Mobile IP

Add it into TCP/IP implementation

Wireless communication techniques

Wireless technique

Distance Transfer

rate

Frequency

Bluetooth

802.15 (WPAN)

10 m 3M bps 2.4 GHz

Wi-Fi (WLAN)

802.11

150 m 54 Mbps

WiMAX

802.16 (WMAN)

50 km for fixed station

5-15 km for mobile one

30 Mbps-

75 Mbps?

2-66 GHz

2-11 GHz?

3G (W-CDMA, TD-SCDMA,...)

384 Kbps-14 Mbps

OFDM-MIMO

1. Introduction

Discuss IP address and routing for mobile host(MH).

• MH moves from one network to another ---> its IP address and routing change

• MH moves within wireless LAN ---> its IP address and routing don’t change

Changing an address is time-consuming, requires

rebooting computer, and breaks all existing TCP

connections

Wireless net Wireless net

CELL CELL R—router H—stationary hosts AP—Access Point MH—mobile host RSR—Roam Supervisor Router

Internet

RHH

RSRAP

MH MH

R Network

R H

AP

MH MH

RSR

2. Mobile IP and some concepts

IETF devised mobile IP, a solution to the mobility

problem. • Transparency.

Applications always use MH’s home address. All open TCP connections survive a change in network

• Interoperability with IPv4

MH can interoperate with stationary hosts that run conventional IPv4 software

• home net. ： the network on which MH registers• foreign net. ：• home address ： IP address obtained on home net.

It is permanent and fixed. Applications use it • care-of address ： IP address obtained at foreign

net. It is temporary (variable). IP layer uses it.• home agent ： a router on home net. It agree to int

ercept and tunnel datagrams to MH. • foreign agent ：

Concepts:

I nternet ①

移动 HA—Home Agent A-- 移动主机 R— Router H—固定主机

移动 I Pv4的工作原理示例

B

HA H

R A

FA H

AP

A

Internet ①

move

HA—home agent A—mobi l e host R— router H—fixed host

Principle of mobi le IPv6

B

HAH

RA

R H

AP

A

3. Overview of mobile IP operation

1) MH finds that itself moves to a foreign network

2) MH obtains a care-of address from FA

3) MH(FA) informs HA of its care-of address

4) HA intercepts datagrams sent to the MH’ home address, and tunnel each datagram to the care-of address

5) when MH returns home, it contact HA to deregister

The issues to be solved are 1), 2), 4)

4. Foreign agent discovery --- for 1)

MH uses ICMP router discovery mechanism to find that itself moves to a foreign network. Recall:

• routers periodically send ICMP router advertisement messages to all nodes on the net.

• a host can send an ICMP router solicitation to prompt for an advertisement:

1) Foreign agent discovery

MH has a default router.

If MH receives an ICMP router advertisement

message from other router, it know that itself moves

to a foreign network.

To confirm it, MH can send an ICMP router

solicitation message to ?HA and waits for a reply

FA

2) Agent registration

MH send registrations request to FA, which then contacts HA on its behalf.

Registration message includes:

{ home address, care-of address, HA, …}

FA

5. Obtains a care-of address --- for 2)

Router advertisement message piggybacks

additional information known as a mobility agent

extension which includes care-of addresses :

In practice, there are two types of care-of addresses• foreign agent care of address IPv4• co-located care-of address IPv6

Care-of address

• Foreign agent care of address is one of FA’ IP addresses so that MH doesn’t consume IP address.

• Co-located care-of address is a new IP address allocated to MH by DHCP.

It requires MH to handle all forwarding itself.

Internet ① 移动

B

HA H

R A

FA H

AP

A

6. Datagram transmission and reception--- for 4)

IPA IPB

Send

?

The mobile creates a datagram that has destination computer’s address in the destination field and the mobile’s home address in the source field.

IPB

shortest path

1) MH sends datagram

⑥ Internet ①

移动

B

HAH

RA

FA H

AP

A

IPB IPA

IPB IPA IPHA IPFA

IPB IPA

Receive

• Datagram will travel to the mobile’s home network. • HA intercepts the datagram and uses IP-in-IP encap

sulation to tunnel the datagram to the care-of address

• FA decapsulates the datagram and transmit the datagram to the mobile.

FAHA

2) MH receives datagram