Editing Satellite Internet access (section)

====Geostationary orbits====
A [[geostationary orbit]] (or geostationary Earth orbit/GEO) is a geosynchronous orbit directly above the Earth's equator (0°&nbsp;latitude), with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero (i.e. a "circular orbit"). An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers. Launchers often place communications satellites and weather satellites in geostationary orbits, so that the satellite antennas that communicate with them do not have to move to track them, but can point permanently at the position in the sky where the satellites stay. Due to the constant 0°&nbsp;latitude and circularity of geostationary orbits, satellites in GEO differ in location by longitude only.

Compared to ground-based communication, all geostationary satellite communications experience higher latency due to the signal having to travel [[1 E7 m|{{convert|35786|km|mi|0|abbr= on}}]] to a satellite in geostationary orbit and back to Earth again. Even at the [[speed of light]] (about 300,000&nbsp;km/s or 186,000 miles per second), this delay can appear significant. If all other signaling delays could be eliminated, it still takes a radio signal about 250 milliseconds (ms), or about a quarter of a second, to travel to the satellite and back to the ground.<ref>{{cite web|url= http://www.its.ohiou.edu/kruse/publications/aiaa96.pdf|title= Data Communications Protocol Performance on Geo-stationary Satellite Links (Hans Kruse, Ohio University, 1996)|website= ohiou.edu|access-date= 28 March 2018}}</ref> The absolute minimum total amount of delay varies, due to the satellite staying in one place in the sky, while ground-based users can be directly below (with a roundtrip latency of 239.6&nbsp;ms), or far to the side of the planet near the horizon (with a roundtrip latency of 279.0&nbsp;ms).<ref>Roundtrip latency numbers are from RFC 2488, Section 2: Satellite Characteristics</ref>

For an Internet packet, that delay is doubled before a reply is received. That is the theoretical minimum. Factoring in other normal delays from network sources gives a typical one-way connection latency of 500 to 700&nbsp;ms from the user to the ISP, or about 1,000 to 1,400&nbsp;ms latency for the total round-trip time (RTT) back to the user. This is more than most dial-up users experience at typically 150–200&nbsp;ms total latency, and much higher than the typical 15 to 40&nbsp;ms latency experienced by users of other high-speed Internet services, such as [[cable Internet access|cable]] or [[very high bit rate digital subscriber line|VDSL]].<ref>{{Cite web|url=https://www.thetripleplay.net/att-internet/|title=AT&T Internet Plans & Packages &#124; AT&T Internet Service Deals, Prices|website=www.thetripleplay.net}}</ref>

For geostationary satellites, there is no way to eliminate latency, but the problem can be somewhat mitigated in Internet communications with [[TCP acceleration]] features that shorten the apparent round trip time (RTT) per packet by splitting ("spoofing") the feedback loop between the sender and the receiver. Certain acceleration features are often present in recent technology developments embedded in satellite Internet equipment.

Latency also impacts the initiation of secure Internet connections such as [[Secure Sockets Layer|SSL]] which require the exchange of numerous pieces of data between web server and web client. Although these pieces of data are small, the multiple round trips involved in the handshake produce long delays compared to other forms of Internet connectivity, as documented by Stephen T. Cobb in a 2011 report published by the Rural Mobile and Broadband Alliance.<ref>{{cite web|url= http://www.rumbausa.net/|title=RuMBA White Paper: Satellite Internet Connection for Rural Broadband |author=Stephen Cobb |website=RuMBA – Rural Mobile & Broadband Alliance |access-date=22 March 2019 |archive-url=https://web.archive.org/web/20120729082818/http://www.rumbausa.net/ |archive-date=2012-07-29|url-status=usurped }}</ref> This annoyance extends to entering and editing data using some Software as a Service or [[SaaS]] applications as well as in other forms of online work.

Functions, like live interactive access to a distant computer—such as [[virtual private network]]s, can be affected by the high latency. Many TCP protocols were not designed to work in high-latency environments.