Networking
It is like…
Encapsulation Is Like Nested Envelopes
Encapsulation is like putting a letter inside envelope after envelope
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Lesson notes
Key points
- Imagine posting a letter to Kumasi: you seal it, put it in an office envelope, then a courier bag.
- Each layer adds its own header around the data, and the receiver strips them off in reverse order.
- Where it breaks: at every router the frame header is replaced with new MACs, while the IP packet inside stays largely the same.
Definitions
- Per-hop framing
- Routers strip and rebuild the Layer 2 frame each hop; source and destination IP stay constant end to end.
Takeaway: Each layer wraps data in a header; frames are rebuilt at every hop.
Quick check: As a packet crosses routers, which addresses change at each hop?
- Source and destination IP
- MAC addresses
- TCP port numbers
Each router builds a new Ethernet frame, so MACs change while IPs stay.
Nested envelopesHeadersRe-framing per hop
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