Network Fundamentals

Network Fundamentals

• A network involves two or more computer systems or devices linked for data exchange.
• Networks enable resource sharing, file exchange, and electronic communication.
• Networked computers can share files or a printer.

Types of Networks

• Local-area network (LAN): computers geographically close, within the same building.
• Wide-area network (WAN): computers farther apart, connected via telephone lines or radio waves.
• Metropolitan-area network (MAN): a data network designed for a town or city.

Importance of Network Standards

• Network standards ensure hardware and software compatibility.
• Network standards are essential for developing a network to share information.

Network Components, Devices, and Functions

• Server: a computer or device that manages network resources and is often dedicated to server tasks.
• Client: an application on a personal computer or workstation that relies on a server for operations.
• Devices: computer devices like CD-ROM drives or printers, including disk drives and modems.
• Transmission Media: includes twisted-pair cable, coaxial cable, and fiber optic cable.
• Network Operating System (NOS): connects computers and devices in a local-area network (LAN).
• Operating System: provides a software platform for application programs.
• Network Interface Card (NIC): an expansion board enabling computer connection to a network.
• Hub: a common connection point for network devices.
• Switch: a device that filters and forwards packets between LAN segments.
• Router: forwards data packets along networks, connecting at least two networks at gateways.
• Gateway: a node on a network that serves as an entrance to another network.
• Bridge: connects two local-area networks (LANs) or segments of the same LAN using the same protocol.
• Modem (modulator-demodulator): enables data transmission over telephone or cable lines.
• Firewall: prevents unauthorized network access, implemented in hardware, software, or both.
• MAC Address: a Media Access Control address, also known as a hardware or physical address.

Network Models

• Networks are simplified by separation into layers, each handling specific tasks independently.
• Control passes between layers, from top to bottom, over the channel to the next station and back up.
• Network models define a set of network layers and their interactions.

TCP/IP Model

• It is a four-layer reference model.
• All protocols in the TCP/IP protocol suite are located in the top three layers of this model.

Network Topologies

• Network topology is the shape/arrangement of elements (links and nodes) in a computer network.
• Network topology defines how network nodes connect and communicate.
• Topologies can be physical or logical.

LAN Topologies

• Bus Topology: devices connect to a central cable called the bus or backbone; it is inexpensive and easy to install for small networks.
• Ring Topology: devices connect in a closed loop, each directly connected to two others.
• Star Topology: devices connect to a central hub; relatively easy to install/manage, but can cause bottlenecks.
• Tree Topology: combines linear bus and star topologies, featuring star-configured workstations connected to a linear bus backbone.

History of the Internet

• 1962: The idea for an "Intergalactic Computer Network" is conceived.
• 1969: ARPANET, the precursor to the Internet, is created by the U.S. Department of Defense.
• 1969: The Unix operating system is developed.
• 1970s: Key technologies are developed.
• 1971: Ray Tomlinson introduces network email.
• 1973: The first international connection to ARPANET is established.
• 1974: Vinton Cerf and Bob Kahn publish "A Protocol for Packet Network Interconnection," detailing the design of TCP.
• 1975: The Department of Defense takes control of ARPANET.
• 1980s: The rise of the internet.
• 1983: ARPANET and the Defense Data Network switch to the TCP/IP standard, marking the official birth of the internet.
• 1984: The Domain Name System (DNS) is invented.
• 1988: Internet Relay Chat (IRC), the first successful live chat system, is launched.
• 1988: The first major malicious internet-based attack occurs.
• 1989: Tim Berners-Lee proposes the World Wide Web.
• 1990s: The World Wide Web and commercialization.
• 1991: Tim Berners-Lee creates the first webpage and web browser.
• 1993: Mosaic, the first graphical web browser for the general public, is launched.
• 1994: Netscape Navigator becomes a popular web browser.
• 1994: The first secure e-commerce transaction occurs.
• 1995: The internet becomes commercialized.
• 2000s: The rise of social media and mobile internet.
• 2003: MySpace gains popularity.
• 2004: Facebook is launched.
• 2007: Apple introduces the iPhone, revolutionizing mobile web browsing.
• 2010s: Mobile First and Beyond.
• 2010: Proliferation of smartphones/mobile devices leads to the rise of the mobile internet.
• 2012: Google Play (formerly Android Market) is launched.
• 2020s: The Internet of Things and Beyond.
• Present: Continues to evolve with new technologies like the Internet of Things, AI, and cloud computing.

Internet Operation

• The Internet functions through a packet routing network, using Internet Protocol (IP), Transport Control Protocol (TCP), and other protocols.

Protocols and Packets

• A protocol is a set of rules specifying how computers communicate on a network.
• Internet Protocol specifies how computers route information by attaching addresses to data.
• Data sent across the Internet is called a message, and is split into packets.
• Packets are sent independently.
• The typical maximum packet size is between 1000 and 3000 characters.
• The Internet Protocol specifies how messages are packetized.

Packet Routing Networks

• A packet routing network routes packets from a source to a destination computer.
• The Internet is a massive network of specialized computers known as routers.
• Each router's job is to move packets from source to destination.
• A packet will move through multiple routers during its journey.
• When a packet moves from one router to the next, it’s called a hop.
• Packets may arrive out of order if a later packet finds quicker path than an earlier one.
• Each packet's header contains information about its order relative to the entire message.
• The Transport Control Protocol reconstructs the message at the destination using this information.
• The Internet Protocol does not guarantee that packets will arrive.
• Packet loss occurs when packets do not arrive.
• Loss typically happens when a router receives more packets than it can process.
• If the destination computer finds are missing packets, it requests the source computer to resend them.

Internet Addresses

• Internet addresses are called IP addresses
• There are two address standards, IPv4 and IPv6.
• IPv4 looks like: 212.78.1.25
• IPv6 looks like: 2001:db8:3333:4444:5555:6666:7777:8888.
• IPv4 is a 32-bit address, whereas IPv6 is a 128-bit address.