The TCP/IP Guide  9  Networking Fundamentals       9  Types and Sizes of Networks

Types and Sizes of Networks 1 2 Segments, Networks, Subnetworks and Internetworks

Difficulties in Categorizing Network Classes

As with most other distinctions and categorizations in the world of networking, the lines between these various definitions are not very concrete. As I mentioned already, wireless LANs are usually not entirely wireless, because they contained wired elements. Similarly, trying to say absolutely when a network is “local” and when it is “wide” is difficult.

It's also somewhat pointless to spend too much energy on differentiating these network classes precisely. In some cases it's not the definitions that decide what technology to use, but rather the technology that indicates what kind of network you have! Since some protocols are designed for wide area networking, if you are using them, many would say you have a WAN, even if all the devices in that technology are near each other. On the other hand, some LAN technologies allow the use of cables that can run for many miles; most would still consider a mile-long Ethernet fiber link to be a LAN connection, even though it may span WAN distances.

There are many dimensions in which local and wide area networking technologies differ; two of the most important are cost and performance. It's easy to establish a high-speed conduit for data between two systems that are in the same room; much more difficult if the two are in different states. This means that in the world of WAN, one either pays a lot more or gets a lot less throughput—and often both.

The blurry line between LAN and WAN is becoming more muddled every years. One reason is the emergence of “intermediate” network types that straddle the line between these more familiar terms.

• Campus Area Networks (CANs): A campus area network (CAN) is one created to span multiple buildings in the same location, such as the campus of a university. Campus area networking is a “gray area”, since neither LANs nor WANs alone are always well-suited for this type of application. Often, a mix of LAN and WAN techniques are used for campus networking, depending on the characteristics of the campus and the needs of the organization.
  
  
• Metropolitan Area Networks (MANs): Another “intermediate” term that you may see sometimes is the metropolitan area network or MAN. As the name implies, this refers to a network that spans a particular small region or a city. Metropolitan area networks can be considered either as “small WANs” that cover a limited geographical area, or as “large LANs” that cover an area greater than that normally associated with a local network. Wireless metropolitan area networks are of course sometimes called WMANs; IEEE 802.16 is an example of a WMAN standard.

Finally, there is one other term occasionally used that should be mentioned: the personal area network (PAN). This type of network generally means a very small LAN with a range of only a few feet, intended mostly to connect together devices used by a single person (or very small group). The term is most commonly used in reference to Bluetooth / IEEE 802.15 wireless technology, so you will sometimes see the terms wireless personal area network (WPAN) and just PAN used interchangeably.

Types and Sizes of Networks 1 2 Segments, Networks, Subnetworks and Internetworks