Quote:they all say that it is not good to share bandwith with ku-band
If your service C band or Ku band, this is not relevant to whether or not it is a good idea to share bandwidth.
If you have many PCs then dedicated bandwidth can be most acceptable. The upper bit rate will be limited due to cost (e.g. $70 per month per 10kbit/s) but the
bandwidth will be all yours and any congestion will be under your local control.
If you just one or two PCs then shared bandwidth is normally preferred. You may have quite high "up to" bit rate (e.g. 1 Mbit/s) but it will only be available occasionally as many other sites share your satellite capacity. Congestion outside your control is the problem. A fair access policy (FAP) is a good idea; it is intended to make sure you get an amount of downloads (Mbytes) proportional to your payment. Shared systems require considerable skill at the hub to assure satisfactory service to all and the high cost of the hub and staff makes it tempting for a service provider to sell the same capacity too many times over, causing congestion.
If you buy dedicated capacity in an iDirect system from MWEB they need to configure the hub accordingly to guarantee you the specified rates each way (e.g. 50kbit/s down and 10kbit/s up). This will be done by allocating you specific time slots on your TDMA uplink direction and a dedicated share of the downlink carrier. If you don't get the agreed dedicated bit rates they have not yet configured it correctly.
Other multi-customer TDMA systems (LinkStar, Hughes HX etc) may also be configured to provide dedicated capacity, but it is unusual to do so and need special skill of the staff at the hub to configure.
Dedicated capacity is more often provided using SCPC modems (e.g. CDM570L) both ways as this avoids the cost and complexity of the VSAT hub and it is simple to understand, implement and maintain.
The estimate of 10% loss due to packet header overheads on the satellite connection is plausible. Your private LAN operates at several Mbit/s so any overhead loss there is of no significance.
To manage your traffic locally you need a PC or managed router, rather like an internet cafe. There are commercial programs to do this and also some free software, but I can offer no advice on this local traffic management.
Best regards, Eric.