Local Area Network

A local area network (LAN) is a group of computers and associated

devices that share a common communications line or wireless link
to a server. Typically, a LAN encompasses computers and
peripherals connected to a server within a small geographic area
such as an office building or home. Computers and other mobile
devices can share resources such as a printer or network storage.
Usually, the server has applications and data storage that are shared in
common by multiplecomputer users.

A local area network may serve as few as two or three users (for
example, in a home network) or as many hundreds of users. Ethernet
and Wi-Fi are the two most commonly used LAN technologies. Other
LAN technologies, includingToken Ring, Fiber Distributed Data
Interfaceand ARCNET have lost favor as Ethernet and Wi-Fi speeds
have increased. The rise of virtualization has fueled the development
ofvirtual LANs (VLANs) which allows network administrators to logically
group network nodes and partition their networks without the need for
major infrastructure changes.

Typically, a suite of application programs can be kept on the LAN server.

Users who need an application frequently can download it once and then
run it from their local device. Users can order printing and other services
as needed through applications run on the LAN server. A user can share
files with others stored on the LAN server; read and write access is
maintained by a network administrator. A LAN server may also be used
as a Web server if safeguards are taken to secure internal applications
and data from outside access.

In some situations, a wireless LAN, or Wi-Fi, may be preferable to a

wired LAN because of its flexibility and cost. Companies are assessing
WLANs as a replacement for their wired infrastructures as the number
of smartphones, tablets and other mobile devices proliferates.

A local area network, or LAN, consists of a computer network at a single site, typically an
individual office building. A LAN is very useful for sharing resources, such as data storage and
printers. LANs can be built with relatively inexpensive hardware, such as hubs, network
adapters and Ethernet cables.
The smallest LAN may only use two computers, while larger LANs can accommodate
thousands of computers. A LAN typically relies mostly on wired connections for increased speed
and security, but wireless connections can also be part of a LAN. High speed and relatively low
cost are the defining characteristics of LANs.
LANs are typically used for single sites where people need to share resources among
themselves but not with the rest of the outside world. Think of an office building where
everybody should be able to access files on a central server or be able to print a document to
one or more central printers. Those tasks should be easy for everybody working in the same
office, but you would not want somebody just walking outside to be able to send a document to
the printer from their cell phone! If a local area network, or LAN, is entirely wireless, it is referred
to as a wireless local area network, or WLAN.
LAN stands for local area network. It covers, as the name suggests, a local area. This usually
includes a local office and they're also pretty common in homes now, thanks to the spread of
Wi-Fi.

Whether wired or wireless, nearly all modern LANs are based on Ethernet. That wasn't the case
in the 80s and 90s, where a number of standards, including NetBEUI, IPX and token ring
and AppleTalk. Thanks in large part to its open technology, Ethernet rules supreme. It's been
around since the early 70s and isn't going away anytime soon.

There are two ways to implement Ethernet: twisted-pair cables or wireless. Twisted pair cables
plug into switches using RJ-45 connectors, similar to phone jacks. (Remember those?). Cables
plug into switches, which can be connected to other networks. A connection to another network
is a gateway that goes to another LAN or the Internet.

The other popular Ethernet access method is over Wi-Fi under the IEEE 802.11 standard.
Almost all new routers can use the b/g/n standards. IEEE 802.11b and g operate in the 2.4 Ghz
spectrum, while n operates in 2.4 and 5 Ghz, allowing for less interference and, thus, better
performance. The downsides to wireless are the potential for interference and potential
eavesdropping.

Metropolitan Area Network

A Metropolitan Area Network (MAN) is one of a number of types of networks (see
also LAN and WAN). A MAN is a relatively new class of network, it serves a role
similar to an ISP, but for corporate users with large LANs. There are three important
features which discriminate MANs from LANs or WANs:
• The network size falls intermediate between LANs and WANs. A MAN
typically covers an area of between 5 and 50 km diameter. Many MANs cover
an area the size of a city, although in some cases MANs may be as small as a
group of buildings or as large as the North of Scotland.
• A MAN (like a WAN) is not generally owned by a single organisation. The
MAN, its communications links and equipment are generally owned by either a
consortium of users or by a single network provider who sells the service to the
users. This level of service provided to each user must therefore be negotiated
with the MAN operator, and some performance guarantees are normally
specified.
• A MAN often acts as a high speed network to allow sharing of regional
resources (similar to a large LAN). It is also frequently used to provide a shared
connection to other networks using a link to a WAN.

