Computer Networks

Course Content

  • Networks: Basic concepts

  • Uses of networks

    • Sharing of resources

    • Backups

  • Common types of networks

    • LAN (Local Area Network)

    • WAN (Wide Area Network)

    • Internet

    • Server-based networks

    • Client-server model

    • P2P (Peer-to-Peer)

  • Network media

  • Wireless networks

  • Threats to networks

  • The internet world

  • Cloud and Cloud Computing

The Computer Network

  • A computer network is defined as a group of computers/devices (Nodes) that use a set of common communication protocols over digital interconnections for the purpose of sharing resources located on or provided by the network nodes.

    • Nodes may include:

    • Personal computers

    • Servers

    • Networking hardware

    • Other specialized or general-purpose hosts

    • Interconnections between nodes can be established using a variety of telecommunication network technologies based on:

    • Physically wired technologies

    • Optical technologies

    • Wireless technologies

  • Communication Protocol is a set of rules for exchanging information over a network.

Network Components

  • Network Diagram includes:

    • The Internet

    • Other LANs

    • Firewall

    • Router

    • Fiber Optic Network Cable

    • Server

    • PC

    • Wireless Network

    • Wired Network

    • Switch

Advantages/Uses of Networks

  • Simultaneous Access allows multiple users to access the same data at the same time.

  • Shared Peripheral Devices enable the sharing of devices like printers and scanners.

  • Personal Communications facilitate communication through digital means.

  • Videoconferencing enables real-time video interaction.

  • Voice over Internet Protocol (VoIP):

    • Transmits voice signals over a network using the Internet Protocol (IP) instead of traditional phone lines.

  • Easier Data Backup provides streamlined methods for backing up important information.

Networking Devices (Nodes)

  1. NIC (Network Interface Card)

    • Physically connects host devices to the network media.

    • Function: Can be a printed circuit board or peripheral device.

    • Media Access Control (MAC) Address: A unique code that identifies each NIC, controlling data communication for the host.

  2. Repeaters

    • Used to regenerate and amplify signals weakened by transmission loss.

    • Note: Repeaters do not make intelligent decisions about packet forwarding.

  3. Hubs

    • Concentrate connections to allow the network to recognize multiple hosts as a single unit.

    • Can be active (regenerates signals) or passive (only concentrates connections).

  4. Bridges

    • Convert data formats and manage basic data transmissions.

    • Connect between LANs and enhance network efficiency by determining if data should cross the bridge.

  5. Switches

    • Provide intelligent data transfer management by directing traffic only to the intended destination without converting data formats.

  6. Routers

    • Combine functionalities of regenerating signals, connecting multiple networks, and managing data transfers.

    • Connect LANs to WANs over large distances.

  7. Gateway

    • Networking hardware that facilitates data flow between different networks using multiple protocols.

  8. Firewall

    • A security device for monitoring and controlling network traffic.

    • Positioned between secure and insecure networks to deny access requests from unrecognized sources.

    • Its role is increasingly vital due to the rise of cyber attacks.

Network Media

  • The primary function of network media is to carry flows of information through a LAN.

Wired Media

  • Ethernet: This category uses copper and fiber media in LAN technology.

1. Copper Cable

  • Common, quick, and economically feasible.

  • Drawback: Signal weakens over distance.

2. Coaxial Cable

  • Longer range compared to twisted pair cables.

  • Speed: 10-100 Mbps

  • Cost: Inexpensive

  • Media and Connector Size: Medium

  • Maximum Cable Length: 500 m

3. Shielded Twisted Pair (STP)

  • Speed: 0-100 Mbps

  • Cost: Moderate

  • Media and Connector Size: Medium to large

  • Maximum Cable Length: 100 m

4. Unshielded Twisted Pair (UTP)

  • Composed of four pairs of insulated copper wires.

  • Speed: 10-100-1000 Mbps (dependent on cable quality)

  • Cost: Least expensive

  • Media and Connector Size: Small

  • Maximum Cable Length: 100 m

  • Implementation: Standardized RJ-45 connector as per EIA/TIA.

5. Fiber Optic Cable

  • Uses glass fibers to carry light pulses for data transmission.

  • Advantages: High-speed performance (10-100 Gbps), low error rate, immune to electromagnetic interference.

  • Advantage: Can be spaced far apart with repeaters.

Communication Protocols

  • Internet Protocol Suite: Commonly known as TCP/IP, this is the foundational framework for modern networking. It outlines the addressing, identification, and routing specifications for both IPv4 and IPv6, forming the set of protocols for the Internet.

Other Key Protocols

  • IEEE 802: A family of standards mostly concerning LANs and metropolitan area networks, operating at levels 1 and 2 of the OSI model.

