BCS041 - Fundamentals of Computer Networks Revision Notes

Computer Networks allows autonomous digital devices to communicate to each other for various purpose using either wired or wireless connection.

• Goals of Computer Networks - Facilitating Communication, Resource Sharing, Data Storage and Access, Cost Effieciency, Reliability and Redundancy
• Application of Computer Networks - Business and Commerce, Education, Healthcare, Government, Scientific Research, Travel and Hospitality.
• Criteria - Delivery & Accuracy, Performance, Reliability, Security, Scalability

Data Communication are the exchange of data between two devices via some transmission medium. It has five components - Message, Sender, Receiver, Transmission medium, Protocol.

Transmission Mode refers to the method by which data is transmitted between devices.

1. Simplex Mode- One direction communication. (Ex- Tv Broadcast, Radio Broadcast, Alarm System)
2. Half-Duplex Mode- Bidirectional communication but not simultaneosly (Ex- Walkie Talkie)
3. Full-Duplex Mode- Both side communication at same time (Ex- Telephone, Internet)

Type of connections in computer networks
→ Point to Point provides dedicated link between two devices. (Ex- Telephone)
→ Multipoint more that two devices share a single link

Difference between Analog Communication and Digital Communication

Difference between Synchronous Transmission and Asynchronous Tranmission

Difference between Serial Transmission and Parallel Transmission

ISO - OSI Model - International Starndard Organisation - Open Systems Interconnection

The modern Internet is not based on OSI, but on the simpler TCP/IP model. However, the OSI 7-layer model is still widely used, as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot networking problems.

Encapsulation - The process of wrapping data packets with header information as they move through different network layers. This header contains details like source and destination addresses, allowing routers and switches to forward the packet to the correct destination.

Decapsulation - reverse process, where the receiving network device strips away the headers from the data packet to access the original information. This allows the device to interpret and process the data appropriately based on its destination and content.

End-to-end Agreement - It is a mutual understanding or contract between the sender and receiver of data packets regarding how communication should be handled. This agreement ensures that the data transmission meets certain requirements or specifications, such as reliability, security, or quality of service. It typically involves protocols and mechanisms implemented at both ends of the communication path to ensure that data is transmitted, received, and processed correctly according to the agreed-upon terms.

Protocol design issues involve addressing various aspects to ensure effective communication between networked devices. Key issues to consider for designing protocols include:

Singal Modulation is the process of varying one or more properties of a carrier signal—such as its amplitude, frequency, or phase—to encode information from a message signal for transmission over a communication channel

Need or Benefits for Signal Modulation

• Efficient Transmission: Enables long-distance communication by converting low-frequency signals into higher frequencies.
• Multiplexing: Allows multiple signals to share the same channel without interference.
• Noise Reduction: Improves signal quality and resilience against noise and interference.
• Antenna Size: Reduces the required size of transmitting and receiving antennas.
• Bandwidth Utilization: Optimizes the use of available bandwidth for transmitting more data.

Types of Signal Modulation

Analog Modulation : Modulation where the carrier signal is varied in a continuous manner in proportion to the message signal.

1. Amplitude Modulation (AM):Varies the amplitude of the carrier signal.Use: AM radio broadcasting.
2. Frequency Modulation (FM):Varies the frequency of the carrier signal.Use: FM radio broadcasting, audio signals.
3. Phase Modulation (PM):Varies the phase of the carrier signal.Use: Digital synthesizers, some communication systems.

Digital Modulation:

4. Amplitude Shift Keying (ASK):Varies the amplitude of the carrier signal to represent digital data.Use: Optical fiber communications, RFID systems.
5. Frequency Shift Keying (FSK):Varies the frequency of the carrier signal to represent digital data.Use: Modems, low-frequency communication.
6. Phase Shift Keying (PSK):Varies the phase of the carrier signal to represent digital data.Use: Wi-Fi, satellite communication.
7. Quadrature Amplitude Modulation (QAM):Combines ASK and PSK to modulate both amplitude and phase.Use: Cable television, broadband internet.
8. Orthogonal Frequency Division Multiplexing (OFDM):Encodes digital data on multiple carrier frequencies.Use: 4G/5G mobile communication, digital television.

Multiplexing

Multiplexing combines multiple data streams into a single transmission medium for efficient resource use. It allows several users or devices to share a channel simultaneously without interference. Key techniques include:

Switching

Switching is a fundamental concept in networking and telecommunications, enabling the routing of data between multiple devices or networks. It involves directing data from its source to its destination through intermediate nodes or switches.

Types of Switching:

Transmission Medium

Transmission medium refers to the physical pathway through which data travels from one device to another. It can be classified into guided and unguided transmission media.

