← Computer Networks learning pathComputer Networks · Module 3 of 10
Physical and data link layers
Move bits and frames across links.
📖 Key ideas
- Physical layer: cables (twisted pair, fibre), signals, Wi-Fi radio.
- Data link layer: framing, MAC addresses, error detection.
- Ethernet is the dominant LAN technology.
- Switches learn MAC addresses to forward frames.
- ARP maps IP addresses to MAC addresses.
💡 Real-life example: MAC addresses are house numbers on a street; switches are postmen who learn which house is where.
MAC addressHardware address of a network card
EthernetWired LAN standard
ARPAddress Resolution Protocol
FrameLayer 2 data unit