OCR A Level Computer Science (H446)Specification point 1.3.3

OCR H446 1.3.3: Networks

The free BugBot lessons that teach this point, a robot to try it on, and the past-paper questions that test it.

What it covers

At GCSE (F10.3) you met bandwidth as "how much data a connection carries each second", and worked out transfer times. At A level you need to be more precise. This lesson looks at how bits actually travel down a link: one at a time or several at once, with or without a shared clock. Then it separates four words that GCSE blurred together: baud rate, bit rate, bandwidth and latency, and ends with why every link needs a protocol.

  • Serial and parallel
  • Synchronous and asynchronous
  • Baud rate and bit rate
  • Bandwidth and latency
  • Protocols
Read the free lesson (25 min)

Or do it in the simulator, with tasks that mark themselves

Lessons that teach it

  1. A12.1 Communication methods Networks and the web
    Serial and parallel, synchronous and asynchronous, baud rate, bit rate, bandwidth, latency and protocols.
  2. A12.2 Topologies and wireless networks Networks and the web
    Physical and logical bus and star; Wi-Fi, SSIDs, WPA2 and CSMA/CA with RTS/CTS.
  3. A12.3 How the Internet works Networks and the web
    Packet switching, routers and gateways, URLs, fully qualified domain names and DNS.
  4. A12.4 The TCP/IP stack and protocols Networks and the web
    The four layers, encapsulation, ports and sockets, and HTTP, HTTPS, FTP, SMTP, POP3 and SSH.
  5. A12.7 Internet security Networks and the web
    Firewalls, packet filtering, proxies and stateful inspection; encryption, certificates and signatures; worms, trojans and viruses.
  6. A12.8 Client server, REST and thin clients Networks and the web
    Peer to peer and client server, websockets, CRUD and REST with JSON, and thin versus thick clients.
  7. A12.10 Project: a reliable link Networks and the web
    Receive a route as packets out of order, reject the damaged one, and drive it.

Try it on a robot

The task from A12.1 Communication methods, running here. Change the program and press Run.

The specification is OCR's own document; this page says which of our lessons teach point 1.3.3 and is not endorsed by the board.