>> What is the similarity and/or different between Download/Upload speed and Bandwidth speed?
They usually use the same unit of measure. The differences depend on the type of line. With ADSL you have asymmetrical speeds meaning one is faster than the other (you can usually download faster than you can upload). With SDSL you have symmetrical speeds, meaning they are the same.
>>Some author use kilobyte kB while other use kilobit kb, what is the different and which one is best to measure down/upload speed and bandwidth speed?
There is no best. Its more like using english units or metric units. Typically bandwidth/throughput speed/etc is measured in bits, so kilobit megabit etc. Storage capacity is usually represented by bytes, so kilobyte and megabyte. It doesn't matter which one you use since you can convert from one to another.
>>Lastly, it is possible to use two (2) broadband internet connections, maybe for reliability sake, on a network with proxy server on windows OS? Please give hints or links on how it can be configured.
Yes. The configuration depends on a lot of things. This is probably looking for an answer with concepts you covered in class so I don't know what to recommend. You can configure failover lines at the router level so the fact that the server is Windows and has a proxy service installed is insignificant in the configuration. I don't know what you're looking for here.
