1 August 2002
Always-on Internet for those on the go
By Jim Strothman
NASA's Glenn Research Center and Cisco Systems are jointly developing a technology both believe has numerous potential applications for managing communication networks.
Called mobile Internet protocol (mobile IP), the technology is standards-based software code that allows entire networks to move, without disrupting Internet connections.
Potential commercial applications include providing ongoing, nonstop Internet connectivity for commercial truck fleets, ships, aircraft, and autos. Manufacturers and equipment vendors could use it to stay in touch with IP-enabled instrumentation from a moving platform.
Emergency vehicles such as ambulances and life-flight aircraft could maintain real-time connectivity to hospitals, enabling medical experts to relay life-saving advice en route. For national defense, the technology could support a "wireless battlefield," speeding troop and weapons deployment.
NASA and Cisco jointly conducted field trials of Cisco's mobile IP implementation, as defined by the Internet Engineering Task Force (IETF) Request for Comment (RFC) 2002. ITEF is a large, open, international community of network designers, operators, vendors, and researchers concerned with the evolution of Internet architecture.
RFC 2002 specifies protocol additions that allow IP datagrams to be transparently routed to mobile Internet nodes. The home address identifies each mobile node, no matter what network it is using.
Mobile IP was designed so nodes could move from one IP "subnet" to another without being disconnected or having service disruption, regardless of the media. For example, mobile IP can move from one Ethernet segment to another and/or move from an Ethernet segment to a wireless LAN. The mobile node always keeps the same IP address.
"If a manufacturer has an equipment rack, or racks, full of IP-compliant instrumentation and wishes to move the racks from one network to another [buildings, areas, company offices], you can have a minirouter running mobile IP and not have to reconfigure any devices," said William D. Ivancic, senior research engineer at NASA's Glenn Research Center in Cleveland.
"One could query these devices from a remote location, no matter where these devices are," Ivancic said. "Another obvious place I see such instrument racks being used is in hospitals. If a medical instrument rack—for example, one used for EKG, heart monitoring, etc.—had instruments that were Internet compliant and addressable, you could query them from a remote location using mobile."
In a mobile IP application, you don't need special software on any queried instrument. Any software that makes it IP capable will do.
Mobile IP network components
According to a "Cisco Mobile IP" white paper, mobile IP has three primary components: mobile node, home agent, and foreign agent.
The mobile node is a device such as a cell phone, personal digital assistant, or laptop whose software enables network roaming.
The home agent is a router on the home network serving as the anchor point for communication with the mobile node. It "tunnels" packets from a device on the Internet, called a correspondent node, to the roaming mobile node. Tunneling has two primary functions: encapsulating a data packet to reach the tunnel end point and decapsulating the packet when it reaches the end point.
The foreign agent is a router that connects, with or without wires, to the mobile node when it roams among foreign networks. The foreign agent delivers packets from the home agent to the mobile node. "Think of your home agent being like your home post office," Ivancic said. "If someone wants to talk [i.e., write] to you, they send to the home agent. The mobile agent, when moving, will connect with the foreign agent and say to the foreign agent, 'Tell the post office to send my messages to you, and you can pass it on to me.' The foreign and home agents have to always have an Internet connection between them."
The mobile IP routing protocol has been a feature of Cisco IOS software since Version 12.0(1)T.
"There are a myriad of voice, data, and video applications for this technology in both the government and commercial sectors," said Ivancic. "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."
At NASA Glenn, NASA and Cisco engineers built a wired and wireless mobile test bed using Cisco 2600, 3600, and 7500 series routers to test mobile networks. Mobile IP enabled four Cisco routers. Another served as a home agent to handle IP tunneling.
Two Cisco routers were foreign agents. The router was equipped with a voice-over-IP interface card to support telephone conversations and three Ethernet network interface cards, 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.
When the van or cart was in the lab, the mobile router accessed a wireless Cisco Aironet antenna, while engineers deployed three other antennas on buildings throughout the Glenn Research Center. These three antennas connected to the foreign agents. "We successfully validated the general mobile routing algorithms," said Ivancic. "The mobile router performed within roundtrip time delays of 3 seconds."
Applications tested included e-mail transfers, Web browsing, voice-over-IP, FTP, SSH Secure Shell, and Telnet. IT
Mobile IP network
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