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Satellite Connectivity

By carolyn.bunch ·
Does anyone know why my clients keep getting session timed out ( while using a satellite ) while connecting to my companies website? Only Satellite users keep getting the session timed out boot and they cannot tell me why .. I believe they are not a continuous connection but direc way says they are.

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Data Latency Issue

by maxwell edison In reply to Satellite Connectivity

TCP/IP is the ?language? of the Internet. It works by sending packets of data, and then waiting for acknowledgments of receipt. These acknowledgments signal the sender to transmit more data. If an acknowledgement does not arrive in a timely manner, TCP assumes the packet was lost or discarded due to network congestion and the packet is resent. TCP then slows the speed at which data is being sent in order to avoid future retransmissions.

TCP works by starting a TCP/IP session slowly, this effect is known as Slow Start. Speed builds as the networks capacity to carry traffic is verified by the rate of the acknowledgments. Since TCP was designed for terrestrial networks that have less latency than a satellite network, the longer satellite latency (>720ms range) causes TCP to expect an acknowledgment before the round trip to the remote site can be completed. TCP interprets this delay as if it were network congestion. If uncorrected, this effect causes all additional data to be sent at the slow-start rate.

The Direcway service is asymmetrical, meaning that 80% of the bandwidth is allocated towards download traffic and 20% is allocated for uploads. For this reason, Direcway does not support applications that require a high-speed upload such as web hosting at the remote site or 2-way video conferencing. Applications that are affected by high latency may have problems. Satellite latency in the range of 720ms - 1500 ms can be expected. These latency affected applications include interactive gaming, VoIP, and non-TCP/IP applications. Even though the satellite latency can be hidden from TCP/IP, applications themselves can be affected by latency.

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By the way

by maxwell edison In reply to Data Latency Issue

My previous post was taken from a larger white paper written by a company that can solve such issues.

Link to paper:

I've had VPN issues because of DirecWay for quite some time, so I know all about thier dismal service. I still have a remote user (in the mountains) who cannot connect via VPN because of it. The Skycasters solution would have cost me several thousand dollars, so we decided to wait until Comcast installs broadband cable in the area.

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More Satellite On The Way

by techrepub In reply to By the way

I've used DirecWay for 2 1/2 years now, and have never been happy with it. But out here, 100 miles from nowhere, it's still better than dial-up. A new company, WildBlue ( is launching a new service fall 2004 that promises to be about 4 times faster than Direcway, each way. I'm looking forward to seeing what they offer. BTW, if your Direcway customers are still using the older USB modems, have them make sure they are using the latest version of the software. When I updated my software, my uploads went from 34k to 135k instantly. That helps with Terminal services and the like.

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Some clarifications

by Oldefar In reply to Data Latency Issue

The satellite hop adds 490 msec to the total time. Any additional time is not satellite related. LEO (low earth orbit) promises to lower that time significantly, but faces its own challanges since the satellite will reguire thrust to maintain position or the ground side will have to track a moving target.

DirecWay is a very specific market offering. The company providing the technology is HNS, which has decades of satellite communications experience. Back in the 80's HNS was heavily involved with EDS (both then owned by GM) in providing business focused satellite communications for X.25 and SNA networks - SNA is very sensitive to latency. There is also a symetrical business class offering of DirecWay available for a premium.

The ground station for DirecWay is in Dulles VA. For the home users, consider that as your entry point to the Internet.

The core issue is one of standardization. TCP/IP has proven to be a workable communications protocol for a large variety of connections and applications. Note - workable. It has served well as a generic approach allowing a host of services to a huge market. It is not the ideal protocol for such services as voice and video, or for such access as dial-up or satellite. It requires tuning when we layer additional protocols like VPN on to it. We trade ease of installation for performance by using TCP/IP as the dominant communication protocol. We will trade a bit of bandwidth for a bit of extra control as we move to IPv6.

If you have a business requirement of TCP/IP, then you have a technical constraint to deal with that may make geosynchronous satellite or at least home market geosynchronous satellite unsuitable. If you have a business requirement of implementation time, cost, or public network use, you again may have forced a specific technology requirement. Change your requirement to that of moving specific data and you open up communications possibilities.

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