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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