Networking and cyber security (A Level) flashcards

Topic 14: Networking and cyber security

Synchronous vs asynchronous transmission

Synchronous: a continuous data stream with sender and receiver clocks kept in step by a timing signal. Asynchronous: characters sent individually, framed by start and stop bits.

Baud rate vs bit rate

Baud rate is the number of signal changes per second. Bit rate is the number of bits transmitted per second; it can be higher than the baud rate if each signal change carries more than one bit.

Why is serial transmission better than parallel over long distances?

There is no skew between bits, no crosstalk between neighbouring wires, and the cable is cheaper with fewer conductors.

Peer-to-peer vs client-server networks

Peer-to-peer: all computers equal; cheap with no dedicated server, but no central control. Client-server: servers provide services that clients request; central backups, security and user management, but server cost and a single point of failure.

Thin client vs thick client

Thin client: processing and storage mostly on the server; cheap terminals, but a fast, reliable network is essential. Thick client: processing and storage on the local machine; lighter network load, but each machine is maintained separately.

How does CSMA/CA with RTS/CTS work?

The sender transmits a Request to Send to the access point, which broadcasts Clear to Send; all other stations stay quiet while the data frame is sent and acknowledged. It solves the hidden-node problem.

How can a wireless network be secured?

Use WPA2 encryption, disable SSID broadcast, and use a MAC address allow list.

What does a packet contain, and what does time to live do?

Source and destination addresses, sequence number, time to live, payload and error detection data. TTL is reduced by 1 at each router and the packet is discarded at 0.