1What does VSAT mean? What about other VSAT technical terms?
Industry professionals use many technical terms and acronyms to describe the various components of VSAT hardware - IDU, ODU, OMT, antenna, etc. For a list of common terms, see our Knowledge Base article, VSAT Terms.
2Is iDirect service shared or dedicated?
iDirect service is available as either shared or dedicated bandwidth. iDirect shared service uses a "share ratio" plan. Each channel is shared among multiple customers, who contend for service as needed. For example, a customer with a share ratio of 10:1 is using a channel that may have up to 10 other customers on it. Service is available in many ratios between 4:1 and 50:1. Please see your service plan for details.
3What is "shared bandwidth"?
Shared bandwidth is network service that is not dedicated to a single customer. For instance, if the customer purchases service of 1024kbit download by 128kbit upload (1024x128) shared, the system may not actually perform at full 1024x128 speeds at all times. Different providers have different schemes for how they share bandwidth.
Providers use shared bandwidth schemes in order to lower the cost of providing internet service. By predicting how frequently a channel will be used, they can split usage of expensive dedicated channels among multiple customers. Shared bandwidth systems typically cost the customer 1/4 to 1/10 as much as dedicated bandwidth.
Shared bandwidth is best suited to small business and home users, and sites supporting less than 30 users on a single VSAT.
4What is "dedicated bandwidth"?
Dedicated bandwidth is network service that is dedicated to the customer. For instance, if the customer purchases service of 256kbit download by 256kbit upload (256x256), the system is guaranteed to have that service at all times. The channel is reserved for the use of that system.
Dedicated bandwidth is very flexible, and usually comes in a number of upload and download levels from 32kbit to 8mbit, depending on the hardware. It is also possible to purchase a dedicated channel and share it across a number of systems that belong to the same customer.
Dedicated bandwidth is best suited to large-enterprise customers such as Internet Service Providers (ISP's) and sites supporting more than 50 users on a single VSAT.
5What is Committed Information Rate (CIR)?
Committed Information Rate (CIR) guarantees a minimum level of service (bandwidth). For instance, a shared bandwidth system that is advertised as "128 kbit upload" does not guarantee 128 kbit speeds. Although such systems have published averages, no guarantee is offered that this is always available. With CIR, a customer is assured that available bandwidth never drops below a certain point.
6How does VSAT Internet Service compare to terrestrial broadband services?
The primary differences between terrestrial (DSL, cable, and modem) and satellite services are round-trip times, vulnerability to weather and radio interference, and cost of subscription.
Terrestrial broadband services have faster round-trip ("ping") times, but similiar actual download rates. Geosyncronous satellites orbit at an altitude of 36,000 km. Because round-trip traffic must make this trip 4 times for each two-way communication, ping times are commonly 500-2000 ms as opposed to the 50-200 ms times seen in terrestrial data links. This means that every single web page loaded requires a minimum of 500-2000 ms to begin loading. However, the data rates are comparable - once a file download begins, it runs at speeds similiar to terrestrial traffic. This limitation is most visible when sending and receiving small data packets.
Because VSAT Internet Service is transmitted as radio waves through the atmosphere, it can be affected by weather conditions at the customer site, the Network Operations Center, and in space. Interference by solar wind and solar flares is a rare occurence, but does happen a few times a year for a few minutes.
Finally, the subscription cost for VSAT Internet Service is typically more expensive than terrestrial services. Terrestrial lines are subsidized by governments and have lower operating and install costs than expensive orbital communications satellites.