Introduction to Networking

Unit 7

Lesson 2 - Switched WAN Services

The Internet

The Internet is not a single WAN technology, like frame relay or ATM. Instead, it is a hybrid combination that uses most of the wide area transmission systems we have discussed thus far. However, we include it as a type of switched WAN solution, because many companies are now using the Internet as a wide area backbone. As the speed and reliability of Internet transmission increases, this trend is likely to continue.

The Internet is a global network of computer networks. Although the idea is simple, its implications are enormous. One of the main features of the Internet is its ability to allow dissimilar computer systems, and even networks of dissimilar systems, to communicate with each other by means of two common protocols: TCP and IP. These two protocols function as a common language that PCs, mainframes, and minicomputers can all use to talk to each other over the Internet.

The Internet could not function without additional standards that provide other details, from the structure of an electronic mail (e-mail) message to rules for building Web pages. Independent organizations govern the Internet by creating and updating these standards and protocols. However, no one organization or government owns the Internet as a whole.

Internet Structure

Internet services, like telephone calls, travel over the telephone network infrastructure. The Internet backbone is the relatively small number of high-volume, high-speed trunks owned by the major telephone interexchange carriers (IXCs). In addition, most countries have their own backbones, each connected to the other.

The Internet is arranged in an informal hierarchy. The biggest corporations, and the largest ISPs, connect their networks directly to this main transmission backbone. The big ISPs, in turn, provide access to smaller service providers and corporations, which in turn provide access to individual users and small businesses. We will discuss various types of Internet access in Unit 8.

Internet, Intranet, and Extranet

New Internet terminology emerges almost daily. One source of confusion is the use of the terms "Internet" (capitalized), "internet" (not capitalized), "intranet," and "extranet."

	The Internet (capitalized) is generally considered the global TCP/IP network. In other words, the Internet connects the world.
	The term "internet" (not capitalized) refers to any interconnection of two or more networks, when the connection uses TCP/IP technology and protocols. This "internet" does not mean that a network is connected to the global Internet.
	An Intranet is a "private Internet." It is a private, internal network that uses Internet applications, tools, and protocols. However, it is designed for private use by company personnel. For example, many company intranets store commonly used information as Web pages, and their employees use Web browsers to retrieve and view the documents.
	An Extranet includes both Internet and intranet capabilities. It is a private intranet shared between closely aligned organizations. While it is external to each organization, it is not available to the general public. For example, a manufacturing company might work closely with a parts supplier for a specific product. Information about parts inventories could be stored in an extranet accessible to both companies.

VPNs

Data packets move across the Internet by being forwarded from one network's router to another until they reach their destinations. Because Internet traffic can be intercepted by any router that forwards it, basic Internet transmission is inherently insecure. To ensure privacy, companies that use the Internet as a WAN backbone often set up a VPN.

A VPN is a connection, set up over a shared network, that behaves like a dedicated link. VPNs use end-to-end network encryption to establish a secure connection from machine to machine. Many encrypted data streams travel over the same public network, such as the Internet, each in a separate secure "envelope" formed by different encryption/key combinations.

The Internet is still not well suited to the time-sensitive traffic that ATM handles so well. However, a company can enjoy a great deal of flexibility with a VPN, because traveling workers and home-officed employees can use their normal Internet connections to access the corporate network.

When is it appropriate to use switched services instead of point-to-point services?

Activities

See the Activities and Extended Activities section in Unit 7 Lesson 2 in your textbook Introduction to Networking to test what you have learned so far.

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