The internet, the web and IP addressing
The internet and the web
- People say "internet" and "web" as if they mean the same thing — they don't.
- The internet is the global infrastructure; the web is just one service on it.
- And every device on it needs an address: an IP address.
Internet vs the World Wide Web
- The internet is a global network of networks using a common protocol suite (TCP/IP).
- The World Wide Web (WWW) is a service that runs over it: hyperlinked documents (URLs) viewed in browsers via HTTP/HTTPS.
- Email and file transfer are other internet services that are not part of the WWW.
What is the relationship between the internet and the World Wide Web?
The internet is the global network; the WWW is one service on it (hyperlinked documents). Email and file transfer are other internet services.
IP addresses
- An IP address uniquely identifies a device on a network.
- IPv4 — 32-bit, four denary numbers 0–255 (
192.168.1.10); only about $4.3 \times 10^9$ addresses (now exhausted). - IPv6 — 128-bit, eight groups of four hex digits; about $3.4 \times 10^{38}$ addresses — vastly more.
How many bits are in an IPv4 address?
IPv4 is 32-bit (four numbers 0–255). IPv6 is 128-bit.
The main reason IPv6 was introduced is that:
IPv4's ~4.3 billion addresses are exhausted; IPv6's 128 bits give about $3.4 \times 10^{38}$ addresses.
Subnetting
- A network can be split into subnets. The IP address divides into a network part and a host part.
- A subnet mask (e.g.
255.255.255.0) marks which bits are the network part (here the first 24). - Subnetting improves management, cuts broadcast traffic, and improves security.
A subnet mask is used to:
The mask (e.g. 255.255.255.0) marks the network bits, splitting the address into network and host portions.
Public/private and static/dynamic
- Private addresses are used inside a LAN and are not routable on the internet (e.g.
192.168.x.x); public addresses are globally unique, assigned by an ISP. - Devices behind NAT with private addresses aren't directly reachable from outside — some protection.
- Static IPs are fixed (for servers that must be found at a known address); dynamic IPs are handed out by DHCP and may change (easier for client devices).
A static IP address is most suitable for:
Servers need a fixed address so clients can always reach them. Client devices usually get dynamic addresses from DHCP.
A private IP address (e.g. 192.168.1.5):
Private addresses work only inside the LAN and are not routed on the internet; NAT lets them share a public address.
You've got it
- the internet = network of networks (TCP/IP); the WWW = one service (web pages) on it
- IPv4 = 32-bit (≈4.3 billion, exhausted); IPv6 = 128-bit (vastly more)
- a subnet mask splits an IP into network + host parts
- private (LAN, not routable) vs public (ISP); static (servers) vs dynamic (DHCP)