Advanced Mobile IP

The Problem

When you move between networks, there’s a delay:

1. You detect you’ve moved
2. You get a new Care-of Address
3. You tell the Home Agent
4. Home Agent updates its records

During this time, packets are lost.

The following protocols try to fix this in different ways.

HMIPv6 (Hierarchical MIPv6)

Problem: Every time you move, you tell the Home Agent. But the Home Agent might be far away. That takes time.

Solution: Add a local anchor called MAP (Mobility Anchor Point).

How HMIPv6 Works

Instead of telling the distant Home Agent every time you move:

• You tell the nearby MAP
• MAP handles local mobility
• Home Agent only knows about MAP, not your exact location

“Don’t bother the faraway Home Agent for local moves.”

Two Addresses in HMIPv6

• Regional CoA (RCoA) - Address at MAP level. Doesn’t change when you move locally.
• Local CoA (LCoA) - Your actual current address. Changes with every move.

When you move within the same region, only LCoA changes. The Home Agent never needs to know.

FMIPv6 (Fast MIPv6)

Problem: You detect you’ve moved after you’ve already moved. By then, packets are lost.

Solution: Predict the handover and prepare before you move.

How FMIPv6 Works

1. Your phone detects signal is getting weak (you’re about to move)
2. Before you disconnect, you get a new CoA from the next network
3. You tell the old router: “Forward my packets to this new address”
4. You move
5. Packets were already being forwarded. No loss!

“Start forwarding before you actually move.”

Two Modes

• Predictive mode - You had time to prepare before moving (best case)
• Reactive mode - You moved too fast, do it after (fallback)

PMIPv6 (Proxy MIPv6)

Problem: MIPv6 requires the phone to do a lot of work. What if the phone doesn’t support MIPv6?

Solution: The network does everything. The phone doesn’t even know mobility is happening.

How PMIPv6 Works

Two new entities:

• MAG (Mobile Access Gateway) - The router you connect to. Detects when you arrive/leave.
• LMA (Local Mobility Anchor) - Central anchor that tracks where you are.

When you move:

1. New MAG detects you
2. New MAG tells LMA: “The mobile node is with me now”
3. LMA updates the tunnel

Your phone does nothing. It thinks it never moved.

“Let the network handle it. Phone doesn’t need to know.”

Comparison

HMIPv6 vs FMIPv6

Similarities:

• Both improve MIPv6
• Both require phone to support MIPv6
• Both reduce handover problems

Differences:

Summary