Transcript Copper Media - Faculty - Genesee Community College

Chapter 8- Physical
Layer
Modified by Profs. Chen and Cappellino
Objectives

In this chapter, you will learn to:


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Explain the role of Physical layer
protocols and services in
supporting communication across
data networks.
Describe the purpose of Physical
layer signaling and encoding as
they are used in networks.
Describe the role of signals used
to represent bits as a frame is
transported across the local media.
Identify the basic characteristics of
copper, fiber, and wireless network
media.
Describe common uses of copper,
fiber, and wireless network media.
OSI Physical Layer - Purpose


Accepts a complete frame from the Data Link
layer and _______________________ signals
that are ______________________________
The delivery of frames across the local media
requires the following Physical layer elements:
 The
physical _____________________________
 A __________________________ on the media
 _____________________________________
 _______________________________________
on the network devices


Purpose of ___________________________
_______________________________________
__________________________ in each frame.
At the ___________________, the Physical layer
_________________________ from the media,
______________________________, and pass
the bits up to the Data Link layer as a complete
frame.
Good summary
of what we’ve
seen so far…
Physical Layer - Operation


The media ______________________, to
represent the bits that make up the frame.
Three basic forms of network media:
______________ For copper cable media, the
signals are patterns of ____________________
_________ For fiber, the signals are ____________.
________________ For wireless media, the signals
are patterns of _____________________________


End of one frame and beginning of the next
is generally handled by what layer?
In many technologies, the Physical layer
may add its own signals to indicate the
beginning and end of the frame
Physical Layer - Standards

The Physical layer consists of
hardware, in the form of _____
___________________________
Standards
set for by electrical and
communications engineering
organizations.

By comparison, the upper OSI
layers are performed by software
and are designed by software
engineers.
The
services and protocols in the
TCP/IP suite are defined by the
Internet Engineering Task Force
(IETF) in RFCs.

Review of standard making body
to the right…
Physical Layer standards define…

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Physical and electrical properties of the media
Mechanical properties (materials, dimensions,
pinouts) of the connectors
__________________ by the signals (encoding)
Definition of control information signals
And also hardware components such as ________
_____________________________________, etc
Three Physical Layer Fundamental Principles are…

The
What
are they?

Encoding
is a _______________________________________
_____________________________________________
Codes are groupings of bits recognized by both the sender and
receiver
Codes used to indicate the data as well as control purposes such as
identifying the beginning and end of a frame.

What
digits represent the signaling on the media?
Depending on the type of media, how are those signals
represented?
The Physical layer standards define what type of signal represents a
"1" and a "0".

Example: A change in the level of an electrical signal or optical pulse or
a more complex signaling method.
Signaling Bits for the Media


The transmission of the frame across the media occurs as
a stream of bits sent one at a time.
Each signal placed onto the media has a ____________
_____________________________ called its _________
 Successful
delivery of the bits requires some ____________________
between transmitter and receiver

 In



accomplished by the use of a clock
LANs, each end of the transmission maintains its own clock.
Signals are processed by the receiving device and
returned to its representation as bits.
The bits are then _____________________________
______________ to determine a complete frame has
been received.
The _________________________________________
to the Data Link layer.
Signaling Methods cont…

Bits are represented on the medium by changing
one or more of the following characteristics of a
signal:
 Amplitude
 Frequency
 Phase


Signaling methods to represent bits on the media
can be complex so we will focus on two basic
types for example:
____________________________ where:
A 0
may be represented by one voltage level on
the media during the bit time
 A 1 might be represented by a different voltage on
the media during the bit time.

