Packet Movement & Encapsulation
Watch data get wrapped at each layer on the way out, then unwrapped on arrival
Sender (192.168.1.10)→ SW1 → R1 → Internet → Receiver (203.0.113.10)
Application
Data
Browser
HTTP GET / — payload handed to transport
Transport
Segment
TCP
adds source/destination ports + seq/ack, checksum
Network
Packet / Datagram
IP
adds source/destination IP addresses + TTL
Data link
Frame
Ethernet
adds MAC addresses + FCS trailer
Physical
Bits
NIC
frames serialised to electrical/optical signals
PDU names at each layer
Application → Data
Transport → Segment
Network → Packet / Datagram
Data link → Frame
Physical → Bits