  • Ethernet (IEEE 802.3): Predominantly used in wired LANs.

  • DARPA: Defense Advanced Research Projects Agency, influential in developing networking protocols.

TCP/IP Protocol Suite Overview


  • OSI model layers versus DARPA layers:

    Application Layer

    Presentation Layer

    Session Layer

    Transport Layer

    Network Layer

    Data Link Layer

    Physical Layer


    HTTP, FTP, SMTP, DNS, RIP, SNMP

    –

    –

    TCP, UDP, IGMP, ICMP

    ARP, IP (IPv4), IPv6, ND, MLD, ICMPv6

    Ethernet

    802.11 wireless, Frame Relay, ATM

    Transitioning from IPv4 to IPv6

    • Address Size Comparison:

      • IPv4: 32-bit

      • IPv6: 128-bit

    • Address Format:

      • IPv4: Decimal (e.g., 192.168.1.1)

      • IPv6: Hexadecimal (e.g., 2001:db8::ff00:42:8329)

    • Number of Addresses:

      • IPv4: Approximately 4.3 Billion ($2^{32}$)

      • IPv6: Approximately 340 Undecillion ($2^{128}$).

    • Configuration Methods:

      • IPv4 supports manual or DHCP

      • IPv6 allows self-configuration (SLAAC) or DHCPv6.

    • Security Features:

      • IPv4 has optional IPSec

      • IPv6 mandates IPSec.

    TCP/IP Protocol Suite Specific Protocols

    • HTTP (Hypertext Transfer Protocol): Facilitates communication between web browsers and servers.

    • FTP (File Transfer Protocol): Specifically designed for file transfers between computers.

    • SMTP (Simple Mail Transfer Protocol): The standard for sending emails.

    • DNS (Domain Name System): Translates user-friendly domain names to IP addresses.

    • RIP (Routing Information Protocol): An older routing protocol superseded by faster alternatives.

    • SNMP (Simple Network Management Protocol): Monitors and controls network devices.

    • TCP (Transmission Control Protocol): Prioritizes reliable data delivery and connection.

    • Three-Way Handshake in TCP:

      1. SYN: Client initiates connection with a sequence number.

      2. SYN-ACK: Server acknowledges readiness with its own sequence number.

      3. ACK: Client confirms connection and data transfer can commence.

    • UDP (User Datagram Protocol): Prioritizes speed over reliability, allowing for faster data transmission with no guaranteed delivery.

    • IGMP (Internet Group Management Protocol): Manages multicast group memberships.

    • ICMP (Internet Control Message Protocol): Handles error reporting and network diagnostics.

    • ARP (Address Resolution Protocol): Translates IP addresses to physical MAC addresses.

    • Neighbor Discovery Protocol (NDP): A comprehensive tool in IPv6 for managing network operations, replacing functions previously handled by other protocols.

    • Multicast Listener Discovery (MLD): Replaces IGMP as IPv6's multicast management protocol.

    Types of Networks

    1. Personal Area Network (PAN):

      • Used for data transmission among personal devices like phones, tablets, and computers.

      • Also referred to as a Home Area Network (HAN).

      • Capable of communication among personal devices and connecting to larger networks.

    2. Local Area Network (LAN):

      • Created through collaboration among companies to develop Ethernet, which is widely used in LAN architecture.

      • Characteristics:

        • High-speed data transmission (up to 10 Gbps),

        • Technologies include Fiber Distributed Data Interface (FDDI) and token ring.

    3. Campus Area Network (CAN):

      • Larger than LANs, but smaller than MANs; typical in universities or businesses across multiple buildings.

    4. Metropolitan Area Network (MAN):

      • Larger than LAN but smaller than WAN; typically 5-50 km in diameter.

      • Owned by a single entity like ISP or telecommunications companies.

    5. Wide Area Network (WAN):

      • Covers large geographical areas, with data transmission via phone or cable lines.

      • The most expansive example is the internet.

    6. Storage Area Network (SAN):

      • Connects various data storage devices to allow expansive user access.

      • Functions similarly to a hard drive connected to a server.

    7. Virtual Private Network (VPN):

      • A secure private network accessible over public internet resources, utilizing encryption for privacy.

      • Provides remote access and establishes a secure connection for users logging into company networks from afar.

      • Ensures confidentiality, integrity, and authentication.

    8. Client/Server Network:

      • Arrangement where network services are offered from a dedicated server, which responds to client requests.

      • Centralizes services via powerful machines equipped with specialized software.

    9. Peer to Peer Network (P2P):

      • Typically smaller networks where workstations share responsibilities and capabilities.

      • Does not require dedicated hubs or switches.

      • Performance may degrade under heavy data loads.