Operating Systems and Computer Networks

  1. What Is a Computer Operating System?

Computers use low-level software called an operating system (O/S) to help people build and run their own programs. Operating system software runs not just on laptop computers but also on cell phones, network routers and other so-called embedded devices.

Types of Operating Systems

The best-known operating systems are those used on personal computers:
  • Microsoft Windows
  • Mac OS X
  • Linux
Some operating systems are designed for certain types of equipment, such as
  • Google Android (a variant of Linux), and Symbian - for cell phones
  • Solaris, HP-UX, DG-UX, and other variants of Unix - for server computers
  • DEC VMS (Virtual Memory System) - for mainframe computers
Other operating systems enjoyed a period of notoriety but are of only historical interest now:
  • Novell Netware was a popular O/S for PCs in the 1990s
  • IBM OS/2 was an early PC O/S that competed with Microsoft Windows for a time but had limited success
  • Multics was an especially innovative operating system created in the 1960s for mainframes, that influenced the later development of Unix

Network Operating Systems

A modern O/S contains much built-in software designed to simplify networking of a computer. Typical O/S software includes an implementation of TCP/IP protocol stack and related utility programs like ping and traceroute. This includes the necessary device drivers and other software to automatically enable a device's Ethernet interface. Mobile devices also normally provide the programs needed to enable Wi-Fi, Bluetooth, or other wireless connectivity. The early versions of Microsoft Windows did not provide any computer networking support. Microsoft added basic networking capability into its operating system starting with Windows 95 and Windows for Workgroups. Microsoft also introduced its Internet Connection Sharing (ICS) feature in Windows 98 Second Edition (Win98 SE). Contrast that with Unix, which was designed from the beginning with networking in view. Nearly any consumer O/S today qualifies as a network operating system due to the popularity of the Internet.

Embedded Operating Systems

A so-called embedded system supports no or limited configuration of its software. Embedded systems like routers, for example, typically include a pre-configured Web server, DHCP server, and some utilities but do not allow the installation of new programs. Examples of embedded operating systems for routers include:
  • Cisco IOS (Internetwork Operating System)
  • DD-WRT
  • Juniper Junos
An embedded OS can also be found inside an increasing number of consumer gadgets including phones (iPhone OS), PDAs (Windows CE), and digital media players (ipodlinux)One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are:
  • LAN - Local Area Network
  • WLAN - Wireless Local Area Network
  • WAN - Wide Area Network
  • MAN - Metropolitan Area Network
  • SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network
  • CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network
  • PAN - Personal Area Network
  • DAN - Desk Area Network
LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution.
Note that these network types are a separate concept from network topologies such as bus, ring and star.

LAN - Local Area Network

A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet.
In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring.

WAN - Wide Area Network

As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth.
A WAN is a geographically-dispersed collection of LANs. A network device called a routerconnects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address.
A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances.
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