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Mobile IP: IP Mobility Support Protocol for IPv4 & IPv6
Mobile IP is the key protocol to enable mobile computing and networking, which brings together two of the world's most powerful technologies, the Internet and mobile communication. In Mobile IP, two IP addresses are provided for each computer: home IP address which is fixed and care-of IP address which is changing as the computer moves. When the mobile moves to a new location, it must send its new address to an agent at home so that the agent can tunnel all communications to its new address timely.
The main components defined in the Mobile IPv6 architecture are shown as follows:
- Mobile node - A mobile unit that can change links, and therefore addresses, and maintain reachability using its home address.
- Home link - The link from which the mobile node originates.
- Home address - An address assigned to the mobile node when it is attached to the home link and through which the mobile node is always reachable, regardless of its location on an IPv6 network.
- Home agent - A router on the home link that maintains registrations of mobile nodes that are away from home and their current addresses.
- Foreign link - A link that is not the mobile node's home link.
- Care-of address - An address used by a mobile node while it is attached to a foreign link. The association of a home address with a care-of address for a mobile node is known as a binding.
- Correspondent node A node that communicates with a mobile node. A correspondent node does not have to be Mobile IPv6-capable.
There are two versions of Mobile IP: Mobile IP for IPv4 and IPv6. The major differences are summarised as follows:
|
Key Features |
Mobile IPv4 |
Mobile IPv6 |
|
Special router as foreign agent |
Yes |
No |
|
Support for route optimization |
Part of the protocol |
In Extensions |
|
Ensure symmetric reachability between mobile nodes and its router at current location |
No |
Yes |
|
Routing bandwidth overhead |
More |
Less |
|
Decouple from Link Layer |
No |
Yes |
|
Need to manage Tunnel soft state |
Yes |
No |
|
Dynamic home agent address discovery |
No |
Yes |
Protocol Structure - Mobile IP Protocol Structure Mobility IPv6 Protocol header structure:
|
8 |
16 |
24 |
32 bit |
|
Next Header |
Length |
Type |
reserved |
|
Checksum |
Data (variable) |
-
Next Header - Identifies the protocol following this header.
- Length - 8 bits unsigned. Size of the header in units of 8 bytes excluding the first 8 bytes.
- Type - Mobility message types.
|
Type |
Description |
|
0 |
BRR, Binding Refresh Request. |
|
1 |
HoTI, Home Test Init. |
|
2 |
CoTI, Care-of Test Init. |
|
3 |
HoT, Home Test. |
|
4 |
CoT, Care-of Test. |
|
5 |
BU, Binding Update. |
|
6 |
Binding Acknowledgement. |
|
7 |
BE, Binding Error. |
-
reserved - MUST be cleared to zero by the sender and MUST be ignored by the receiver.
- Checksum - The 16 bit one's complement checksum of the Mobility Header.
- Data - Variable length.
Related Protocols
IP , UDP , IGMP , ICMP
Sponsor Source
Mobile IP standard is defined by IETF (http://www.ietf.org ) RFC 3344, and RFC 3775.
Reference
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