Bandwidth

When we talk on the phone, it doesn't take forever for the other person's voice to reach us. When we watch TV, the show doesn't appear in slow motion. When we listen to the radio, the songs bang out in perfect rhythm. But when we surf the Web, it can sometimes take FOREVER for a page to download. And forget those big color pictures! Go get a snack and check back later.

Why does it take so long for Web sites to display? Will that change in the near future? What can we do as Web publishers to speed things up?

Dots

If you get your eyeball right up to your computer screen, you'll be able to see something like this:

The words on your computer screen are made up of tiny little dots called pixels.

The typical computer screen is made up of about a half-million of those pixels. The files we send on the Internet tell our various programs (email, browsers, etc.) what to do with those half-million pixels.

If you are emailing, the file tells your email program how to squirt the words on the screen that contain the message of the email. If you are browsing the Web, the files tell your browser how to squirt the words and pictures that make up the site.

Sender - Signal - Receiver

The basic problem is that on the Internet, the signal (our files of words and pictures), contains more information than can easily fit through the telephone network, the original home of the Internet.

Every signal on the Internet ends up in a bunch of little carrying cases called packets. They are the containers that get your email messages from one point to another and the containers that hold pieces of web pages as they go from servers to your computer.

Internet software knows about packets and breaks up your various message and web pages into packets, shoots them off across the network, and puts them back together again at the other end for you.

The telephone network was built to carry the human voice, not a bunch of packets. And as it turns out, the human voice is a lot easier to transmit than your average web site.

So we end up in a situation where we are attempting to transmit a signal containing a huge amount of information through a network that was designed from the ground up to transmit something completely different and much smaller. That's why you wait forever for those pictures to download.

The Slowest Link in the Chain

Not only that, an Internet connection is as slow as the slowest part of the link. So if the host server is speedy, the trip through the Internet backbone is speedy, the trip to your Internet Service Provider (ISP) is speedy, but the trip from your ISP to you is slow, the whole thing will be slow.

Bandwidth

Bandwidth is a measure of the information that can flow from one point to another in a certain amount of time. On the Internet, we measure bandwidth in how many bits (all those 0s and 1s) of information move from one place to another in a second and we call it bits per second, or bps.

If you have an Internet connection with high bandwidth (e.g., if your school or office has a T1 line), Web pages will display very quickly. If you have a connection with low bandwidth (e.g., an old modem at home), Web pages will display very slowly.

Here are some typical bandwidths:

	28K         modem        28,000 bps
	56K         modem        56,000 bps
	T1 line               1,500,000 bps
	T3 line              45,000,000 bps
	Optical Carriers    155,000,000 to  
	                 9,600,000,000+ bps

Optical (fiber optic) carriers and T3 lines typically form the backbone of the Internet network. The rest of us usually have slower access, even though a number of schools use T1 lines. So why don't we all just get T3 lines? If you have tens of thousands of dollars a month you don't know what to do with, you're in the ballpark.

Using Bandwidth

How much bandwidth do the typical parts of a web site use? Words don't use much; pictures use a lot, sound and video use a huge amount. A five-thousand word chapter in a book would take about the same time to transmit as a 3x5 color picture; the entire book would take about the same time to transmit as a few seconds of good quality audio or video.

The Future

Cars have been around for almost a century now and we still have huge traffic jams every day. Will bandwidth increase enough on the Internet so that we can all download pictures, sound and video as fast as we download text? Eventually; high-speed (i.e., broadband) access is now becoming widely available. Nevertheless, for the forseeable future, bandwidth will be expensive. So as web creators, it's our responsibility to use bandwidth intelligently. This not only wisely uses a scarce resource, it will make your web site visitors happy, since they won't have to wait forever for the download.

Using Bandwidth Intelligently

How can we use bandwidth intelligently?

  • Use pictures but only use what you need. Smaller may not be better but it's definitely quicker.
  • Use the same image over again; it only has to be downloaded once.
  • Use the right file format: JPEG for photos and PNGs or GIFs for other graphics. And when you're using PNGs or GIFs, use only the colors you need. A GIF that uses 4 colors downloads a lot faster than one that uses 256.
  • Use the color features of HTML (Five Easy Pieces - Color).

Intro | Comm | Pub | Five Easy | Web Ed | Found | Squeezing | Standards | Animate | Epilogue

 

All contents copyright (C) 1999-2007 Wanda Wigglebits. All rights reserved.