Networking Fundamentals

What's the Internet?

• The Internet is a "network of networks" that connects millions of devices (hosts/end systems) globally.
• It provides services to applications such as web, email, games, and e-commerce through interconnected ISPs (Internet Service Providers).
• Protocols control the sending and receiving of messages between devices.

Network Edge

• The network edge consists of end systems, access networks, and links.
• End systems/host devices are clients (e.g., desktops, laptops, smartphones) and servers (e.g., web servers, email servers).
• Access networks connect end systems to the Internet using various technologies such as fiber, copper, radio, and satellite.

Network Core

• The network core consists of packet switches (routers) that forward packets (chunks of data) between devices.
• Packet switches use routing tables to determine the path for packet transmission.
• Routers are used in the network core, while link-layer switches are used in access networks.

Internet Devices

• There are approximately 15.14 billion connected IoT devices as of 2023.
• Examples of Internet devices include web-enabled toasters, picture frames, and refrigerators.

Internet Infrastructure

• The Internet infrastructure provides services to applications through distributed applications that involve multiple end systems exchanging data.
• Internet applications run on end systems, not in packet switches in the network core.
• End systems provide an Application Programming Interface (API) to applications, allowing them to "connect" to the Internet.

Protocols

• A protocol is a set of rules that govern communication between devices.
• Human protocols (e.g., "what's the time?", "I have a question") are different from computer network protocols.
• Protocols define the format, order, and actions taken when sending and receiving messages between network entities.

Network Structure

• The network edge consists of end systems, access networks, and links.
• Access networks include home networks, enterprise networks, and wide-area wireless access networks.
• Home networks can use fiber-to-the-home (FTTH) technology, which provides high-speed Internet access rates.

Home Access Networks

• Home access networks use fiber-to-the-home (FTTH) technology, which provides high-speed Internet access rates.
• FTTH architecture consists of an optical network terminator (ONT) connected to a neighborhood splitter, which is connected to an optical line terminator (OLT) in the telco's central office.

Enterprise Access Networks

• Enterprise access networks use Ethernet LAN technology, which provides high-speed transmission rates (e.g., 100Mbps, 1Gbps, 10Gbps).
• Enterprise access networks typically consist of an institutional router, Ethernet switch, and institutional mail and web servers.

Wireless Access Networks

• Wireless access networks use base stations (access points) to connect end systems to routers.
• Wireless LANs (WLANs) provide high-speed transmission rates (e.g., 11Mbps, 54Mbps) within a building or campus.
• Wide-area wireless access networks provide Internet access over a larger geographical area (e.g., cellular networks).

Physical Media

• Physical media include twisted pair (TP), coaxial cable, fiber optic cable, and radio.
• Guided media (e.g., copper, fiber) have signals that propagate in a solid medium, while unguided media (e.g., radio) have signals that propagate freely.
• Different physical media have different transmission rates, error rates, and characteristics.

Physical Media: Coax, Fiber

• Coaxial cable has two concentric copper conductors and supports bidirectional broadband transmission.
• Fiber optic cable uses glass fibers to carry light pulses and supports high-speed, low-error transmission.

Physical Media: Radio

• Radio signals propagate in the electromagnetic spectrum and are affected by the environment (e.g., reflection, obstruction, interference).
• Different types of radio links include terrestrial microwave, LAN (e.g., WiFi), and wide-area (e.g., cellular) networks.

This quiz covers the basics of networking, including end systems, access networks, links, packet switching, circuit switching, and network structure.