What is Simple IP and Mobile IP?
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The IS-2000 network using SO33 (see Packet Data Service Configurations ) for high speed packet data transmission supports connections to the public network or a private network using either mobile IP or simple IP protocol.
A packet data session begins when the user invokes packet data service. A packet data session ends when the user or the network terminates packet data service. During a particular packet data session, the user may change locations (point of attachment).
For simple IP protocol, a wireless device must obtain a new IP address (and lose existing connections) every time it changes its point of attachment. That is, moving from the coverage area of one PDSN to another PDSN constitutes a change in packet data session because a new IP address is assigned by the new PDSN. A packet data session and a PPP session are concurrent in simple IP, that is, the existence of the packet data session is dependent upon a PPP session.
For mobile IP protocol, a wireless device is allowed to maintain the same IP address as it moves from link to link (network to network) and preserve existing connections during moves. That is, the packet data session can exist through several changes of the PPP session. The mobile IP allows the PPP session to be terminated and reestablished without the termination of the packet data session. A packet data session can span several PDSNs as long as the user continuously maintains mobility bindings at the Home Agent (the IP address is persistent).
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The IS-2000 network using SO33 (see Packet Data Service Configurations ) for high speed packet data transmission supports connections to the public network or a private network using either mobile IP or simple IP protocol.
A packet data session begins when the user invokes packet data service. A packet data session ends when the user or the network terminates packet data service. During a particular packet data session, the user may change locations (point of attachment).
For simple IP protocol, a wireless device must obtain a new IP address (and lose existing connections) every time it changes its point of attachment. That is, moving from the coverage area of one PDSN to another PDSN constitutes a change in packet data session because a new IP address is assigned by the new PDSN. A packet data session and a PPP session are concurrent in simple IP, that is, the existence of the packet data session is dependent upon a PPP session.
For mobile IP protocol, a wireless device is allowed to maintain the same IP address as it moves from link to link (network to network) and preserve existing connections during moves. That is, the packet data session can exist through several changes of the PPP session. The mobile IP allows the PPP session to be terminated and reestablished without the termination of the packet data session. A packet data session can span several PDSNs as long as the user continuously maintains mobility bindings at the Home Agent (the IP address is persistent).
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What is Mobile IP?
The Mobile Internet Protocol, or better known as Mobile IP, is a protocol that adds to the already existing Internet Protocol by making the movement of a node transparent to applications on its original network.
Problem with the Internet Protocol
One knows that a host address is made up of a network number and a host part. This network number tells the user what network the host is attached to. Original Internet Protocol algorithms tell certain routers how to get packets to their correct networks. Now with the regular Internet Protocol if the host disconnected itself from its original network and joined another network, the host would never receive any packets because the host has the same IP address from its old network that would not be recognized by the network in which it joined. In essence the host would seem to be missing because its IP address does not match its new network number and therefor would never recieve any packets.
Solution
Because this problem exists, Mobile IP was created so that mobile nodes could freely move from network to network without the fear of losing data or interrupting current computer applications and settings.
How Does Mobile IP Work?
The next logical step after figuring out what Mobile IP is is to discover exactly how it works. Mobile IP is unique because it allows the mobile node to use two IP addresses. One of those addresses is the mobile nodes “home address”. The “home address” is an IP address that makes it seem like the mobile node will always be able to receive data on its “home network”. A “home agent”, which is a network node, has the function of acquiring all data that is being sent to the mobile node and then arranging for it to be sent to the mobile nodes current location. When a mobile node is not on its home network, it is said to be on a “foreign network”. This “foreign network” uses another IP address for the “foreign agent”, a network node that the mobile node is attached to, which is known as the “care-of address”. This IP address changes depending on the nodes point of attachment. The mobile node then registers with the “foreign agent” and gives it the address of its home agent. This allows the home network to know exactly where the mobile node is located and therefore will be able to know where to send packets or data. In essence whenever the mobile node moves, it registers another “care-of address” with the mobile nodes “home agent”. This is a simplified overview of how Mobile IP functions.
How Is the Care-of Address Discovered?
In order to discover the Care-of Address , Mobile IP has built on top of the already existing protocol called Router Advertisement. Router advertisements contain information about the default routers and no other information. Mobile IP extended this protocol by adding the Care-of Address to the existing routing advertisement. This new form of the routing edvertisement is called the Agent Advertisement. To summarize without going into added detail, the agent advertisement performs the following functions:
1)allows for detection of mobility agents
2) lists all care-of addresses needed, be it one or more
3) informs the mobile node of special features provided by foreign agents
4) lets mobile nodes determine the network number and the status of their link to the internet
5) lets the mobile node know what kind of agent it is attached to, the home agent, foreign agent or maybe even both of them. This in essence tell the mobile node if it is on its home network or not.
How is the Care-of Address Registered?
In order to make use of this care-of address, the home agent must know about it before it can begin packet forwarding. The mobile nodes registers this care-of address by following four steps:
1) sending a registration request that contains the care-of address information to its home agent
2) having the home agent add the necessary information to its routing table once it recieves the request
3) approving the request and lastly
4) having the home agent send a registration reply back to the mobile node.
Overview
In essence Mobile IP uses two IP addresses, a home address and a care-of address that changes whenever the mobile node changes networks. By using these two addresses the mobile nodes computing activities are not disrupted when the node changes the computers point of attachment. By using the Mobile Internet Protocol the mobile nodes' reconnections occur without any activity, essentially automatically
Another explaination for Mobile IP
Mobile IP provides IP address mobility for the duration of the user’s Internet session.
Mobile IP is handled at network layer 3, and therefore can operate across the entire
Internet, not just within a single wireless provider’s network.
The basic idea behind Mobile IP is that the user’s wireless provider maintains a
"Home Agent" (HA) through which all the user’s traffic will be routed. The user’s mobile node connects to the network via an arbitrary PDSN, which functions as a "Foreign Agent" (FA). The FA contacts the HA on behalf of the user, and a tunnel is established between the FA and the HA to carry the user’s traffic. The user’s mobile node is assigned an IP address that is maintained by the HA. As the mobile node connects with each new PDSN, a new tunnel is established from the new PDSN (FA) to the same HA. The HA is able to keep the user’s IP address constant, and simply route the mobile node’s traffic to the current FA via the tunnel.
The AAA server plays a key role in supporting a Mobile IP infrastructure. The AAA server is the focal point for establishing a tunnel for the user. Both FA and HA
perform authentication requests against the AAA server prior to admitting the user to the network. In addition to its normal functions of authenticating the user and providing an IP address, the AAA server also provides keying information to both FA
and HA to allow them to securely set up a tunnel for the user.
Simple IP
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Simple IP provides a low level of IP address mobility. What IP address mobility there is handled at network layer 2 of the wireless provider’s infrastructure. Essentially, multiple cells may be connected to a single PDSN. As long as the user moves among those cells, the PDSN can keep track of the mobile node and assign it the same IP address each time it reconnects via a new cell.
Simple IP can guarantee IP address mobility only within a restricted geographic area, and only within the network of a single provider. If the user moves to a cell handled by a different PDSN, a new IP address will be assigned.
Despite its drawbacks, Simple IP will continue to have a role even as 3G is implemented. Simple IP may be the level of service available to subscribers who
choose not to upgrade their handsets. In addition, wireless providers may offer it as a lower-cost option for wireless Internet access