This article is a comparison of latency and throughput in telecommunications. A common misunderstanding of communication is that having more throughput means a faster (lower-latency (engineering)) connection. But, in many cases, the reverse is true, depending on context and needs.

= Definitions =

; , so you should divide your bandwidth by 8 to get the transfer rate in bytes. However, adding in overhead and other factors that slow down the transmission, it is likely that your actual data transfer rate will be lower. A good rule of thumb is to divide by 10 to get the data transfer rate. Note: Because throughput is often increased by increasing the bandwith the terms are often used synonymously.

:Example: A connection with a signaling rate of 1.5 Mbit/s (1.5 million bits per second) gives a rough data transfer rate of (1.5 /Mbit/s)/10 = 0.15 MB/s or 150 KB/s. Note that this is in decimal kilobytes (1000 bytes) and not binary kilobytes (1024 bytes, also called kibibytes) as measured by an operating system. Since it s an approximation the distinction is not important. See Binary prefix for more details.

; s. 1000 ms is equal to 1 second.

= How latency and throughput interplay =

Latency and throughput together determine the perceived speed of a connection, and the perceived speed of a connection can vary widely depending on your needs.

To view a web page over a 56 kbit/s Modem (56,000 bits per second) from a server 3,000 miles away is done very effectively over the Internet. Latency is fairly low (typically about a quarter of a second) and the size of an average web page (around 30100 kilobytes) will transfer in 1030 seconds.

However, to transfer the contents of a DVD over a modem could take a week or more at this rate. Simply packing the DVD into an envelope and mailing would be faster!

Using a T1 line with similar latencies, you could download that web page in under a second, which is a significant improvement. To download a 5 gigabyte DVD over this 1.5 Mbit/s connection would take about 7.4 hours.

= The postal service is faster than the Internet =

The Mail has a latency of about 3 days in most cases, but the amount of information that can be put into a box (e.g. many DVD discs) is incredible.

Assume that you ship 500 DVDs in a medium sized-box from LA to New York. To match this amount of bandwidth, you d have to transfer 9.6 MB of information every second. This is roughly 65 T1 lines worth of throughput!

It has been reported recently that Netflix transferred more information in an average day than the entire Internet. From the above, you can see this is very likely true.

= Conclusion =

This relationship between throughput and latency would also explain why satellite Internet has not been very popular. Although the throughput of a satellite connection can be very high and very economical, the latency added by the round trip through the satellite (12 seconds) makes low-latency Internet tasks such as network gaming a very bad experience.

Similarly, video is currently a high-bandwidth, high-latency application. If all Broadcast television system in use were to be transferred over the Internet, the network would buckle immediately as the infrastructure is insufficient by several orders of magnitude to handle the amount of information required. However, the high latency inherent in driving to your local video store and renting a movie to watch is perfectly acceptable.

Understanding this key difference in speed can greatly help one understand the implications of speed.

= External links =