Overview
This lecture explains the basic structure of the internet, focusing on packet switching, routing, and the roles of routers and gateways.
Physical Structure of the Internet
- The internet is a massive network of connected computers and devices.
- Physical internet connections include thousands of miles of undersea fiber-optic cables between continents.
- These cables form the backbone of the internet, handling large volumes of daily data transfer.
Abstract Structure and Domain Name Servers (DNS)
- The internet can be viewed as a vast collection of domain name servers (DNS) and routers.
- DNS servers map web addresses (domain names) to IP addresses, guiding computers to websites.
- DNS servers exist at multiple levels: local ISPs, regional, and large network service providers.
Packet Switching and Routing
- Data sent over the internet is split into packets that may take different routes to the destination.
- Different packets from the same message can travel by different paths based on channel latency and bandwidth.
- Routing uses routing tables to determine the best path for each packet.
Routers and Gateways
- A router forwards packets to their destinations using addresses and chooses the best route using routing tables and algorithms.
- Routers can be either wired or wireless devices.
- A gateway functions like a router but can connect networks using different protocols.
- Gateways remove header information from incoming packets and recreate headers for the destination network and protocol.
Key Terms & Definitions
- Internet — A global network of interconnected computers and devices.
- Backbone — The core infrastructure of the internet, often undersea cables and major data lines.
- Domain Name Server (DNS) — System mapping domain names to IP addresses.
- Packet Switching — Method of sending data in small packets via multiple possible routes.
- Router — Device that forwards data packets to their destination using routing tables.
- Routing Table — Database in routers listing paths to various network destinations.
- Gateway — Device enabling communication between networks using different protocols by modifying packet headers.
Action Items / Next Steps
- Review previous video on the structure of packets and packet switching for more detail.