Communications technology (A Level) flashcards

Topic 14: Communications technology

Physical vs logical topology

Physical topology is the cabling layout; logical topology is how data flows. A hub-based star is a physical star but a logical bus.

Hub vs switch

A hub broadcasts to all ports. A switch sends a frame only to the port of the destination MAC address.

Bridge vs router vs gateway

A bridge joins two segments using the same protocol. A router forwards packets between networks by IP address. A gateway joins networks that use different protocols.

What does a repeater do, and what does a WAP do?

A repeater regenerates a weak signal. A wireless access point joins wireless devices to a cabled LAN.

What does a proxy server do?

It acts as a go-between for internet requests: it filters them, caches pages and hides internal addresses.

Packet vs circuit vs message switching

Packet: data split into packets that take separate routes and are reassembled. Circuit: a dedicated channel for the whole session. Message: the whole message is stored and forwarded node by node.

Static vs dynamic routing

Static routing uses manually set tables: secure, but cannot adapt. Dynamic routing updates automatically: it adapts to changes but uses bandwidth.

How does BitTorrent transfer a file?

The file is split into pieces downloaded from many peers at once, and each peer also uploads pieces to others.

How is data sent by satellite?

Data is encoded and modulated, sent from a ground station uplink, amplified by the satellite's transponder, sent down on another frequency, and decoded by the receiving dish.

How can the effects of a disaster on a network be minimised?

UPS and surge protection, passwords and access control, anti-malware, off-site back-ups and a tested restore plan.