Lecture 9: Mobile IP - Linköping University · 2006-07-24 · Lecture 9: Mobile IP Literature: Forouzan ch.27 Article: Mobile IP by Charles E. Perkins, ... Double Crossing. TSIN02

TSIN02 - Internetworking

© 2004 Image Coding Group, Linköpings Universitet

Lecture 9: Mobile IPLiterature:

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 interactionsin 3G networks by Faccin, S.M.; Lalwaney, P.; Patil, B.Communications Magazine, IEEE ,Volume: 42 , Issue: 1 , Jan. 2004, Pages:113 -120


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Lecture 9: Mobile IPGoals:


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Lecture 9: Mobile IP

Outline:

Mobile IP - Introduction

Addressing

Agents

Three Phases

Agent discovery

Registration

Data transfer

Inefficiency


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Mobile IP - Introduction

Wireless connections to the Internet are now common.

802.x series

Bluetooth

GPRS

3G

Mobility is sometimes a desired feature. This means thatsessions are transferred between network accesspoints “on- the- fly”.


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Addressing

The IP addresses are designedThe IP addresses are designedto work with stationaryto work with stationary

hosts because part of the addresshosts because part of the addressdefines the network todefines the network to

which the host is attached.which the host is attached.


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Addressing cont.

Possible solutions:

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

Get a new IP- address. This requires thatconfiguration files are changed, the computer must berebooted, DNS tables need to be revised and anyongoing transmission will be interrupted.

Two addresses:

Home address

Care- of address


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Host address and Care- of Address

Mobile IP has two addresses for a mobile host: one home address and one care-Mobile IP has two addresses for a mobile host: one home address and one care-of address. The home address is permanent; the care- of address changes as theof address. The home address is permanent; the care- of address changes as themobile host moves from one network to another.mobile host moves from one network to another.


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Agents

The change of address should be transparent to the restof the Internet. This is achieved through the use ofagents:

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

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

Sometimes the mobile host can act as a foreign agent(co- located care- of address)


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Home Agent and Foreign AgentTSIN02 - Internetworking

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Three Phases

These three phases describes how to communicate witha remote host:

1) Agent discovery – the mobile host needs to discoverthe addresses of both home and foreign agent.

2) Registration – update information stored by home andforeign agents

3) Data transfer


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Agent AdvertisementTSIN02 - Internetworking

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Agent Advertisement cont.

Description of the fields:

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 agentaccepts requests

Code (8 bits)

List of care- of addresses

Bit Meaning0 Registration required1 Agent busy2 Agent acts as home agent3 Agent acts as foreign agent4 Agent uses minimal encapsulation5 Agent uses generic routing encapsulation6 Agent supports header compression7 Unused


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Router Advertisement MessageTSIN02 - Internetworking

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Registration

There are four aspects of registration. The mobile agentmust:

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 ReplyTSIN02 - Internetworking

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Registration Request Format

Sent using UDP port 434


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Registration reply format

Sent using UDP port 434


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Data Transfer


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Data Transfer cont.

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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Double Crossing


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Triangle RoutingTSIN02 - Internetworking

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Mobile IP v6

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

MIPv6 supports route optimization

Both care- of address and home address are sentalong with the message so that the remote host canuse the care- of address for direct transmission.

Message overhead have been reduced


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Mobile IP in 3G Networks

There are two dominating 3G networks:

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

care- of address.

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

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 Mobile IP

The Session Initiation Protocol (SIP) has been chosenfor the support of IP multimedia services (IMS) in both3GPP and 3GPP2.

In 3GPP IPv6 is used for IMS.

Both IPv4 and IPv6 are allowed for IMS in 3GPP2networks.

SIP also supports mobility.


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SIP and MIPv4

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

With SIP, the packet payload also needs modification bythe NAT. This requires an ALG, since NATs normallydoes not modlfy the payload.

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


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SIP and MIPv6

At SIP registration an IP address is provided.

When Mobile IP is used, there are two addressesavailable, home address and care- of address

The home address should be used for SIPcommunication to make the changes in IP addressestransparent to applications.

The care- of address should be used for SIP signaling toavoid 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 beenstandardized.

Documents

Lecture 9: Mobile IP - Linköping University · 2006-07-24 · Lecture 9: Mobile IP Literature: Forouzan ch.27 Article: Mobile IP by Charles E. Perkins, ... Double Crossing. TSIN02