What is Mobile IP?

Mobile IP is a proposed standard protocol that builds on the Internet Protocol by making mobility transparent to applications and higher-level protocols like TCP. This paper aims at discussing the design principles of Mobile IP and how it can be incorporated into the already existing Internet architecture.

How Mobile IP Works?

Mobile Internet Protocol is a new recommended Internet protocol designed to support the mobility of a user (host). Host mobility is becoming important because of the recent blossoming of laptop computers and the high desire to have continuous network connectivity anywhere the host happens to be. The development of Mobile IP makes this possible.
There are mainly three processes in Mobile IP: 
  1. Agent Discovery: The process by which a Mobile node determines its current location and obtains the care of address. 
  2. Registration: The process by which a Mobile node request service from a foreign agent on a foreign link and informs its home agent of its current care-of address. 
  3. Tunneling: The specific mechanism by which packets are routed to and from a Mobile node that is connected to a foreign link. 
Mobile Computing is becoming increasingly important due to the rise in the number of portable computers and the desire to have continuous network connectivity to the Internet irrespective of the physical location of the node. The Internet infrastructure is built on top of a collection of protocols, called the TCP/IP protocol suite. Transmission Control Protocol (TCP) and Internet Protocol (IP) are the core protocols in this suite. IP requires the location of any host connected to the Internet to be uniquely identified by an assigned IP address. This raises one of the most important issues in mobility because when a host moves to another physical location, it has to change its IP address. However, the higher level protocols require IP address of a host to be fixed for identifying a connection.
The Mobile Internet Protocol (Mobile IP) is an extension to the Internet Protocol proposed by the Internet Engineering Task Force (IETF) that addresses this issue. It enables mobile computers to stay connected to the Internet regardless of their location and without changing their IP address. 
Mobile IP specifies enhancements that allow transparent routing of IP datagrams to mobile nodes on the Internet.  Each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet.

Mobile IP Architecture

mobile IP architecture

Mobile IP Tunneling

Mobile IP requires the use of encapsulation to deliver datagrams from the home network to the current location of the mobile node (its care-of address). In the most general encapsulation (tunneling) case, illustrated in Figure 4. The source, encapsulator, decapsulator, and destination are separate nodes. The encapsulator node is considered the entry point of the tunnel, and the decapsulator node is considered the exit point of the tunnel. Multiple source-destination pairs can use the same tunnel between the encapsulator and the decapsulator. 

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