IP routing is based on the IP reference, which is uniquely individualities a node ‘s point of fond regard to the cyberspace [ 1 ] . When a device moves its place web and enters a new one, it has to alter its IP reference and restore a new TCP connexion. If a communicating with this traveling device happened at that clip, the communicating has to be disconnected until it gets the new IP reference of the traveling device. To work out this mobility issue, a working group within Internet Engineering Task Force ( IETF ) proposed a solution, which is the Mobile IP Protocol.
The thought of nomadic IP is similar to postal service bringing: one time you move to a new location, you ask your place station office to direct your mail to your new location ‘s reference by the local station office at that place. Thus, a nomadic device foremost leaves its place web and connects to a foreign web. The agent so sends packages locally to the nomadic device sing that web.
Mobile IP provides crystalline Routing of IP datagram over Internet. Each nomadic node is identified with his place reference regardless of where its current location is. When a node is moved outside its place web as the node associated with a Care-of Address ( CoA ) , which provides information on its current place.
Mobile IP specifies how a Mobile ‘s device registered with their place agent and how place agent routers connects to the nomadic device through a tunnel. Mobile IP provides an efficient and scalable mechanism for Rolling over the Internet. When utilizing Mobile IP, the devices can alter their connexion to the Internet without altering its IP reference. This means that the device can keep a connexion to Transport bed or higher bed when the device moves and changes its location.
A nomadic node may hold two references, a lasting ( place ) and a impermanent reference ( care-of reference ) , that alterations at each new point of fond regard. By utilizing those both address a nomadic calculating device can be changed its location and moved to a new web without altering its place IP reference and without fring bing connexions. And the traffic redirect automatically between Home reference and care-of reference. There are two versions of nomadic IP, Mobile IPv4 and Mobile IPv6. Mobile IPv4 will be described in more item in this chapter.
When IP packages are exchanged between a host and nomadic device the undermentioned stairss occurs that shown in the figure 4.1:
Server x attempt to link to mobile device by directing IP package with A ‘s place reference in the IP heading. The IP reference is routed to the place web.
The place agent intercept the entrance package and encapsulate the full datagram inside a new IP care-of reference and convey the datagram as burrowing to the foreign agent.
The outer IP heading is removed by the foreign agent and sends the original IP datagram to A through the foreign web.
A nomadic device received the message and direct IP package to X utilizing X ‘s IP reference to the foreign agent across the foreign web.
The foreign web routed the IP package to the X waiter straight across the cyberspace utilizing X ‘s IP reference.
Figure 4.1 Mobile IP Operations [ 2 ]
4.2 Mobile IP Terminology
Mobile IP has the undermentioned elements and entities that required for optimal functionality:
Mobile Node ( MN ) : is a traveling cyberspace connected device which location and point of fond regard to the cyberspace can be changed while maintaining on-going communicating without break via utilizing its place fixed address. This sort of device is normally IP phone, laptop computing machine or router.
Home Address: An IP reference assigned to Mobile device within the web for drawn-out period of clip. It remains the same regardless of where the device is attached to the cyberspace.
Home Agent ( HA ) : is a router on the nomadic device ‘s place web. It tracks the nomadic device location ( attention of reference ) , intercept and tunnels packages to the nomadic device when it is off from place, and maintain s current location information for the nomadic device.
Home Network: is the web within which device its identifying place IP reference. The IP routing mechanism will present packages destined to mobile device ‘s Home Address to the nomadic device ‘s Home Network.
Foreign Agent ( FA ) : is a router on nomadic device ‘s visited web. It provides the care-of-address to the nomadic device and routing service to the nomadic device while registered, act as a default router for datagram generated by the nomadic device. The foreign agent decapsulate and delivers datagram to the nomadic device that were encapsulate by the nomadic device ‘s place agent
Foreign Network: Any web other than the nomadic device ‘s Home Network, which Mobile device can be runing successfully when off from its place web.
Case-of-address: is a impermanent IP reference assigned to mobile device while it is off from place web.
Correspondent Node ( CN ) : A device that sends or receives packages to or from nomadic device ; the letter writer device may be another nomadic device or a non nomadic cyberspace device.
A nomadic device may hold two references, lasting place reference and a Care-of Address ( CoA ) .A care-of reference is a impermanent IP reference that identifies a nomadic device ‘s current point of fond regard to the cyberspace and allows it to link from different location by maintaining its place reference. When a nomadic device is go forthing its place web and linking to any foreign web, it is assigned a care-of reference. This may be a “ foreign agent care-of reference ” which is a inactive reference of a foreign agent with which the Mobile device is registered, and a “ co-located care-of reference ” which is a impermanent IP reference assigned to the nomadic device. A collocated care-of reference is assigned by Dynamic Host Configuration Protocol ( DHCP ) , Point -to Point IP control protocol ( PPP ) , or manual constellation.
