Web Performance Tuning, 2nd Edition

Chapter 14. Lines and Terminators

In this chapter, I’ll cover the various kinds of lines and terminators at each link in the chain between client and server, pointing out when higher-speed connections are worth the investment, and suggesting how you can get connections to work better.

A line is a connection between two points. Every connection segment on the Internet is composed of a physical line made of metal, optical fiber, or simply space, as well as a pair of terminators, one at each end-point. The physical properties of the line put theoretical bounds on the performance of the line, but the terminators determine the low-level line protocol and, ultimately, how close you can get to that theoretical maximum performance. The copper telephone line most people use to connect to their Internet Service Provider (ISP) is bounded by two modems, although there is a telco switch in the middle. At the ISP, there are probably two Ethernet cards connecting a modem bank and a router. The router feeds a T1 bounded by two CSU/DSUs. And so on.

Millions of web surfers curse their local lines and modems because of slow access, but their wrath is, in part, misdirected. Even with infinite throughput to their local ISP, web surfing would not be incredibly fast. The bottleneck would simply move to the ISP’s access point; if you could defeat that bottleneck, it would move to the closest Network Access Point (NAP), which is where ISPs exchange packets. The Internet as a whole, on average, ...