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Networks

Tuesday, April 19, 2005

Some Common Networking Protocols

Here are some common Networking Protocols. Somethings which is essential for the MSCE exam 70-058 and also as a basic networking knowledge.

Network Basic Input/Output System (NetBIOS)

Most of the services and applications that run within the Windows operating system use the NetBIOS interface or interprocess communication (IPC). NetBIOS was developed on LANs and has evolved into a standard interface for applications to use to access networking protocols in the transport layer for both connection-oriented and nonconnection-oriented communications. NetBIOS interfaces exist for NetBEUI, NWLink, and TCP/IP. NetBIOS requires an IP address and a NetBIOS name to uniquely identify a computer.

NetBIOS performs four primary functions:

  • NetBIOS name resolution Each workstation on a network has one or more names. NetBIOS maintains a table of the names and any aliases. The first name in the table is the unique name of the NIC. Optional user names can be added to provide a user-friendly identification system. NetBIOS then cross-references the names as required.
  • NetBIOS Datagram service This function allows a message to be sent to any name, group of names, or to all users on the network. However, because this does not use point-to-point connections, there is no guarantee that the message will arrive at its destination.
  • NetBIOS Session service This service opens a point-to-point connection between two workstations on the network. One workstation initiates a call to another and opens the connection. Because both workstations are peers, they both can send and receive data concurrently.
  • NetBIOS NIC/session status This function makes information about the local NIC, other NICs, and any currently active sessions available to any application software using NetBIOS.

Originally, IBM offered NetBIOS as a separate product, implemented as a terminate-and-stay-resident (TSR) program. This TSR program is now obsolete; if you should encounter one of these systems, you should replace it with the Windows NetBIOS interface.


NetBEUI


NetBEUI is the acronym for NetBIOS Extended User Interface. Originally, NetBIOS and NetBEUI were tightly tied together and considered one protocol. However, several network manufacturers separated out NetBIOS, the session-layer protocol, so that it could be used with other routable transport protocols. NetBIOS (network basic input/output system) is an IBM session-layer LAN interface that acts as an application interface to the network. NetBIOS provides the tools for a program to establish a session with another program over the network and, because so many application programs support it, it is very popular.

NetBEUI is a small, fast, and efficient transport-layer protocol that is supplied with all Microsoft network products. It has been available since the mid-1980s and was supplied with the first networking product from Microsoft: MS-NET.

Advantages of NetBEUI include its small stack size (important for computers running MS-DOS), its speed of data transfer on the network medium, and its compatibility with all Microsoft-based networks.


X.25 Packet Switching
A set of WAN protocols, X.25 is incorporated in a packet-switching network made up of switching services. The switching services were originally established to connect remote terminals to mainframe host systems. The network breaks up each transmission into multiple packets and places them on the network. The pathway between nodes is a virtual circuit that looks like a single, continuous, logical connection to the upper layers. Each packet can take different routes from the source to the destination. After the packets arrive, they are reassembled into their original data message.

A typical packet includes 128 bytes of data; however, the source and destination can negotiate a different packet size after making the virtual connection. The X.25 protocol can support a theoretical maximum of 4095 concurrent virtual circuits across a physical link between a node and the X.25 network. Typical data-transmission speed for X.25 is 64 Kbps.

The X.25 protocol works in the physical, data-link and network layers of the OSI reference model. It has been around since the mid-1970s and has been well debugged; therefore, it is a stable network environment. It does, however, have two shortcomings:

  • The store-and-forward mechanism causes delays. Typically, the delay is about .06 second and has no effect on large blocks of data. However, in a flip-flop type of transmission, the delay might be noticeable.
  • A large amount of buffering is required to support the store-and-forward data transfer

X.25 and TCP/IP are similar in that they both use packet-switched protocols. However, there are several differences between the two:

  • TCP/IP has only end-to-end error checking and flow control; X.25 has error checking from node to node.
  • To compensate for the fact that a TCP/IP network is completely passive, TCP/IP has a more complicated flow control and window mechanism than X.25 has.
  • X.25 has tightly specified the electrical and link levels; TCP/IP is designed to travel over many different kinds of media, with many different types of link service.


Xerox Network System (XNS)


Xerox developed Xerox Network System (XNS) for its Ethernet LANs. XNS became widely used in the 1980s, but has been slowly replaced by TCP/IP. It is a large, slow protocol, but produces more broadcasts, causing more network traffic.

Advanced Program-to-Program Communication (APPC)
Advanced Program-to-Program Communication (APPC ) is IBM's transport protocol developed as part of its Systems Network Architecture (SNA). It was designed to enable application programs running on different computers to communicate and exchange data directly.

AppleTalk
AppleTalk is Apple Computer's proprietary protocol stack designed to enable Apple Macintosh computers to share files and printers in a networked environment. It was introduced in 1984 as a self-configuring LAN technology. AppleTalk is also available on many UNIX systems that use third-party freeware and commercial packages. The AppleTalk protocol suite encompasses high-level file sharing using AppleShare, LaserWriter printing services and print spoolers, along with lower-level data streams and simple datagram delivery.


OSI Protocol Suite

The OSI protocol suite is a complete protocol stack. Each protocol maps directly to a single layer of the OSI reference model. The OSI protocol suite includes routing and transport protocols, IEEE 802 series protocols, a session-layer protocol, a presentation-layer protocol, and several application-layer protocols designed to provide full networking functionality, including file access, printing, and terminal emulation.

DECnet
DECnet is Digital Equipment Corporation's proprietary protocol stack. It is a set of hardware and software products that implement the Digital Network Architecture (DNA). It defines communication networks over Ethernet LANs, Fiber Distributed Data Interface metropolitan area networks (FDDI MANs), and WANs that use private or public data-transmission facilities. DECnet can also use TCP/IP and OSI protocols as well as its own protocols. It is a routable protocol.

DECnet has been updated several times; each update is called a "phase." The current revision is DECnet Phase V, and the protocols used are both proprietary to Digital and offer a fairly complete implementation of the OSI protocol suite.

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