VSAT Question

See this example Private VSAT network for Southern Africa

If you need a star network (as you describe), I suggest a single, Vipersat CDM-570L shared outlink carrier from your headquarter site to all the remote sites and either thin SCPC incoming from each remote or a TDMA incoming carrier.  Use a large dish at the hub and smaller dishes at the remotes.   Use the largest dishes you can afford so as to enable 16-QAM if possible and thus halve your space segment costs.

If you need a mesh network, with the possibility of connection direct from one remote to another remote then use moderate size dishes at all sites.  You will need additional demodulators at each site depending on how many incoming carriers are needed at each site.  A Vipersat managment system will dynamically allocate space segment capacity - up to the bandwidth total of your transponder lease.

iDirect also do a low cost entry level hub suitable for small networks. 

Don't underestimate the skills, training and documentation needed to install and operate the system.

Best regards, Eric.

A CDM570L modem will transmit one carrier and receive one carrier.  If a site needs to receive multiple carriers (i.e. mesh network) you can buy additional CDM562L or CDM564L, which have dual or quad demods.

Read more here: Comtech satellite modems

For example:  If you have a network of 9 remote sites you might have one CDM570L at each remote site.  At the hub (your headquarters) you would have one CDM570L and two CDM564L so at the hub you can transmit one carrier shared to all sites and receive 9 carriers in total (1+4+4).  The outlink might be a 500kbit/s carrier with its capacity assigned with QoS rules.  The return links might be 40 kbit/s each.   VoIP phone calls need 10.8kbit/s each and the hub CDM570 will process up to 64 simultaneous calls. The capacities are just illustrative.  Actual arrangements can be quite complex with dynamic bit rate allocation according to site need.

3xDES Encryption is possible.

In the CDM570L, the acceleration provided for TCP/IP traffic is only packet header compression and packet payload compression.   This is not as good as some acceleration client/server solutions which involve a server PC at the hub which intercepts all internet download traffic and compresses it and substitutes its own alternative to TCP/IP.  The server needs matching decompression/cache software loaded in the end user customer PCs.

Best regards, Eric.