BASICS OF NETWORK
Introduction:The Information and Communication Technology (ICT) revolution has brought significant changes to how organizations operate. In today's networked environment, organizations often require multiple individuals, sometimes located in different places, to input and process data simultaneously. This shift has led to the adoption of computer networking models, replacing the traditional standalone computing approach.
Computer networks connect separate but interconnected computers, greatly enhancing productivity. A key feature of computer networks is their flexibility, allowing data to enter or leave at any point and be processed on any workstation. This unit will provide you with fundamental insights into computer networks, including various network types, their applications, and the different network topologies used in both Local Area Networks (LAN) and Wide Area Networks (WAN). We'll also delve into networking devices and access methods in LAN and WAN environments.
NETWORK CONCEPT AND CLASSIFICATION
Definition of a Computer Network:
A computer network is formed by connecting two or more computers together, enabling them to share resources, applications, and facilitate communication among them. This networked environment can take various forms. Computers in a network can be interconnected using cables, telephone lines, or wireless access points, depending on the specific network setup and requirements.
Components of a Computer Network:
A computer network encompasses various components, including:
1. Network Operating System: Client and server machines run a network operating system that facilitates communication and resource sharing.
2. Cables: These connect different computers and devices within the network, enabling data transmission.
3. Hardware Devices: Network hardware includes bridges, routers, and switches, which manage and direct data traffic efficiently.
4. Wireless Components: In wireless systems, antennas and towers play a crucial role in establishing wireless connections.
5. Firewall: Positioned between the network and the Internet, a firewall provides essential security measures to protect the network from external threats and unauthorized access.
These components collectively form the infrastructure of a computer network, enabling data sharing, communication, and secure operation.
Advantages of Networks
Advantages of Computer Networks:
1. Resource Sharing: Computer networks enable the sharing of programs, equipment, and data among users, regardless of their physical location. This promotes efficient utilization of computational resources.
2. Reliability: Computer networks are essential for applications where reliability is critical, such as military, banking, air traffic control, and nuclear reactor safety. Networks achieve high reliability through redundancy, with data replicated on multiple machines to ensure continued operation in case of hardware failure.
3. Cost Savings: Small computers, like personal computers, offer a favorable price/performance ratio compared to larger mainframes. This cost-effectiveness has led to the adoption of client-server models, where individual users have personal computers, and data is stored on shared file server machines. This approach reduces costs while maintaining performance.
4. Economy: Computer networks allow organizations to economize on hardware and software resources. Instead of equipping each user with a powerful standalone machine, multiple users can share resources like printers, storage, and processing power.
5. Efficient Communication: Computer networks facilitate efficient person-to-person communication, enabling users to exchange information, collaborate on projects, and communicate in real-time. This enhances productivity and teamwork.
6. Scalability: Networks can easily scale to accommodate growing demands. Additional devices, users, or resources can be integrated into the network as needed.
7. Centralized Management: Networks enable centralized management of resources, security, and user access. This simplifies administrative tasks and ensures consistent policies.
8. Data Backup and Recovery: With data replication and backup strategies, computer networks provide a robust framework for data backup and recovery, reducing the risk of data loss.
9. Remote Access: Users can access network resources remotely, providing flexibility and accessibility, especially in today's mobile and remote work environments.
10. Security: Network security measures, including firewalls and encryption, help protect sensitive data and prevent unauthorized access.
11. Scalability: The ability to increase system performance gradually as the workload grows just by adding more processors. Unlike centralized mainframes, where a full system replacement is necessary when capacity is reached, the client-server model allows for the addition of new clients and servers as needed, reducing expenses and disruptions.
12. Communication Medium: A computer network serves as a powerful communication medium connecting users located far apart. Through a computer network, individuals working on the same project, even if they are geographically distant, can collaborate in real time. When one team member makes a change to an online document, others can instantly see the update, eliminating the need to wait for days for a physical letter. This real-time collaboration was previously impossible and significantly enhances teamwork.