Guided Transmission Media: Use physical paths to transmit data signals. Common types include: Twisted Pair Cable, Coaxial Cable

Unguided Transmission Media: Transmit data through air or space without a physical pathway. Common types include: Radiowave, Micowave, Infrared

Transmission Medium	Definition	Working	Examples	Advantages	Disadvantages	Image Representation
Twisted Pair Cable (UTP and STP)	Consists of twisted copper wires; UTP lacks shielding, while STP has additional shielding	Signals transmitted through twisted pairs; STP provides better protection against interference	Telephone lines, Ethernet connections	UTP: Affordable, easy to install; STP: Better protection against electromagnetic interference	UTP: Susceptible to interference; STP: More expensive
Coaxial Cable	Central copper conductor surrounded by insulating material and a metallic shield	Signals transmitted through the central conductor; shield provides protection against interference	Cable television networks, high-speed internet connections	High bandwidth, less susceptible to interference	Costlier than twisted pair cables
Optical Fiber	Transmits data using light pulses through a glass or plastic fiber	Signals transmitted as light pulses through fiber; immune to electromagnetic interference	Long-distance telecommunications, high-speed internet connections	High bandwidth, low attenuation, immune to electromagnetic interference	Expensive to install and maintain
Wireless Transmission (Radio Waves)	Utilizes electromagnetic waves to transmit data wirelessly	Signals transmitted as radio waves through the air	Wi-Fi, Bluetooth, cellular networks	Offers mobility, flexibility	Signal interference, limited range	Can't be seen through eyes
Microwave Transmission	Uses high-frequency radio waves for long-distance transmission	Signals transmitted as high-frequency radio waves between antennas	Long-distance telephone networks, cellular backhaul connections	High data rates, long-distance transmission	Requires line-of-sight, vulnerable to weather conditions
Infrared Transmission	Utilizes infrared light waves for short-range wireless communication	Signals transmitted as infrared light waves between devices	Remote controls, proximity sensors, short-range data transfer	Secure communication, immunity to radio interference	Requires line-of-sight, limited range

Connectors

The connectors are the interface for communication between computers/ computers to hub, switch, router etc. In LAN basically used connector are discussed as follows:

Type & Image	Details
RJ45	Standard Ethernet connector for networking computers in LANs. Commonly used in both residential and commercial networks. Supports speeds up to 10 Gbps over twisted-pair cables. Easy to install and widely available, but limited to 100 meters without signal boosters.
RJ11	Telephone line connector for connecting phones and modems. Typically used for DSL internet connections and traditional telephony. Simple and cost-effective, but lower data transmission rates compared to RJ45. Supports up to 4 wires, primarily used in residential telephone networks.
BNC	Quick connect/disconnect for video signals, RF, and networking. Commonly used in television production, amateur radio, and network testing equipment. Secure connection with good shielding, but bulky and not suitable for very high-frequency applications. Requires proper alignment for optimal performance.
F-Type	Screw-on connector for cable TV, satellite TV, and broadband. Provides a strong, reliable connection. Commonly found in residential setups for connecting TV and internet services. Requires proper installation to avoid signal loss and ensure optimal performance. Suitable for frequencies up to 1 GHz.
SC	Push-pull connector for data centers and telecom networks. Used in fiber optic networks for its easy connect/disconnect feature. High performance with low signal loss, but bulkier than other connectors. Commonly used in high-speed internet and cable TV networks. Known for its square-shaped design.
ST	Bayonet-style fiber optic connector for data communication. Reliable and easy to use, but bulkier and not suitable for high-density applications. Commonly used in long-distance networks and networking environments where quick connection and disconnection are required. Features a twist-on mechanism for secure connection.
LC	Smaller push-pull connector for high-density fiber optic networks. Compact and high performance, making it ideal for densely packed data centers. More fragile than larger connectors but offers superior performance in space-constrained environments. Common in modern high-speed networks and telecommunications.
SMA	Coaxial RF connector for antennas and Wi-Fi devices. Reliable with good performance at higher frequencies. Commonly used in wireless communication devices, including Wi-Fi equipment and RF amplifiers. Requires precise installation for optimal performance, supporting frequencies up to 18 GHz.
U.FL	Miniature coaxial RF connector for laptops, GPS, and Wi-Fi cards. Compact and suitable for tight spaces. Fragile and limited to lower power applications, but essential in devices where space is at a premium. Common in modern electronics requiring compact RF connections.

Classification of Networks

LAN, or Local Area Network, is a network that connects computers and devices within a limited geographical area, such as a building or campus. It typically employs Ethernet or Wi-Fi technology for data transmission and is commonly used in homes, offices, and schools.

MAN, or Metropolitan Area Network, spans a larger area than a LAN but is smaller than a WAN. It covers a city or a large campus, connecting multiple LANs together. MANs often use fiber optic cables or wireless technologies and are found in urban environments, facilitating communication within a metropolitan area.

WAN, or Wide Area Network, transcends geographical boundaries to connect multiple LANs and MANs over a broad area, such as a country or continent. It includes the Internet and multinational company networks, utilizing various technologies like leased lines, satellites, or submarine cables to facilitate long-distance communication.

Network Topology refer to the way in which a network is laid out physically or the geometric representation of the relationship of all the links and linking devices to one another.

Types of Topologies

MAC(Media Access Contorl)

it refers to the set of protocols and mechanisms used to control access to a shared communication medium in a network. The MAC layer is responsible for managing how devices on the network access and transmit data over the physical medium, such as Ethernet cables or wireless radio frequencies.

