The Internet Encyclopedia (Volume 3)

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MEASURINGWEBSITETRAFFIC ANDBANDWIDTH 701

1M 10M 100M 1B 10B

10GB 100GB 1TB 10TB 100TB

500kbps 5mbps 50mbps 500mbps 5gbps 50gbps

Shared/Virtual Servers

Dedicated Servers

Collocated and Managed Servers

Peak Bandwidth:

Monthly Transfer:

Monthly Page Views: 100K

Figure 3: Service categories compared by traffic volume.

WEB SITE TRAFFIC

The second criterion used to segregate the four classes

of Web-hosting services is the amount of Internet traffic

their customers’ Web sites generate.

Figure 3 allows one to pinpoint a Web site according

to its traffic volume. For instance, if a site will deliver

approximately 5 million page views per month, shared

servers will be unsuitable. Dedicated servers or colocation

(with or without managed services) should be considered

instead. If a site will deliver only 100,000 page views per

month, shared servers will likely be the best alternative.

All three of the traffic measurements (page views, trans-

fer, and peak bandwidth) are related to one another (see

Measuring Web Site Traffic and Bandwidth), but the re-

lationships are not simple. If the monthly page views in-

crease, for example, so will the volume of data transfer

and the demand for peak bandwidth. But the ratios of

these measurements (ormetrics) to one another are not

constant. For instance, two Web sites may each deliver

one million page views per month, but if the pages on one

site are twice the size of the pages on the other, the former

site’s data transfer will be twice that of the latter site.

MEASURING WEB SITE TRAFFIC

AND BANDWIDTH

The measurements shown in Figure 3 are the three most

commonly used in analyzing Web-site traffic volume.

Page views.The number of Web pages delivered to users.

This metric is used most in Internet advertising, be-

cause page views orimpressionsof banner ads are one

way by which ad campaigns are planned and mea-

sured. The most popular sites, such as Yahoo!, deliver

on the order of 5 billion (5 B) page views each month.

Monthly transfer.The metric most commonly used by

shared- and dedicated-server Web-hosting services.

This is a count of all the data (measured in bytes) that

a Web site’s servers transfer to or from the Internet. If

a user knows the average size of its Web site’s pages, it

can directly compute the monthly transfer as the num-

ber of page views multiplied by the average page size.

For example, if a site’s average page size is 40 K bytes,

and the site delivers 1 million pages each month, it will

transfer 40 billion bytes (40 gigabytes or 40 GB) per

month. (Note that the average page size may need to

be adjusted according to the frequency of delivery of

pages, because some sites deliver large pages more fre-

quently than small pages, or vice versa.)

Peak bandwidth.Used by colocation and managed ser-

vice providers. If a Web site’s connection to the Internet

is envisioned as a pipe,bandwidth(the capacity of the

pipe) is a measurement of the diameter of the pipe that

is required to handle a site’s traffic, whereas page views

and monthly transfer are measurements of the actual

number of data that flow through the pipe.

Think of the electrical service that enters a home or

office: Opening the service panel might reveal a circuit

breaker labeled “200 amperes.” This is the maximum

amount of electricity that can be used at one time and

is like bandwidth. The bill each month from the utility

company for the amount of electricity actually used is

comparable to monthly transfer.

Just because a colocation service or MSP charges by

bandwidth as opposed to transfer does not mean using

this method of measurement will cost more. In fact, be-

cause sites hosted at colocation facilities or by MSPs tend

to be larger and busier than those hosted by shared- or

dedicated-sever vendors, their actual cost of connectivity

to the Internet is typically less due to volume discounting.

Most colocation vendors and MSPs use the95th per-

centile rule.The most important factor to understand is

that under the 95th percentile rule bandwidth is not billed

according to the absolute peak, orburst, but rather ac-

cording to the greatest usage that is sustained over certain

units of time. Using the electricity comparison again, the

200-ampere circuit breaker will not trip just because of