Network topologies

N e t w o r k F u n d a m e n t a l s M I D T E R M 2 | P a g e
Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Professor: Mr. Marck Anthony Cipriano
For Assignment &Project in COMPO01
Network topologyby: Jem Mercado
Network topology is the arrangement of the various elements (links, nodes, etc.)
of a computer or biological network. Essentially, it is the topological structure of a
network, and may be depicted physically or logically. Physical topology refers to the
placement of the network's various components, including device location and cable
installation, while logical topology shows how data flows within a network, regardless
of its physical design. Distances between nodes, physical interconnections,
transmission rates, and/or signal types may differ between two networks, yet their
topologies may be identical.
A good 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
There are two basic categories of network
topologies:
• Physical topologies
• Logical topologies
The shape of the cabling layout used to link devices is called the physical
topology of the network. This refers to the layout of cabling, the locations of nodes, and
the interconnections between the nodes and the cabling. The physical topology of a
network is determined by the capabilities of the network access devices and media, the
level of control or fault tolerance desired, and the cost associated with cabling or
telecommunications circuits.
The logical topology, in contrast, is the way that the signals act on the network
media, or the way that the data passes through the network from one device to the next
without regard to the physical interconnection of the devices. A network's logical
topology is not necessarily the same as its physical topology. For example, the original
twisted pair Ethernet using repeater hubs was a logical bus topology with a physical star
topology layout. Token Ring is a logical ring topology, but is wired a physical star from
the Media Access Unit.
The logical classification of network topologies generally follows the same
classifications as those in the physical classifications of network topologies but
describes the path that the data takes between nodes being used as opposed to the
actual physical connections between nodes. The logical topologies are generally

3 | P a g e M I D T E R M N e t w o r k F u n d a m e n t a l s
GlaizaCaracaz
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Daniello A. Mercado
determined by network protocols as opposed to being determined by the physical layout
of cables, wires, and network devices or by the flow of the electrical signals, although in
many cases the paths that the electrical signals take between nodes may closely match
the logical flow of data, hence the convention of using the terms logical topology and
signal topology interchangeably.
Logical topologies are often closely associated with Media Access Control
methods and protocols. Logical topologies are able to be dynamically reconfigured by
special types of equipment such as routers and switches.
The study of network topology recognizes eight
basic topologies:
• Point-to-point
• Bus
• Star
• Ring or circular
• Mesh
• Tree
• Hybrid
• Daisy chain
Point-to-point
The simplest topology is a permanent 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.

Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Switch
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
Bus network topology
In local area networks where bus topology is used, each
node is connected to a single cable. Each computer or
server is connected to the single bus cable. 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.
Since 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, since only
one cable is utilized, it can be the single point of failure. If the network cable is
terminated on both ends and when without termination data transfer stop and when
cable breaks, the entire network will be down.
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 transmitted
between nodes in the network is transmitted over this common transmission medium
and is able to be received by all nodes in the network simultaneously.
Note: When the electrical signal reaches the end of the bus, the signal "echoes" back
down the line, causing unwanted interference. As a solution, the two endpoints of the
bus are normally terminated with a device called a terminator that prevents this echo.
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).

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Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Star
In local area networks with a star topology, each network host is connected to a
central hub with a point-to-point connection. In Star topology every node
(computer workstation or any other peripheral) is connected to central
node called hub 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 (the 'hub' of the star) 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')

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Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Ring
A network topology that is set up in a circular fashion in which data travels
around the ring in one direction and each device on the right 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.
Mesh
The value of fully meshed networks is proportional to the exponent of the number of
subscribers, assuming that communicating groups of any two endpoints, up to and
including all the endpoints, is approximated by Reed's Law.
Fully connected mesh topology
A fully connected network is a communication network in
which each of the nodes is connected to each other. A fully
connected network doesn't need to use switching nor
broadcasting. However, its major disadvantage is that the
number of connections grows quadratically with the number of
nodes, 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.

