Mobile IP

About

While Internet technologies largely succeed in overcoming the barriers of time and distance, existing Internet technologies have yet to fully accommodate the increasing mobile computer usage. A promising technology used to eliminate this current barrier is Mobile IP. The emerging 3G mobile networks are set to make a huge difference to the international business community. 3G networks will provide sufficient bandwidth to run most of the business computer applications while still providing a reasonable user experience. However, 3G networks are not based on only one standard, but a set of radio technology standards such as cdma2000, EDGE and WCDMA.

Mobile IP is defining a Home Agent as an anchor point with which the mobile client always has a relationship, and a Foreign Agent, which acts as the local tunnel-endpoint at the access network where the mobile client is visiting. Depending on which network the mobile client is currently visiting; its point of attachment Foreign Agent) may change. At each point of attachment, Mobile IP either requires the availability of a standalone Foreign Agent or the usage of a Co-located care-of address in the mobile client itself.

Abstract

The Mobile IP protocol was designed to support seamless and continuous Internet connectivity for mobile computing devices such as notebook PCs, cell phones, PDAs, etc. Utilizing Mobile IP, the mobile computing device is able to stay connected as it moves about and changes its point of attachment to the Internet. Both home and local resources, such as location based services, instant messaging, and email, are continuously accessible.

Reverse Tunneling

Another problem is that many Internet Routers strictly filter out packets that are not originating from a topologically correct sub-net. The solution to these problems is a technique called “reverse tunneling”. Essentially reverse tunneling means that in addition to the “forward tunnel” (from the Home Agent to the Foreign Agent), the Foreign Agent also tunnels packets, from the mobile node, back to the Home Agent instead of directly sending them to the Corresponding Node.

How A Mobile Node Sends Packets

Tunneling is generally not required when the mobile node sends a packet.The mobile node transmits an IP packet with its home agent address as the source IP address.The packet is routed directly to its destination without unnecessarily traversing the home network.This technique fails,however,in networks that do source IP address checking,so reverse tunneling can be used if necessary.

ARP Resolution

IP is logical address, for actual communication link level address (called MAC address) is required. IP addresses are resolved into physical address using ARP (Address Resolution Protocol). But when the Mobile Node is away from home network it hinders the normal working of ARP because Mobile Node is not present in the home network to resolve the ARP request. To handle this problem Mobile IP describes two special use of ARP—Proxy ARP and Gratuitious ARP.

Private and Public Networks

We use the concept “public network” in the sense of meaning that a “public network” is an IP network with public IP addresses. All public networks are interconnected via routers and thereby form the Internet. A private network, on the other hand, is an IP network that is isolated from the Internet in some way. A private network may use private or public IP addresses – it may be connected to the Internet via a network address translator or a firewall. However, it is not a part of the Internet since its internal resources are protected from the Internet. Private Networks may use the Internet to interconnect a multi-site private network, a multi-site VPN solution.

AAA And Mobile IP Interworking

AAA (Authentication, Authorization and Accounting) protocols used in IP environments include the well-known RADIUS [11] protocol as well as the upcoming Diameter protocol [3,4]. Diameter is the successor of the well-known RADIUS protocol and features e.g. more advanced security functions as well as increased means for peer availability. Diameter is still undergoing standardization within the IETF AAA working group.

Conclusions

In this paper we have touched multiple areas related to mobility in IP design - such as Multi Access Network Mobility applicable for both wire-line and wireless networks. We emphasize on application independent mobility with inherent support for all IP-based applications. Mobile IP together with AAA combines personal and terminal mobility with roaming services.