Figure 4.2 Mobile IP Components [ 3 ]
4.3 Mobile IP Functionality
Mobile IP map can be spliting by utilizing three mechanisms [ 6 ] :
Detecting the Care-of Address ;
Registering the Care-of Address ;
Burrowing to the Care-of Address ;
4.3.1 Detecting the Case-of Address
The find procedure in Mobile IP is based on the ICMP ( Internet Control Message Protocol ) . The nomadic device is responsible for find procedure by determine if it is attached to its place web or foreign web. Because handoff from place web to the foreign web occurs at the physical bed, a passage between those two different webs can be happened at any clip without presentment to the upper bed ( web bed, i.e. the IP bed ) . The find procedure for nomadic device is a uninterrupted. A particular message called Agent Advertisement is sporadically airing by the place agent or foreign agent to publicize their handiness to any affiliated links. A nomadic device listens to these Agent Advertisement message and compare the web part of the router ‘s IP reference with the web part of its ain place reference. If the web parts lucifer, so the nomadic device is on a place web ; but if it does n’t fit, so the nomadic device is on the foreign web.
If the nomadic device corsets in its place web, so it will work without Mobile IP functionality.
If the nomadic device gets a foreign agent attention of reference, so the foreign agent will be the terminal of the tunnel and will execute the de-capsulation and will present the message to the nomadic device. In the other instance if the nomadic device gets a collocated care-of reference, so the nomadic device it self will execute the decapsulation for the tunneling.
4.3.2 Registering the Care-of Address
Once the nomadic device gets attention of reference and recognized that it is on a foreign web, it is need to state the place agent where it is. And request place agent to send on its IP traffic. This done harmonizing to the undermentioned procedure that is shown in the ( Figure 4.3 ) :
Mobile device petitions send oning procedure by directing a enrollment petition to the foreign agent that nomadic device moved to. This petition contains place reference of nomadic device, care-of reference of the nomadic device and the enrollment life-time.
The foreign agent passes this petition to the place agent of the nomadic device. In some instances, the nomadic device may register straight with the place agent.
Home agent receives the enrollment petition, it either accepted or denied. If the petition accepted, the place agent updates its path tabular array tie ining the place IP reference of the nomadic device with its care-of reference. The place agent keeps the association until the enrollment life-time expired.
The foreign agent frontward this answer to the nomadic device
Registration in Mobile IP must be secured so that malicious enrollment can be detected and rejected.Otherwise, aggressor in the cyberspace could interrupt communicating between the place agent and the nomadic device.Though Mobile IP supply some hallmark methods like designation field and timestamp.
Figure 4.3- Registration procedure
4.3.3 Burrowing to the Care-of Address
Once the nomadic device registries to its place agent, the place agent will be able to stop the IP packages that send to the nomadic device ‘s place reference so that these packages can de transmitted utilizing burrowing. Encapsulation mechanism is used to send on the IP datagram to the care-of-address by infixing the full IP datagram into an outer IP datagram by the place agent. Three different type of encapsulation are used in Mobile IP: IP-within IP Encapsulation, Minimal Encapsulation and Generic Routing Encapsulation ( GRE ) .
IP-within-IP Encapsulation, in this scenario the full original IP package becomes the warhead in the new IP package ( figure 4.4 ) . In the old IP heading, the beginning reference refers to the corresponded device that is directing the original message and the finish reference is the place reference of the nomadic device. In the new IP heading the beginning reference refer to the IP reference of the place agent and the finish reference refer to the care-of reference for the nomadic device.
Minimal Encapsulation, in this scenario the new heading is inserted between the original IP heading and the original IP warhead ( figure 4.5 ) this can be used if both place and foreign agent accepted to make so. Minimal encapsulation consequences in less operating expense.
Home agent encapsulates the datagram as it shown in the ( figure 4.5 ) through the tunneling and direct across the cyberspace to the case-of reference. This minimum heading is de-capsulated to the original heading by either foreign agent or the nomadic device itself.
Generic Routing Encapsulation ( GRE ) is an optional tunneling method used by nomadic IP. GRE tunnel built a practical point-to-point nexus between two routers at distant point over an IP internetwork. GRE is good in certain application because it is support multiprotocol and supply bar of recursive encapsulation.
Figure 4.4 IP within IP encapsulation [ 4 ]
Figure 4.5 Minimal Encapsulation [ 5 ]
[ 1 ] H. Hansen, “ IPSec and Mobile IP in Mobile Ad Hoc Networking “ , Helsinki University of Technology, April 2000.
[ 2 ] hypertext transfer protocol: //www.cisco.com/web/about/ac123/ac147/images/ipj/ipj_4-2/figure1.gif
[ 3 ] hypertext transfer protocol: //www.cisco.com/en/US/tech/tk827/tk369/technologies_white_paper09186a00800a4444.shtml
[ 4 ] hypertext transfer protocol: //www.cisco.com/web/about/ac123/ac147/images/ipj/ipj_4-2/figure4a.gif
[ 5 ] hypertext transfer protocol: //www.cisco.com/web/about/ac123/ac147/images/ipj/ipj_4-2/figure4b.gif
[ 6 ] C. Perkins, “ Mobile Networking through Mobile IP ” , online tutorial
hypertext transfer protocol: //www.computer.org/internet/v2n1/perkins.htm. October 2002