Ok here's the scenario:

We want to link up two of our offices, they are located in two separate islands several miles away.
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Project Objectives:
- file sharing
- remote desktop access (software maintenance & troubleshooting)
- Voice Communications (VoIP)
- Video Conference
- data synchronization
- Dial up access for mobile users
- centralized email system (mail server located at office A)

Current status:
Office A (main office): 40 Workstations
Office B: 15 Workstations

Internet Access:
Both have 2048Mbps DSL connection
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Problem:
We would like to figure out what's the best and most appropriate WAN solution. so far we are aware of VPN, Frame Relay, ISDN, Lease line services, but we do not know what works best for the given scenario.

Well, it really depends on budget and needs. ISDN i would consider as a last result. Compared to other wan soulutions that one is just not used anymore when thier are faster services. Leased lines are expensive according to distance so if you require dedicated bandwidth but dont mind the possible expense than go for it. Frame Relay is a popular option only because its a shared infrastructure that can mimic leased lines and its CHEAPER..Again, it really depends on budget and needs.

First stop would be to talk to your telephone vendor as to frame or Point to point between the islands.

Next talk would be with your ISP concerning available internet bandwidth at each island.

Then you would compare costs/bandwidth between the two. You would include what hardware would be required at each end. VPN routers tend to be cheaper than wan routers [cisco and IOS].

Understand that frame relay is SHARED bandwidth. They will tell you that you can burst to port speed [1.54mbps] but this is not true in my experience. You are limited in frame to CIR [committed information rate] which is usually HALF your port speed. So make sure you compare apples to apples.

For example:

ISP 2mb at each end with vpn
Telco frame with 768 CIR
Telco ptp 1.54mbps

In this case [depending on hardware costs] the VPN, then ptp then frame would be your decending list of choices.

Hope this helps

Give a person a fish, they eat for a day. Suggest they internet search and they learn a skill for a lifetime.