A metropolitan area network, or MAN, consists of a computer network across an entire city,
college campus or small region. A MAN is larger than a LAN, which is typically limited to a
single building or site. Depending on the configuration, this type of network can cover an area
from several miles to tens of miles. A MAN is often used to connect several LANs together to
form a bigger network. When this type of network is specifically designed for a college campus,
it is sometimes referred to as a campus area network, or CAN.
A metropolitan area network (MAN) (not to be confused with "manpages" in the Unix and Linux
world) connects nodes located in the same metro area. For example, a company located in the
San Francisco Bay Area might have its buildings in San Francisco, Oakland and San Jose
linked together via a network.

One of the most common ways for organizations to build this kind of network is to use
microwave transmission technology. You might have seen a microwave antenna on a TV news
van, extended high in the air, beaming video and sound back to the main TV studio. It's also
possible to wire buildings together using fiber-optic cable, but as with WANs, most organizations
that use wires will lease them from another carrier. Laying cable themselves is quite expensive.

Wide Area Network

A wide area network (WAN) is a geographically dispersed
telecommunications network. The term distinguishes a broader
telecommunication structure from a local area network (LAN). A wide
area network may be privately owned or rented, but the term usually
connotes the inclusion of public (shared user) networks. An intermediate
form of network in terms of geography is a metropolitan area network
(MAN).
 A WAN spans a large geographic area, such as a state, province or country.
WANs often connect multiple smaller networks, such as local area
networks (LANs) or metro area networks (MANs).
The world's most popular WAN is the Internet. Some segments of the Internet,
like VPN-basedextranets, are also WANs in themselves. Finally, manyWANs are
corporate or research networks that utilize leased lines.
WANs generally utilize different and much more expensive networking equipment
than do LANs. Key technologies often found in WANs include SONET, Frame
Relay, and ATM.

A wide area network, or WAN, occupies a very large area, such as an entire country or the
entire world. A WAN can contain multiple smaller networks, such as LANs or MANs. The
Internet is the best-known example of a public WAN.
WAN, in contrast to a LAN, refers to a wide area network. The name is exactly what it sounds
like: a network that covers an area wider than a LAN. Beyond that, the definition is less clear.
Distances can range from a network connecting multiple buildings on a corporate or college
campus to satellite links connecting offices in different countries. The most popular WAN is the
one you're using to read this article: the Internet. It's actually a collection of other networks,
including other LANs and WANs - hence, the name.

WANs can be wired, using fiber-optic cable, for example, or wireless. A wireless WAN might use
microwave or infrared (IR) transmission technology, or even satellite. Laying fiber may make
sense when connecting a campus but becomes more expensive when connecting greater
distances. To save money, an organization may opt for wireless technology or lease lines from
a third party.
Analog Signals and Digital Signals
Analog Signals
An analog or analogue signal is any continuous signal for which the time
varying feature (variable) of the signal is a representation of some other
time varying quantity, i.e., analogous to another time varying signal. It
differs from a digital signal in terms of small fluctuations in the signal which
are meaningful. Analog is usually thought of in an electrical context;
however, mechanical, pneumatic, hydraulic, and other systems may also
convey analog signals.
   
Digital Signals
A digital signal is a chemical signal that is a representation of a sequence
of discrete values (a quantified discrete-time signal), for example of
arbitrary bit stream, or of a digitized (sampled and analog-to-digital
converted) analog signal. The term digital signal can refer to

• a continuous-time waveform signal used in any form of digital

communication.
• a pulse train signal that switches between a discrete number of voltage
levels or levels of light intensity, also known as a a line coded signal,
for example a signal found in digital electronics or in serial
communications using digital baseband transmission in, or a pulse
code modulation (PCM) representation of a digitized analog signal.
A signal that is generated by means of a digital modulation method (digital
pass band transmission), produced by a modem, is in the first case
considered as a digital signal, and in the second case as converted to an
analog signal.
 Transmission is the method by which computer networks send electrical signals.
Data communication is concerned with the process of exchanging data
electronically between two communication devices. In a local area network, all
communication functions are performed through direct cables. Computers
located far away are connected through a special form of data communication
link. The existing telephone or telegraphic network may also be used for
connecting computers located at remote locations.

