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CHAPTER 55

Networking

IN THIS CHAPTER

• A Quick and Dirty Introduction to Networking 1245
• An Overview of Oracle Networking 1248
• Host/Terminal Connections 1249
• Client/Server Connections 1250
• Web/Internet Connections 1254
• Database-to-Database Connections 1256
• SQL*Net 1 1259
• SQL*Net 2 1263
• Net/3 1264
• ODBC, JDBC, and OLE 1265
• Other Middleware Vendors 1265
• Sample Configurations 1267
• Network Development Tips 1270

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Welcome to the world of database networking. Some people come rushing into this world based on promises they have heard about magnificent performance or the capability to use their graphical user interfaces (GUIs) on personal computers for applications that access large corporate databases in a friendly and efficient manner. Others are dragged into this world kicking and screaming, however. The architectures are so complex. You have to learn all those networking terms. It can take forever for your support staff to get all those drivers loaded correctly so that you can access your databases. Finally, you have to rely on the network administrators in addition to the system administrators to keep the system up so that you can access your data.

The good news is that client/server and networking to access databases have moved beyond the point of radical new technology and into the realm of the stable production environment. Sure, you have to pay some dues to learn the new terms and understand what hardware and software components you are using to get your information. I, for one, never want to go back to the days of the dumb terminal when it comes time to write a production application. Very few business users can be wowed by the traditional terminal interface in which they have to learn to navigate through a series of menus or enter commands at the command line.

This chapter has the ambitious goal of providing you with an understanding of networking as it relates to Oracle databases. Because many users are inexperienced in using modern networking environments (using a Novell server to print your documents does not count), the terms serve as an initial stumbling block that you must overcome . The next layer of complexity comes from the fact that many people are designing network components. There are standards, but a number of vendors are competing with one another to set "the" standard. You need to be aware of the common products and how they work. Finally, Oracle itself presents a number of networking challenges that originate from Oracle's large customer base, which has many different needs. As a result, Oracle offers a wide range of products with which you might have to become familiar.

To approach these challenges, this chapter is divided into the following sections:

• A quick introduction to some basic networking concepts
• A discussion of the basic types of networking you might encounter on your Oracle systems
• Coverage of the more common alternative database networking architectures
• An overview of SQL*NetOracle's most basic networking product familyand its successor, Net/3
• An introduction to some common middleware products (the software that enables your applications and databases to interface with your networks)
• An overview of how you can use gateways to connect Oracle to non-Oracle databases, such as IBM's DB2

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• A presentation of some sample database network configurations to give you a feel for some working environments
• Tips on developing and implementing network database environments

A Quick and Dirty Introduction to Networking

Although this definition might seem a bit basic, you can think of a computer network as a collection of hardware and software that enables multiple computers to communicate with one another. Network engineering types might think of more precise or elegant definitions, but this definition will serve the purposes of this chapter. Figure 55.1 is a basic drawing that illustrates this definition. The concept is quite simple: You have two or more computers that are connected together to exchange information. Later in this chapter, you'll examine the details of different network transmission standards. For now, though, you'll just focus on the basic concepts of computers and a network that somehow connects them together.

Figure 55.1.
Basic concepts behind a
computer network.

Part of the problem when setting up networks to support databases is dealing with all the components, versions, standards, and so on that exist in the networking market. The network folks have designed a very useful tool to diagram this process; they use a stacking diagram that shows various layers of functionality and how those layers stack on one another to build a complete network connection. Typically, a seven-layer model is used, which details more of the networking environment and also supports a wide range of application uses. Although this model makes an interesting discussion, in the interest of efficiency, I simplified the model to deal more closely with the database networking models you will come across; Figure 55.2 shows this seven-layer database model. Networking purists might argue that I sometimes combine layers of the traditional seven-layer model and split a layer into two layers. This is how Oracle and other vendors tend to bundle their products, however, so it is an easier way for a DBA or developer to view networking.

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Figure 55.2.
A seven-layer database
network stacking
model.

The lowest layer is the networking transmission system. Typically, your local computer networking staff arranges this for you. The transmission equipment is designed to transmit the signals between computers. It usually transmits only a limited range of transmission formats (types of signaling) and protocols (the addressing and packaging of the transmission). The equipment also tends to limit the types of physical connections you can use to tap into the network with your network interface cards. Because this part of the network usually is arranged for you, it actually can help narrow down the large number of possibilities you have to consider. As a result, the transmission formats and protocols are excellent places to start when designing your systems.

The second layer up provides the physical and electronic interface between your computer and the network transmission system. This layer consists of some cabling and a network interface card that plugs into your computer. With servers, you typically do not have many choices for a network interface card (usually one or two cards per transmission protocol); with PCs, you have a large number of choices for the various transmission protocols. The most important thing to ensure is that the card you choose is compatible with your operating system ( especially when you are using newer operating systems, such as Windows NT).

The next layer to consider is the transmission format. This layer tracks when your computer can make a transmission on the network and ensures that the signals are correct so that other computers can detect them. The transmission format typically is the domain of the electronics engineers who worry about signal voltages and such details. Three types of common transmission formats exist:

• Ethernet: This is perhaps the simplest and most common signaling format. With this format, everyone transmits their signals onto a wire whenever they want to, and the systems detect and resolve any conflicts that arise. The typical speed is 10 million bits per second (bps), which is limited to about 3 million bps as a sustained transmission rate. A 100-million bps version is starting to appear on the market. If you are buying new equipment or cabling, you should seriously consider the dual 10 Mbps/100 Mbps cards, wires, and concentrators to give your system the capability to grow in the future.

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