The Problem
Your phone has an IP address. When you move from one network to another, you get a new IP address.
But any ongoing connections (video call, download) break. The other side is still sending packets to your old address.
The Solution: Two Addresses
Mobile IP gives your device two addresses:
Home Address (HA)
Your permanent address. Never changes.
This is what other devices use to reach you. Think of it like your permanent mailing address.
Care-of Address (CoA)
Your temporary address. Changes every time you move.
This is where you actually are right now. Think of it like your hotel address when traveling.
How It Works
Someone sends a packet to your Home Address. But you’re not home.
Your Home Agent (a router at your home network) knows you’ve moved. It forwards the packet to your current Care-of Address.
You receive it wherever you are.
The Mail Analogy
Imagine you’re traveling but still want to receive mail:
- Home Address is like your permanent home address, where people send letters
- Care-of Address is like the hotel you’re staying at right now
- Home Agent is like a family member at home who forwards your mail to your hotel
The sender doesn’t need to know you moved. They keep sending to your home address, and it gets forwarded to wherever you are.
Why This Matters
| Without Mobile IP | With Mobile IP |
|---|---|
| Connection breaks when you move | Connection stays alive |
| Apps need to reconnect | Seamless handover |
| Downloads restart | Downloads continue |
Mobile IP = Location transparency. Move anywhere, keep the same address.