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الخميس، 16 مارس 2017

Mobile IP - Internet Protocol of Mobile


Connectivity to the Internet while in motion is becoming an extremely important part of computing research and development. Mobile IP, created by the Internet 

Engineering Task Force (IETF), is a standard protocol that builds on Internet Protocol by making mobility of a user transparent to applications and higher-level protocols such as Transfer Control Protocol. Mobile IP can be seen as the least common mobility denominator – providing seamless macro mobility solutions among the diversity of access. This paper will attempt to introduce Mobile IP from a technical point of view, while taking into consideration that the reader may not know anything about Mobile IP. However, the reader should know some networking basics before reading further. Building on these concepts, this paper will then discuss effective implementations of Mobile IP, the protocols used by Mobile IP and the importance of Mobile IP. This paper will also introduce Mobile IP from a consumer perspective, i.e. electronic devices (and their Operating Systems) which allow networking mobility.


2.1.         Introduction of Mobile IP

The Internet is an excellent source of information which is readily accessible from almost any computer with a fixed connection to some kind of a network, however with increasing popularity of mobile devices such as PDA’s, internet ready cell phones, PC Tablets, etc, there is a need to provide access to the Internet from a device that may be constantly in motion or wireless access to the Internet. Mobile IP, a standard proposed by the Internet Engineering Task Force (IETF) aims to make mobile computing a reality. The principal advantage of Mobile IP is that it frees the user from a fixed location. Mobile IP makes invisible the boundaries between attachment points, it is able to track and deliver information to mobile devices without needing to change the device’s long-term Internet Protocol (IP) address . 

2.2.         Concept of Computing Mobility 

Before studying Mobile IP, it is important to define the concept of ‘computing mobility’. Computing mobility can be defined as allowing the user some degree of freedom for his/her computing tasks. There are essentially two kinds of computing mobility – Personal mobility and Terminal mobility.

Terminal mobility means that the user and the terminal are mobile as one entity. The terminal may change its point of attachment with the home network without:
  • ·         Informing the network to which it is connected to
  • ·         Having any impact on ongoing network services

Terminal mobility is tied to the Mobile IP protocol itself. Mobile IP does these two things in a seamless and lossless manner, in fact, ideally, the user should not ever be aware of the processes in the background which allow the mobility. This mobility is handled in the network layer; hence application session continuity is inherently provided for, as they will not even have to deal with mobility.

Mobile IP faces many obstacles, but ingenuity in modifying existing technology and communication protocols and adding new technologies have made Mobile IP a reality. Once the technology is perfected, users will enjoy the convenience of seamless untethered roaming and application transparency of nomadic computing. 

2.3.         features of Mobile IP

·         No geographical limitations
·         No physical connection required
·         Modifications to other mobile devices/routers is not required
·         Mobile IP leaves transport and higher-level protocols unaffected
·         No modifications to the current IP address of the mobile device or the format of the IP address
·         Supports security or implements some kind of authentication scheme to provide security

2.4.         Why Mobile IP

Mobile IP faces many obstacles, but ingenuity in modifying existing technology and communication protocols and adding new technologies have made Mobile IP a reality. Once the technology is perfected, users will enjoy the convenience of seamless untethered roaming and application transparency of nomadic computing.
To maintain existing transport-layer connections the node must maintain a single IP address. In Transfer Control Protocol (TCP), the overwhelmingly popular protocol for Internet connections, the connections are indexed by a quadruplet that is analogous to someone’s geographical home address. This set of numbers is what allows for delivery of a packet of data.  If any of these numbers are changed then the connection will most likely be lost. Correct delivery of data packets to the node depends on the network number contained within the node’s IP address.

If the node is mobile, packets sent to this node may never make it as, logically, mobility will force a new IP address to be associated with the node every time it changes its connection point. Constantly changing IP address of a node will make transparent mobility impossible.
Mobile IP was designed to solve this problem by allowing the node to use two IP addresses:
  • ·         Home address
  • ·         Care-of address 


IP addresses are typically associated with a fixed non-mobile location such as a router or a client computer. IP routes packets from a source to a destination by allowing routers to forward packets from incoming network interfaces to outbound interfaces according to routing tables. These routing tables typically maintain the next-hop information for each destination IP address, which is based on the number of networks to which that IP address is connected. The network number is derived from the IP address by masking off some of the low order bits. Thus, the IP address specifies the node’s point of attachment.

logically connected to the home network. Mobile IP enables mobile nodes to surf the Internet, but remain addressable via their home network [4.CP.1996]. The care-of address changes at each new point of attachment; it indicates the network number and thus identifies the mobile node’s point of attachment with respect to the network topology.

The home address makes it appear that the mobile node is continually able to receive data on its home network where a network node known as the home agent assists in this operation. The home agent’s principal job is to get data packets intended for the mobile node and deliver them transparently to the mobile node’s current point of attachment. Whenever the mobile node is in a foreign network, delivery of data to the mobile node is taken care of by the foreign agent. 

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