The Internet
Packets, protocols, routing and fault tolerance.
The internet is a network of networks that moves data in small chunks called packets. Each packet carries part of the message plus addressing information, and routers forward packets hop by hop toward their destination. Packets from one message may take different routes and arrive out of order; the receiving computer reassembles them.
Protocols are agreed rules that make this work. IP handles addressing and routing, TCP makes delivery reliable by numbering packets and resending lost ones, and HTTP carries web pages on top. Because there are many possible paths, the internet is fault tolerant: if one link fails, traffic is routed around it.
Key ideas
- IPv4 addresses are 32 bits ( billion); IPv6 uses 128 bits.
- DNS translates names like example.com into IP addresses.
- Bandwidth is how much data per second a link carries; latency is the delay.
- Redundant paths provide fault tolerance but cost more.
Worked example
How long does it take to send a 50 megabyte file over a 100 megabit-per-second connection, ignoring overhead?
- Convert bytes to bits: megabits.
- Time seconds.
- Real transfers take longer because of protocol overhead and latency.
Answer: seconds
Common mistakes
- Mixing up megabytes (MB) and megabits (Mb).
- Assuming packets always travel the same route in order.
- Thinking the web and the internet are the same thing; the web is one service that runs on the internet.
Practice questions
Try each one, then open the answer. Numerical answers on this page are verified by an automated calculation check.
1.How many addresses does a 32-bit address space hold?
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2.Time (s) to send 200 megabits at 25 megabits per second.
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3.Which protocol resends lost packets: IP or TCP?
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TCP