Network Architectures



Network Architectures



Ethernet is the most popular physical layer LAN technology; Other LAN types include Token Ring, Fast Ethernet, Fiber Distributed Data Interface (FDDI), Asynchronous Transfer Mode (ATM) and Local Talk. Ethernet is popular because it strikes a good balance between speed, cost and ease of installation. The Institute for Electrical and Electronic Engineers (IEEE) defines the Ethernet standard as IEEE Standard 802.3. This standard defines rules for configuring an Ethernet network as well as specifying how elements in an Ethernet network interact with one another. By adhering to the IEEE standard, network equipment and network protocols can communicate efficiently.


Fast Ethernet:


Fast Ethernet is a local area network (LAN) transmission standard that provides a data rate of 100 megabits per second (referred to as “100BASE-T”).The Fast Ethernet specifications include mechanisms for Auto-Negotiation of the media speed. This makes it possible for vendors to provide dual-speed Ethernet interfaces that can be installed and run at either 10-Mbps or 100-Mbps automatically. Gigabit Ethernet is a future technology that promises a migration path beyond Fast Ethernet so the next generation of networks will support even higher data transfer speeds.


Token Ring:


A Token Ring network is a local area network (LAN) in which all computers are connected in a ring or star topology and a bit- or token-passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time. Token Ring protocol is the second most widely-used protocol on local area networks after Ethernet. The IBM Token Ring protocol led to a standard version, specified as IEEE 802.5. Both protocols are used and are very similar. The IEEE 802.5 Token Ring technology provides for data transfer rates of either 4 or 16 megabits per second. The Fiber Distributed-Data Interface (FDDI) also uses a Token Ring protocol. The token scheme can also be used with bus topology LANs.




FDDI (Fibber-Distributed Data Interface) is a standard for data transmission on fibber optic lines in a local area network that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol. In addition to being large geographically, an FDDI local area network can support thousands of users.




Protocol is the special set of rules that network protocols are standards that allow computers to communicate through network. A protocol defines how computers identify one another on a network, the form that the data should take in transit, and how this information is processed once it reaches its final destination.


The main types of network protocols in use today:

TCP/IP for UNIX, Windows NT, Windows 95 and other platforms,

IPX for Novell NetWare,

DECnet for networking Digital Equipment Corp. computers,

AppleTalk for Macintosh computers.


Protocol independence:


Each network protocol is different; they all share the same physical cabling. This common method of accessing the physical network allows multiple protocols to peacefully coexist over the network media, and allows the builder of a network to use common hardware for a variety of protocols; this concept is known as protocol independence.


Some Important Protocols and their work:

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