13. Increased Productivity: Networks contribute to increased productivity by allowing multiple users to simultaneously access, share, evaluate, and process data. This simultaneous data handling from different locations reduces the time required for tasks, ultimately cutting costs and improving efficiency.
Network Classification
Computer networks come in various types, each designed for specific purposes and characterized by their size, connection type, and functional relationships. Let's explore the classification of computer networks based on these factors:
1. Based on Size:
a. Personal Area Network (PAN):
- Size: Small, typically within a range of a few meters.
- Purpose: Connects devices like smartphones, tablets, and laptops for personal use.
b. Local Area Network (LAN):
- Size: Covers a limited geographical area, such as a single building or campus.
- Purpose: Connects devices within an organization for sharing resources like files and printers.
c. Metropolitan Area Network (MAN):
- Size: Larger than a LAN but smaller than a WAN, covering a city or a large campus.
- Purpose: Connects multiple LANs within a city for high-speed data transfer.
d. Wide Area Network (WAN):
- Size: Spans a large geographical area, often a country or continent.
- Purpose: Connects LANs and MANs over long distances, typically using public or private communication links.
2. Based on Type of Connection:
a. Wired Networks:
- Connection: Physical cables, such as Ethernet or fiber optics.
- Advantages: High reliability and speed.
- Examples: Ethernet LANs, fiber optic backbones.
b. Wireless Networks:
- Connection: Wireless signals, such as Wi-Fi or cellular networks.
- Advantages: Mobility, flexibility, and ease of deployment.
- Examples: Wi-Fi networks, 4G/5G cellular networks.
3. Based on Functional Relationships:
a. Client-Server Network:
- Structure: Clients (devices) request services or resources from servers (centralized systems).
- Purpose: Common in business environments for centralized data storage and management.
b. Peer-to-Peer Network:
- Structure: All devices have equal status and can act as both clients and servers.
- Purpose: Common in small networks for easy sharing of resources like files and printers.
c. Hybrid Network:
- Structure: Combines elements of both client-server and peer-to-peer models.
- Purpose: Offers flexibility by allowing certain functions to be centralized while enabling direct device-to-device communication.
LOCAL AREA NETWORK (LAN) OVERVIEW
Computer networks come in various types, each designed for specific purposes and characterized by their size, connection type, and functional relationships. Let's explore the classification of computer networks based on these factors:
1. Based on Size:
a. Personal Area Network (PAN):
- Size: Small, typically within a range of a few meters.
- Purpose: Connects devices like smartphones, tablets, and laptops for personal use.
b. Local Area Network (LAN):
- Size: Covers a limited geographical area, such as a single building or campus.
- Purpose: Connects devices within an organization for sharing resources like files and printers.
c. Metropolitan Area Network (MAN):
- Size: Larger than a LAN but smaller than a WAN, covering a city or a large campus.
- Purpose: Connects multiple LANs within a city for high-speed data transfer.
d. Wide Area Network (WAN):
- Size: Spans a large geographical area, often a country or continent.
- Purpose: Connects LANs and MANs over long distances, typically using public or private communication links.
2. Based on Type of Connection:
a. Wired Networks:
- Connection: Physical cables, such as Ethernet or fiber optics.
- Advantages: High reliability and speed.
- Examples: Ethernet LANs, fiber optic backbones.
b. Wireless Networks:
- Connection: Wireless signals, such as Wi-Fi or cellular networks.
- Advantages: Mobility, flexibility, and ease of deployment.
- Examples: Wi-Fi networks, 4G/5G cellular networks.
3. Based on Functional Relationships:
a. Client-Server Network:
- Structure: Clients (devices) request services or resources from servers (centralized systems).
- Purpose: Common in business environments for centralized data storage and management.
b. Peer-to-Peer Network:
- Structure: All devices have equal status and can act as both clients and servers.
- Purpose: Common in small networks for easy sharing of resources like files and printers.
c. Hybrid Network:
- Structure: Combines elements of both client-server and peer-to-peer models.
