IP routing takes one giant leap into space
The potential of Internet Routing in Space to reduce the latency -- and limits on transmission volumes -- inherent in current satellite communications potentially offers a host of new military and commercial opportunities.
A joint venture between the Defense Department, Cisco and Intelsat reached a major milestone with the launch of the Intelsat 14 (IS-14) satellite that contains an Internet router designed for the rigors of operation in space. The router onboard IS-14 is intended to demonstrate Internet Routing in Space (IRIS) capabilities to the military.
Because of its ability to reduce the latency, and corresponding transmission volumes inherent in current satellite communications, IRIS has potential to open up a host of new military and commercial opportunities.
"Right now, IRIS is a demonstration project to show how Internet routing in space could be a benefit to military users and others," said Don Brown, vice president of Hosted Payloads at Intelsat General. "We have a series of military and commercial evaluations over the next 15 months that will demonstrate the value of IRIS."
The Joint Capabilities Technology Demonstration (JCTD) program set out three years ago to deliver Internet Protocol (IP) routing intelligence on board a satellite. The Defense Department sponsored the project with a grant to Intelsat General Corporation, a wholly owned subsidiary of Intelsat, Ltd. NASA also has been exploring an Internet in space with its Deep Space Network.
Conventional satellite services typically provide physical layer capacity akin to a leased line in the sky. The latency induced by the 44,600 mile round-trip path for geosynchronous satellites, however, reduces the throughput of TCP/IP-based applications, which includes the bulk of Internet traffic. The theoretical download speed of a Web page tops out according to the latency even if bandwidth and other network resources are plentiful.
"The performance of remote applications like enterprise resource planning and Web-based services are dramatically impacted by long delays in the communication path," Brown said.
Satellite networks are often deployed in a hub-and-spoke configuration where traffic from a remote site passes through a fixed teleport earth station, or hub. If the traffic is then redirected back to another remote site in the same network, a double satellite hop occurs and the round-trip latency doubles to roughly one second, exacerbating the throughput issue.
IRIS can mitigate such effects by removing the double hop and more importantly improve the delivery reliability.
"Removing the double-hop improves the safety and productivity of the warfigher," said Brown.
Excessive latency affects interactive real-time applications as well, but in a different manner. The delay induced by the satellite path for applications such as voice-over-IP (VOIP) is noticeable to end users once it reaches about 150ms. As the delay increases, callers begin to "step on" each other's speech by assuming the other has finished speaking. Callers eventually get used to the delay, but their manner of speech begins to resemble old-fashioned radio-speak.
By performing IP routing on the satellite, traffic can be directed to the destination site without going through a central hub, thereby enhancing VOIP performance.
"IRIS can determine the optimal route between users and removes expense and latency by avoiding the double-hop to the teleport," said Brown. "Voice and video are enhanced by reducing the latency which makes two-way communications more natural and efficient."
A satellite-based network not tied to a fixed central hub opens up enormous possibilities for end-user applications, particularly with respect to mobility. Warfighters can set up site-to-site communication independent of a central hub and experience true peer-to-peer connectivity. This, coupled with the latency reduction, would significaly improve the ability of soldiers and others to set up and tear down communications systems quickly in remore locations. The solution also reduces the hardware, capacity and operational costs involved with the central hub facility.
"There is no need to deploy a hub in order to set up a new network of users," Brown said. "This saves cost and time."
The IRIS payload also in increases satellite transponder utilization by regenerating and increasing the power of the signal it receives. This reduces the size of the terminal used on the ground, which is of particular value for handheld mobile devices.
"This signal gain can increase the total capacity of the transponder resulting in more megabits per megahertz," said Brown. "The IRIS payload enables on-demand access of satellite bandwidth, similar to how bandwidth is managed on terrestrial fiber networks. This allows more flexible service and better utilization of the satellite resources. When a user is not consuming bandwidth, it can be automatically allocated to other users."
Additionally, the satellite can redirect inbound C-band or Ku-band traffic to either band on the outbound transmission. This allows for contiguous networks to be built across geographic areas where war fighters are deployed but where capacity in one band or the other is limited.
"The IRIS payload has two Ku-band beams, one aimed at Europe/Africa and the other at South America, and single C-band beam providing coverage of the rest of the network," Brown said. "The on-board router allows cross-switching between the C- and Ku-band transponders, meaning users on one band can communicate with users on the other without the extra step of going through the router at a ground station."
The IRIS capability also frees up capacity that would be used when communication unnecessarily cuts through a central earth station. Bandwidth between the satellite and the earth station hub is only used if traffic must be passed upstream beyond the satellite network, but not for direct site-to-site traffic.
"By eliminating the hub, satellite bandwidth is also saved because the voice or video doesn't need to land and then return to the satellite before reaching the other user," said Brown.
The onboard router runs the standard Cisco Interoperating System software and otherwise looks like a regular Cisco router. This allows for existing services to be seamlessly integrated with the satellite router.
"The IRIS payload contains the same, fully featured routing software that is found in the rest of the network," Brown said. "This means new services are possible, including security services, voice services, content management services all hosted on the satellite."
The JCTD will be managed by Cisco and Intelsat General. The demonstration will begin in January 2010 and will last for three months, after which the IRIS payload will convert to commercial use. The demonstration will be guided by the Defense Information Systems Agency, who will also develop the means for the government to use the IRIS capability in operation.
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