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Tuesday, 3 April 2012

Protocol and Cabling


·         10/100/1000 Mbps Ethernet
·         100 Mbps FDDI
·         155/620 Mbps ATM
·         4/10/45 Mbps Wireless

What is a Protocol?
        A protocol is a set of rules that governs the communications between computers on a network.
        These rules include guidelines that regulate the following characteristics of a network:
1.       access method,
2.       allowed physical topologies,
3.       types of cabling, and
4.       speed of data transfer.

        Protocol (communications protocol)= standards that specifically address how the devices on a network communicate, i.e
1.       How the data is packaged for transmission
2.       How receiving devices acknowledge signals from sending devices
3.       How errors are detected and handled

Logical topologies are bound to network protocols and describe how data is moved across the network.
        Ethernet, LocalTalk,Token ring for wired networks
        TCP/IP and WAP for internet
        WiFi for wireless networks
        Bluetooth, for short range wireless network

Protocol : Ethernet
        the most widely used wired networks protocol
        Early Ethernet network were half duplex, uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection) a system where LAN Technology Detection), each computer listens to the cable before sending anything through the network to avoid collisions.
        Since 1997 Ethernet uses full duplex communication, that does not require listening to other messages and no collisions occur.
        The Ethernet protocol allows for linear bus, star, or tree topologies. Data can be transmitted over wireless access points, twisted pair, coaxial, or fiber optic cable.
        Early Ethernet protocols (10BASE-T) support 10BASE transmissions rate 10 Mbps
1.       100BASE-T or 100BASE-TX – 1000Mbps (1Gbps
2.       10Gigagbit Ethernet – 10Gbps

Protocol : Localtalk
        a network protocol that was developed Macintosh computers.
        used a method called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance), where a computer signals its intent to transmit before it actually does so.
        allows for linear bus, star, or tree topologies using twisted pair cable.
        disadvantage : slow speed (only 230 Kbps).

Protocol : Token Ring
        developed by IBM in the mid-1980s.
        access method involves token-passing.
        the computers are connected so that the signal travels around the network from one computer to another in a logical ring.
        A single electronic token moves around the ring from one computer to the next. If a computer does not have information to transmit, it simply passes the token on to the next workstation. If a computer wishes to transmit and receives an empty token, it attaches data to the token. The token then proceeds around the ring until it comes to the computer for which the data is meant- the data is captured by the receiving computer

        Cable is the medium through which information usually moves from one network device to another .
        several types of cable are commonly used with LANs.
        In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types

Types of Cables
1.       Unshielded Twisted Pair (UTP) Cable
2.       Shielded Twisted Pair (STP) Cable
3.       Coaxial Cable
4.       Fiber Optic Cable

1.            Unshielded Twisted Pair (UTP) Cable
The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices.
The standard connector for unshielded twisted pair cabling is an RJ-45 connector
A disadvantage of UTP is that it may be susceptible to radio and electrical frequency interference.

1.                   Shielded Twisted Pair (STP) Cable
STP is a type of cable consists of two individual wires wrapped in a foil shielding to help provide a more reliable data communication.
        suitable for environments with electrical interference;
        however, the extra shielding can make the cables quite bulky.
        often used on networks using Token Ring topology.

2.                   Coaxial Cable
Coaxial cabling has a single copper conductor at its center.
A plastic layer provides insulation between the center conductor and a braided metal shield
The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.

Coaxial Cable Connectors
• The most common type of connector used with coaxial cables is the BayonetllCl ( C) Neill-Concelman BNC) connector
• Different types of adapters are available for BNC connectors, including a Tconnector, barrel connector, and terminator.

4.            Fiber Optic Cable
• consists of a center glass core surrounded by several layers of protective materials
• It transmits light rather than electronic signals eliminating the problem of electrical interference.
• ideal for certain environments that contain a large amount of electrical interference..
• able to transmit signals over much longer distances than coaxial and twisted pair.


        Software that controls a network and its message (e.g. packet) traffic and queues, controls access by multiple users to network resources such as files, and provides for certain administrative functions, including security. coordinate the activities of multiple computers
        across a network.
        acts as a director to keep the network running smoothly.
        A NOS is not the same as the networking tools provided by some existing OSs, Windows XP for instance.
        An NOS is an OS that has been specifically written to keep networks running at optimal performance.
        Some popular NOSs include:
        Windows NT , IBM AIX, Sun Solaris, Windows 2000 Server, Windows Server 2003,Inferno Novell NetWare, Red Hat Linux, BSD
        The two major types of network operating systems are: :
1.       Peer to Peer
2.       Peer-to-– Client/Server

1.            Peer to Peer
·         In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network
        allow users to share resources and files located on their computers and to access shared resources found on other computers.
        do not have a file server or a centralized management source
        designed primarily for small to medium local area networks.
        AppleShare and Windows for Workgroups are examples of programs that can function as peerto- peer network operating systems.

        Less initial expense - No need for a dedicated server.
        Setup - An operating system such asWindows XP/…) already in place may onlyneed to be reconfigured for peer-to-peer operations.

        Decentralized - No central repository for files and applications.
        Security - Does not provide the security available on a client/server network.

2.            Peer-to-– Client/Server
allow the network to centralize functions and applications in one or more dedicated file servers
        the file servers become the heart of the system, providing access to resources and providing security.
        individual workstations (clients) have access to the resources available on the file servers.
        Novell Netware and Windows 2000 Server are examples of client/server network operating systems.

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