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NOS Network Operating System
An operating system that includes special functions for connecting computers and devices into a local-area network (LAN). Some operating systems, such as UNIX and the Mac OS, have networking functions built in. The term network operating system, however, is generally reserved for software that enhances a basic operating system by adding networking features. Novell Neetware, Microsoft Windows Server, are examples. Some multi-purpose operating systems, such as Windows NT come with capabilities that enable them to be described as a network operating system.
TCP/IP (1977) Transmission Control Protocol/Internet Protocol
Developed by the U.S. Department of Defense to connect and internetwork dissimilar systems. TCP provides the data-transport functions, while IP provides the routing mechanism. TCP/IP is a routable protocol. Every client and server in a TCP/IP network requires an IP address, which can be assigned either permanently or dynamically (meaning that it draws from a pool of addresses each time the machine starts up).
NetBIOS Network Basic Input/Output System
originally developed by IBM and Sytek as an Application Programming Interface (API) for client software to access LAN resources, has become the basis for many other networking applications. NetBIOS is a session layer interface specification for accessing networking services; that is, it is a layer of software developed to link a network operating system with specific LANAs (Local Area Network Adapters or NIC cards). In other words, NetBIOS is a software interface between computer programs and a Local Area Network Adapter LANA.

NetBIOS does not obey the rules of the OSI model in that it does not talk only to the layers above and below it. Programs can talk directly to NetBIOS, skipping the application and presentation layers.

In NetBIOS, connection (TCP) oriented and connectionless (UDP) communications are both supported. NetBIOS supports both broadcasts and multicasting; and supports three distinct services: Naming, Session, and Datagram.

SMB (Server Message Block) and NBT (NetBIOS over TCP/IP work very closely together and both use ports 137, 138, 139. Port 137 is NetBIOS name UDP. Port 138 is NetBIOS datagram UDP. Port 139 is NetBIOS session TCP. In order to quickly identify a serverŐs registered NetBIOS names and services, issue the following NBTSTAT command from a DOS prompt:

nbtstat -A [ipaddress]
nbtstat Đa [hostname]

NetBEUI (1983) NetBIOS Extended User Interface
Pronounced "net booey." This is Windows' native network protocol. NetBEUI does not contain a network address, so it is a nonroutable protocol. This means data cannot be routed from one network to another.

NetBEUI is a protocol that enhances versions of the NetBIOS interface specification used by network operating systems. NetBEUI is a protocol that formalizes the transport layer frame that was never standardized in NetBIOS. It does not map directly to the OSI model in that it overlaps Transport, Network and the LLC part of Data Link Layer, NetBEUI talks directly to NDIS, which starts at the MAC layer in DataLink.

It does not map directly to the OSI model in that it overlaps Transport, Network and the LLC part of Data Link Layer, NetBEUI talks directly to NDIS, which starts at the MAC layer in DataLink. Thus, it is not routable. NetBEUI implements the OSI LLC2 protocol. NetBEUI is the original PC networking protocol and interface designed by IBM for the LanManager Server. This protocol was later adopted by Microsoft for its networking products. NetBEUI specifies the way that higher level software sends and receives messages over the NetBIOS frame protocol. This protocol runs over the standard 802.2 data-link protocol layer.

The preferred configuration in an enterprise environment is to use NetBIOS over TCP/IP or (NetBT). Every computer that uses NetBT or NBT (or NetBEUI for that matter) has a "NetBIOS name" to which "client" software on other computers can refer when attempting to access file and printer resources on that named "server" computer. In order for NetBT services to function properly, the software must be able to take a NetBIOS name and associate it with (resolve it to) an IP address.

WINS Windows Internet Name Service
WINS servers dynamically build lists of NetBIOS names and IP addresses from computers that are configured to point to them. UGA has two campus-wide WINS servers to perform NetBIOS name resolution, and, whose IP addresses are and, respectively.
IPX/SPX (1989) Internetwork Packet Exchange/Sequenced Packet Exchange
This is a Novell NetWare-based protocol that is used to route messages from one network node to another. IPX/SPX is a routable protocol, and because IPX packets include network addresses, data can be exchanged between different networks. SPX ensures that an entire message (a data IPX packet) arrives intact.
PPP (1994) Point-to-Point Protocol
PPP is the Internet standard for serial communications. Newer and better than its predecessor, SLIP, PPP defines how your modem connection exchanges data packets with other systems on the Internet.
What is a protocol, really? It is software that resides either in a computerŐs memory or in the memory of a transmission device, like a network interface card. When data is ready for transmission, this software is executed. The software prepares data for transmission and sets the transmission in motion. At the receiving end, the software takes the data off the wire and prepares it for the computer by taking off all the information added by the transmitting end.

In brief: Within the context of the OSI reference model, a protocol is a formal set of rules and conventions that governs how computers exchange information between peer layers. Interfaces define how information is passed between adjacent layers in a given computer.

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last updated 1 Dec 2004