Computer Network Chapter 1

Study Notes

A network is an interconnection between two or more devices that can send or receive data, enabling the sharing of files and information (email, instant message, voice, video, etc.).
The internet is a global network of networks, and a mobile communication system (e.g. Asia Cell) can be described as a wireless network.

Devices: end-user devices (e.g. cell phone, PC, IP phone, security cameras) generate messages and have their own address; they can be clients or servers.
Intermediary devices (e.g. switches, routers, firewalls) make it possible to deliver data from source to destination; they regenerate and retransmit data signals, determine pathways through the network, and notify other devices of errors and communication failures.
Medium: provides the channel over which the message travels from source to destination; modern networks primarily use three types of media.

Rules: standards and protocols that specify how messages are sent and directed through the network.
Services: include many common network applications like email.

Local Area Network (LAN): spans a single geographical area, providing services and applications to people within a common organizational structure (e.g. a single business, campus, or region).
Wide Area Network (WAN): connects multiple LANs in geographically separated locations.
Internet: created by the interconnection of networks belonging to Internet Service Providers (ISPs), providing access for millions of users worldwide.
Intranet: a private connection of LANs and WANs belonging to an organization, accessible only by authorized members or employees.

IP routing forwards IP packets between networks using routing tables that contain network topology information
Routers examine destination IP addresses to determine the best path for packet forwarding
Routing protocols like RIP, OSPF, and BGP dynamically update routing tables

TCP/IP is a suite of protocols for interconnecting devices on the internet
TCP provides reliable, error-checked, and sequential data delivery between devices
IP provides logical addressing and routing of packets between devices
UDP provides best-effort, connectionless data delivery between devices
Other TCP/IP protocols include ICMP, IGMP, and DNS

Network topology refers to the physical and logical arrangement of devices and connections
Bus topology uses a single cable to connect devices in a linear sequence
Star topology connects devices to a central hub or switch
Ring topology connects devices in a circular configuration
Mesh topology connects each device to every other device
Hybrid topology combines two or more topologies

Wi-Fi is a wireless technology using radio waves to connect devices to a network
Wi-Fi operates on 2.4 GHz and 5 GHz frequency bands
Devices use MAC addresses to identify themselves on a network
Wi-Fi networks use SSIDs to identify themselves to devices
Wi-Fi security protocols include WEP, WPA, and WPA2 for encryption and authentication