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Mobile IP is most effective in the current environment where mobility is popular and the existing models cannot give the competent solution for the requirements of the users. "It is an open standard of the Internet Engineering Task Force (IETF) that allows users to hold the same IP address without terminate the session and maintain current applications while moving different networks". But later on it was found that Mobile IP cannot work efficiently. So, to adjust this problem Mobile IP enhanced to Mobile IPv6 and cellular IP.
Review of Mobile IP
Mobile IP means that now there are many network attachable devices including handset devices which can be connected to the network. Now what is the problem, whenever you go, there have to be some way in which the physical connection is made and the connection maybe wireless, it could be wired although the wireless connection is more dominant but the problem is what happens with the IP address? Your device has a particular IP address which it gets from your home base but if you move to some other place and the correspondent host wants to talk to you; it will be using your IP address that what is known to him. So, it will try to reach you using the old IP address but using the old IP it will land up your home base, you are no longer in your home network. So, that is the problem with the mobile IP that when a particular network device is travel from one network to another network than how to keep communicating.
To solve this issue the mobile IP was introduced to have the same IP address during the device moves to the other network so that the connection or the session of the device is not being terminated. This is just because of mobility function of Mobile IP which works on the network layer instead of physical layer. So the mobile device maintains the connections and the current applications through the different kinds of wireless and wired network. For example, remote login, printing and file transfer processes where it is unsuitable to disturb the session during the mobile device moves through different networks edges.
Terminologies of Mobile IP
This session covers the Mobile IP basic concepts. It can implement both on IPv4 and Ipv6. First of all, terms of Mobile IP this used rest of this topic.
Mobile Node (MN)
Mobile Node is device that travels through different networks.
Home Agent (HA)
Home agent is the device from where Mobile node registered first time and later on it tunnels The IP datagram to the care of address
Foreign Agent (FA)
Foreign Agent is the devices which server the mobile node during its visit to foreign network.
Care-of Address (COA)
This is the temporary address which Foreign Agent assigns to the Mobile node on visit.
Correspondent Node (CN)
A device which communicates with the mobile node during it foreign visit
How Mobile IP Works
Mobile Node is equipment like a cell phone, personal digital assistant, or laptop whose software allows the network roaming facility. Home agent is a communication center of the mobile node's home network which provides the IP identification to the mobile node. The mobile node is assigned a care of address, so this is the new address. One the mobile nodes which is remain constant which is actually belongs to the network in the home base but it also gets the care of address from the foreign network. This address is used to deliver the datagram for the mobile node. This can be either being the foreign agent or it can be "co-located" with the mobile node, so that is also possible.
In the above figure, A is a mobile device that moves from the home network to another network which is visited network of A. On home network there is a home agent who is helping in the communication and the visited network it looks or finds the foreign agent for keep the communication. The foreign agent gives the care of address to the mobile node and sends the information to the home network of the mobile node through internet. Suppose some source want to send something to A, so it will use the A's actual IP address and it will routed to the home network of A. Home network send this routed information to the home agent. Home agent knows that the mobile node is no longer to home network and it also knows its temporary IP address (COA). So, it tunnels the communication to the visited network agent using the temporary address. Foreign agent delivers the message to the A because it knows the current location of A. now A directly reply back to source because it knows the original IP address of the correspondent node
Mobile IP functionality is based on three main tasks. First task is an Agent Discovery; the home agent has to aware of its current location. The second task is, Registration which means, the mobile device has to register in the visited network. Finally, the most important task is to inform the HA about its new place and HA can send packets to the right direction, called tunneling.
Mobility agents should advertise their service that means some mobile nodes comes to know that this foreign agent or home agent is available and a mobile node can request for mobility agents that is also possible.
When a mobile node is travel from home to the foreign network, it must register a temporary IP address called care of address with its home agent. So, the home agent can tunnel the information to mobile node through Care of address.
There are various methods of tunneling such as, IP-in-IP encapsulation, minimal encapsulation etc.
In the above diagram, the original message which was sent from the source and which landed in the home network of the destination. So, this IP header will contain the actual home address of A with its datagram. So, what it does in when it launch into the home agent. Home agent knows that this has been sent somewhere else. It keeps the inner IP header and datagram in-tag. This whole thing is considered now as a pay load and then you add another IP header with some options if necessary and the new IP header will have as its destination the tunnel in point that means care-of-address. So, the inner packet would be actually in the packet. The whole thing is encapsulated as this a pay load and sent to the foreign network in the care-of-address. It will reach the visited network agent and the agent will then send this part to the mobile node who is currently connected and its MAC address known to the foreign agent. The mobile agent or the mobile node will receive the whole packet including the inner IP header. Now you donot require any kind of change in the software which handles it just like a normal packet. Its mean as it was in the home network and got this original packet.
