Network Administration

In today’s world, network technologies have become one of the most important infrastructures enabling communication among individuals and institutions. Now, not only computers but also smartphones, tablets, smart home systems and even industrial machines are connected to the internet. According to research, the number of internet-connected devices worldwide is expected to reach 50 billion by 2025. This development further underscores the critical role networks play in our lives.

Networks are structures that enable data exchange and consist of specific components. These components can be grouped under three main categories:

End devices are the devices directly accessed by users on the network. These devices communicate via IP addresses and perform the core functions of the network.

Examples of end devices include:

• Computers (desktops, laptops, servers)
• Smartphones and tablets
• Network printers
• IP cameras and security systems
• VoIP phones
• Smart home systems (thermostats, smart lights, etc.)

These devices serve as the starting point or destination of data within the network.

For example, an employee connecting to a company server or a smartphone accessing the internet via Wi-Fi are instances of end device usage.

Intermediary devices are responsible for routing and transmitting data across the network.

Devices in this category include:

• Routers: Devices that direct data packets between networks.
• Switches: Devices that optimize data transmission between devices within the same network.
• Firewalls: Devices that monitor incoming and outgoing traffic to ensure security.
• Access Points: Devices that enable wireless devices to connect to the network.

For example, in a company office where multiple computers and printers share the same network, a switch (switch) is used to connect these devices. If the company needs to secure its internet connection, a firewall (firewall) is implemented.

This component determines how data is physically transmitted across the network. Transmission media define the method by which data is carried and can be of three different types:

• Copper Cables: Transmit data using electrical signals. Examples include Ethernet cables (UTP, STP).
• Fiber Optic Cables: Transmit data using light signals, offering high speed and long-distance advantages.
• Wireless Transmission: Enables data transmission through electromagnetic waves. Technologies such as Wi-Fi, Bluetooth, and 4G/5G are used for wireless communication.

^{What is End Device}

Networks are classified into different categories based on their size, purpose, and coverage area.

A LAN is a network type that connects devices within a small area. It is commonly used in homes, offices, schools, and small businesses.

Characteristics:

A WAN is a larger network that connects multiple LANs. For example, the internet is a massive WAN.

Characteristics:

^{What Is WAN? LAN vs. WAN -} Huawei

In a robust network design, the following four elements must be considered:

• Ensures the network continues to operate even when a problem occurs.
• Prevents network failure through redundant connections and routing protocols.

• The network must be designed to accommodate an increasing number of users.
• Large-scale enterprise networks should not experience performance degradation when new devices are added.

• Voice, video, and data traffic on the network must be prioritized.
• For example, QoS technology is used to ensure uninterrupted video conferencing.

• Data confidentiality, integrity, and availability must be ensured.
• Security measures such as firewalls, VPNs, and IDS/IPS must be implemented.

Network technologies are continuously evolving and adapting to new trends:

• Bring Your Own Device (BYOD): Allows employees to use their personal devices in the workplace.
• Cloud Computing: Enables storage of data on internet-based systems rather than physical servers.
• Smart Homes and IoT (Internet of Things): Systems where devices are interconnected and capable of automated data exchange.
• 5G and Wireless Networks: Enhance network communication efficiency by providing higher speeds and lower latency.

Network communication is not achieved merely by connecting hardware; it requires devices to exchange data according to specific rules. Computers, phones, and other network devices use certain protocols and models to communicate with each other. This section will examine the importance of network protocols, reference models, and data encapsulation processes.

For networks to function properly, specific rules must be established. These rules define how communication occurs and ensure devices can operate compatibly. The rules created by network protocols consist of the following components:

• Message Encoding: The process of converting information into an appropriate format for transmission. Data is transformed into electrical signals, radio waves, or light signals for transmission.
• Message Formatting and Encapsulation: Ensures data is transmitted in a standardized format. Headers and control information are added to enable routing and error detection.
• Message Size: The size of each message during data transfer must be kept within a defined limit. For example, Ethernet frames have a specified maximum size.
• Message Timing: Controls the flow of data. It includes components such as flow control, timeout periods, and access methods.
• Message Delivery Options: Determines how messages are delivered using methods such as unicast (one-to-one communication), multicast (communication to a specific group), and broadcast (communication to all devices).