Two types of signals are widely used for transmission. They are

• Analog signals

• Digital signals

Analog Signal Transmission

Transmission of data in analog form is done in the form of continuous waveforms. An

analog signal resembles the one shown in Figure.
                                            

Information is first converted into an electrical signal known as base band electrical
signal. Transmission is done by sending this base band signal directly. A special process
called modulation is used in analog transmission to accommodate more than
one information signal into a single channel. Modulation means varying anyone of the
parameters of a high frequency waveform proportional to the amplitude of the base
band signal. The parameters of the carrier often used forthe modulation are amplitude,
frequency, and phase. A model amplitude modulated waveform is shown in Figure.
                                         

Digital Signal Transmission

Digital data transmission is the transmission of discrete data using two distinct electric
states. A '1' for "on" and '0' for "off" represents these two states. Digital communication
is more efficient than analog communication due to its discrete nature. Communication
between computers is carried out in digital, as computers can recognize only binary
data.

Digital signals also can be modulated or encoded to represent binary data. Following are
some of the techniques used in current state strategies

• Amplitude shift keying

• Frequency shift keying

• Phase shift keying

Amplitude shift keying encodes data using two signals of same frequency but different
amplitudes. For example, a binary a might be represented by a 1volt signal and a binary
1might be represented by a 4 volts signal.

 
Frequency shift keying encodes binary data by varying the signal's frequency between
two or more values. For example, the signal used for representing a binary 0 would be in
one frequency and the signal for a binary 1 would be in some other frequency.

Phase shift keying encodes binary data by varying the phase of the signal to indicate a
value. For example, a 180" phase-shifted signal could represent binary 1, and signal
without phase shift could represents a binary 0. Figure illustrates the three keying
schemes.

synchronous and asynchronous transmissions are two different methods

of transmission synchronization. Synchronous transmissions are synchronized by an external
clock, while asynchronous transmissions are synchronized by special signals along the
transmission medium.

Methods of synchronization
Data is transmitted between communication devices in multiples of fixed-length units,
typically 8-bits. For example, if the computer is transferring a source program, the data
will be made up of a block of 8-bit binary-encoded characters. On the other hand, if the
data is in the form of a compiled object code of the program, the data will be made up of
a block of 8-bit bytes. At the receiving end, the following parameters are determined to
decode and interpret the message correctly.

1. The start of each bit period.

2. The start and end of each character or byte.

3. The start and stop of each complete message block.

These three parameters are known as bit synchronization, character, or byte

synchronization, respectively.

 
In general, there are two transmission modes; they are synchronous and asynchronous
modes. In a synchronous mode, the transmitter and the receiver use the same clock. But
in an asynchronous mode, two independent clocks are used on either side.

There are two ways to synchronize the two ends of the communication.

The synchronous signalling methods use 2 different signals. A pulse on one signal indicates
when another bit of information is ready on the other signal.

The asynchronous signalling methods use only 1 signal. The receiver uses transitions on that
signal to figure out the transmitter bit rate ("autobaud") and timing, and set a local clock to the
proper timing, typically using a phase-locked loop (PLL) to synchronize with the transmission
rate. A pulse from the local clock indicates when another bit is ready.

Synchronous transmission
 Asynchronous transmission is used only when the rate at which characters generated is
unknown or the transmission data rate is too low. For the transmission of a large block of data at
relatively higher bit rates, synchronous transmission is used. In synchronous mode, the sending
and receiving devices are synchronized with a common clock signal. This eliminates the need for
the start and stop bits. The complete block of data is transmitted with fixed time interval
between the bits. Before the start of transmission, clocks at both ends are to be synchronized.
This is achieved by sending special character bytes called sync bytes or sync characters between
the sender and the receiver. The sender informs the receiver about the start of a block. The
receiver figures out the start of each character by knowing the coding scheme used. If the sender
is idle or does not transmit any character, the receiver searches for the next group of sync
characters. The devices are then resynchronized to receive the next block of characters. The
block length varies from few bytes to many hundreds of bytes. The most commonly
used protocol is the BISYNC or Bit Synchronous Protocol.
In synchronous communications, the stream of data to be transferred is encoded as fluctuating
voltage levels in one wire (the 'DATA'), and a periodic pulse of voltage on a separate wire
(called the "CLOCK" or "STROBE") which tells the receiver "the current DATA bit is 'valid' at this
moment in time".

