Chapter 1: Computer Networks and the Internet

1.1: What is the Internet?

The Internet is a computer network that interconnects hundreds of millions of computing devices throughout the world.

1. Hosts (end systems)
   • Computing devices (servers, desktops, phones, laptops)
   • Run network apps
2. Routers
   • Forward packets (chunks of data) to destinations
3. Communication Links
   • Connect hosts & routers
   • Fiber, copper, radio, satellite
   • Transmission rate = bandwidth (bits/second)
4. Protocols
   • Control sending/receiving of messages (e.g. TCP, IP, HTTP, FTP, SMTP)

Internet: “network of networks” - loosely hierarchical. Mostly decentralized; no single authority

Internet Standards

• IETF: internet Engineering Task Force
• RFC: Request for comments

Protocols define format, order of messages sent and received among network entities, and actions taken on message transmission/receipt

Image from lecture slides

Network edge - applications and hosts

Network core - routers and links

1.2: The Network Edge

Computers and devices connected to the Internet are often referred to as end systems because they sit at the edge of the Internet. End systems can include desktop computers (PCs, Macs, and Linux boxes), servers (Web and email-servers), and mobile computers (laptops, smartphones, and tablets).

Host = end system

Hosts can be divided further into clients and servers.