|  | 1.5 | Digital Bandwidth
| 1.5.5 | Data transfer calculation

An important part of networking involves making decisions about which medium to use. This often leads to questions regarding the bandwidths that the user's applications require. The graphic summarizes a simple formula that will help you with such decisions. The formula is Estimated Time = Size of File / Bandwidth (see Figure). The resulting answer represents the fastest that data could be transferred. It does not take into account any of the previously discussed issues that affect throughput, but does give you a rough estimate of the time it will take to send information using that specific medium/application.

Now that you are familiar with the units for digital bandwidth, try the following sample problem:

Which would take less time, sending a floppy disk (1.44 MB) full of data over an ISDN line, or sending a 10 GB hard drive full of data over an OC-48 line? Use figures from the bandwidth chart shown earlier to find the answer.