Mobile IP is the IETF proposed standard solution for handling terminal mobility among IP subnets and was designed to allow a host to change its point of attachment transparently to an IP network. Mobile IP works at the network layer, influencing the routing of datagrams, and can easily handle mobility among different media (LAN, WLAN, dial-up links, wireless channels, etc.). Mobile IPv6 is a protocol being developed by the Mobile IP Working Group (abbreviated as MIP WG) of the IETF (Internet Engineering Task Force).

The intention of Mobile IPv6 is to provide a functionality for handling the terminal, or node, mobility between IPv6 subnets. Thus, the protocol was designed to allow a node to change its point of attachment to the IP network such a way that the change does not affect the addressability and reachability of the node. Mobile IP was originally defined for IPv4, before IPv6 existed. MIPv6 is currently becoming a standard due to inherent advantages of IPv6 over IPv4 and will therefore be ready soon for adoption in 3G Mobile networks. Mobile IPv6 is a highly feasible mechanism for implementing static IPv6 addressing for mobile terminals. Mobility signaling and security features (IPsec) are integrated in the IPv6 protocol as header extensions.

LIMITATIONS OF IPv4
The current version of IP (known as version 4 or IPv4) has not changed substantially since RFC 791, which was published in 1981. IPv4 has proven to be robust, and easily implemented and interoperable. It has stood up to the test of scaling an internetwork to a global utility the size of today's Internet. This is a tribute to its initial design.

However, the initial design of IPv4 did not anticipate:
" The recent exponential growth of the Internet and the impending exhaustion of the IPv4 address space
Although the 32-bit address space of IPv4 allows for 4,294,967,296 addresses, previous and current allocation practices limit the number of public IP addresses to a few hundred million. As a result, IPv4 addresses have become relatively scarce, forcing some organizations to use a Network Address Translator (NAT) to map a single public IP address to multiple private IP addresses.
" The growth of the Internet and the ability of Internet backbone routers to maintain large routing tables
Because of the way that IPv4 network IDs have been (and are currently) allocated, there are routinely over 85,000 routes in the routing tables of Internet backbone routers today.
" The need for simpler configuration

Most current IPv4 implementations must be either manually configured or use a stateful address configuration protocol such as Dynamic Host Configuration Protocol (DHCP). With more computers and devices using IP, there is a need for a simpler and more automatic configuration of addresses and other configuration settings that do not rely on the administration of a DHCP infrastructure.

" The requirement for security at the IP level Private communication over a public medium like the Internet requires cryptographic services that protect the data being sent from being viewed or modified in transit. Although a standard now exists for providing security for IPv4 packets (known as Internet Protocol Security, or IPSec), this standard is optional for IPv4 and proprietary security solutions are prevalent.
" The need for better support for real-time delivery of data-also called quality of service (QoS)

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