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CHAPTER 2: NETWORKING AND THE INTERNET

  • Discusses network fundamentals, the Internet, WWW, protocols, and security.

NETWORK CLASSIFICATIONS

  • Networks can be classified based on various parameters:

    • Scope:

    • Local Area Network (LAN): Network covering a small geographical area such as a home, office, or building.

    • Metropolitan Area Network (MAN): Larger than a LAN, spanning a city.

    • Wide Area Network (WAN): Covers broad areas, connecting multiple LANs and MANs.

    • Ownership:

    • Closed Networks: Restricted access, controlled by a single organization.

    • Open Networks: Open for use by the public or anyone within a geographic range.

    • Topology (Configuration):

    • Bus Topology:

      • All devices are connected to a single central cable, known as the bus.

      • Example: Ethernet configurations.

    • Ring Topology:

      • Devices are connected in a circular format where messages travel in one direction.

    • Star Topology:

      • Central switch or wireless access point connects all devices individually.

      • Most common in wireless networks today.

    • Irregular Topology:

      • Ad-hoc configurations that do not conform to standard types.

NETWORK TOPOLOGIES

  • Visual representation of various network topologies:

    • Bus Topology:

    • Illustrated with computers aligned on a single central cable (Figure 4.1a).

    • Ring Topology:

    • Illustrated where message flows in a single direction among connected computers (Figure 4.1b).

    • Star Topology:

    • Illustrated where all computers connect to a central point (Figure 4.1c).

    • Irregular Topology:

    • Represented by various connected devices without a uniform structure.

PROTOCOLS

  • Protocol: A set of rules governing the format and transmission of data.

    • Carrier Sense Multiple Access with Collision Detection (CSMA/CD):

    • Framework in which devices listen to a channel before sending data to avoid collisions.

    • Primarily utilized in Ethernet (Bus network).

    • Silent Bus: Allows for new message initiation once the bus is clear.

    • Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA):

    • Similar to CSMA/CD but focuses on avoiding collisions from occurring in the first place, frequently used in WiFi.

    • Hidden Terminal Problem:

      • A situation where end systems within range of an access point cannot hear each other, causing communication issues. Illustrated by accessing ranges A, B, and C (Page 10).

CONNECTING NETWORKS

  • Devices that connect different types of networks:

    • Repeater: Extends the range of a network by amplifying signals.

    • Bridge: Connects two compatible networks enabling communication.

    • Switch: Connects multiple compatible networks, efficiently directing data.

    • Router: Interfaces two incompatible networks, forming an internet or interconnected system.

BUILDING A LARGE BUS NETWORK FROM SMALLER ONES

  • Strategies for expanding networks:

    • Use of Repeaters or Bridges to connect smaller bus networks.

    • Utilizing Switches to consolidate multiple bus networks.

ROUTERS CONNECTION

  • Illustration of routers linking different network types (WiFi and Ethernet).

INTER-PROCESS COMMUNICATION

  • Client-server Model:

    • Structure where one server communicates with multiple clients.

    • Server remains continuously active to handle client requests.

  • Peer-to-peer (P2P) Model:

    • Framework in which two processes communicate directly as equals.

    • Peer processes can be transient in nature.

THE CLIENT/SERVER MODEL VS PEER-TO-PEER MODEL

  • Comparison:

    • Client-Server Model:

    • Requires a server prepared to handle simultaneous requests from multiple clients.

    • Peer-to-Peer Model:

    • Peer communication occurs on a one-to-one basis without a dedicated server.

A TYPICAL UNIVERSAL RESOURCE LOCATOR (URL)

  • Structure:

    • Example: http://ssenterprise.aw.com/authors/Shakespeare/Julius_Caesar.html

    • Protocol: Specifies the access method (http).

    • Host: Mnemonic name identifying the server holding the document.

    • Directory Path: Defines the document's location within the host's file system.

    • Document Name: Identifies the specific resource requested.

PACKAGE-SHIPPING EXAMPLE

  • Analogy for message transmission:

    • Originating entity prepares a package, transfers it to a shipping company, which then handles the logistics until it reaches the final destination (recipient).

INTERNET SOFTWARE LAYERS

  • Layers involved in the internet's functioning:

    • Application Layer: Constructs a message and adds an address.

    • Transport Layer: Segments the message into packets.

    • Network Layer: Manages packet routing through the internet.

    • Link Layer: Facilitates the actual transmission of packets.

FOLLOWING A MESSAGE THROUGH THE INTERNET

  • Step-by-step process of message transmission:

    • Application Layer: Prepares the message and adds destination address.

    • Transport Layer: Segments message into packets and assigns an intermediate address.

    • Network Layer: Transfers packets to their intermediate addresses, assigning new addresses as needed.

    • Link Layer: Receives and transmits packets, ensuring correct delivery.

DATA COMMUNICATION CHANNELS

  • Communication Channel: Pathway for transmitting digital information between locations, can be:

    • Physical Transmission Medium: Includes tangible, wired connections.

    • Wireless Transmission Medium: Utilizes radio or microwave signals.

PHYSICAL TRANSMISSION MEDIUM

  • Types of wired connections:

    • Twisted-pair Wire: Consists of two insulated copper wires twisted together.

    • Coaxial Cable: Designed to allow high-speed data transmission with minimal distortion.

    • Fibre Optic Cable: Uses light to transmit data, offering high speed and bandwidth.

WIRELESS COMMUNICATION

  • Transmission methods:

    • Microwave and Radio Signals: Signals travel in straight lines, suitable for line of sight communication.

    • Satellite Communication: Overcomes line of sight limitations, involving uplink and receiving antennas.

SECURITY

  • Types of Attacks:

    • Malware: Includes viruses, worms, Trojan horses, spyware, phishing.

    • Denial of Service (DoS): Disrupts service availability.

    • Spam: Unsolicited messages.

  • Protection Measures:

    • Firewalls: Monitor and control incoming and outgoing network traffic.

    • Spam Filters: Reduce unwanted emails.

    • Antivirus Software: Detects and removes malicious software.

ENCRYPTION

  • Types of encryption protocols:

    • FTPS, HTTPS, SSL: Secure protocols for data transmission.

    • Public-Key Encryption:

    • Public Key: Used to encrypt messages.

    • Private Key: Used to decrypt messages.

    • Utilizes certificates and digital signatures to enhance security.

FIGURES

  • Figure 4.16 Public-Key Encryption:

    • Alice and Carol hold public keys to send encrypted messages to Bob, who holds the private key for decryption. Carol cannot decrypt messages from Alice, demonstrating the security of public-key encryption.