2. Basic Concepts
Five general concepts provide the basis for the
relationship between the communicating devices.
Line configuration
Topology
Transmission mode
Categories of Networks
Internetworks
3. (Line configuration)
~ refers to the way two or more communication devices attach to a
link
~ defines the attachment of communication devices to a link
Line configurationLine configuration
MultipiontMultipiontPoint-to-pointPoint-to-point
4. Line configuration (cont’d)
(Point-to-point)
~ provides a dedicated link between two devices.
(Multipoint) : multidrop
~ is configuration in which more than two specific devices share
a single link
9. (Topology)
~ refers to the way a network is laid out, either physically or
logically
~ defines the physical or logical arrangement of link in a
network
A consideration when choosing a topology is the relative
status of the devices to be linked.
peer-to-peer : the devices share the link equally (ring, mesh)
primary-secondary : one device controls traffic and the others
must transmit through it (star, tree)
11. (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.
13. Mesh (cont’d)
Advantages
The use of dedicated links guarantees that each
connection can carry its data load.
Mesh topology is robust.
Privacy and security.
Point-to-point links make fault identification and fault
isolation easy.
14. Mesh (cont’d)
Disadvantages
~ are related to the amount of cabling and the number of
I/O ports
because every device must be connected to every other
device, installation and reconfiguration are difficult
More wiring space requirement
the hardware required to connect each link (I/O port and
cable) can be prohibitively expensive
15. (Star )
Each device has a dedicated point-to-point link only to a
central controller, usually called a hub
17. Star (cont’d)
Advantage
Each device needs only one link and one I/O port to
connect it to any number of others (easy to install and
reconfigure)
Robustness
if one link fails, only that link is affected
Disadvantage
failure of the central hub leads to the failure of the entire
network.
18. (Tree)
is a variation of a star
active hub(central hub)
~ contains a repeater, which is a hardware device that
generates the received bit patterns before sending
them out
passive hub
~ provides a simple physical connection between the
attached devices
21. (Bus)
is multipoint. One long cable acts as a backbone to link all
the devices in the network
Nodes are connected to the bus cable by drop lines and
taps
drop line
~ is a connection running between the device and the main cable
tap
~ is a connector either splices into the main cable or punctures the
sheathing of a cable to create a contact with the metallic core
23. Bus (cont’d)
AdvantagesAdvantages
– ease of installation
– best suited for small networks.
DisadvantagesDisadvantages
– cable length is limited. This limits the number of stations that can be connected
– difficult reconfiguration and fault isolation
Twenty network devices on a segment, and the segment cannot exceed 185 meters in total length
By using repeater we can have up to five segments on a network.
However, only three of these segments can have devices attached to them.
The other two segments are used to link the three populated segments, giving you a maximum number of
sixty devices with a total network length of 925 meters.
24. (Ring)
Each device has a dedicated point-to-point line configuration only with the two
devices on either side of it
AdvantageAdvantage
– Relatively easy to install and reconfigure
– Fault isolation is simplified
– Central node is not required
DisadvantageDisadvantage
unidirectional traffic
break in the ring (due to failure of a node or a link) can disable the entire network
needs dual ring
27. 2.3 (Transmission mode)
~ is used to define the direction of signal flow between
two link devices
(Simplex)
is unidirectional, as on a one-way street (keyboard, monitor)
(Half-Duplex)
each station can both transmit and receive, but not at the same
time
(Full-Duplex)
both stations can transmit and receive simultaneously
32. 2.4 (Categories of Networks)
three primary categories
(LAN)
(MAN)
(WAN)
size, ownership, distance it cover, physical architecture
33. Categories of Networks (cont’d)
Metropolitan area network
(MAN)
Metropolitan area network
(MAN)
Local area networks
(LAN)
Local area networks
(LAN)
Wide area network
(WAN)
Wide area network
(WAN)
NetworkNetwork
34. Categories of Networks (cont’d)
LAN(Local Area Networks)
~ is usually privately owned and links the devices in a
single office, building or campus
39. Categories of Networks (cont’d)
WAN(Wide Area networks)
~ provides long-distance transmission of data, voice,
image, and video information over large geographical
areas that may comprise a country, a continent, or even
the whole world
41. 2.5 (Internetworks)
~ is an interconnection of networks by the use of internetworking
device (router and gateway)
internet: an interconnection of networks
Internet: a specific worldwide network
Internet is a global system of interconnected computer
networks that use the standard Internet protocol suite
(TCP/IP) to serve billions of users worldwide.
