The bandwidth is (pretty much) irrelevant

Last year we posted an article urging people to check their DNS settings in order to ensure they were getting the full benefit of CDNs by delivering content from nearby.

A critical aspect of this is latency and we explained how the major determinant of download speed is latency rather than bandwidth. We analogised bandwidth with lanes on a motorway and latency as distance: when you only have one car the number of lanes doesn’t matter, it is how far you need to go that affects how long it’ll take to get there.

This topic more recently came up on our VUC interview with the specific example of a user with a high bandwidth line but unable to achieve any more than about 5Mbps of download speed.

Whilst we’d recommend re-reading our article or listening to the VUC to understand this more fully, we’ve just come across an old paper put out by Google showing the relationship between bandwidth, latency and experienced performance. The conclusion is the same but they experiment by varying the elements and graphing the result. For those who’d like to put numbers to the theory, this is well worth a read.