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Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Tree
This particular type of network topology is based on a hierarchy of nodes. The
highest level of any tree network consists of a single, 'root'
node, this node connected either a single (or, more
commonly, multiple) node(s) in the level below by (a)
point-to- point link(s). These lower level nodes are also
connected to a single or multiple nodes in the next level down. Tree
networks are not constrained to any number of levels, but as tree
networks are a variant of the bus network topology, they are prone to
crippling network failures should a connection in a higher level of nodes
fail/suffer damage. Each node in the network has a specific, fixed number of nodes
connected to it at the next lower level in the hierarchy, this number referred to as the
'branching factor' of the tree. This tree has individual peripheral nodes.
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.
If the nodes in a network that is based upon the physical hierarchical
topology are required to perform any processing upon the data that is transmitted
between nodes in the network, the nodes that are at higher levels in the hierarchy will
be required to perform more processing operations on behalf of other nodes than the
nodes that are lower in the hierarchy. Such a type of network topology is very useful
and highly recommended.
Advantages
It is scalable. Secondary nodes allow more devices to be connected to a central
node.
Point to point connection of devices.
Having different levels of the network makes it more manageable hence easier
fault identification and isolation.

Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Disadvantages
Maintenance of the network may be an issue when the network spans a great
area.
Since it is a variation of bus topology, if the backbone fails, the entire network is
crippled.
Definition: Tree topology is a combination of Bus and Star topology.
An example of this network could be cable TV technology. Other examples are in
dynamic tree based wireless networks for military, mining and otherwise mobile
applications. The Naval Postgraduate School, Monterey CA, demonstrated such tree
based wireless networks for border security.In a pilot system, aerial cameras kept aloft
by balloons relayed real time high resolution video to ground personnel via a dynamic
self-healing tree based network.
Hybrid
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 star topologies connected using a
multi-station 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.
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.
Definition: Hybrid topology is a combination of Bus, Star and ring topology.
 Daisy chain
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

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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.
Centralization
The star topology reduces the probability of a network failure by connecting all
of the peripheral nodes (computers, etc.) to a central node. When the physical star
topology is applied to a logical bus network such as Ethernet, this central node
(traditionally a 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 remaining peripheral nodes will be unaffected. However, the
disadvantage is that the failure of the central node will cause the failure of all of the
peripheral nodes also,
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 round trip
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.
A tree topology (a.k.a. hierarchical topology) can be viewed as a collection of
star networks arranged in a hierarchy. This tree has individual peripheral nodes (e.g.
leaves) which are required to transmit to and receive from one other node only and are
not required to act as repeaters or regenerators. Unlike the star network, the
functionality of the central node may be distributed.
As in the conventional star network, individual nodes may thus still be isolated
from the network by a single-point failure of a transmission path to the node. If a link
connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an
entire section of the network becomes isolated from the rest.
To alleviate the amount of network traffic that comes from broadcasting all
signals to all nodes, more advanced central nodes were developed that are able to keep
track of the identities of the nodes that are connected to the network. These network
switches will "learn" the layout of the network by "listening" on each port during normal
data transmission, examining the data packets and recording the address/identifier of
each connected node and which port it is connected to in a lookup table held in

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Irish Cabiles
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memory. This lookup table then allows future transmissions to be forwarded to the
intended destination only.
 Decentralization
In a mesh topology (i.e., a partially connected mesh topology), there are at
least two nodes with two or more paths between them to provide redundant paths to be
used in case the link providing one of the paths fails. This decentralization is often used
to advantage to compensate for the single-point-failure disadvantage that is present
when using a single device as a central node (e.g., in star and tree networks). A special
kind of mesh, limiting the number of hops between two nodes, is a hypercube. The
number of arbitrary forks in mesh networks makes them more difficult to design and
implement, but their decentralized nature makes them very useful. This is similar in
some ways to a grid network, where a linear or ring topology is used to connect
systems in multiple directions. A multidimensional ring has a toroidaltopology, for
instance.
A fully connected network, complete topology, or full mesh topology is a
network topology in which there is a direct link between all pairs of nodes. In a fully
connected network with n nodes, there are n(n-1)/2 direct links. Networks designed with
this topology are usually very expensive to set up, but provide a high degree of reliability
due to the multiple paths for data that are provided by the large number of redundant
links between nodes. This topology is mostly seen in military applications.

