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Mobile IP: The unsung hero

Despite the recent downturn in technology stocks, mobile data services and wireless computing still hold the imagination of the public, the allure of investors, and the promise of value-added applications for service providers. While most of the attention has been placed on the applications themselves and the various access technologies, there is often little discussion of the underlying technology that enables it all to happen - mobile Internet Protocol (IP).

In wireless computing, mobile IP is the technology that enables a user to receive information such as emails and files directly to one's laptop, without the sender's knowledge of the serving network IP address (which may be a wireless LAN). Instead, information is sent to the laptop user as normal. Mobile IP allows for the rerouting of information to the served network for wireless computing just as it does for mobile data services based on 2.5G and 3G technologies. With both applications, the users are not in a fixed location, which creates the need for mobile IP technology. The standard is underappreciated for the role that it plays in allowing the seamless delivery of information to its destination.

So why is mobile IP so important? By one measure, the Gartner Group estimates that 40% of all business-to-business e-business outside North America will be from a portable cellular-enabled device by 2004. With total global projected mobile phone subscribers expected to reach 1.37 billion (according to Strategis Group), mobile IP is poised to represent a key technology for enabling various non-voice and multimedia services. The key market drivers for mobile IP are the deployment of 2.5G and 3G packet data networks and the proliferation of wireless networking driven largely by continued reduction in the cost for wireless LAN equipment and improvements in bandwidth availability.

Mobile IP technology standards were approved by the Internet Engineering Steering Group (IESG) in June 1996 and published in November 1996. These standards are the recommended solution for mobility at the Open Systems Interconnection (OSI) layer 3 of IP. Mobile IP plays a central role for mobile data applications and wireless computing in that it enables IP nodes to retain the same IP address and maintain existing communications when away from the home area. This is analogous to the ability to using one's mobile phone when roaming. It used to be that you could not reach someone directly by dialing their mobile phone number when they traveled to a different mobile network service area. Instead, the caller had to dial something called a roamer port number and then dial the regular mobile phone. Mobile IP is analogous to the voice roaming services offered today in that it enables roaming with support for seamless IP based services such as General Packet Radio Service (GPRS).

GPRS is an example of a 2.5G packet network technology used in GSM networks that acts as the bearer for a variety of mobile data applications. As mobile network operators deploy GPRS, special support nodes called Gateway GPRS Support Nodes (GGSN) and Gateway Serving GPRS Support Nodes (SGSN) are deployed. SGSNs provide the direct access point for GPRS phones, subtending from GGSNs that provide the gateway to SGSNs across mobile networks that the user may visit. The GGSN also is the access point for other packet data networks, allowing someone to, for instance, send an email from a (fixed network) PC to someone with a GPRS phone. GPRS uses GPRS Tunneling Protocol (GTP) to forward packets from GGSN to SGSN to reach a mobile device, dynamically setting up tunnels between GGSN and its home network and allowing the mobile unit to have its home network served beyond the GGSN Internet Gateway.

Much of the focus of 2.5G and 3G technologies is on improved data speeds and various applications enabled by packet data network's "always-on" capability - the ability to receive content and services autonomously and seamlessly. While most people recognize that this capability is allowed through the communication between the GGSN in the home network and the SGSN in the serving network, many do not appreciate that mobile IP is the core technology that enables the seamless delivery of information. Without mobile IP capabilities, the GPRS network would have no way of forwarding packets from the GGSN, destined for the mobile customer, through the SGSN, and ultimate delivery to the GPRS enabled mobile phone.

In future installments of mobile IP coverage, we shall discuss the concepts and specific capabilities behind mobile IP and discuss specific examples of mobile IP in practice by leading companies such as Cisco. In addition, we shall assess the potential for advanced services through mobile IP synergies with other emerging technologies such as Bluetooth and address expectations for corporate and consumer customer demand of mobile IP enabled services.

Gerry Christensen is co-author of the book Wireless Intelligent Networking and editor of the Web site Mobile IN.

For more information:

IETF Charter for IP Routing for Wireless/Mobile Hosts (mobileip)

OSI Reference Model illustrated at

Cisco IOS Configuration and Reference Guide

Dig Deeper on Wireless LAN (WLAN)

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