Practically all parallel communications protocols use synchronous transmission. For example, in

a computer, address information is transmitted synchronously—the address bits over
the address bus, and the read or write 'strobe's of the control bus.

Asynchronous transmission
Asynchronous mode is also known as start-stop mode. This mode is used when data to
be transmitted is generated at random intervals. For example, when a user
communicates with a computer using a keyboard, the time interval between two
successive keystrokes is random. This means that the signal on the transmission line
will be in idle state for a long time interval between characters. With this type of
communication, the receiver must be able to resynchronize at the start of each new
character received. To accomplish this, each transmitted character or byte is
encapsulated between an additional start bit and one or more stop bits. This mode is
mainly used for the transmission of characters between a keyboard and a computer.
Asynchronous transmission can also be used for the transmission of a block of
characters or bytes between two computers. The time interval between successive
characters is a variable entity.

                            

In telecommunications, asynchronous communication is transmission of data, generally

without the use of an external clock signal, where data can be transmitted intermittently rather
than in a steady stream.[1] Any timing required to recover data from the communication symbols
is encoded within the symbols. A notable exception is the RS-232 port, and some derivatives,
which are asynchronous, but still have an external clock signal available, although not
commonly used. The most significant aspect of asynchronous communications is that data is
not transmitted at regular intervals, thus making possible variable bit rate, and that the
transmitter and receiver clock generators do not have to be exactly synchronized all the time.

Synchronization can also be embedded into a signal on a single wire. In NRZ Manchester

encoding, each transition from a low to high or high to low represents a logical zero. A logical
one is indicated when there are two transitions in the same time frame as a zero. In the
Manchester coding a transition from low to high indicates a one and a transition from high to low
indicates a zero. When there are successive ones or zeros, an opposite transition is required on
the edge of the time frame to prepare for the next transition.and signal.

The most common asynchronous signalling, asynchronous start-stop signalling, uses a near-

constant 'bit' timing (+/- 5% local oscillator required at both end of the connection). Using this,
the receiver detects the 'first' edge transition... (the START BIT), then waits 'half a bit duration'
then reads the DATA bit state. A further delay of one 'whole bit duration' is executed before the
next data bit is 'read' - repeating for length of the whole serial word (typically 7/8-data bits).
Finally an optional STOP bit is appended to identify the end of the data word.

The word structure used in typical asynchronous serial communications is START-DATA[0:7]-

STOP[0:1] (followed by an optional PARITY bit). These formatting variables are specified when
configuring the transmit and receive nodes before communications take place. The bit duration
is determined from the nominated 'bit rate' in bps... 300, 1200, 9600, 19200, 115200 etc. The
use of the word BAUD is not strictly correct in the modern application of serial channels.

Special level & timing conditions are detected to identify an open-circuit condition (BREAK)
The sync token might be a single pulse (a "start bit" as noted above), or it may be a more
complicated syncword or self-synchronizing code such as HDLC or 8B/10B encoding.

Advantages and disadvantages[edit]

Advantages Disadvantages

• Simple, doesn't require synchronization

of both communication sides

• Cheap, because asynchronous

• Large relative overhead, a
transmission requires less hardware
high proportion of the
Asynchronous
• Setup is faster than other transmissions, transmitted bits are uniquely
transmission
so well suited for applications where for control purposes and thus
messages are generated at irregular carry no useful information
intervals, for example data entry from
the keyboard, and the speed depends
on different applications.
Synchronous • Slightly more complex
• Lower overhead and thus, greater
transmission
throughput • Hardware is more expensive

Network topology 
Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer
network. Essentially, it is thetopological[3] structure of a network and may be depicted physically
or logically. Physical topology is the placement of the various components of a network,
including device location and cable installation, while logical topology illustrates how data flows
within a network, regardless of its physical design. Distances between nodes, physical
interconnections, transmission rates, or signal types may differ between two networks, yet their
topologies may be identical.

