TSIN02 - Internetworking
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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TSIN02 - Internetworking
TSIN02 - Internetworking
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
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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 care- of address)
Mobile IP has two addresses for a mobile host: one home address and one careof address. The home address is permanent; the care- of address changes as the
mobile host moves from one network to another.
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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 care- of 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
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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 care- of address and home address are sent
along with the message so that the remote host can
use the care- of 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
care- of 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 care- of 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 care- of 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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