^{Protocols Requirements}

For two or more devices on a network to communicate seamlessly, they must adhere to a defined set of rules. This entire set of rules is called a protocol. Protocols are standards that determine how messages are sent, received, and interpreted.

Some commonly used protocols in network communication include:

• Ethernet (IEEE 802.3): Defines data transmission for wired networks.
• Wi-Fi (IEEE 802.11): Specifies standards for wireless network connections.
• TCP/IP (Transmission Control Protocol / Internet Protocol): The foundational protocol suite of the internet, enabling global device communication.
• HTTP/HTTPS (Hypertext Transfer Protocol): Used for displaying web pages.
• DNS (Domain Name System): Translates domain names into IP addresses.
• DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses to devices.

These protocols determine how devices create, transmit, and interpret data packets.

^Protocols

Network communication does not occur through a single protocol. Various protocols work together to form a more comprehensive and functional structure. These groups of protocols are called protocol suites.

1. TCP/IP Protocol Suite: Forms the foundation of the internet and is divided into four main layers:

2. OSI Protocol Suite: This seven-layer model was developed to ensure interoperability between systems from different manufacturers. The OSI model provides a structure covering all stages from physical connections to the application level.

3. AppleTalk: A protocol suite developed by Apple, specifically designed for Mac devices. It enabled communication among Macintosh computers during the pre-IP era.

4. Novell NetWare: A network operating system protocol suite developed by Novell, based on IPX/SPX protocols. It was widely used in LAN-based networks.

^{Network Protocols -} Cisco

Various models have been developed to better understand how communication occurs in networks. The most widely known are the OSI Model and the TCP/IP Model.

^{OSI vs TCP/IP -} Cisco

The OSI model provides an open standard by dividing network communication into seven layers:

1. Physical Layer: Defines electrical signals, cables, and physical connections. Copper cables, fiber optic cables, and wireless signals operate at this layer.
2. Data Link Layer: Enables devices to identify and communicate with each other using MAC addresses. Switches operate at this layer.
3. Network Layer: Handles IP addressing and routing. Routers operate at this layer.
4. Transport Layer: Includes TCP and UDP protocols that ensure reliable data delivery. Manages flow control and error correction mechanisms.
5. Session Layer: Initiates, manages, and terminates communication sessions. Used in systems such as remote desktop applications.
6. Presentation Layer: Performs operations such as data encryption, compression, and formatting. For example, SSL/TLS protocols operate at this layer.
7. Application Layer: Includes protocols directly interacted with by users, such as HTTP, FTP, and SMTP.

^{OSI Model - Cisco}

The TCP/IP model, which forms the foundation of the internet, has a simplified structure consisting of four layers:

1. Network Access Layer: Responsible for physical connections and data transmission. Includes technologies such as Ethernet and Wi-Fi.
2. Internet Layer: Performs IP addressing and routing. Routers handle data forwarding at this layer.
3. Transport Layer: Ensures reliable data delivery. Includes protocols such as TCP and UDP. TCP is connection-oriented and prevents data loss, while UDP is faster but does not provide error correction.
4. Application Layer: Contains protocols that directly interact with user applications. Services such as DNS, HTTP, and FTP operate at this layer.

While the OSI model provides a theoretical framework, the TCP/IP model is an active system used in the real world. The TCP/IP model is more widely used than OSI because it was developed as the foundational protocol suite of the internet.

^{TCP/IP Layers -} Cisco

Before data is transmitted across a network, it undergoes a process called encapsulation. During this process, each layer adds its own header to ensure smooth communication. The data encapsulation process consists of the following stages:

1. Application Layer: The data sent by the user is received.
2. Transport Layer: The data is divided into segments and TCP or UDP headers are added.
3. Network Layer: IP addresses are added, and the data is packaged into packets.
4. Data Link Layer: MAC addresses are added to form a frame.
5. Physical Layer: The data is converted into bits for transmission.

On the receiving device, this process is reversed to restore the data to its original form.