- Purpose: Offers flexibility by allowing certain functions to be centralized while enabling direct device-to-device communication.
Classification of computer networks based on these factors helps determine the most suitable network architecture for specific needs and requirements.
LAN Access Methods
In computer networks, access methods determine how devices handle data transmission. IEEE (Institute of Electrical and Electronics Engineers) has defined various LAN (Local Area Network) protocols and standards, such as IEEE 802.3 (Ethernet), 802.4 (Token Bus), and 802.5 (Token Ring), for data communication between different manufacturers' equipment. Let's focus on Ethernet:
Ethernet:
- Ethernet is a widely used LAN protocol (IEEE 802.3).
- It's known for its ease of implementation, management, and cost-effectiveness.
- Ethernet uses a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.
- CSMA/CD helps avoid data collisions by having devices listen before transmitting.
- IEEE 802.3 divides the data link layer into Logical Link Control (LLC) and Media Access Control (MAC) sub-layers.
- Ethernet uses physical addresses called MAC addresses (48-bit) to identify devices.
- Frames in Ethernet have several fields:
- Preamble: Synchronizes frame reception.
- Start Delimiter: Indicates the frame's beginning.
- Destination Address (DA): The recipient's MAC address.
- Source Address (SA): The sender's MAC address.
- Length of Data Field: Specifies data length.
- Data: Actual information, minimum 46 bytes.
- Pad: Added if data is less than 46 bytes.
- Frame Checksum (FCS): Contains error-checking information using CRC-32.
- Ethernet frames have a minimum length of 64 bytes to avoid collision issues.
- Maximum frame length is 1518 bytes, with the data field's maximum being 1500 bytes.
Ethernet is popular in LANs due to its simplicity, cost-effectiveness, and flexibility. It uses MAC addresses to identify devices and employs CSMA/CD to manage data transmission. Minimum frame length ensures reliable collision detection, and FCS helps in error checking.
When a network device in Ethernet wants to transmit a frame, the following steps are taken:
1. The MAC starts the transmission by taking the LLC information and putting it into the MAC frame buffer.
2. First, it adds the preamble and start delimiter to the frame.
3. Next, it includes both the destination and source MAC addresses.
4. The number of bytes in the LLC data is counted, and this count is inserted into the Length/Type field.
5. The actual LLC data bytes are then placed in the Data field.
6. If the number of LLC data bytes is less than 46, padding is added to reach a minimum length of 46 bytes.
7. An FCS (Frame Checksum) value is generated over the Destination Address (DA), Source Address (SA), Length/Type, and Data fields, and it's appended to the end of the Data field.
8. After assembling the frame, the actual transmission depends on whether the MAC operates in half-duplex or full-duplex mode. In half-duplex, the MAC can either transmit or receive but not both simultaneously. Full-duplex allows simultaneous transmission and reception.
Token Bus:
- Token bus is a network where a small data frame (the token) circulates among devices in a predetermined order.
- The device that possesses the token can transmit data over the network.
- When a device wants to send data, it must wait for the token and then send its data.
- After transmitting, the token is released for other devices to use.
- Token-passing networks, like token bus, are deterministic, meaning you can calculate the maximum time before a device gets the chance to transmit data.
- Token bus combines features of both Ethernet and token ring but is used in specific situations requiring real-time processing and minimal delay, such as factory automation and process control.
- It physically resembles a bus topology but operates as a logical ring using tokens.
- Devices are organized into a logical ring, and when a device wants to transmit, it checks if the media is busy. If not, it sends the signal.
- Each device receives the signal and checks if the message is addressed to it. If not, it disregards the message.
- Proper termination is essential in bus networks to prevent signal bouncing and collisions.
Ethernet and token bus are two different approaches to network communication, with Ethernet being widely used for its ease of implementation and token bus suitable for situations requiring deterministic, real-time processing.
