Mobile IP could liberate network-bound computers

Routers such as those in the Cisco 3200 Mobile Access series let mobile clients jump from one subnet to another.

An emerging networking standard called Mobile IP could add a lot of range to mobile computing.

Just as cell phone users can roam from one provider's region to another without adjusting their phones, Mobile IP would let users of mobile computing devices move from network to network without reconfiguration.

This could prove invaluable to government agencies making greater use of wireless networks.
The small, lightweight, software-defined radios to be developed under Cluster 5 of the Army's Joint Tactical Radio System will incorporate Mobile IP, according to Byron Tarver, director of engineering for the communication network division of the C4 Systems unit of General Dynamics Corp. of Falls Church, Va.

General Dynamics recently won a contract worth up to $1 billion to develop the radios, which are to be used by military service members. General Dynamics is also rumored to have won the pending $10 billion Warfighter Information Network-Tactical contract to build a high-speed, high-capacity infrastructure network. Wireless will be a crucial part of this network, and General Dynamics plans to incorporate Mobile IP, Tarver said.

'The military has a lot of mobile nodes that join different networks at different times,' Tarver said. For instance, ships might be deployed to a certain tactical area and must join a network for that theater of operations. 'The nodes come and go from different networks, and that presented a tremendous problem technically from an IP standpoint.'

In traditional IP-based networks, each node'say a workstation'is assigned a fixed Internet address, which is held by the routers sending data to that workstation from other networks. While this approach works well with computers that remain in one place, if a computer is moved to another network'such as another LAN'its fixed Internet address is not recognized by that network's Internet gateway. Administrators must manually update the network settings of both the client and the host network's own routers, switches and gateways.

Developed by a working group of the Internet Engineering Task Force, Mobile IP eliminates this step by allowing individual nodes to join different networks without reconfiguration.

Mobile IP assigns a second address to a mobile node, in addition to the standard home network static address. The second address serves as a send-in-care-of address. Each network with mobile clients will have a home agent, a server that keeps track of where roaming clients are.

The home agent intercepts all the packets destined for a wandering client and forwards them to the new destination, using the care-of address. Likewise, each network that hosts outside clients will have a foreign agent, a server that routes forwarded data to visiting clients.

Mobile IP would be valuable to pretty much every federal agency, said Chris Josephs, director of homeland security for Cisco Systems Inc.

Cisco, like most network gear manufacturers, has added Mobile IP support to its operating system software.

'You will get better productivity from people because you're bringing technology to the way people live rather than forcing people to live in a way to use the technology for work,' Josephs said.

While integrators and hardware vendors introduce Mobile IP to government agencies, standards bodies are trying to enhance the protocol for more elaborate uses.

The IETF also is working on an extension to Mobile IP called Mobile Ad-hoc Networks. Josephs said that Mobile Ad-hoc Networks are temporary networks of multiple components that can be set up quickly, without coordinating with the home networks. Such instant networks would be particularly valuable for first responders who coordinate communication at a disaster site.

An IETF working group is developing another concept called Mobile Router. Whereas mobile IP allows one device to jump from one subnet to another, mobile routing can transfer an entire set of addresses.

This technique could be quite handy for spacecraft, for instance, which can hold a number of IP-enabled devices sending data back to their terrestrial program managers. As a craft moves through space, it switches data communications links from one ground station to another, depending on which one is in view.

Mobile routing would allow all the craft's components to communicate with their home networks, no matter which ground station they use, said Phil Paulsen, who works at the space communications office at NASA's Glenn Research Center in Cleveland.

'So now, instead of making and breaking a lot of individual threads, I just have one. The router itself establishes the communication path,' Paulsen said.

NASA tested the mobile routing concept in 2002 on a Coast Guard ship, the Neah Bay, on Lake Erie [GCN, April 21, 2003]. Using a Cisco Mobile Access Router with the mobile router code, NASA gave the ship's network Internet access and ran a number of Internet applications such as video conferencing and IP telephony. Initial access came via a WiFi antenna. As the ship moved out of WiFi range, the router sensed the loss of connection and switched automatically to satellite communications.

'It was totally seamless. You had no idea that [the switchover] happened,' Paulsen said.

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