Media Access Control (MAC) is essential in networking for several reasons:

• Efficient Resource Utilization: MAC protocols help optimize the use of network resources, ensuring that multiple devices can share the same communication medium effectively.
• Collision Avoidance: In shared network environments, such as Ethernet LANs, MAC protocols prevent collisions by regulating when devices can transmit data, thereby maximizing network efficiency.
• Fairness: MAC protocols aim to provide fair access to the network for all devices, ensuring that no single device monopolizes the network resources, which is crucial for maintaining network performance and user satisfaction.
• Priority Handling: Some MAC protocols support prioritization mechanisms, allowing certain types of traffic to be transmitted with higher priority than others. This is essential for applications that require low latency or guaranteed quality of service (QoS).
• Error Detection and Correction: MAC protocols often incorporate error detection mechanisms to identify and correct transmission errors, ensuring data integrity and reliability.
• Security: MAC protocols can also contribute to network security by implementing access control mechanisms to prevent unauthorized devices from accessing the network.

MAC Techniques

MAC techniques are methods used to control how data packets are transmitted between multiple devices over a shared communication channel. The primary categories include:

1. Random Access - Aloha(Pure, Slotted), CSMA
2. Round Robin - Polling, Token Passing
3. Reservation - Centralized, Decentralized

TCP/IP Protocol

The TCP/IP model, also known as the Internet Protocol Suite, is a set of communication protocols used to interconnect network devices on the internet. It is divided into four abstraction layers, each serving specific functions to ensure the smooth transfer of data from one device to another.

Application Layer

• Web Browsing: Facilitates accessing and interacting with web content through browsers.
• File Transfer: Enables the upload and download of files over a network.
• Email Services: Supports sending, receiving, and storing email messages.
• Domain Name Resolution: Translates human-readable domain names into IP addresses.
• Remote Login and Management: Allows users to access and control remote computers securely.
• Network File Services: Provides access to files over a network as if they were on local storage.

Transport Layer

• Reliable Data Transfer: Ensures data is delivered accurately and in the correct sequence, providing acknowledgment and retransmission mechanisms.
• Unreliable Data Transfer: Sends data without ensuring delivery or order, suitable for applications needing speed over reliability.
• Flow Control: Manages the rate of data transmission to prevent network congestion and ensure efficient communication.
• Error Detection and Recovery: Detects errors in transmitted data and initiates retransmissions if necessary to ensure data integrity.
• Segmentation and Reassembly of Data: Breaks large messages into smaller segments for transmission and reassembles them at the destination.

Internet Layer

• Logical Addressing: Assigns IP addresses to devices, allowing them to be uniquely identified on the network.
• Routing and Forwarding of Packets: Determines the best path for data packets to travel across networks and forwards them to their destination.
• Error Reporting: Provides feedback about network issues, such as unreachable hosts or networks, to help diagnose problems.
• Network Diagnostics: Helps diagnose network problems using tools like ping and traceroute to identify connectivity issues.
• Address Resolution: Maps IP addresses to physical MAC addresses for local network communication, ensuring proper data delivery.
• Multicast Management: Handles the delivery of data to multiple recipients simultaneously, optimizing network resource usage.

Link Layer (Network Access Layer)

• Physical Addressing: Uses MAC addresses to identify devices on a local network segment, enabling local communication.
• Access to Physical Transmission Medium: Controls how data is placed onto and taken off the physical medium, such as Ethernet cables or wireless signals.
• Data Framing: Encapsulates network layer data into frames for transmission and processes received frames to extract the data.
• Error Detection on Physical Medium: Identifies errors that occur at the physical layer and discards corrupted frames to maintain data integrity.
• Flow Control over the Physical Medium: Manages the rate of data transmission between devices, ensuring smooth and efficient communication.
• Encapsulation of Network Layer Data: Wraps network layer packets into frames for transmission over the physical medium, ensuring proper data handling.

Error detection is a method used in communication systems to identify errors that may occur during the transmission of data over a network. This ensures the integrity of the transmitted data. Below are some commonly used error detection methods along with their steps:

Parity Bit Method

The parity bit method adds a single bit to the data to make the number of 1's either even (even parity) or odd (odd parity).

Steps for Parity Bit Method:

1. Choose parity type (even/odd).
2. Calculate parity bit based on the number of 1's:
   • For even parity, if the count is odd, set the parity bit to 1; if even, set it to 0.
   • For odd parity, if the count is even, set the parity bit to 1; if odd, set it to 0.
3. Append parity bit to data.
4. Transmit data with parity bit.
5. Receiver checks parity:
   • Even parity: Count of 1's should be even.
   • Odd parity: Count of 1's should be odd.

Cyclic Redundancy Check (CRC)

CRC is a more robust error detection method that uses polynomial division to detect changes in raw data.

Steps for CRC:

1. Choose a generator polynomial.
2. Append zeros to data.
3. Perform binary division using the generator polynomial.
4. Append CRC remainder to data.
5. Transmit data with CRC.
6. Receiver performs division:
   • If remainder is zero, data is correct.
   • If remainder is non-zero, an error is detected.