An example is a local area network (LAN): Any given node in the LAN has one or more physical
links to other devices in the network; graphically mapping these links results in a geometric
shape that can be used to describe the physical topology of the network. Conversely, mapping
the data flow between the components determines the logical topology of the network.
Point-to-point[edit]
The simplest topology with a dedicated link between two endpoints. Switched point-to-
point topologies are the basic model of conventional telephony. The value of a permanent point-
to-point network is unimpeded communications between the two endpoints. The value of an on-
demand point-to-point connection is proportional to the number of potential pairs of subscribers
and has been expressed as Metcalfe's Law.

Permanent (dedicated)

Easiest to understand, of the variations of point-to-point topology, is a point-to-

point communications channel that appears, to the user, to be permanently associated
with the two endpoints. A children's tin can telephone is one example of a physical
dedicated channel.
Within many switched telecommunications systems, it is possible to establish a
permanent circuit. One example might be a telephone in the lobby of a public building,
which is programmed to ring only the number of a telephone dispatcher. "Nailing down"
a switched connection saves the cost of running a physical circuit between the two
points. The resources in such a connection can be released when no longer needed, for
example, a television circuit from a parade route back to the studio.
Switched:

Using circuit-switching or packet-switching technologies, a point-to-point circuit can be

set up dynamically and dropped when no longer needed. This is the basic mode of
conventional telephony.

Bus[edit]
In local area networks where bus topology is used, each node is connected to a single
cable, by the help of interface connectors.This central cable is the backbone of the
network and is known as the bus (thus the name). A signal from the source travels in
both directions to all machines connected on the bus cable until it finds the intended
recipient. If the machine address does not match the intended address for the data, the
machine ignores the data. Alternatively, if the data matches the machine address, the
data is accepted. Because the bus topology consists of only one wire, it is rather
inexpensive to implement when compared to other topologies. However, the low cost of
implementing the technology is offset by the high cost of managing the network.
Additionally, because only one cable is utilized, it can be the single point of failure.
Linear bus
The type of network topology in which all of the nodes of the network are connected to a
common transmission medium which has exactly two endpoints (this is the 'bus', which
is also commonly referred to as the backbone, or trunk) – all data that
is transmittedbetween nodes in the network is transmitted over this common
transmission medium and is able to be received by all nodes in the network
simultaneously.

Distributed bus
The type of network topology in which all of the nodes of the network are connected to a
common transmission medium which has more than two endpoints that are created by
adding branches to the main section of the transmission medium – the physical
distributed bus topology functions in exactly the same fashion as the physical linear bus
topology (i.e., all nodes share a common transmission medium).

Star
In local area networks with a star topology, each network host is connected to a central
hub with a point-to-point connection. So it can be said that every computer is indirectly
connected to every other node with the help of the hub. In Star topology every node
(computer workstation or any other peripheral) is connected to a central node called hub,
router or switch. The switch is the server and the peripherals are the clients. The
network does not necessarily have to resemble a star to be classified as a star network,
but all of the nodes on the network must be connected to one central device. All traffic
that traverses the network passes through the central hub. The hub acts as a signal
repeater. The star topology is considered the easiest topology to design and implement.
An advantage of the star topology is the simplicity of adding additional nodes. The
primary disadvantage of the star topology is that the hub represents a single point of
failure.
Extended star

A type of network topology in which a network that is based upon the physical star
topology has one or more repeaters between the central node and the peripheral or
'spoke' nodes, the repeaters being used to extend the maximum transmission distance
of the point-to-point links between the central node and the peripheral nodes beyond that
 which is supported by the transmitter power of the central node or beyond that which is
supported by the standard upon which the physical layer of the physical star network is
based.
If the repeaters in a network that is based upon the physical extended star topology are
replaced with hubs or switches, then a hybrid network topology is created that is referred
to as a physical hierarchical star topology, although some texts make no distinction
between the two topologies.
Distributed Star

A type of network topology that is composed of individual networks that are based upon
the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no
central or top level connection point (e.g., two or more 'stacked' hubs, along with their
associated star connected nodes or 'spokes').

Ring
A network topology is set up in a circular fashion in such a way that they make a closed
loop. This way data travels around the ring in one direction and each device on the ring
acts as a repeater to keep the signal strong as it travels. Each device incorporates a
receiver for the incoming signal and a transmitter to send the data on to the next device
in the ring. The network is dependent on the ability of the signal to travel around the ring.
When a device sends data, it must travel through each device on the ring until it reaches
its destination. Every node is a critical link.[4] In a ring topology, there is no server
computer present; all nodes work as a server and repeat the signal. The disadvantage of
this topology is that if one node stops working, the entire network is affected or stops
working.