___________________________ where:
A 0
is represented by a high to low voltage
transition in the middle of the bit time.
 A 1 is a low to high voltage transition in the middle
of the bit time.
Next slide
contains graphics
NRZ and Manchester Encoding
graphics…
NRZ– suited for slow speed
data links
Manchester Encoding – also
best used at lower signaling
speeds
Ethernet Encoding-- FYI

10BaseT uses Manchester encoding

100BaseT uses 4B/5B encoding

1000BaseT uses 8B/10B encoding.
Encoding – Grouping Bits

__________________________________ being presented to the media.
 _______________
before the signals are placed on the media ______________
______________________________
 Allows more ________________________________________

The Physical layer of a network device needs to be able to detect legitimate
data signals and _________________________________ that may also be
on the physical medium.
 Each
frame with a pattern of signals representing bits that the Physical layer
recognizes as denoting the _____________________________
 Another pattern of bits will signal the ________________________________
 Signal bits not framed in this manner are ignored by the Physical layer standard
being used.
Encoding – Code Groups

Encoding techniques at the Physical layer
use _____________________________.
A ___________________________________
______________________ that are
interpreted and mapped as data bit patterns.
Used to ________________________________
______________________________
 Used as an intermediary encoding technique for
higher speed LAN technologies.
 For example, code bits 10101 could represent the
data bits 0011.


Although using code groups introduces overhead in the form of
extra bits to transmit, they improve the robustness of a
communications link.
Code Groups 4B/5B Example

In this technique, 4 bits of data are turned
into 5-bit code symbols for transmission
over the media system.
 These
symbols represent the data to be
transmitted as well as a set of codes that help
control transmission on the media.
Data Carrying Capacity
Different physical media support the
transfer of bits at different speeds.
 Data transfer can be measured in three
ways as described on the following slides:

 Bandwidth
 Throughput
 Goodput
More to come…
Data Carrying Capacity: ________

_______________________________________
______________________
of information that can flow from one
place to another in a given amount of time.
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
Bandwidth is typically measured in kilobits per second
(kbps) or megabits per second (Mbps).
Bandwidth is determined by a combination of factors:
The

__________________________________________
Some media just is not made to have a high bandwidth
The
___________________________________ and detecting
network signals.
The _________________________________
What is a nibble?
Data Carrying Capacity: _________

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The __________________________________
across the media over a given period of time.
Throughput __________________ to bandwidth
Why?

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
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the
the
the ___________________________________________ on the
network being measured.
Throughput _____________________________
of the path from source to destination.
It
will only take one segment in the path with low throughput to
create a bottleneck
Data Carrying Capacity: _________

A third measurement- goodput- has been
created to _____________________________
___________________________________
measure
that is of most interest to network users.
___________________________________________________
______________________________________________

Measured from Application layer of source to Application layer of
destinatin
As an example,
consider two hosts on a LAN transferring a file.
The
bandwidth of the LAN is 100 Mbps.
Due to the sharing and media overhead the throughput
between the computers is only 60 Mbps.
With the overhead of the encapsulation process of the TCP/IP
stack, the actual rate of the data received by the destination
computer, goodput, is only 40Mbps.
Types of Physical Media

The Physical layer is concerned with network
media and signaling.
This
layer produces the representation and groupings
of bits as voltages, radio frequencies, or light pulses.

Standards for copper media, for example, are
defined as follows:
Type
of copper cabling used
Bandwidth of the communication
Type of connectors used
Pinout and color codes of connections to the media
Maximum distance of the media
See summary charts that follow…
Chart summaries
Copper Media
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______________________ for data
communications
_____________ consists of a ____________
__________________ that form circuits
dedicated to specific signaling purposes.
_______________________ that runs
through the center of the cable with insulation
surrounding the copper core
Copper media can be used to connect nodes
on a LAN to intermediate devices, such as
routers and switches.
Also
used to connect WAN devices to a data
services provider such as a telephone company.

