Free Students Note: network topologies

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<h2>
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Computer labs are
useful for any type of organisation.<o:p></o:p></div>
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Computer labs are used
in businesses, government agencies, colleges and other organisations and
perform critical functions in each. For businesses and government agencies,
computer labs are areas for group meetings and planning sessions, where the
computer is the medium from which to build a strategic plan. In schools, computer
labs are classrooms where students learn how to use what is perhaps the most
critical tool for education since the invention of the book. In other
organisations, like science labs, computer labs are areas for computation.
Building a computer lab, above all else, requires taking into consideration the
purpose of the lab.<o:p></o:p></div>
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<h2 style="text-align: left;">
Instructions </h2>
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v  1<o:p></o:p></div>
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Decide on the purpose
of the computer lab. Its purpose will impact its overall design and the quality
of the computers that are needed within the lab. For example, if the computer
lab is meant to teach students English in India, it is unlikely to require the
same advanced and expensive programs and security protocols of a U.S.
intelligence agency.<o:p></o:p></div>
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v  2<o:p></o:p></div>
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Select a
well-ventilated and cool room in which to build the lab. Computers in a warm,
humid environment are susceptible to overheating, whereas computers in a cool,
air-conditioned environment are likely to last for a ON time.<o:p></o:p></div>
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v  3<o:p></o:p></div>
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Create a security
protocol for entering the lab. For schools, it is likely sufficient to require
that a code is punched into a lock on the door in order to gain access to the
room. The code can be distributed to all administrators and teachers to protect
the computers from being damaged by students. For organisations that require
greater security, a key card security system with a surveillance camera or two
should be adequate to protect the computer lab. The key card should only be
owned by those deemed trustworthy by the supervisor of the lab.<o:p></o:p></div>
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v  4<o:p></o:p></div>
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Acquire a number of
computers sufficient for handling the workload that is anticipated to take
place within the computer lab. For example, if the computer lab is meant as a
graphic design workstation, each graphic designer should have a computer to
work with in the lab at all times; however, if the computer lab is in a
standard U.S. middle school, then it only requires the same amount as the
average number of student per classroom or slightly more to be sufficient for
class lessons held in the computer lab.<o:p></o:p></div>
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v  5<o:p></o:p></div>
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Place each computer
roughly a full shoulder's length apart from one another (i.e., two to three
feet). This will ensure that people using the lab do not end up crowding each
others' space.<o:p></o:p></div>
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The question is that which topology
should we use?<o:p></o:p></div>
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                                         Star networks are one of the most
common computer network topologies. In its simplest form, a star network
consists of one central switch, hub or computer, which acts as a conduit to transmit
messages. This consists of a central node, to which all other nodes are
connected; this central node provides a common connection point for all nodes
through a hub. [1] Thus, the hub and leaf nodes, and the
transmission lines between them, form a graph with the topology of a star. If the central node
is passive, the originating node must be able to tolerate the
reception of an echo of its own transmission, delayed by the two-way
transmission time (i.e. to and from the central node) plus any delay generated
in the central node. An active star network has an active
central node that usually has the means to prevent echo-related problems.<o:p></o:p></div>
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The star topology reduces
the chance of network failure by connecting all of the systems to a central
node. When applied to a bus-based network, this central hub rebroadcasts all
transmissions received from any peripheral node to all peripheral nodes on the
network, sometimes including the originating node. All peripheral nodes may
thus communicate with all others by transmitting to, and receiving from, the
central node only. The failure of a transmission line linking any peripheral
node to the central node will result in the isolation of that peripheral node
from all others, but the rest of the systems will be unaffected. [2]<o:p></o:p></div>
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It is also designed with each node (file
servers, workstations, and peripherals) connected directly to a central network
hub, switch, or concentrator.<o:p></o:p></div>
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Data on a star network passes through the
hub, switch, or concentrator before continuing to its destination. The hub,
switch, or concentrator manages and controls all functions of the network. It
is also acts as a repeater for the data flow. This configuration is common
with twisted pair cable. However, it can also be
used withcoaxial cable or optical fibre cable.<o:p></o:p></div>
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Advantages<o:p></o:p></div>
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§ 
Better performance: star topology prevents the passing of
data packets through an excessive number of nodes. At most, 3 devices and 2
links are involved in any communication between any two devices. Although this
topology places a huge overhead on the central hub, with adequate capacity, the
hub can handle very high utilization by one device without affecting others.<o:p></o:p></div>
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Isolation of devices: Each device is inherently isolated by
the link that connects it to the hub. This makes the isolation of individual
devices straightforward and amounts to disconnecting each device from the
others. This isolation also prevents any non-centralized failure from affecting