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Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Types of Network Cables
Networking cables are used to connect one network device to other network devices
or to connect two or more computers to share printer, scanner etc. Different types of
network cables like Coaxial cable, Optical fiber cable, Twisted Pair cables are used
depending on the network's topology, protocol and size. The devices can be
separated by a few meters (e.g. via Ethernet) or nearly unlimited distances (e.g. via the
interconnections of the Internet).
While wireless may be the wave of the future, most computer networks today still
utilize cables to transfer signals from one point to another.
 There are SIXTypes of Internet Wire Connections
1. Twisted pair
2. Fiber Optic cable
3. Coaxial cable
4. Patch cable
5. Ethernet crossover cable
6. Power lines
Twisted pair
Twisted pair cabling is a form of wiring in which pairs of wires (the forward and return
conductors of a single circuit) are twisted together for the purposes of canceling out
electromagnetic interference (EMI) from other wire pairs and from external sources.
This type of cable is used for home and corporate Ethernet networks.
There are three types of twisted pair cables: shielded, unshielded, and foil.
Fiber Optic cable
An optical fiber cable consists of a center
glass core surrounded by several layers of
protective material. The outer insulating jacket
is made of Teflon or PVC to prevent
interference. It is expensive but has
higher bandwidth and can transmit data
over longer distances.
While coax and twisted- pair cabling carry
electronic signals, fiber optics uses light to
transmit a signal. Ethernet supports two
fiber specifications: • Single mode fiber –
consists of a very small glass core, allowing
only a single ray or mode of light to travel across it. This greatly reduces the attenuation
By: Jasper Carera& Manuel Bong Diño

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Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
and dispersion of the light signal, supporting high bandwidth over very long distances,
often measured in kilometers. • Multi mode fiber – consists of a larger core, allowing
multiple modes of light to traverse it. Multimode suffers from greater dispersion than
single mode, resulting in shorter supported distances. Single mode fiber requires more
precise electronics than multimode, and thus is significantly more expensive. Multimode
fiber is often used for high-speed connectivity within a data center.
Optical fiber consists of a core and a cladding layer, selected for total internal reflection
due to the difference in the refractive
index between the two. In practical
fibers, the cladding is usually coated
with a layer of acrylate polymer or
polyimide. This coating protects the
fiber from damage but does not
contribute to its optical waveguide
properties. Individual coated fibers (or
fibers formed into ribbons or bundles)
then have a tough resin buffer layer
and/or core tube(s) extruded around
them to form the cable core. Several layers of protective sheathing, depending on the
application, are added to form the cable. Rigid fiber assemblies sometimes put light-
absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber
from entering another. This reduces cross-talk between the fibers, or reduces flare in
fiber bundle imaging applications.
*Left: LC/PC connectors; *Right: SC/PC connectors
All four connectors have white caps covering the ferrules.
For indoor applications, the jacketed fiber is generally enclosed, with a bundle of flexible
fibrous polymer strength members like aramid (e.g. Twaron or Kevlar), in a lightweight
plastic cover to form a simple cable. Each end of the cable may be terminated with a
specialized optical fiber connector to allow it to be easily connected and disconnected
from transmitting and receiving equipment.
An optical fiber breakout cable
For use in more strenuous environments, a much more robust cable construction is
required. In loose-tube
construction the fiber is laid
helically into semi-rigid tubes,
allowing the cable to stretch
without stretching the fiber
itself. This protects the fiber
from tension during laying and
due to temperature changes.
Loose-tube fiber may be "dry
block" or gel-filled. Dry block
offers less protection to the fibers than gel-filled, but costs considerably less. Instead of

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Irish Cabiles
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a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called
"tight buffer" construction. Tight buffer cables are offered for a variety of applications,
but the two most common are "Breakout" and "Distribution". Breakout cables normally
contain a ripcord, two non-conductive dielectric strengthening members (normally a
glass rod epoxy), an aramid yarn, and 3 mm buffer tubing with an additional layer of
Kevlar surrounding each fiber. The ripcord is a parallel cord of strong yarn that is
situated under the jacket(s) of the cable for jacket removal. Distribution cables have an
overall Kevlar wrapping, a ripcord, and a 900 micrometer buffer coating surrounding
each fiber. These fiber units are commonly bundled with additional steel strength
members, again with a helical twist to allow for stretching.
A critical concern in outdoor cabling is to protect the fiber from contamination by water.
This is accomplished by use of solid barriers such as copper tubes, and water-repellent
jelly or water-absorbing powder surrounding the fiber.
Finally, the cable may be armored to protect it from environmental hazards, such as
construction work or gnawing animals. Undersea cables are more heavily armored in
their near-shore portions to protect them from boat anchors, fishing gear, and even
sharks, which may be attracted to the electrical power that is carried to power amplifiers
or repeaters in the cable.
Modern cables come in a wide variety of sheathings and armor, designed for
applications such as direct burial in trenches, dual use as power lines, installation in
conduit, lashing to aerial telephone poles, submarine installation, and insertion in paved
streets.
Coaxial cable
Coaxial lines confine the electromagnetic wave to area inside the cable, between the
center conductor and the shield. The transmission of
energy in the line occurs totally through the dielectric
inside the cable between the conductors. Coaxial
lines can therefore be bent and twisted (subject to
limits) without negative effects, and they can be
strapped to conductive supports without
inducing unwanted currents in them and
though.
The most common use for coaxial cables is for
television and other signals with bandwidth of
multiple megahertz. Although in most homes coaxial cables have been installed for
transmission of TV signals, new technologies (such as the ITU-T G.hn standard) open
the possibility of using home coaxial cable for high-speed home networking applications
(Ethernet over coax).
In the 20th century they carried long distance telephone connections.

Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Patch cable
A patch cable is an electrical or optical cable used
to connect one electronic or optical device to
another for signal routing. Devices of different
types (e.g. a switch connected to a computer, or a
switch connected to a router) are connected with
patch cords. It is a very fast connection speed.
Patch cords are usually produced in many different
colors so as to be easily distinguishable, and are
relatively short, perhaps no longer than two meters.
Ethernet crossover cable
An Ethernet crossover cable is a type of
Ethernet cable used to connect
computing devices together directly
where they would normally be
connected via a network switch, hub
or router, such as directly connecting
two personal computers via their
network adapters. Some newer
Ethernet devices support the use of
cross-over cables in the place of patch cables.
Power lines
Although power wires are not designed for
networking applications, new technologies like Power
line communication allows these wires to also be
used to interconnect home computers, peripherals or
other networked consumer products. On December
2008, the ITU-T adopted Recommendation
G.hn/G.9960 as the first worldwide standard for high-
speed powerline communications.G.hn also specifies
communications over phonelines and coaxial

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REPEATER
a repeater is an electronic device that receives a signal andretransmits it at a higher
level or higher power, or onto the other side of an obstruction, so that the signal can
cover longer distances.
The term "repeater" originated with telegraphy in the 19th century, and referred to
an electromechanical device used to regenerate telegraph signals. Use of the term
has continued in telephony and data communications.
In telecommunication, the term repeater has the following standardized meanings:
An analog devicethat amplifies aninput signal
regardless of its nature (analog
or digital).A digital device that amplifies,
reshapes, retimes, or performs a combination of
any of these functions on a digital input signal
for retransmission. A repeater that includes the
retiming function is also known as
a regenerator.
In computer networking, because repeaters
work with the actual physical signal, and do not
attempt to interpret the data being transmitted,
they operate on the physical layer, the first layer
of the OSI model. Repeaters are used to
increase the range of a transmitted signal by re-
transmission. For a conducted signal, an
amplifier is used. Optical systems don't amplify
but all these devices give the appearance of doing so.Some of the energy traveling as
direct current through a conductor is converted to heat energy. This causes a drop in
potential energy (a voltage) across the ends of the conductor proportional to the current
times the inverse of the
conductor's conductance.
Energy passing as alternating
current is also lost as it travels
but, since it changes direction,
there is an additional loss
proportional to the capacitive
reactance times the current.
Since alternating voltage and its
current are out of phase, total
losses equal the vector sum
(rather than linear sum) of the
two losses.Similarly, light, which consists of photons rather than electrons, suffer
attenuation due to scattering and absorption.An optical communications
repeater receives light as input and outputs light. The output signal power source is
external to the input power, but the output power may be driven by input power. Radio
repeaters are used in radio communication services such as Commercial or Amateur

