DCN286 INTRODUCTION TO DATA
COMMUNICATION TECHNOLOGY
Network Media, Connectors and
Standards
OSI Model
OSI Layers
OSI Layers
•Provides connectivity and path selection between two host
•Provides Logical address
•No error correction, best effort delivery.
OSI Layers
OSI Layers
OSI Layers
OSI Layers
OSI Layers
Names for Data at Each Layer
Digital Signal Transmission
1. By varying an electrical signal when it
passes over a wire that is typically made
of copper.
2. By varying the power of light as sent over
a glass optical fiber.
3. By varying the radio waves sent through
space, which is commonly referred to as
wireless communications.
Main Types of Electrical Materials
Material
Insulator
Definition
Examples
Difficult for electrical Plastic, paper, rubber,
current to flow
dry wood, air, pure
water, glass
SemiElectrical flow easily Carbon, germanium,
conductor controlled
gallium arsenide,
silicon
Conductor Easy for electrical
current to flow
Metals such as
Copper, gold, silver,
solder, water with
ions, human body
Popular Copper Media Standards
TIA (Telecommunications Industry
Association) and EIA (Electronic Industries
Alliance) work together to publish
commercial building telecommunications
cabling standards TIA/EIA-568-B which
defines how to use the pins on the
connectors on the ends of the cables.
IEEE (Institute of Electrical and Electronic
Engineers) publishes LAN standards such
as IEEE802.3 which will define cable
requirement.
Coaxial cable
Gradually outdated from LAN
Can run for longer distances than either
STP or UTP
Less expensive than fiber-optic cable
though it is expensive than STP or UTP
Still popular for TV and home internet
service
STP (Shielded Twisted Pair) cable
 Shielding provides better electrical
signals by reducing noise and
attenuation.
 Shielding makes the cable more
expensive, heavier and hard to
bend.
STP - 3 insulations
Total 3 insulations:
1.Each thin wire is covered
in color-coded plastic
insulation
2.Each pair of wires is
twisted with a insulator
called a pair shield around
them
3.All the wires in the cable
(usually 4 pairs) are
covered by a shield called
the overall shield.
ScTP (Screened Twisted Pair)
ScTP is also called FTP (Foil Twisted Pair)
ScTP does not have pair shield. Thus, it
has only two insulations: wire insulation
and overall shield.
Cheaper than STP
UTP (Unshielded Twisted Pair)
Flexible and easy install
Offer the same data speeds
Inexpensive
RJ45 connector (RJ11 is for phone cable).
UTP cable categories
UTP cable
category
Category 1
Purpose
Comments
Telephone
Not suitable for data
Category 2
Token Ring
4Mbps Token Ring
Category 3
10Mbps
Category 4
Telephone and
10BASE-T
Token Ring
Category 5
Ethernet
Category 5e
Ethernet
10BASE-T and 100BASET
Same cable and
connector. Support gigabit
Category 6
Ethernet
16Mbps Token Ring
Support 1Gbps. May
support 10Gbps
TIA/EIA568-A and B pin outs
Pin #
1
2
3
4
5
6
7
8
Function
TD+
TDRD+
Unused
Unused
RDUnused
Unused
568A wire color
White/Green
Green
White/Orange
Blue
White/Blue
Orange
White/Brown
Brown
568 B wire color
White/Orange
Orange
White/Green
Blue
White/Blue
Green
White/Brown
Brown
Straight through cable
Can be used to connect PC and other
network equipments to LAN hub/switch
Wire 1 and 2 are used to transmit data
Wire 3 and 6 are used to receive data
Cross-over cable
It is used to connect two same equipments
such as PC-to-PC.
Both ends need to send data on pin 1 and
2; receive data on pin 3 and 6.
In 568B, one end has white/orange and
orange on pin 1 and 2; another has
white/orange and orange on pin 3 and 6.
In 568B, one end has white/green and
green on pin 3 and 6; another end has
them on pin 1 and 2.
Rollover cable
Usually used as console cable.
Change the sequence on another end.
Most commonly used to connect a
computer terminal to a router’s console
port.
This cable is typically flat to help distinguish
it from other types of network cabling.
It gets the name rollover because the pointouts on one end are reversed from the
other end.
Connector and Adapter
The 8 Position 8 Contact
(8P8C) (often called
RJ45) connector
Cross over adapter
Gigabit crossover
All four pairs crossed
Optic media
 Fiber-optic cable has the strongest ability to resist
EMI (electromagnetic interference), RFI (Radio
Frequency Interference)
 Fiber’s bandwidth is much higher than any other
media.
 Fiber is highly secure and it is easy to detect
intrusion.
 Fiber uses light signal transmission and its
attenuation is much less than electrical signals. Its
length could be very long
Duplex
A duplex communication system is a
system composed of two connected
parties or devices which can communicate
with one another in both directions. (The
term duplex is not used when describing
communication between more than two
parties or devices.)
Half duplex cannot send/receive in same
time.
Optical fiber cable components
 Core: usually made by
silicon dioxide (from
sand)
 Cladding: coated on the
core to reflect light and
seal it inside
 Buffer: physical protect
cladding and core
 Jacket: prevent damage
from abrasion, solvents
and other contaminants
Multimode fiber
Fiber with large (greater than 10 μm) core
diameter may allow light coming in with
different angles. (It must be in limit of
acceptance cone)
Single mode fiber
Fiber with a core diameter less than about
ten times the wavelength of the
propagating light and it can only allow light
coming in from one direction.
Some thumbnail rules
Inexpensive LED transmitter is usually
used with inexpensive multimode cable
Expensive laser transmitter is usually used
with expensive single mode cable
Single mode cable with laser transmitter
can support longer cable distance than
multimode cable with LED transmitter.
Optical Fiber Connector (Optional)
LC/PC connector and
SC/PC connectors
have caps covering
the ferrules
Other connectors are
ST, SC, MT, MT-RJ,
MU, etc, etc
Wireless tech introduction
 Infrared
 Bluetooth
 Microwave
 Radio
 Wi-Fi
In general, wireless network is secondary because
of two concerns: speed and security. But, it does
offer mobility and convenience.
Main wireless components
Access point: linking wireless network to
the wired world.
Wireless NIC on each hosts in the network
Wireless hub, switch and router:
functioning as same as regular wire
connected equipments
WLAN standards organizations
IEEE published the WLAN standard.
FCC (Federal Communication
Commission) will specify restriction on
power and radio frequencies in US.
Industry Canada is taking care of radio
frequency usage in Canada.
Frequency use/approval may be different
in various areas, regions and countries.
WLAN standards: IEEE802.11
Question
Any question?
If you do not have question,
please search internet and
collect more information of
those cables, connectors and
standards.
1. Please be comfortable to
draw the shape of popular
connectors.
2. Please be familiar with those
organizations’ full name and
main responsibilities.