the network.<o:p></o:p></div>
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Benefits from centralization: As the central hub is
the bottleneck, increasing its capacity, or connecting additional devices to
it, increases the size of the network very easily. Centralization also allows
the inspection of traffic through the network. This facilitates analysis of the
traffic and detection of suspicious behavior.<o:p></o:p></div>
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Easy
to detect faults and to remove parts.<o:p></o:p></div>
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No
disruptions to the network when connecting or removing devices.<o:p></o:p></div>
<h2 style="text-align: left;">
 Network Switch </h2>
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 A network
switch or switching hub is a computer networking device that connects network
segments.<o:p></o:p></div>
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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.<o:p></o:p></div>
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The first Ethernet switch was introduced by Kalpana in 1990.[1]<o:p></o:p></div>
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Function<o:p></o:p></div>
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The network switch plays an integral part in
most modern Ethernet local area networks (LANs). Mid-to-large sized LANs contain a
number of linked managedswitches. Small office/home office (SOHO) applications typically use a single
switch, or an all-purpose converged device such as a residential gateway to access small office/home broadband services such as DSL or cable
internet.
In most of these cases, the end-user device contains a router and
components that interface to the particular physical broadband technology. User
devices may also include a telephone interface for VoIP.<o:p></o:p></div>
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An Ethernet switch operates at the data link
layer of the OSI model to create a separate collision
domain for each
switch port. With 4 computers (e.g., A, B, C, and D) on 4 switch ports, A and B
can transfer data back and forth, while C and D also do so simultaneously, and
the two conversations will not interfere with one another. In the case of a
hub, they would all share the bandwidth and run in half duplex, resulting
in collisions, which would then necessitate retransmissions. Using a switch is
called microsegmentation. This
allows computers to have dedicated bandwidth on a point-to-point connections to
the network and to therefore run in full duplex without collisions.<o:p></o:p></div>
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<h2 style="background-position: initial initial; background-repeat: initial initial; border: none; margin: 0in 0in 0.1in; padding: 0in;">
Role of switches in networks<o:p></o:p></h2>
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Switches may operate at one or more layers of
the OSI model, including data link and network. A device
that operates simultaneously at more than one of these layers is known as a multilayer
switch.<o:p></o:p></div>
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In switches intended for commercial use,
built-in or modular interfaces make it possible to connect different types of
networks, including Ethernet, Fibre
Channel,ATM, ITU-T G.hn and 802.11. This
connectivity can be at any of the layers mentioned. While Layer 2 functionality
is adequate for bandwidth-shifting within one technology, interconnecting
technologies such as Ethernet and token ring is easier at Layer 3.<o:p></o:p></div>
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Devices that interconnect at Layer 3 are
traditionally called routers, so "Layer-3 switches" can also be
regarded as (relatively primitive) routers.<o:p></o:p></div>
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In some service provider and other
environments where there is a need for a great deal of analysis of network
performance and security, switches may be connected between WAN routers as
places for analytic modules. Some vendors provide firewall,[2][3] network intrusion detection,[4] and performance analysis modules that can
plug into switch ports. Some of these functions may be on combined modules.[5]<o:p></o:p></div>
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In other cases, the switch is used to create
a mirror image of data that can go to an external device. Since most switch
port mirroring provides only one mirrored stream, network hubs can be useful for fanning out data to several
read-only analyzers, such as intrusion detection systems and packet
sniffers.<o:p></o:p></div>
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<h2 style="text-align: left;">
 LAN</h2>
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Definition: A local area network (LAN) supplies
networking capability to a group of computers in close proximity to each other
such as in an office building, a school, or a home. A LAN is useful for sharing
resources like files, printers, games or other applications. A LAN in turn
often connects to other LANs, and to the Internet or other WAN.<o:p></o:p></div>
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Most
local area networks are built with relatively inexpensive hardware such as
Ethernet cables, network adapters, and hubs. Wireless LAN and other more
advanced LAN hardware options also exist.<o:p></o:p></div>
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Specialized
operating system software may be used to configure a local area network. For
example, most flavors of Microsoft Windows provide a software package called
Internet Connection Sharing (ICS) that supports controlled access to LAN
resources.<o:p></o:p></div>
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The
term LAN party refers to a multiplayer gaming event where participants bring
their own computers and build a temporary LAN.<o:p></o:p></div>
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Also
Known As: local area network<o:p></o:p></div>
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Examples:<o:p></o:p></div>
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The
most common type of local area network is an Ethernet LAN. The smallest home
LAN can have exactly two computers; a large LAN can accommodate many thousands
of computers. Many LANs are divided into logical groups called subnets. An
Internet Protocol (IP) "Class A" LAN can in theory accommodate more
than 16 million devices organized into subnets.<o:p></o:p></div>
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<h2 style="text-align: left;">
About
Wired LANs</h2></div></div>

How To Build Computer Lab

Computer labs are useful for any type of organisation. Computer labs are used in businesses, government agencies, colleges and oth...