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Radio. A radio repeater consists of aradio receiver connected to a transmitter. The radio
signal is received, amplified and retransmitted, usually on a different frequency. Higher
radio frequencies are limited to line-of-sight transmission, their range is blocked by
mountains and the curvature of the Earth, and so repeaters are located on hills and
mountains, to retransmit the signal beyond the obstruction. Radio repeaters are also
used extensively in broadcasting, where they are known as broadcast relay stations.
These extend thebroadcast coverage area to remote communities, outside the range of
the main broadcast station.
A digipeater is a blend meaning "digital repeater", particularly used in amateur
radio. Store and forward digipeatersgenerally receive a packet radio transmission and
then retransmit it on the same frequency.
When providing a point-to-point telecom link using radio beyond line of sight, one uses
repeaters in a microwave radio relay. A reflector, often on a mountaintop, that relays
such signals around an obstacle, is called a passive repeater.
Extraneous noises and other type of natural interference can cause the repeater to
undesirably retransmit such a signal. To reduce this issue a tone (code) filter such
as CTCSS can be added to the repeater's receiver. To access this type of arraignment
the (input) user's signal would require the tone to be transmitted, along with other
intelligence such as a (audio) voice transmission at the same time.
Advantages
• Makes it easy to expand a network over a large distance.
• Connection between various types of media e.g. fibre optic, UTF, coaxial cable]
is possible.
Disadvantages
• Traffic cannot be filtered to ease congestion.
• A repeater cannot work across multiple network architectures.

GlaizaCaracaz
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Router by: Chelsea Alesna
A router is a device that forwards data packets between computer networks, creating
an overlay internetwork. A router is connected to two
or more data lines from different networks. When a data
packet comes in one of the lines, the router reads the
address information in the packet to determine its
ultimate destination. Then, using information in its
routing table or routing policy, it directs the packet to
the next network on its journey. Routers perform the
"traffic directing" functions on the Internet. A data
packet is typically forwarded from one router to another through the networks that
constitute the internetwork until it reaches its destination node.
The most familiar type of routers are home and small office routers that simply pass
data, such as web pages, email, IM, and videos
between the home computers and the Internet. An
example of a router would be the owner's cable or
DSL modem, which connects to the Internet through
an ISP. More sophisticated routers, such as enterprise
routers, connect large business or ISP networks up to
the powerful core routers that forward data at high
speed along the optical fiber lines of the Internet
backbone. Though routers are typically dedicated hardware devices, use of software-
based routers has grown increasingly common.
Functions and Purposes
When multiple routers are used in interconnected networks, the routers exchange
information about destination addresses using a dynamic routing protocol. Each router
builds up a table listing the preferred routes between any two systems on the
interconnected networks. A router has interfaces for different physical types of network
connections, (such as copper cables, fiber optic, or wireless transmission). It also
contains firmware for different networking Communications protocol standards. Each
network interface uses this specialized computer software to enable data packets to be
forwarded from one protocol transmission system to another.
Routers may also be used to connect two or more logical groups of computer devices
known as subnets, each with a different sub-network address. The subnets addresses
recorded in the router do not necessarily map directly to the physical interface
connections. A router has two stages of operation called planes:

Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Control plane: A router records a routing table listing what route should be used to
forward a data packet, and through which physical interface connection. It does these
using internal pre-configured addresses, called static routes.
A typical home or small office router showing the ADSL telephone line and Ethernet
network cable connections
Forwarding plane: The router forwards data packets between incoming and outgoing
interface connections. It routes it to the correct network type using information that the
packet header contains. It uses data recorded in the routing table control plane.
Routers may provide connectivity within enterprises, between enterprises and the
Internet, and between internet service providers (ISPs) networks. The largest routers
(such as the Cisco CRS-1 or Juniper T1600) interconnect the various ISPs, or may be
used in large enterprise networks. Smaller routers usually provide connectivity for
typical home and office networks. Other networking solutions may be provided by a
backbone Wireless Distribution System (WDS), which avoids the costs of introducing
networking cables into buildings.
All sizes of routers may be found inside enterprises. The most powerful routers are
usually found in ISPs, academic and research facilities. Large businesses may also
need more powerful routers to cope with ever increasing demands of intranet data
traffic. A three-layer model is in common use, not all of which need be present in
smaller networks.
Access
Distribution
Security
Core
Internet connectivity and internal use
Access
Access routers, including 'small office/home office' (SOHO) models, are located
at customer sites such as branch offices that do not need hierarchical routing of
their own. Typically, they are optimized for low cost. Some SOHO routers are
capable of running alternative free Linux-based firmware’s like Tomato, OpenWrt
or DD-WRT.

