Whenever possible, find out what your actual values are. For bandwidth, remember that upload and download speeds are often different (the link is asynchronous). For RTT, try running a "ping" between the client and server locations at different times of the day and under different network conditions. If you are unsure what the actual values are, here are some common figures to use as a starting point:
Link bandwidth (Kbps): ADSL = 384–2500 | Cable = 500–10000 | T1 = 1544 | T3 = 45000 | OC-3 = 155520 | Gigabit = 1000000
Estimated RTT ranges (ms): Local ~ 10–30 | Continental internet ~ 30–90+ | Worldwide ~ 100+ (often 300–500) | Satellite ~ 400–2000
Because it is based on TCP, FTP can be affected by a few other variables. We have assumed a realistic scenario for these by using the following defaults:
Packet Loss: 0.5% – Internet average is 0.6%
Max TCP Window: 65536 (Kb) – This is usually set at the OS level. Aging operating systems Like Windows™ 2000 are even lower, which degrades performance.
Packet payload: 1472 – Again, this is set at the OS level. Windows™ typically uses 1024 which is slightly less efficient.