___________________________ is used
widely in LANs with one type of media and in
some WANs with another media type.
Copper Media: External Signal Interference

Data is transmitted on copper cables as ______________.
These
__________________________________________ from
outside the communications system which can _____________
_______________________ being carried by copper media.
Potential sources of interference:

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Minimize/limit signal degradation due to electronic noise…
With
__________________________________________
By selecting the _______________________________________
in a given networking environment
Designing a cable infrastructure to ________________________
_____________________________________________
Using cabling techniques that include the __________________
__________________________________________________
Copper Media: Unshielded Twisted Pair (___) cable


__________________________ used
in Ethernet LANs
Consists of _____________________
that have been twisted together and
then encased in a flexible plastic
sheath.
The
________________________
_________________________________

_______________________ is the
_______________________________
_______________________________
________________ in the cable.
Signal
transmitted on one wire creates
interference in another wire
The cancellation resulting from _________
the wires also ______________________
The different pairs of wires that are twisted
in the cable use a different number of twists
per meter to help protect the cable from
crosstalk between pairs.
Unshielded Twisted Pair cont…
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The UTP cabling conforms to the standards established
jointly by the Telecommunications Industry Association
(TIA) and the Electronics Industries Alliance (EIA).
________________A stipulates the commercial cabling
standards for LAN installations such as:
________________________________
________________________________
________________________________

The electrical characteristics of copper cabling are defined
by the Institute of Electrical and Electronics Engineers
(______________).
Category
5 (Cat5) cable is used commonly in 100BASE-TX.
Enhanced Category 5 (______) cable and Category 6 (_______).

As
Cables in
new gigabit speed Ethernet technologies are being developed
and adopted, Cat5e is now the minimally acceptable cable type

Unshielded Twisted Pair cont…
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Different situations require UTP
cables to be _____________
________________________
The following are main cable
types:
Ethernet
Ethernet


Using a crossover or straightthrough cable incorrectly
• Crossoverbetween devices may not
• Straight-throughdamage the devices, but
connectivity and
communication between the
devices will not take place.
Should
be the ______________
___________________________
__________________________
Copper Media: Shielded Twisted-Pair (___)
STP uses four pairs of wires
________________________
___________________
 _______________________
____________________
within the cable

Also
pairs.

___________________
STP __________________
__________ than UTP cabling
More

expensive than UTP
Not as popular as UTP
Copper Media: Coaxial (_________) Cable
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Consists of a _________________________
_________________________________
Over this insulating material is a ________
_______________________ the amount of
outside electromagnetic ________________.
Coax used to be used in Ethernet installations
 UTP

replaced Coax in LAN installations
Coax is an important type of cable that is
____________________________________
__________________________
 Coax
cables are used to attach antennas to
wireless devices.
 Cable carries radio frequency (RF) energy
between the antennas and the radio
equipment.

Cable providers are currently converting their
one-way systems to two-way systems using a
combination of fiber and coax referred to as
hybrid fiber coax (HFC).
Copper Media Safety

Electrical Hazards
A potential
problem with copper media is that the
____________________________________________
_______________________
Present undesirable voltage levels when used to
connect devices that have power sources with different
ground potentials.
Copper cabling _____________________ caused by
lightning strikes to network devices.

Fire Hazards
________________________________________
produce toxic fumes when heated or burned.


or
__________________ is coated with a _________________
(usually Teflon) so that in case of a fire it does not give off toxic
gasses and smoke as it burns.
Minimize hazards with __________________
___________________________________ etc
Fiber Media

_________________________________________
__________________ from source to destination.
The
bits are encoded on the fiber as _______________.
Has very ___________ raw data bandwidth rates.

Advantages of Fiber Compared to Copper Cabling
Fiber
is ___________________________________ and
will not conduct unwanted electrical currents.
Optical fibers are thin and have relatively low signal loss,
they can be _________________________________
(many kilometers) than copper media.

Optical fiber is often ________________________ for high-traffic
connections and for the interconnection of buildings
Fiber Media

Disadvantages of Fiber Compared to Copper
Cabling
Generally
__________________ than copper
media over the same distance (but for a higher
capacity)
Different ___________________________
____________________ the cable infrastructure

Harder to terminate
More
careful handling than copper media
Fiber Media cont…
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Cable Construction
____________________________
surrounding the glass or plastic
fiber is also _______________________________ from the fiber.
Because light can only travel in one direction over optical fiber,
_____________________________________________________

Process of _____________________________
Either ______________________________ that are
used to represent the transmitted data on the media.

