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Oct 4th, 2006 at 6:03pm
Computer3 you said:
I am trying to find out whether it's possible to simply purchase the technical equipment and then use internet/phone/voip via satellite rather than going via a satellite internet company and paying monthly fees.
PAT: No, you cannot simply buy the equipment and gain access to a satellite connection without paying monthly fees. You may be able to pay annually in advance, for example, but satellite bandwidth is a commodity paid for monthly like any utility service. You do not necessarily have to have a satellite link that goes to the Internet, you can set it up between any two sites that can be seen from the same satellite; but VoIP by its very nature is designed to go over the Internet to a VoIP termination provider.
You said: I would also like to hear from anyone who has general (good or bad) experience with companies offering bi-directional satellite internet & phone/VOIP service.
PAT: As you can see from the responses, VoIP does not work on many satellite services. However, as Eric indicated, there is a very wide range of VSAT services available. Residential and small office/home office class services generally will not provide good support (or often any support) for VoIP service. However, business class voice quality is very possible and is used by thousands of people every day. You need an enterprise class system that provides the following features:
CIR - committed information rate - this is dedicated bandwidth. Using VoIP is like turning on a faucet. A steady, continuous flow of bandwidth is required and must be guaranteed or your VoIP won't work, or will work very poorly. A critical component for CIR is to ensure that the network operator does not oversubscribe CIR, because if they do, it is no longer "committed" and can not be counted on to be there when needed to deliver good voice quality.
QoS - quality of service. You need a system that will prioritize your VoIP so that the voice packets are handled before other non-critical traffic such as browsing or email packets.
Jitter control - it's not latency that kills voice, it's inconsistent latency. Anyone can easily learn to live with reasonable satellite latency (500 - 700ms), but inconsistent latency will kill voice quality. You need a system that provides the technology to minimize inconsistent latency. Most systems deliver VoIP packets in "clumps" which leads to jitter, rather than spacing them out. VoIP packets need to be evenly and smoothly spaced and delivered to ensure minimum jitter. One component of this is....
SAR - segment assembly/reassembly. Even with Qos, a large FTP packet for example, can hold up the smaller VoIP packets, creating jitter. SAR breaks the big packets up into smaller chunks, evenly spaces small VoIP packets between them, and then reassembles the large packet at the other end of the satellite connection.
cRTP - compressed real time protocol, is not a required feature for good VoIP, but it significantly reduces the amount of TCP overhead and thus the amount of CIR required for each VoIP line. Using cRTP a G.723 codec will require about 11 Kbps per VoIP line and a G.729 codec will require about 14 Kbps per VoIP line.
Most "shared" satellite services are unable to provide these features. iDirect-enabled services delivered by a knowledgeable and experienced network operator are able to do so by providing a mix of shared bandwidth for data use and CIR for VoIP or other critical applications. Contact me me with your location (UK?) offline and I'll provide you with a quote for iDirect-enabled services.
Altternatively 100% dedicated services called SCPC (single channel per carrier) will deliver good VoIP providing you use external equipment to provide the QoS and other features necessary for good quality. For a couple PCs and a single VoIP line, this is probably not going to be cost effective.
Hope this helps,
Pat
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