LAN - Local Area Network
A LAN[->0] 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[->1] and Token Ring[->2]. WAN - Wide Area Network
As the term implies, a WAN[->3] 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 router[->4] connects 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[->5], Frame Relay[->6] and X.25[->7] for connectivity over the longer distances. LAN, WAN and Home Networking
Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP)[->8] using a broadband modem[->9]. The ISP provides a WAN IP address[->10] to the modem, and all of the computers on the home network use LAN (so-calledprivate) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central gateway, typically abroadband router[->11], to reach the ISP. Other Types of Area Networks
While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others: ·
Wireless Local Area Network - a LAN based on WiFi[->12] wireless network technology ·
Metropolitan Area Network - a network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned an operated by a single entity such as a government body or large corporation. ·
Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus. ·
Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel. ·
System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network.
Software Protocol Layers
(September 20, 1995)
Daniel Z. Tabor Jr.
New Jersey Institute of Technology
"protocols are to computer communication as what programming languages are to computation." ·
Layers are conceptually stacked modules of hardware-dependent or independent protocol software.
Complex data communication systems require a set of cooperative protocols (called a protocol family or protocol suite) which solve the following communication problems: o
Packet delay or loss.
Error detection and/or correction.
Redundant packet arrival.
Functionality of Layers:
A set of goals and constraints governing a particular communication problem is usually set by a standards organization (organizations optimize the functionality) ·
Choice of different approaches
The design of an internet architecture and the organization of protocol software are interrelated.
Protocol Type by Layer:
Hardware/Firmware protocols usually reside at the Physical and Link Layers. ·
Software protocols conceptually reside above hardware protocols and can be located within: o
Device drivers - lowest software layers, hardware dependent. o
The operating system - middle software layers, hardware independent. o
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