Networks and the Internet

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infoWhy this? A technical model of networks explains how connected devices exchange data and share services. Understanding hardware, addressing, packet switching, protocols, and performance enables us to explain web communication, diagnose simple problems, and reason about network security.

scheduleWhy now? Knowledge of digital representation and encryption can now be applied to data travelling between systems. The unit also prepares us to build websites with an understanding of clients, servers, DNS, HTTP, and HTTPS, rather than treating webpages as isolated files.

A network is a set of connected devices that share data and resources.
A LAN covers a small local area, while a WAN spans larger geographic distances.
The Internet is a global network of interconnected networks that use the TCP/IP protocol suite, whereas the World Wide Web is a service accessed over the Internet.
Many network communications follow a client-server model (clients request services; servers provide them).
A protocol is an agreed set of rules for communication between devices and services.
Switches forward frames within a LAN using MAC addresses (hardware/device addresses).
Routers forward packets between different networks using IP addresses.
Wireless access points connect wireless devices to a wired network.
An IP address identifies a device on a network.
Packet switching breaks data into packets that can travel independently.
Packets can take different routes and may arrive out of order; reliable delivery and reassembly are handled by protocols (commonly TCP).
Ports help direct network traffic to the correct service on a device (e.g., web traffic to a web service).
DNS translates domain names into IP addresses.
HTTP is a web protocol for requesting and sending web resources.
HTTPS is HTTP secured using encryption (TLS).
Bandwidth is the maximum amount of data that can be transferred per second.
Latency is the delay between sending data and receiving a response.
Packet loss is when some packets fail to reach their destination.

rocket_launchYou must be able to

Explain the role of core networking hardware in data transfer, including the difference between switching and routing.
Describe the path from entering a URL to receiving webpage data using client/server and protocol language.
Explain, at a conceptual level, why HTTPS improves security over HTTP.
Diagnose simple performance issues using network metrics.

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