The other option is the minimal encapsulation. It means that you do not keep the entire IP header intaged in this thing so you want to just retain the minimal information in the minimal header and then construct an outer IP header. So, outer IP header tunnel end points as the source and destination are still be there and some of the message of the IP header will also attach.So, you have to make some deconstruction and reconstruction at both places.
So, this is called mobile IP, one way in which mobility can be handled and your IP address can be recomputed.
Advantages of Mobile IP
Mobility was an issue which was not considered at the time when the internet protocols was intended. As the time pass the use of phones increased and also with that the use of mobile devices increased and there was an issue raised that how to communicate between these devices. Therefore to overcome this situation, networking was adapted to interact and exchange information with the network devices. Basically mobile IP is set of principles which are used to become accustomed to an increasing mobile environment.
The main advantage of Mobile IP is the continuous connectivity to the internet during the travel of mobile device in different networks. Previously, it always reconnect with the each network where it travels but the mobile IP introduce the easy way of hand off, through this the device travels anywhere without connection lose.
The mobile IP is constructed for large networks which can hold up to thousands of wireless clients, these networks are flexible and easily can be extended to include a bigger area and it can also allow the better communication and connectivity between the wireless users. Therefore the mobile IP setup can easily be enlarged to add new links and connections.
Consistency is the main feature of mobile IP. During travels all the networks, a device maintains the constant IP that authenticate the visited network router to send them their incoming and outgoing information through tunnel.
Mobile IP configuration was implemented as a standard and many advanced network devices used this standard. Companies like Cisco, uses mobile IP standard with their several products because of its easy installation and growth.
Another benefit of mobile IP which make it more attractive, it can integrate with the current network. No need of the extra network design. This feature make mobile IP setup more flexible in any conditions whether to configure another network for communication with the main network.
Issues of Mobile IP
As mobile IP is increasing very quick but still it has some problems which affect its performance. Below we discuss the few problems of Mobile IP
Two away Routing Problem
Triangular routing is one of the main problems of mobile IP. As mentioned above that Correspondent node talks with mobile host through home agent. On the other hand mobile host replies directly to the correspondent host. Both are using different routes which arises the triangular routing issue. It specially effects when the mobile node and the correspondent user are close to each other and the home agent is far away.
Problem in frequent handoff
When mobile node travel form its own network to other networks, the mobile agent tunnel the data through temporary address assign by visited network agent. Now mobile device travels to another foreign network area and there it gets another address which is unknown for mobile agent during the time starts of mobile device leaves the first visited network and finish when mobile agent receive the new address. This will causes the communication problem especially when the handoff is continuously processed or mobile device have more distance with home agent.
Problem in Internal network movement
Sometimes the mobile device travels in the small area and a regular handoff occurs. Therefore, there will be many registration offers generated over the network which can create the problem.
The mobile network has several variations like topology, few recourses, unexpected bandwidth problems and error. With these varying it is difficult to offer the QoS in the mobile IP environment.
Solution/Enhancement of Mobile IP
Mobile IP is not sufficient process in the micro areas of the network. Cellular IP was introduced to solve this problem. There were two different IPs used for the coverage. The micro areas of the network handle by cellular IP while macro area handled by mobile IP. Simplify caches and packets update is another feature of cellular IP.
The new mobility host protocol called Cellular IP optimized for wireless access networks and highly mobile hosts. The main purposes of cellular IP is making the communication simpler. It also makes the communication scalable and improves its processes. It can also be used on the head usual IP router. Second purpose is scalability. It is only possible with organized circulation of locations of cellular IP, which allows using the same topology nodes in all kind of systems like indoor systems, huge area. Because of this, mobile devices can openhandedly travel among the areas of different characteristics.
The main demand of the mobile host protocol is Performance transparency which is not good in wireless environment. It also provides the ability to the network extend on demand. Because the cost of the devices and installation can be boast up when the combined capacity is determined.
There are following features in Mobile IPv6 which makes superior it than mobile IPv4.
In the Mobile IPv4 the packet tunneling to the mobile device uses encapsulation while in Mobile IPv6 uses the routing header. This requires the less extra bytes for header that added to the packet.
Mobile IPv6 provides the updated features to the mobile node like automatic configuration of address and neighbor detection. As in Mobile IPv4 there is no need to install the specific routers for visited agent.
Mobile IPv6 solves the triangular routing problem by providing the best selection of route feature. This feature allows the direct routing between mobile device and the correspondent device. Now there is no need to send the data through home agent.
For traffic control the mobile IPv4 and its best route selection needs extra UDP packets while mobile IPv6 follows the piggy backed solution on any available packets.
Mobile IPv4 the mobile home agent receive any packet for the mobile host by using the ARP while mobile IPv6 has the feature of neighbor detection for this purpose.
Mobile IP believes on a security methods for data binding while Mobile IPv6 consume IP security which meets the all security requirements.