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Electronic semi-conductor devices _____________________
___________________________ that can then be reconstructed
into data frames.
Note: The laser light transmitted over fiber-optic
cabling can damage the human eye
Avoid
looking into the end of fiber
Fiber optic cables classified into two
basic types:

_______________________
Carries
a _______________ of light
Generally ___________________


Can transmit optical pulses for
_____________________________
_______________________
Typically
uses ___________ emitters
Light from an LED _________________
__________________________ and
therefore takes different amounts of time to
travel down the fiber

Travels ___________________________
____________________________
fiber
Wireless Media

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
Wireless media carry ____________________
______________________________ that
represent the binary digits of data
communications.
Wireless data communication technologies work
well in ______________________________
________________________ caused by:
_____________________,
certain _______________,
microwave ovens, etc
Certain construction material, _____________ etc

____________________________________
network administration.
Requires
no access to a physical cable
Wireless Media- 4 common standards

IEEE ___________ - Commonly referred to as Wi-Fi
WLAN

technology using CSMA/CA media access process.
IEEE ____________ - Known as “________________“
Wireless
Personal Area Network (_______________) __________
able to communicate over distances from 1 to 100 meters.

IEEE __________________ - known as __________
(Worldwide Interoperability for Microwave Access)
Uses
______________________ to provide wireless broadband
access.


Global System for Mobile Communications (_____) – uses
General Packet Radio Service (GPRS) protocol to provide
data transfer over ________________________________
Other wireless technologies such as satellite
communications provide data network connectivity for
locations without another means of connection.
The Wireless LAN

A wireless LAN requires the
following network devices:
_________________
(AP) ______________________
and generally ____________
_______________________
______________ adapters ________________________
___________________ to
each network host.
IEEE 802.11 in more detail…

IEEE _________________ - Operates in the _____
frequency band and offers speeds of up to _________
 Has
a smaller coverage area and is less effective at penetrating building
structures than 802.11b but has __________________________
 It is __________________________________________________

IEEE _________________ - Operates in the ________
frequency band and offers speeds of up to ___________
 Longer
range and are better able to penetrate building structures than
devices based on 802.11a.

IEEE ________________ - Operates in the __________
frequency band and offers speeds of up to ___________
 Operate
at the same radio frequency and range as 802.11b but with the
bandwidth of 802.11a.

IEEE _____________ - Currently in draft form but proposed
standard defines ___________________________ with
expected ________________________________ with a
______________ range of up to ___________________
Media Connectors

Media connectors may look the same but may be
wired differently according to the Physical layer
specification for which they were designed.
Punch block- ____________________
__________________________________
______________________________
•One side has a place for each RJ45 plug
•The back side has the punch down
blocks that provide connectivity
Socket found in wall receptacle
•One side has a place for each RJ-45
plug
• Other ________________________
___________________________
Correct Connector Termination

When copper cabling is
terminated, there is the possibility
of signal loss and the introduction
of noise to the communication
circuit.
If
__________________ cable is a
potential source of Physical layer
____________________________

Proper termination is essential to
ensure optimum performance
with current and future network
technologies.
Common Optical Fiber Connectors:


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
Straight-Tip (____) - widely used with
_____________________________
Subscriber Connector (_____) - This connector
type is widely used with ___________________
Lucent Connector (____) - A small connector for
use with ____________________ and also
__________________________
Terminating and splicing fiber-optic cabling
requires skill
 Incorrect



termination- such as:
Misalignment
End gap where the cable does not completely touch
the connection
Etc
will result in diminished signaling distances or
transmission failure.

____________________ and finding any faults
can be done with an Optical Time Domain
Reflectometer (_________________)
 Or-
a basic test with a bright flashlight and
observing if light passes to the other end of the
cable.