Wireless technology allows data transmission between devices without the need for physical wires, making it invaluable in challenging geographic areas where wired networks are impractical. There are three primary types of wireless media:
1. Radio: Radio waves cover a wide range of frequencies from 10 KHz to 1 GHz. Within this range, various frequency bands are allocated for specific purposes. Radio communication is commonly used for wireless networking.
2. Microwave: Microwave communication uses extremely high frequencies to transmit and receive data. Due to the high frequency involved, microwave stations need to be positioned approximately 30 kilometers apart, and there must be a direct line of sight between them for effective communication.
3. Infrared: Infrared and millimeter waves are employed for short-range communication. Devices like television remote controls use infrared signals for communication.
Wireless technology has seen significant growth and importance, particularly in wireless networking. It enables portable computers to communicate using radio transmission. The demand for uninterrupted network access from anywhere and at any time has driven the adoption of wireless technologies.
In recent years, the wireless industry has made substantial progress in overcoming various challenges, including different standards, limited bandwidth, and high infrastructure and service costs. Wireless technologies have found applications in connecting computers, enabling remote monitoring and data collection, enhancing access control and security, and providing solutions in situations where traditional wired connections are impractical.
Wireless networks are typically set up with strategically placed base stations throughout the network area. These base stations can be interconnected using optical fiber cables. The transmission power of both the base stations and portable devices must be adjusted correctly to ensure continuous wireless access for users. Unlike cellular telephone systems, where each cell typically has one channel, wireless networks often have more bandwidth available, typically ranging from 1 to 2 Mbps.
Wi-Fi (Wireless Fidelity):
- Wi-Fi is a term associated with certified products based on IEEE 802.11 standards.
- It's often thought to stand for "Wireless Fidelity," although it officially doesn't have a specific meaning.
- Wi-Fi Alliance certifies devices for interoperability, ensuring they can work together.
- Many devices, including computers, game consoles, laptops, smartphones, and printers, support Wi-Fi.
- Wi-Fi is commonly used for home and office networks, offering internet access and device connectivity.
- Public Wi-Fi hotspots are available in places like airports, hotels, and restaurants.
- Wi-Fi allows devices to connect directly to each other, useful in peer-to-peer applications.
- Wireless routers provide internet access and connect devices wirelessly.
- Advantages include cost savings, global standards, and WPA2 security.
- Limitations include slow data rates and quality of service issues.
WiMAX (Worldwide Interoperability for Microwave Access):
- WiMAX stands for "Worldwide Interoperability for Microwave Access."
- It's a telecommunications technology for wireless data transmission.
- WiMAX offers broadband data rates of up to 3 Megabits/second.
- The IEEE standard for WiMAX is 802.16.
- WiMAX can connect Wi-Fi hotspots to the internet, provide wireless broadband access, and support data and telecommunications services.
- It's suitable for disaster management and can be a replacement for cellular technologies like GSM and CDMA.
- WiMAX uses a scheduling algorithm that reduces contention compared to Wi-Fi's contention access.
- It operates in the 2 to 11 GHz frequency range and supports multiple antennas for improved coverage.
- WiMAX subscriber units are available for indoor and outdoor use, with outdoor units resembling a laptop in size and installation similar to a satellite dish.
keywords:
1. Ethernet:
- Definition: A system for connecting a number of computer systems to form a local area network, with protocols to control the passing of information and to avoid simultaneous transmission by two or more systems.
2. MAC Address:
- Definition: A media access control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet.
3. Routers:
- Definition: Small physical devices that join multiple networks together. Technically, a router is a Layer 3 gateway device.
4. WAP (Wireless Application Protocol):
- Definition: Short for the Wireless Application Protocol, a secure specification that allows users to access information instantly via handheld wireless devices such as mobile phones, pagers, two-way radios, smartphones, and communicators.
5. Wi-Fi:
- Definition: A facility allowing computers, smartphones, or other devices to connect to the Internet or communicate with one another wirelessly within a particular area.
6. WiMAX:
- Definition: WiMAX is a wireless communications standard designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations.
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