Mobile IP – Agent Discovery – Registration – Tunneling
Mobile IP is a communication protocol that allows users to move from one network to another with the same IP address.
It ensures that the communication will continue without the user’s sessions or connections being dropped.
Home Network: The home network of a mobile device is the network within which the device receives its identifying IP address (home address). In other words, a home network is a sub net to which a mobile node belongs to as per its assigned IP address. Within the home network, there is no need of mobile IP.
Home Address (HA): The home address of a mobile device is the IP address assigned to the device within its home network. The IP address on the current network is known as home address.
Foreign Agent (FA): The foreign agent is a router in a foreign network that functions as the point of attachment for a mobile node when it roams to the foreign network. The packets from the home agent are sent to the foreign node which delivers it to the corresponding mobile node.
Foreign Network: The foreign network is the current sub net to which the mobile node is visiting. It is different from home network. In other words, a foreign network is the network in which a mobile node is operating when away from its home network
Mobile IP (or MIP): It is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining a permanent IP address.
It enables the transfer of information to and from mobile computers, such as laptops and wireless communications.
The mobile computer can change its location to a foreign network and still access and communicate with and through the mobile computer’s home network.
Care-of-Address (COA): It is the address that is used to identify the present location of a foreign agent. The packets sent to the MN are delivered to COA.
The COA can be any of the following two types:
(a) Foreign agent COA: The COA is an IP address of foreign agent (FA).
(b) Co-located COA: When the mobile node (MN) acquires a temporary IP address, that address acts as the COA.
Home Agent (HA): It is located in home network and it provides several services for the MN. HA maintains a location registry. The location registry keeps track of the node locations using the current care-of-address of the MN.
Why the traditional IP cannot be used in a mobile network?
What are the main differences between the traditional IP and the mobile IP?
How does mobile IP support mobile hubs?
IP is responsible for routing a packet to any host, connected to the Internet, uniquely identified by an assigned IP address. The nodes in the LAN are assigned an address based on the LAN address.
In the traditional IP addressing scheme, when a host moves to a different location, it may move to another network. As a result, it needs to change its IP address.
The mobile IP allows mobile computers to stay connected to the Internet regardless of their location and without changing their IP address.
The traditional IP does not support user mobility.
Mobile IP was created by extending IP to enable users to keep the same IP address while traveling to a different network.
Mobile IP for better Mobility
Mobile IP – A technology which supports mobile data and applications that are dealing with wireless connectivity. A user may now disconnect his computer in the office and reconnect from another site within the same office or elsewhere.
Components of a Mobile IP Network
Mobile IP has three major components as mentioned below –
- Mobile Node − A device such as a cell phone, personal digital assistant, or laptop whose software enables network roaming capabilities.
- The Home Agent − A router on the home network serving as the anchor point for communication with the mobile node; its tunnel packets from a device on the Internet, called a correspondent node, to the roaming mobile node.
- The Foreign Agent − A router that may function as the point of attachment for the mobile node when it roams to a foreign network delivers packets from the home agent to the mobile node.
The Mobile IP process has three main phases –
Phase I: Agent Discovery
This is the phase where mobile node discovers its foreign and home agents.
A mobile node first determines its connected location by using ICMP router discovery messages.
If it’s connected location is with the local network, then the normal IP routing is used for the communication.
When a mobile node determines that it has moved to a foreign network it obtains a care-of address from the foreign agent reflecting its current location.
Phase II: Registration
This the phase, where a mobile node registers its current location with the foreign agent and the home agent.
If the connected location is identified as foreign location, then the mobile node looks for a foreign agent and registers itself with the foreign location and the foreign agent, in turn, notifies the home agent and creates a tunnel (called tunneling) between itself and the home agent.
During this phase, the Mobile node sends a registration request message to the foreign agent which forwards the message to the home agent. The home agent sends back a reply after updating its registration table with the home address and “care-of” address mapping.
Phase III: Tunneling
This is the phase where a reciprocal tunnel is set up by the home agent to the care-of address to route packets to the mobile node as it roams.
The method by which mobile IP receives information from a network is called tunneling.
It has two primary functions −
- Encapsulation of the data packet to reach the tunnel endpoint.
- De-capsulation, when the packet is delivered at that endpoint.
After the registration phase, the home agent now encapsulates all the packets intended for the mobile node and forwards those packets through the tunnel to the foreign agent.
The foreign agent de-encapsulates the packet and forwards them to the mobile node.