GlaizaCaracaz
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Distribution
Distribution routers aggregate traffic from multiple access routers, either at the
same site, or to collect the data streams from multiple sites to a major enterprise
location. Distribution routers are often responsible for enforcing quality of service
across a WAN, so they may have considerable memory installed, multiple WAN
interface connections, and substantial onboard data processing routines. They
may also provide connectivity to groups of file servers or other external networks.
Security
External networks must be carefully considered as part of the overall security
strategy. Separate from the router may be a firewall or VPN handling device, or
the router may include these and other security functions. Many companies
produced security-oriented routers, including Cisco Systems' PIX and ASA5500
series, Juniper's Netscreen, Watchguard's Firebox, Barracuda's variety of mail-
oriented devices, and many others.
Core
In enterprises, a core router may provide a "collapsed backbone" interconnecting
the distribution tier routers from multiple buildings of a campus, or large
enterprise locations. They tend to be optimized for high bandwidth, but lack some
of the features of Edge Routers.
Internet connectivity and internal use
Routers intended for ISP and major enterprise connectivity usually exchange
routing information using the Border Gateway Protocol (BGP). RFC 4098
standard defines the types of BGP-protocol routers according to the routers'
functions:
Edge router: Also called a Provider Edge router, is placed at the edge of
an ISP network. The router uses External BGP to EBGP protocol routers
in other ISPs, or a large enterprise Autonomous System.
Subscriber edge router: Also called a Customer Edge router, is located at
the edge of the subscriber's network, it also uses EBGP protocol to its
provider's Autonomous System. It is typically used in an (enterprise)
organization.

Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Inter-provider border router: Interconnecting ISPs, is a BGP-protocol
router that maintains BGP sessions with other BGP protocol routers in ISP
Autonomous Systems.
Core router: A core router resides within an Autonomous System as a
back bone to carry traffic between edge routers.
Within an ISP: In the ISPs Autonomous System, a router uses internal
BGP protocol to communicate with other ISP edge routers, other intranet
core routers, or the ISPs intranet provider border routers.
"Internet backbone:" The Internet no longer has a clearly identifiable
backbone, unlike its predecessor networks. See default-free zone (DFZ).
The major ISPs system routers make up what could be considered to be
the current Internet backbone core. ISPs operate all four types of the
BGP-protocol routers described here. An ISP "core" router is used to
interconnect its edge and border routers. Core routers may also have
specialized functions in virtual private networks based on a combination of
BGP and Multi-Protocol Label Switching protocols.
Port forwarding: Routers are also used for port forwarding between private
internet connected servers.
Voice/Data/Fax/Video Processing Routers: Commonly referred to as
access servers or gateways, these devices are used to route and process
voice, data, video, and fax traffic on the internet. Since 2005, most long-
distance phone calls have been processed as IP traffic (VOIP) through a
voice gateway. Voice traffic that the traditional cable networks once
carried (clarification needed). Use of access server type routers expanded
with the advent of the internet, first with dial-up access, and another
resurgence with voice phone service.

GlaizaCaracaz
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Switchby: Glaiza Caracas
A switch is a telecommunication device that receives a message from any
device connected to it
and then transmits the
message only to the
device for which the
message was meant.
This makes the switch a
more intelligent device
than a hub (which
receives a message and
then transmits it to all
the other devices on its
network). 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 managed switches. 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.
A network switch or switching hub is a computer networking device that links
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 called layer-3 switches
or multilayer switches.
Switches exist for various
types of networks including Fiber Channel, Asynchronous Transfer Mode,
InfiniBand, Ethernet and others. The first Ethernet switch was introduced by
Kalpana in 1990

Glaiza Caracas
Chelsea Alesna
Manuel Bong Diño
Irish Cabiles
Jasper Carera
Jem Mercado
Role of switches in a network
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.
In switches intended for commercial use, built-in or modular interfaces make it
possible to connect different types of networks, including Ethernet, Fiber
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.
Devices that interconnect at layer 3 are traditionally called routers, so layer-3
switches can also be regarded as (relatively primitive) routers.
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, network intrusion detection, and
performance analysis modules that can plug into switch ports. Some of these
functions may be on combined modules.
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.
Layer-specific functionality
A modular network switch with three network modules (a total of 24 Ethernet and 14
Fast Ethernet ports) and one power supply.
While switches may learn about topologies at many layers, and forward at one or more
layers, they do tend to have common features. Other than for high-performance
applications, modern commercial switches use primarily Ethernet interfaces.
At any layer, a modern switch may implement power over Ethernet (PoE), which avoids
the need for attached devices, such as a VoIP phone or wireless access point, to have
a separate power supply. Since switches can have redundant power circuits connected
to uninterruptible power supplies, the connected device can continue operating even
when regular office power fails.

Network topologies

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