09-07-2011, 03:19 PM
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SKY X TECHNOLOGY
Satellites are attractive option for carrying internet and other IP traffic to many locations across the globe where terrestrial options are limited or [censored] prohibitive. But data networking on satellite is faced with overcoming the large latency and high bit error rate typical of satellite communications as well as the asymmetric bandwidth design of most satellite network.Satellites are ideal for providing internet and private network access over long distance and to remote locations. However the internet protocols are not optimized for satellite conditions. So the throughput over the satellite networks is restricted to only a fraction of available bandwidth.Mentat , the leading supplies of TCP/IP to the computer industry have overcome their limitations with the development of the Sky X product family.The Sky X system replaces TCP over satellite page link with a protocol optimized for the long latency, high loss and asymmetric bandwidth conditions of the typical satellite communication. The Sky X family consists of Sky X Gateway, Sky X Client/Server and Sky X OEM products.Sky X products increase the performance of IP over satellite by transparency replacing. The Sky X Gateway works by intercepting the TCP connection from client and converting the data to Sky X protocol for transmission over the satellite. The Sky X Client /Server product operates in a similar manner except that the Sky X client software is installed on each end users PC.Connection from applications running on the PC is intercepted and send over the satellite using the Sky X protocol.
INTRODUCTION
Satellites are ideal for providing internet and private network access over long distance and to remote locations. However the internet protocols are not optimized for satellite conditions and consequently the throughput over the satellite networks is restricted to only a fraction of available bandwidth. We can over come these restrictions by using the Sky X protocol.
The Sky X Gateway and Sky X Client/Servers systems replaces TCP over satellite page link with a protocol optimized for the long latency, high loss and asymmetric bandwidth conditions of the typical satellite communication. Adding the Sky X system to a satellite network allows users to take full advantage of the available bandwidth. The Sky X Gateway transparently enhances the performance of all users on a satellite network without any modifications to the end clients and servers. The Sky X Client and the Sky X Server enhance the performance of data transmissions over satellites directly to end user PC’s, thereby increasing Web performance by 3 times or more and file transfer speeds by 10 to 100 times. The Sky X solution is entirely transparent to end users, works with all TCP applications and does not require any modifications to end client and servers
Sky X products are the leading implementation of a class of products known variously as protocol gateway TCP Performance Enhancing Proxy (TCP/PEP) , or satellite spoofer.The Sky X gateways are available as ready to install hardware solutions which can be added to any satellite network.
The Sky X family consists of the Sky X Gateway, Sky x Client/Server and the sky X OEM products. The Sky X Gateway is a hardware solution designed for easy installation into any satellite network and provides performance enhancement for all devices on the network. The Sky X Client/Server provides performance enhancement to individual PC’s.
PERFORMANCE OF TCP OVER SATELLITE
Satellites are an attractive option for carrying Internet and other IP traffic to many locations across the globe where terrestrial options are limited or price prohibitive. However data networking over satellites is faced with overcoming the latency and high bit error rates typical of satellite communications, as well as the asymmetric bandwidth of most satellite networks
Communication over geosynchronous satellites, orbiting at an altitude of 22,300 miles has round trip times of approximately 540 m/s, an order of magnitude larger than terrestrial networks. The journey through the atmosphere can also introduce bit errors into the data stream. These factors, combined with backchannel bandwidth typically much smaller than that available on the forward channel, reduce the effectiveness of TCP which is optimized for short hops over low-loss cables or fiber.Eventhough the TCP is very effective in the local network connected by using cables or optical fibers by using its many features such as LPV6, LPsec and other leading-edge functionality. Also it will work with real time operating systems.TCP is designed for efficiency and high performance ,and optimized for maximum throughput and the highest transaction speeds in local networks.
But the satellite conditions adversely interact with a number of elements of the TCP architecture, including it s window sizing, congestion avoidance algorithms, and data acknowledgment mechanisms, which contribute to severely constrict the data throughput that can be achieved over satellite links. Thus the advantages achieved by TCP in LAN’s are no longer effective in the satellite link. So it is desirable to design a separate protocol for communication through the satellite to eliminate the disadvantages of using TCP over the satellite link. The adverse effects of using TCP over satellite page link in its various features are as follows:
Window size
TCP utilizes a sliding window mechanism to limit the amount of data in flight. When the window becomes full, the sender stops transmitting until it receives new acknowledgement. Over satellite networks, where acknowledgements are slow to return, the TCP window size gradually sets a hard limit on the maximum throughput rate. The minimum window size needed to fully utilize an error-free page link known as the “bandwidth-delay product” is 100 KB for a T1 satellite page link and 675 KB for a 10 Mbps link. However many implementations of TCP are limited to maximum window size of 64 KB and most operating systems use a default window size of only 8 KB , imposing a maximum throughput rate over a satellite page link of only 128 Kbps per connection , regardless of the bandwidth available. So the high bandwidth available in the network is no longer effective, thus the data availability in a client is restricted to a small fraction of the available bandwidth. Thus the window sizing mechanism of the TCP limits the rate of flow of data through satellite link.
The simple, heuristic data acknowledgment scheme used by TCP does not adapt well to long latency or highly asymmetric bandwidth conditions. To provide reliable data transmission, the TCP receiver constantly sends acknowledgments back to the sender. The sender does not assume that any data is lost or corrupted until a multiple of the round-trip time has passed without receiving an acknowledgment. This algorithm does not respond well over satellite networks where the round-trip time is long and error rates can be high. Further, this constant stream of acknowledgments wastes precious back channel bandwidth and if the back channel is small, the return of the acknowledgments to the sender can become the system bottleneck. The acknowledgements and error messages will always dominate the data transfer and the rate of flow reduces very much.
