Forum Moderators: phranque
As a rough figure however, you will always know how it performs, dialup speed maxes at about 5 kB per second, 6 if it's a great connection, top level.
So simply go to the webpage, save it using save all in firefox, don't use MSIE, it adds a bunch of code when you save pages, it will put it all the page elements in a folder, then right click on the whole page folder, make a new one for each test, select properties, it will show you how many kB the folder is. Divide by 5, that's how many seconds it takes to download.
However, that won't show you for example what an image heavy page actually looks like as it loads [very very bad], especially graphically based nav bars, those are really bad because they contain way too many discreet images.
But dialup, I mean, a modem + an isp phone number + username and password, you don't even need to have a dialup account, just use a friend's connection information for testing. Why emulate something that is so easy and standard to do? Makes no sense to me at all. Plus those emulators don't actually work like dialup, all they do is throttle the bandwidth to some predetermined speed, real dialup has these unpredictable connection speeds, fluctuations, etc, that's what you actually want to see.
The amount of data they can move over a standard phone line is I believe a technical restriction, it's physically how much you can move an analog signal over a standard twisted pair copper wire set.
This hasn't changed at all for I think 5 years, they maxed out at a theoretical 56 kbit rate, it's never risen since they hit that point, so I assume it's a technical restriction, earlier they thought they could only get 28kbit, but I guess they figured out some tricks to make it faster.
Here's one article [windowsnetworking.com] that sort of explains it, with the numbers, but I haven't really followed this for years since it hasn't changed for years.
The wide variations in connection speeds, times of day, how many subscribers are using the modem banks, lots of stuff, is why it's pretty pointless trying to emulate this, you want to see how it really works on a real connection.
In fact, I'd recommend anyone who hasn't surfed recently using a modem do it for a day or two now and then, it will make you significantly rethink how you code your websites, and how you treat images.