6th week: topology

What is network topology?

-is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially:

- logical (virtual) and

- physical (real)

-interconnections between nodes

Logical topology

Is…….

the mapping of the flow of data between the nodes in the network determines the logical topology of the network

Physical topology

Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that determines the physical topology of the network.

Types/classification

1.  Linear Bus

©      creates a network by connecting 2 or more hosts to a length of coaxial backbone cabling.

©      consists of a main run of cable (with terminator at each end)

©      all nodes connected to the linear cable.

©      Example: Think of the data as water; in this respect, the terminator must be placed in order to prevent the water from flowing out of the network.

©      The bus topology is regarded as one of the major network topologies of the networking world.

©      Ethernet and LocalTalk networks use a linear bus topology

Advantages

      Easy to connect a computer or peripheral to a linear bus

      Requires less cable length than a star topology

Disadvantages

v  Entire network shuts down if there is a break in the main cable.

v  A faulty cable or workstation will take the entire LAN down.

v  Terminators are required at both ends of the backbone cable.

v  Difficult to identify the problem if the entire network shuts down.

v  Not meant to be used as a stand-alone solution in a large building.

2.  Star

©      A star topology creates a network by arranging 2 or more host machines around a central hub.

©      A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator

©      Data on a star network passes through the hub or concentrator before continuing to its destination.

©      The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow.

©      This configuration is common with twisted pair cable.

©      usually Ethernet or LocalTalk use this

Advantages

      Easy to install, and wire.

      Easy to add new workstations

      No disruptions to the network when connecting or removing devices.

      Any non-centralised failure will have very little effect on the network

      Easy to detect faults and to remove parts.

      Centralized control

      Centralized network/hub monitoringges

Disadvantages

v  Requires more cable length than a linear topology.

v  If the hub or concentrator fails, nodes attached are disabled.

v  More expensive than linear bus topologies because of the cost of the concentrators.

3.  Star-Wired Ring

©      A star-wired topology may appear (externally) to be the same as a star topology.

©      Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring

©      The Token Ring protocol uses this.

4.  Tree

©      A tree topology combines characteristics of linear bus and star topologies.

©      It consists of groups of star-configured workstations connected to a linear bus backbone cable.

©      Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantages

      Point-to-point wiring for individual segments.

Disadvantages

v  Overall length of each segment is limited by the type of cabling used.

v  If the backbone line breaks, the entire segment goes down.

v  More difficult to configure and wire than other topologies.

Can refer to this website:

©     Click on the colour word =)

·        http://asiabizz.com/2232/various-types-of-computer-networks-and-network-topology/

·        http://errajib.hubpages.com/hub/Types-of-Networks

1.       A network interface controller (also known as a network interface card, network adapter, LAN adapter and by similar terms) is a computer hardware component that connects a computer to a computer network. Whereas network interface controllers were commonly implemented on expansion cards that plug into a computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard.

2.       A networking operating system (NOS)(also referred as the Dialoguer) is the software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions. The network operating system is designed to allow shared file and printer access among multiple computers in a network, typically a local area network (LAN), a private network or to other networks. The most popular network operating systems are Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, and Novell NetWare.

3.       A network switch (or switching hub) is a computer networking device that connects network segments or network devices. The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer (layer 2) of the OSI model. Switches that additionally process data at the network layer (layer 3) and above are often referred to as layer-3 switches or multilayer switches.The first Ethernet switch was introduced by Kalpana in 1990.

4.       A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.

5.       LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. LocalTalk specifies a system of shielded twisted pair cabling, plugged into self-terminating transceivers, running at a rate of 230.4 kbit/s. CSMA/CA was implemented as a random multiple access method.

6.       Token ring local area network (LAN) technology is a local area network protocol which resides at the data link layer (DLL) of the OSI model. It uses a special three-byte frame called a token that travels around the ring. Token-possession grants the possessor permission to transmit on the medium. Token ring frames travel completely around the loop.Initially used only in IBM computers, it was eventually standardized with protocol IEEE 802.5.

7.       Ethernet has largely replaced competing wired LAN technologies. In the OSI reference system, Ethernet is at the Data Link layer. Systems communicating over Ethernet divide a stream of data into individual packets called frames. Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted.

By Mhui