Transcript Communications and Networks

Communications and Networks
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Communications and Networks
Five general concepts provide the basis for the relationship between the
communicating devices:
 line configuration.
 Topology.
 Network Architectures
 Internetworks.
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Communications and Networks
Line configuration
Its refers to the way two or more communication devices attach to a
link.
Link is the physical communication pathway that transfers data
from one device to another.
There are two possible line configurations

point-to-point

multipoint
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Communications and Networks
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Communications and Networks
Point-to-Point

It is provides a dedicated link between two devices.

The entire capacity of the channel is reserved for
transmission between those two devices.
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Communications and Networks
Multipoint
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Communications and Networks
Multipoint also called multidrop
 It is one in which more than two specific devices
share a single link.
 The capacity of the channel is shared, either
spatially or temporally.
 If several devices can use the link simultaneously, it
is spatially line configuration.
 If users must take turns, it is a time-shared line
configuration.
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Communications and Networks
Topology
The term topology refers to the way a network is
laid out.
There are 5 basic topologies possible:
 Mesh
 Star
 Tree
 Bus
 Ring
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Communications and Networks
Mesh
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Communications and Networks
Mesh
Every device has a dedicated point –to-point link to every
other device.

A fully connected mesh network therefore has n(n-1)/2
physical channels to link n devices.

Every device on the network must have n-1
input/output (I/O) ports.
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Communications and Networks
Mesh
Advantages
1.
Eliminating the traffic problems that can occur when links
must be shared by multiple devices.
2.
It is robust. it one link becomes unusable, it does not
incapacitate the entire system.
3.
It is privacy or security.
4.
Point-to-point links make fault identification and fault
isolation easy.
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Communications and Networks
Mesh
disadvantages
1. Installation and reconfiguration are difficult.
2. The sheer bulk of the wiring can be greater than the
available space can accommodate.
3. The hardware required to connect each link ( I/O
ports a cable) can be expensive.
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Communications and Networks
Star
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Communications and Networks
Star
Each device (node) has a dedicated point-to-point link only
to a central controller, usually called Hub.
Advantages
1.
2.
3.
4.
It is less expensive than a mesh topology.
It is easy to install and maintain.
It is robustness. If one node fails, only that node is
affected.
Easy fault identification and fault isolation.
It has one disadvantage if the hub fails, the entire network is
inoperable until the hub is repaired.
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Communications and Networks
Tree
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Communications and Networks
Tree
 Is a variation of a star.

nodes in a tree are linked to a central hub that
controls the traffic to the network.
 Not every device plugs directly into the central hub.
 The majority of devices connect to a secondary hub
that in turn is connected to the central hub.
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Communications and Networks
Tree
 The central hub in the tree is an active hub, which
contains a repeater.
 The secondary hubs may be active or passive hubs.
 A passive hub provides a simple physical connection
between the attached devices.
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Communications and Networks
Tree
 It allows more devices to be attached to a
single central hub and can increase the
distance a signal can travel between devices.
 It allow the network to isolate and prioritize
communications from different computers.
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Communications and Networks
Bus
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Bus

Consists of a single central cable, to which all
computers and other devices connect.

The bus in a bus network transmits data, instruction
and information in both directions.

Bus network are popular on LANs because they are
inexpensive and easy to install.
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Communications and Networks
Bus

That failure of one device usually does not affect the
rest of the bus network.

Difficult reconfiguration and fault isolation.

A fault or break in the bus cable stops all transmission,
even between devices on the same side of the
problem.
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Communications and Networks
Ring
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Communications and Networks
Ring
A cable forms a closed loop (ring) with all computers and
devices arranged along the ring.
 Data transmitted on a ring network travels from
device to device around the entire ring, in one
direction.
 If a computer or device on a ring network fails, all
devices before the failed device are unaffected, but
those after the failed device cannot function.
 It can span a larger distance than a bus network,
but it is more difficult to install.
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Hybrid topologies
It is a network combines several topologies as subnetworks
linked together in a larger topology.
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Communications and Networks
Network Architectures
 CLINET/SERVER
 PEER TO PEER
 INTERNET PEER TO PEER (P2P)
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Communications and Networks
Network Architectures
 CLINET/SERVER
one or more computer as a server; the other computers on the
network request services from the server.
Its provides an efficient means to connect 10 or more computers.
Most client/server networks require a person to serve as a network
administrator because of the large size of the network
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Communications and Networks
Network Architectures

PEER-TO-PEER
One type of peer-to-peer network is a simple, inexpensive network
that typically connects fewer than10 computer.
1.
Each computer, called a peer, has equal responsibilities and
capabilities.
2.
Sharing hardware as a printer, data, or information with other
computers on the peer-to-peer network.
3.
Each computer on the network contains both the network
operating system and application software.
4.
Each computer stores files on its own storage devices.
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Communications and Networks
Network Architectures

Internet PEER-TO-PEER ( P2P )
Another type of peer-to-peer. Describe an Internet network.
sometimes is called a file sharing network because users with
compatible SW and an internet connection copy files from
someone else’s HD to their HD.
example of networking SW that support P2P are BitTorrent,
Grokster, Gunutella and Kazaa, which allow users to swap MP3
music and other files via the web
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Communications and Networks
Categories of networks
Into which category a network falls is determined its size, ownership, the
distance it covers and its physical architecture.
 LAN a Local area network
 MAN
 WAN
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Communications and Networks
LAN a Local area network
 Is a network that connects computers and devices in a limited
geographical area such as a home, school computer laboratory,
office building, or closely positioned group of buildings.
 Is usually privately owned.
 It use only one type of transmission media (often are connected via
cable ) and topology.
 Wireless LAN ( WLAN ) is a LAN that uses no physical wires.
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Communications and Networks
MAN a metropolitan area network
Is a high-speed network that connects local area network in a
metropolitan area such as a city or town and handles the bulk of
communications activity across that region.
 MAN typically includes one or more LANs, but covers a smaller
geographic area than a WAN.
 Its usually is managed by consortium of users or by single network
provider that sell the service to the users.
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Communications and Networks
WAN a wide area network
Is a network that covers a large geographic area such as country, or the
world.
 Using a communications channel that combines many types of
media such as telephone lines, cables, and radio waves.
 A WAN can be one large network or can consist of two or more
LANs connected together.
 The Internet is the world's largest WAN
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Communications and Networks
Internetworks
If 2 or more networks are connected, they become an internetwork, or
internet.
Individual networks are joined into internetworks by the use of
interworking devices.
These devices, which include routers and gateways.
The term internet should not be confused with Internet.

internet used to mean an interconnection of networks.

Internet is the name of specific worldwide network.
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Communications and Networks
R
LAN
LAN
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WAN
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LAN
LAN
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