages. TCP/IP makes networks reliable with the ability to recover automatically from device failures, so it requires little to no central management.
The architecture of TCP/IP, similar to that of the OSI model, consists of layers. The four layers of TCP/IP are:
Application layer
Transport layer
Internet layer
Link layer
In the newer version of the model, the link layer has been split into the data link layer and the physical layer. Additionally, the internet layer has been renamed as the network layer. So the newer model of TCP/IP is as follows:
Application layer - The application layer consists of application protocols such as File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), and Simple Mail Transfer Protocol (SMTP).
Transport layer - The most common transport protocols are TCP, and User Datagram Protocol (UDP).
Network layer - Routers and IP operate at the network layer.
Data Link layer - Ethernet and common switches operate the data link layer.
Physical layer - Everything physical such as the ethernet cables and network interface cards (NICs) operates in the physical layer.
Common Network Protocol Examples
Earlier in this blog post, we already mentioned the Internet Protocol (IP) and the File Transfer Protocols (FTP), which are probably the most common network protocols. In addition to them, here are a few more commonly used protocols:
1. Hypertext Transfer Protocol (HTTP)
The World Wide Web functions based on communication between web clients, i.e. browsers, and web servers in the cloud. This communication between client and server happens through the HTTP request/response circle. HTTP is an application layer protocol that is sent over a TCP connection.
The HTTP protocol fetches resources such as HyperText Markup Language (HTML) documents, functioning as the foundation of data exchange on the web. In addition to fetching HTML documents, it can also fetch images and videos or post content to servers.
Hypertext transfer protocol secure (HTTPS) is the secure version of HTTP, which is encrypted in order to increase the security of data transfer.
2. Secure Socket Shell (SSH)
Secure Socket Shell (SSH) is a network protocol that enables users and system administrators to access network devices over an unsecured network. SSH uses a strong password and/or a cryptographic key pair for authentication.
SSH thus allows users to remotely connect to computers or applications and execute commands in a secure way. The SSH protocol is typically used by administrators for executing system management tasks.
3. User Datagram Protocol (UDP)
User Datagram Protocol (UDP) is a communication protocol that facilitates data transfer between network devices. Similar to TCP, UDP also operates in the transport layer and serves as an alternative to TCP where transmissions are time-sensitive and reliability is not as important.
UDP does not formally establish a connection before starting the data transfer, thus speeding up the data transfer. However, this can cause a loss of packets. UDP finds use in voice and video communications since they are time-sensitive and designed to handle some amount of packet loss.
For example, UDP is used for real-time communication such as Voice over Internet Protocol (VoIP) telephony. In this case, UDP is preferred over TCP because some loss in voice quality is preferable to heavily delayed transmission.
Conclusion
There are thousands of communication protocols used all around us and computer networking could not exist without them. For example, right now you are using the Internet Protocol Suite, also called TCP/IP, and the Hypertext Transfer Protocol (HTTP) that are enabling you to connect to the Internet and access the World Wide Web.
Understanding communication protocols is essential for anyone who wants to understand computer networks. Understanding the network protocols, their types, and how they work is essential for effective network administration and security.
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