How long does it take to download a 5MB file at 61.56 Kbps?

Answer 1

It is not really possible to predict the total time necessary to download N bytes over a link with a nominal speed of S (in bits per second), but you can say it will most certainly take longer than 8*N/S:

• The download speed usually quoted is a nominal figure, and the real figure may be substantially lower.
• The transfer uses a protocol, such as TCP/IP, maybe even another protocol on top of that (such as HTTP). Each protocol adds overhead, thus increasing the total payload N to N'.
• The data transfer generally requires more than one transaction, and each transaction requires processing time. This time needs adding to the total time taken to transfer the data. The time requires can be substantial, if sophisticated security algorithms are involved.
• Latency causes delays in packet traversal from the source to the destination. For example, while a packet with N' raw bytes (including all the protocol overhead) may take 8*N'/S' seconds, where S' is the true speed at that time, a latency is generally experienced to the start of receipt of that packet. For example, the latency for a transatlantic data transfer across the internet can easily amount to 100ms, often more.
• For an amount of data to traverse a network from A to B, each packet passes a number of devices along the way. Each of these devices add latency as discussed, and must be generally capable of supporting the required throughput.

Answer 2

It'll take around 5 hours to download 5 GB data at a speed of 4.5 Mbps.

Answer 3

83.1708902 SECONDS