SKY X TECHNOLOGY
Satellites are attractive option for carrying internet and other IP traffic to many locations across the globe where terrestrial options are limited or [censored] prohibitive. But data networking on satellite is faced with overcoming the large latency and high bit error rate typical of satellite communications as well as the asymmetric bandwidth design of most satellite network.Satellites are ideal for providing internet and private network access over long distance and to remote locations. However the internet protocols are not optimized for satellite conditions. So the throughput over the satellite networks is restricted to only a fraction of available bandwidth.Mentat , the leading supplies of TCP/IP to the computer industry have overcome their limitations with the development of the Sky X product family.The Sky X system replaces TCP over satellite page link with a protocol optimized for the long latency, high loss and asymmetric bandwidth conditions of the typical satellite communication. The Sky X family consists of Sky X Gateway, Sky X Client/Server and Sky X OEM products.Sky X products increase the performance of IP over satellite by transparency replacing. The Sky X Gateway works by intercepting the TCP connection from client and converting the data to Sky X protocol for transmission over the satellite. The Sky X Client /Server product operates in a similar manner except that the Sky X client software is installed on each end users PC.Connection from applications running on the PC is intercepted and send over the satellite using the Sky X protocol.
INTRODUCTION
Satellites are ideal for providing internet and private network access over long distance and to remote locations. However the internet protocols are not optimized for satellite conditions and consequently the throughput over the satellite networks is restricted to only a fraction of available bandwidth. We can over come these restrictions by using the Sky X protocol.
The Sky X Gateway and Sky X Client/Servers systems replaces TCP over satellite page link with a protocol optimized for the long latency, high loss and asymmetric bandwidth conditions of the typical satellite communication. Adding the Sky X system to a satellite network allows users to take full advantage of the available bandwidth. The Sky X Gateway transparently enhances the performance of all users on a satellite network without any modifications to the end clients and servers. The Sky X Client and the Sky X Server enhance the performance of data transmissions over satellites directly to end user PC’s, thereby increasing Web performance by 3 times or more and file transfer speeds by 10 to 100 times. The Sky X solution is entirely transparent to end users, works with all TCP applications and does not require any modifications to end client and servers
Sky X products are the leading implementation of a class of products known variously as protocol gateway TCP Performance Enhancing Proxy (TCP/PEP) , or satellite spoofer.The Sky X gateways are available as ready to install hardware solutions which can be added to any satellite network.
The Sky X family consists of the Sky X Gateway, Sky x Client/Server and the sky X OEM products. The Sky X Gateway is a hardware solution designed for easy installation into any satellite network and provides performance enhancement for all devices on the network. The Sky X Client/Server provides performance enhancement to individual PC’s.
PERFORMANCE OF TCP OVER SATELLITE
Satellites are an attractive option for carrying Internet and other IP traffic to many locations across the globe where terrestrial options are limited or price prohibitive. However data networking over satellites is faced with overcoming the latency and high bit error rates typical of satellite communications, as well as the asymmetric bandwidth of most satellite networks
Communication over geosynchronous satellites, orbiting at an altitude of 22,300 miles has round trip times of approximately 540 m/s, an order of magnitude larger than terrestrial networks. The journey through the atmosphere can also introduce bit errors into the data stream. These factors, combined with backchannel bandwidth typically much smaller than that available on the forward channel, reduce the effectiveness of TCP which is optimized for short hops over low-loss cables or fiber.Eventhough the TCP is very effective in the local network connected by using cables or optical fibers by using its many features such as LPV6, LPsec and other leading-edge functionality. Also it will work with real time operating systems.TCP is designed for efficiency and high performance ,and optimized for maximum throughput and the highest transaction speeds in local networks.
But the satellite conditions adversely interact with a number of elements of the TCP architecture, including it s window sizing, congestion avoidance algorithms, and data acknowledgment mechanisms, which contribute to severely constrict the data throughput that can be achieved over satellite links. Thus the advantages achieved by TCP in LAN’s are no longer effective in the satellite link. So it is desirable to design a separate protocol for communication through the satellite to eliminate the disadvantages of using TCP over the satellite link. The adverse effects of using TCP over satellite page link in its various features are as follows:
Window size
TCP utilizes a sliding window mechanism to limit the amount of data in flight. When the window becomes full, the sender stops transmitting until it receives new acknowledgement. Over satellite networks, where acknowledgements are slow to return, the TCP window size gradually sets a hard limit on the maximum throughput rate. The minimum window size needed to fully utilize an error-free page link known as the “bandwidth-delay product” is 100 KB for a T1 satellite page link and 675 KB for a 10 Mbps link. However many implementations of TCP are limited to maximum window size of 64 KB and most operating systems use a default window size of only 8 KB , imposing a maximum throughput rate over a satellite page link of only 128 Kbps per connection , regardless of the bandwidth available. So the high bandwidth available in the network is no longer effective, thus the data availability in a client is restricted to a small fraction of the available bandwidth. Thus the window sizing mechanism of the TCP limits the rate of flow of data through satellite link.
The simple, heuristic data acknowledgment scheme used by TCP does not adapt well to long latency or highly asymmetric bandwidth conditions. To provide reliable data transmission, the TCP receiver constantly sends acknowledgments back to the sender. The sender does not assume that any data is lost or corrupted until a multiple of the round-trip time has passed without receiving an acknowledgment. This algorithm does not respond well over satellite networks where the round-trip time is long and error rates can be high. Further, this constant stream of acknowledgments wastes precious back channel bandwidth and if the back channel is small, the return of the acknowledgments to the sender can become the system bottleneck. The acknowledgements and error messages will always dominate the data transfer and the rate of flow reduces very much.
