One of the important books to study for front end performance is Ilya Grigorik’s High Performance Browser Networking from O’Reilly. I’m going to summarize some of the key chapters. If you’re interested, pick it up!
Speed is Key
Users expect speed from web applications. The faster you go, the more users you can retain, you get better conversion. It’s clear that users gravitate toward good sites that are fast too. Consider performance a feature and you will be rewarded.
There are two things that dictate network speed: bandwidth and latency. Bandwidth is the amount of data that you can put through the pipes at one time, latency is the time that it takes to get there. Grigorik then lists some common types of delays that occur when transmitting data over the internet, from propagation to transmission.
A Light Issue
Sadly, there is a hard cap on the rate that we can get information from one place to the other: the speed of light. We don’t transmit data over the internet at the speed of light, but (through marvelous engineering) we’ve gotten within a small constant of it. This is an issue because the round trip time (RTT) to distant places can be quite long in fiber (Grigorik cites New York to Sydney at 160ms). Add to that the processing time, getting to the users computer from the main line, etc. and long trips can easily take more than 300ms, the time at which the user perceives things as sluggish.
This is why CDNs (content delivery networks) are key, as they bring content closer to your users, reducing RTT and thus increasing overall speed.
Unfortunately, for many users, reducing the distance isn’t the only thing adding to RTT time. Most users deal with a large amount of last mile latency as their router does many hops to just get to their ISP’s main router. You can try this yourself with traceroute foo.com Grigorik points out that, “As an end user, if you are looking to improve your web browsing speeds, low latency is worth optimizing for when picking a local ISP.”
Edgy Topic
Grigorik ends the chapter by discussing the issues of edge of the network” the last mile while customers have different setups, there are many hops to main routers and encourages his readers to go through the rest of the book so that they can give their customers the best experience possible.