Mesh
A fully connected network is a communication network in which each of the nodes is
connected to each other. In graph theory it known as a complete graph. A fully connected
network doesn't need to use switching or broadcasting. However, its major disadvantage is that
the number of connections grows quadratically with the number of nodes, as per the formula
and so it is extremely impractical for large networks. A two-node network is technically a fully
connected network.
Partially connected
 The type of network topology in which some of the nodes of the network are connected
to more than one other node in the network with a point-to-point link – this makes it
possible to take advantage of some of the redundancy that is provided by a physical fully
connected mesh topology without the expense and complexity required for a connection
between every node in the network.

A tree topology is essentially a combination of bus topology and star topology. The nodes of bus
topology are replaced with standalone star topology networks. This results in both
disadvantages of bus topology and advantages of star topology.

For example, if the connection between two groups of networks is broken down due to breaking
of the connection on the central linear core, then those two groups cannot communicate, much
like nodes of a bus topology. However, the star topology nodes will effectively communicate with
each other.

It has a root node, intermediate nodes, and ultimate nodes. This structure is arranged in a
hierarchical form and any intermediate node can have any number of the child nodes.

But the tree topology is practically impossible to construct, because the node in the network is
nothing, but the computing device can have maximum one or two connections, so we cannot
attach more than 2 child nodes to the computing device (or parent node).[citation needed] There are
many sub structures under tree topology, but the most convenient is B-tree topology whereby
finding errors is relatively easy.[citation needed]

Many supercomputers use a fat tree network,[6] including the Yellowstone (supercomputer),

the Tianhe-2, the Meiko Scientific CS-2, the Earth Simulator, the Cray X2, the CM-5, and
many Altix supercomputers.

• A network that is based upon the physical hierarchical topology must have at least three
levels in the hierarchy of the tree, since a network with a central 'root' node and only one
hierarchical level below it would exhibit the physical topology of a star.

• A network that is based upon the physical hierarchical topology and with a branching
factor of 1 would be classified as a physical linear topology.

• The branching factor, f, is independent of the total number of nodes in the network and,
therefore, if the nodes in the network require ports for connection to other nodes the
total number of ports per node may be kept low even though the total number of nodes
is large; – this makes the effect of the cost of adding ports to each node totally
 dependent upon the branching factor and may therefore be kept as low as required
without any effect upon the total number of nodes that are possible.

• The total number of point-to-point links in a network that is based upon the physical
hierarchical topology will be one less than the total number of nodes in the network.

Hybrid[edit]
Hybrid networks use a combination of any two or more topologies, in such a way that the
resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For
example, a tree network connected to a tree network is still a tree network topology. A hybrid
topology is always produced when two different basic network topologies are connected. Two
common examples for Hybrid network are: star ring network and star bus network

• A star ring network consists of two or more ring topologies connected using a multistation
access unit (MAU) as a centralized hub.

• A Star Bus network consists of two or more star topologies connected using a bus trunk (the
bus trunk serves as the network's backbone).

While grid and torus networks have found popularity in high-performance

computing applications, some systems have used genetic algorithms to design custom networks
that have the fewest possible hops in between different nodes. Some of the resulting layouts are
nearly incomprehensible, although they function quite well.[citation needed]

A Snowflake topology is really a "Star of Stars" network, so it exhibits characteristics of a hybrid

network topology but is not composed of two different basic network topologies being
connected.

Daisy chain[edit]
Except for star-based networks, the easiest way to add more computers into a network is
by daisy-chaining, or connecting each computer in series to the next. If a message is intended
for a computer partway down the line, each system bounces it along in sequence until it reaches
the destination. A daisy-chained network can take two basic forms: linear and ring.

• A linear topology puts a two-way link between one computer and the next. However, this
was expensive in the early days of computing, since each computer (except for the ones at
each end) required two receivers and two transmitters.

• By connecting the computers at each end, a ring topology can be formed. An advantage of

the ring is that the number of transmitters and receivers can be cut in half, since a message
will eventually loop all of the way around. When a node sends a message, the message is
processed by each computer in the ring. If the ring breaks at a particular link then the
transmission can be sent via the reverse path thereby ensuring that all nodes are always
connected in the case of a single failure.