What is bandwidth or data transfer rate?
The amount of bandwidth you are allotted by your web host will determine the number of visitors you are allowed in a given time period.
Bandwidth or data transfer rate is the measurement of the amount of data transmitted over an internet connection in a given time.
Most web hosts measure bandwidth by the month.
Estimating bandwidth consumption.
To estimate bandwidth usage multiply the size of an average HTML page, plus the combined size of images included in the page, by the number of times that page will be viewed in a given month.
Multiply that number by the number of pages in your website.
If the average page on your site was 22,000 bytes (22k), and was viewed 500 times and you had 100 pages, your bandwidth usage for the month would be: 1,100,000,000 bytes or 1.1 GB(1.1 BILLION BYTES). Of course this is only a rough estimate.
Actual measurements can be determined by looking at your website stats at the end of the month.
Reducing bandwidth consumption
Your bandwidth consumption can be reduced by building small pages with small or very few images. Use embedded or linked style sheets in your pages rather than inline coding.
The use of SSL, large audio or video files will increase your bandwidth substantially.
CPU Share and Shared Web Hosting
The keyword in understanding shared web hosting is SHARED. Depending on the ethical standards of your web host (not usually on your side) , you could be sharing your server with 200 to 500 other customers or more.
Each server has a CPU or multiple CPUs. You share that CPU with the same number of customers.
On a shared web hosting account, your share of the CPU could be as much as 4.5 to 5%. Exceed it and your website stops working. If you exceed your CPU share, your web host can actually remove your website from his server. ( You'll find all this information in your user agreement, usually under fair access. )
This concept in itself completely negates the claim of UNLIMITED web hosting when it comes to shared hosting accounts.
Add a little streaming video, bulk email transmissions or poorly written scripts to your website and you'll exceed your CPU share with a minimum number of visitors to your website.
Web host controls
Web hosts can control bandwidth by limiting the number of simultaneous connections to the site, throttling (reducing data flow-bps) and reduction of timeout settings for keep-alive functions. The later 2 slow the performance of your website, and can even turn away or refuse visitors.
To avoid slow downs because of web host server controls, purchase web hosting packages that stipulate larger amounts of bandwidth.
Many web hosts ( usually shared hosting accounts) are now offering 15 Terabytes ( 15,000 GB) of bandwidth per month and more. This is just another way of saying UNLIMITED. These huge numbers on shared hosting accounts should be viewed by the buyer as sales hype.
Flash or Multimedia websites, or sites that run a lot of streaming video, use tons of bandwidth. Hosting for websites built in flash will be more costly. Some web hosts will even charge by the number of visitors per month. If you have a limited budget, stay away from flash and streaming video.
YouTube pays more than a million dollars a month for hosting.
In my opinion streaming VIDEO is the worst thing that has ever happened to the internet. The internet is not an infinite expanse. When Johnny posts his personal video about the time he discovered his first pubic hair, it's usually on a shared server. People who post this kind of drivel should not be allowed space on shared servers.
Degrading website performance for legitimate web authors on shared servers will eventually be a major problem that needs to be addressed.
Note: It has been addressed, through the concept of CPU Share!