Volume 10, Number 2 • March/April 2002 • Advanced Technologies

Mobile Internet Technology Offers New Applications

For more than a decade, data roaming services using private and proprietary wireless technologies have enabled delivery trucks, police, fire and other emergency vehicles to communicate with networks. New advances in Internet Protocol (IP) standards afford the ability to offer mobile IP to NASA programs and millions of users at a much lower cost, with better features, easier scalability and less maintenance required than ever before. To this end, NASA worked with Cisco Systems to conduct field trials of the Cisco implementation of mobile IP, as defined by the Internet Engineering Task Force (IETF) RFC 2002. The effort later tested the Cisco enhancement—Mobile Networks— that is an additional mobile IP feature that eliminates the need for a mobile IP client on each mobile node. The Cisco Mobile Networks solution is available with Cisco IOS® Software Release 12.2(4)T.

Businesses, government and consumers want the mobility of the cellular phone in their wireless IP devices, whether roaming the campus, continent or world. The mobile IP routing protocol has been a feature of Cisco IOS Software since version 12.0(1)T. It enables hosts to roam seamlessly among IP subnetworks while keeping their original IP addresses and uses tunneling and several specialized discovery protocols.

Mobile IP is also an architecture for network mobility that includes a router called a home agent that tunnels data grams for delivery to a mobile node that can be a laptop, a computer on a satellite, a wireless personal digital assistant, a router or other client device, and maintains the same IP address wherever it goes. The third element is a router on a remote network called a foreign agent that provides routing services to a registered mobile node.

“There are a myriad of voice, data and video applications for this technology in both the government and commercial sectors,” according to William D. Ivancic, senior research engineer at NASA Glenn Research Center in Cleveland, Ohio where the mobile IP trials took place. “We see using it for space communications in both satellite networks and planetary rovers. In the commercial sector, cars, mobile phones, emergency vehicles, ships, trucks and airplanes could all become mobile nodes.”

With the mobile networks implementation in Cisco IOS Software, a router can be a mobile node. Once this mobile router registers with the home agent, it injects its networks into the home agent’s routing table and redistributes these routes. In contrast to the existing mobile IP implementation, with a mobile router a second tunnel is established between the home agent and the mobile router in addition to the tunnel between the home agent and foreign agent. The home agent performs two encapsulations of any packet destined for the mobile router and forwards all packets for the mobile network to the foreign agent. The foreign agent then performs one de-encapsulation and passes the packet to the mobile router. The mobile router performs the second de-encapsulation and forwards the packets to the devices on its network.

“As the mobile router moves, it registers with its home agent on its whereabouts by using various foreign agents,” says Ivancic. “Mobile router transforms the mobile node into a network rather than a single host. So an entire network can roam.”

Such standards-based mobile IP networks that are able to roam at the Layer 3 protocol level and do not require special software on client devices running on mobile LANs will be of interest to just about everybody, according to NASA and Cisco engineers. The resources of other networks (i.e., foreign agents and antennas) can be shared to cut costs. Security is already addressed through IP Security (IPSec) and other protocols.

NASA and Cisco engineers built a wired and wireless mobile testbed at NASA Glenn with Cisco 2600, 3600 and 7500 Series routers to test mobile networks. Four Cisco routers were enabled by mobile IP. Another served as a home agent to handle IP tunneling. Two Cisco routers were foreign agents, one based at NASA Glenn and the other at NASA’s Ames Research Center. These had two wireless bridges each that were IEEE 802.11 standard. A Cisco 3640 router was the mobile client or node that served as a mobile router. It was installed on a rolling cabinet that was used within the lab and driven around the NASA Glenn grounds in a van. This router was equipped with a voice-over-IP interface card to support telephone conversations and three Ethernet network interface cards (NICs), two of which were configured as roaming interfaces to perform the task of agent discovery through a wired or wireless connection to a foreign agent. The third interface was the connection to the LAN and functioned as both a wireless access point and a wired hub.

This van served as the mobile test bed when the Mobile Router LAN was field-tested at NASA Glenn Research Center.

Two additional routers were configured as bridges between the mobile router and a foreign agent to provide an interface for a satellite channel emulator. A workstation connected to the home agent acted as a network address translator.

When the van or cart was in the laboratory, the mobile router accessed a wireless Cisco Aironet® antenna, and three other antennas were deployed on buildings throughout the Glenn Research Center. These three antennas were connected to foreign agents that had no delay and simulated delay.

Driven from one end of Glenn to another, the van’s mobile router started the trip connected to a delayed, non-preferred path that simulated a satellite link. It then switched to a preferred path, then back to another delayed, non-preferred link. Switching between these paths is initiated by the discovery of new foreign agents with higher priority interfaces or the result of broken connections to the preferred path.

“We successfully validated the general mobile routing algorithms,” says Ivancic. “The mobile router performed within roundtrip time delays of three seconds.” Applications tested included e-mail transfers, Web browsing, voice-over-IP, FTP file transfers, Secure Shell (SSH) and Telnet.

Mobile IP and mobile networks will play a major role in several current NASA programs, including the Small Aircraft Transportation System (SATS), Weather Information Communication (WINCOMM) and Advanced Aeronautical Transportation Technology (AATT) Free-Flight. These initiatives require continuous network connectivity and mobility between subnetworks.

“Mobile IP has been somewhat held back by the difficulty of putting the code on the clients’ software because that is unwieldy,” says Dan Shell of Cisco, senior consulting systems engineer for Federal Operations. “Mobile networks will enable mobile IP connections from many types of mobile platforms at a new level of cost-effectiveness, efficiency and ease.” Q

For more information, contact Will Ivancic at NASA Glenn Research Center, 216/433-3494, William.d.Ivancic@grc.nasa.gov or Sandy Levine at Advice Unlimited, 301/924-0330, slevine@adviceunlimited.net. Please mention you read about it in Innovation.

NASA Official: Jonathan Root • Web Design: Printing & Design Office, NASA Headquarters • Credits