Today's online transaction processing increasingly requires support for transactions that span a network and may include more than one company.

Networks are categorized as internets, intranets and extranets:

• Internet is a collection of individually managed networks, connected by intermediate networking devices, that function as a single large network. Internetworking refers to the industry, products, and procedures that help to create and administer internets.
• Intranet is a privately maintained computer network that can be accessed only by authorized persons and is limited to one institution.
• Extranet is an extension of an institution's intranet, used to connect business partners. In today's IT environment, the World Wide Web is the enabler for communication between the institution, business partners, and people it deals with, often by providing limited access to its intranet.

Before the advent of the Internet, employees in a corporation perceived the network as the terminals that served the company's business transactions. This workload was rather predictable both in transaction rate and mix of transactions, and much of the work could be done after hours through batch processing on the mainframe.

The paradigm used today is online transaction processing (OLTP). OLTP is a class of program that facilitates and manages transaction-oriented applications, typically for data entry, order entry and retrieval transactions in a number of industries, including banking, airlines, mail order, supermarkets, and manufacturers. Probably the most widely installed OLTP product, excluding the web servers that front-end most OLTP, is the IBM Customer Information Control System, or CICS (pronounced "kicks").

New OLTP software uses client/server processing and brokering software that allows transactions to run on different computer platforms in a network.

Today's networks and transactional systems must be able to support an unpredictable number of concurrent users and transaction types. Most transaction programs need to respond in short time periods--fractions of a second in some cases.

For example, inside a bank branch office or through the Internet, customers are using online services when checking an account balance or transferring fund balances.

In fact, an online transaction system has many of the characteristics of an operating system:

• Managing and dispatching tasks
• Controlling user access authority to system resources
• Managing the use of real memory
• Managing and controlling simultaneous access to data files
• Providing device independence

Most of the traffic in a network involves transaction processing where one side initiates the transaction and the other side processes, authorizes, and approves or declines the transaction.

Examples of activities that result in network traffic include:

• Ordering and receiving parts to assemble automobiles
• Cash withdrawal from an automated teller machine (ATM)
• Purchasing merchandise at a retail point-of-sale (POS)
• Paying bills over the web using a home banking application
• Receiving loan approval to buy a home
• Such e-business as flight and car rental reservations

In fact, even receiving a traffic citation can generate network traffic. How else can the patrol officer check for outstanding warrants?