Lecture 9: Mobile IP

TSIN02 - Internetworking


Lecture 9: Mobile IP Goals:

Lecture 9: Mobile IP

Literature:

Forouzan ch.27

Article: Mobile IP by Charles E. Perkins,

IEEE Communications Magazine,Vol. 40 , Issue: 5 , May 2002, Pages:66 - 82

Article: IP multimedia services: analysis of mobile IP and SIP interactions in 3G networks by Faccin, S.M.; Lalwaney, P.; Patil, B. Communications Magazine, IEEE ,Volume: 42 , Issue: 1 , Jan. 2004, Pages:113 120

© 2004 Image Coding Group, Linköpings Universitet

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Lecture 9: Mobile IP

Mobile IP - Introduction

Outline:

Wireless connections to the Internet are now common.

Mobile IP - Introduction

802.x series

Addressing

Bluetooth

Agents

GPRS

Three Phases

3G

Agent discovery

Registration

Data transfer

Mobility is sometimes a desired feature. This means that sessions are transferred between network access points “on- the- fly”.

Inefficiency 3

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Addressing

Addressing cont. Possible solutions:

The IP addresses are designed to work with stationary hosts because part of the address defines the network to which the host is attached.

Keep IP- address and update routing tables. Not realistic to update all routers every time a host moves to a new network.

Get a new IP- address. This requires that configuration files are changed, the computer must be rebooted, DNS tables need to be revised and any ongoing transmission will be interrupted.

Two addresses:

Home address

Care- of address

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Host address and Care- of Address

Agents The change of address should be transparent to the rest of the Internet. This is achieved through the use of agents:

A home agent – acts on behalf of the mobile host.

A foreign agent – handles the connection between the mobile host and its home agent.

Sometimes the mobile host can act as a foreign agent (co- located careof address) Mobile IP has two addresses for a mobile host: one home address and one careof address. The home address is permanent; the careof address changes as the mobile host moves from one network to another. 7

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Home Agent and Foreign Agent

Three Phases These three phases describes how to communicate with a remote host: 1) Agent discovery – the mobile host needs to discover the addresses of both home and foreign agent. 2) Registration – update information stored by home and foreign agents 3) Data transfer

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Agent Advertisement

Agent Advertisement cont. Description of the fields:

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Type (8 bits) - set to 16

Length (8 bits) – total length of extention message

Sequence number

Lifetime (16 bits) – the number of seconds that the agent accepts requests

Code (8 bits)

List of careof addresses

Bit 0 1 2 3 4 5 6 7

Meaning Registration required Agent busy Agent acts as home agent Agent acts as foreign agent Agent uses minimal encapsulation Agent uses generic routing encapsulation Agent supports header compression Unused

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Router Advertisement Message

Registration There are four aspects of registration. The mobile agent must:

Register with the foreign agent

Register with the home agent

Renew registration if expired

Cancel registration when returning home

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Registration Request and Reply

Registration Request Format

Sent using UDP port 434 15

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Registration reply format

Data Transfer

Sent using UDP port 434

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Data Transfer cont.

Double Crossing

1) From remote host to home agent 2) From home agent to foreign agent 3) From foreign agent to mobile host 4) From mobile host to remote host Not very efficient!

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Triangle Routing

Mobile IP v6

There is no need for foreign agents in MIPv6 since there are plenty addresses available.

MIPv6 supports route optimization

Both careof address and home address are sent along with the message so that the remote host can use the careof address for direct transmission.

Message overhead have been reduced

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Mobile IP in 3G Networks

SIP and Mobile IP

There are two dominating 3G networks:

The Session Initiation Protocol (SIP) has been chosen for the support of IP multimedia services (IMS) in both 3GPP and 3GPP2.

GPRS/UMTS (Specified by 3GPP) The mobile host gets IP connectivity through a GGSN which provides the careof address.

In 3GPP IPv6 is used for IMS.

MIP is not explicitly supported, but can be used to support mobility in multi- access networks.

Both IPv4 and IPv6 are allowed for IMS in 3GPP2 networks. SIP also supports mobility.

CDMA2000 (Specified by 3GPP2) Here a PDSN (Packet Data Switching Node) provides the link between the radio network and the Internet. MIPv4 is deployed, MIPv6 is only partly supported.

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SIP and MIPv4

SIP and MIPv6

When a mobile host connects to an IPv4 network, NATs are needed to connect to a IPv6 SIP infrastructure.

At SIP registration an IP address is provided. When Mobile IP is used, there are two addresses available, home address and careof address

With SIP, the packet payload also needs modification by the NAT. This requires an ALG, since NATs normally does not modlfy the payload.

The home address should be used for SIP communication to make the changes in IP addresses transparent to applications.

There are some routing issues that makes IMS services over MIPv4 complex and inefficient.

The careof address should be used for SIP signaling to avoid tunneling

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Closing remarks

MIPv4 has been a standard for some years

MIPv6 is not yet a standard

The interworking of SIP and MIP has not yet been standardized.

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