Data Flows

Surfing the web from a library computer terminal

Step 1. Library user logs on.

A web user logs in at the library home screen.

She enters her patron ID and password onto the screen. Once the library’s Integrated Library System validates her log-in credentials, she can use the computer to access the web.


Integrated Library System: a relational database with patron-facing and staff-facing interfaces that allows the library to manage acquisitions, cataloging, circulation and reserves, serials holdings, and the online public access catalog.

log-in credentials: a username and password created by the user

Step 2. Http request travels "locally."

The user types a url—for example,—in the web browser.

This address or http request is sent through the library’s router and travels from the router to the modem. The requested website is transmitted as information packets, and as secure if https is included in the address. Packets can include other information in addition to the request, such as a password and username (see below, Step 5b.).


http request: a set of instructions that tells a computer to get content or data stored on a web server

router: a device that moves or “directs” data traffic between computer networks

modem: a device that transmits digital data over telephone wires

http vs. https: hypertext transfer protocol and secure hypertext transfer protocol; technical standards that allow computers on the internet to respond to requests for and transmit content or data stored on web servers; https encrypts the data transfer

packets: the form or unit of data that travels on the internet and is comprised of user data, such as the content of your email, and information about the data, such as the IP addresses of the source/sender and destination/receiver

Step 3. Request travels to ISP.

Like a home modem, the library modem connects to an Internet Service Provider (such as Time Warner Cable or Verizon) by a series of cables. The requested web site travels as information packets through these cables to the Internet Service Provider.


Internet Service Provider: an organization that provides means of accessing the Internet

Step 4. Request travels the internet.

The ISP is connected by cables to a hub called an internet router. This hub connects via cables to other hubs, creating a network of networks that make up the Internet.

Domain name servers dot these networks, checking whether the requested website is valid. If not, the domain name server sends back an error message to the device where the computer sits. If yes, the web site request travels through various hubs until it reaches its destination – the web host.


internet router: a very powerful router that forwards data along the “Internet backbone” or main arteries of the Internet

domain name server: a service that forms part of a larger domain name system, essentially the Internet’s “phone book” or directory that contains the numeric versions of web addresses (aka, domain names)

error message: in this context, a failed http request which results when content has been moved or deleted and is no longer associated with the specified web address or url

web host: a company that provides an individual or organization with a server to store content, such as a personal web page

Step 5. Host found, answers request.

The web host can contain just one web server or multiple ones. The request in this example will pull information from the web servers with the address.

Once the request is received, the web server for The New York Times sends back the requested information in a series of packets. These packets can include photo files, articles, or videos, as well as other http requests (for content hosted elsewhere by a third party, including advertisements).


third party: a company that is neither the user nor the content provider, in this case the Advertiser Network.

Step 5b. Additional requests made, served by host, third-parties.

If a patron requests a website address that requires a username and password—for example,, a host’s web server may send a web cookie to the user’s browser.

A cookie sent by the web host most commonly stores login credentials, sending these back to the web host, so the user doesn’t have to re-login at each page request.

A web cookie sent by third parties, typically an advertiser, sends back user behavior back to the advertiser or advertising network’s servers. This helps advertisers to send targeted ads to the user during a current web session or in future sessions on web sites that feature cookies belonging to the same ad networks.

End. Library user logs out.

Once the web surfer is finished with her session, she will log out, or, if time runs out, she will be automatically logged out from the computer session via the library’s reservation software. Browser history and cookies are cleared, and temporary files are purged.