Comp tia n+_session_02

CompTIA N+ Certification: Network Communications Installation
Installing Windows XP Professional Using Attended Methods

Objectives

In this session, you will learn to:
Identify the primary network transmission methods.
Identify the main types of media access methods.
Identify the major network signaling methods.
Identify the elements of the data addressing and delivery
process.
Identify common network connection mechanisms.
Identify techniques for ensuring reliable network data delivery.

Ver. 1.0 Session 2 Slide 1 of 51


Transmission Methods

The primary transmission mechanisms that are
implemented on the networks are:
Unicast transmission
Broadcast transmission
Multicast transmission



Unicast Transmission

• Unicast transmission is a transmission method in which
data is transferred from a specific source address to a
specific destination address.
Receives transmission

Ignores transmission Ignores transmission



Broadcast Transmission

• Broadcast transmission is a transmission method in which
data goes from a source node to all other nodes on a
network.



Multicast Transmission

• Multicast transmission is a transmission method in which
data is sent from a server to specific nodes that are defined
as members of a multicast group.

Multicast group Multicast group

Ignores transmission



Media Access Methods

• The media access method determines whether or not a
particular node can place data on the network at a given
time.
• Two categories of media access methods are:
Contention-based or competitive media access
Controlled or deterministic media access

Central device
determines access

Contending
for access



Media Access Methods (Contd.)

The common media access methods are:
Multiplexed Media Access
Polling
Token-Based Media Access
Carrier Sense Multiple Access/ Collision Detection
(CSMA/CD)
Carrier Sense Multiple Access/ Collision Avoidance
(CSMA/CA)
Contention Domains




• Multiplexing is a controlled media access method in which
a central device combines the signals from multiple nodes
and transmits the combined signal across the medium.
• The different methods of multiplexing are:
Time-Division Multiplexing (TDM)
Frequency-Division Multiplexing (FDM)
A central device called as multiplexer or mux is used to
manage the multiplexing process.

mux



Polling

• Polling is a controlled media access method in which a
central device contacts each node in turn to see whether it
has data to transmit.
Client polled
for data

• Demand priority is a polling technique in which nodes
signal their state—either ready to transmit or idle—to a hub.




• Token-based media access is a media access method in
which computers pass a special sequence of bits called a
token between them.
Node with token
can transmit



Carrier Sense Multiple Access/ Collision Detection (CSMA/CD)

Carrier Sense Multiple Access/Collision Detection
(CSMA/CD) is a contention-based media access method in
which nodes can transmit whenever they have data to send.
They detect and manage the inevitable collisions that occur
when multiple nodes transmit at once.
5. Wait

1. Data to transmit 4. Collision

2. Check network 3. Transmit



Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA)

• Carrier Sense Multiple Access/Collision Avoidance
(CSMA/CA) is a contention-based media access method
in which nodes can transmit whenever they have data to
send.
• The steps that they take to ensure media is unused are:
5. Transmit
6. Monitor for jam signal

1. Data to transmit 4. Wait
4. Wait

2. Check network 3. Jam signal



Contention Domains

• A contention domain, also called a collision domain, is a
group of nodes on a contention-based network that
compete with each other for access to the media.

Contention Domain A Contention Domain B



Signaling Methods

The electronic signals that are put onto the communication
media of the networks are categorized as:
Analog Signals
Digital Signals
The signaling techniques used in network communication
are:
Digital Data Transmission
Serial Data Transmission
Parallel Data Transmission
Baseband Transmission
Broadband Transmission



Analog Signals

An analog signal is one that oscillates over time between
maximum and minimum values and can take on any value
between those limits.
The signaling techniques used in network communication
are: Cycle Phase

Amplitude
Cycle Peak

Frequency
Phase
Wavelength
Amplitude Valley

Wavelength

One-second frequency



Digital Signals

A digital signal is one that oscillates between two discrete
values over time, never holding an interim value.
The discrete values in digital signals are either ones and
zeros.
The units of digital data are given specific names:
Crumb
Bit
+
Nibble
Byte 0
Word
-



Modulation and Demodulation

• A modulation is a process in which the lower frequency
data signal is superimposed over the carrier’s waveform.
• The demodulation is a process in which the receiver
decodes the signal, removing the data from the carrier.




Digital transmissions use voltage differences to directly
represent the 1s and 0s that make up the data and are not
modulated over a carrier.
Data is converted into a digital waveform using the following
techniques:
On-off keying: Is a digital transmission encoding scheme in
which a change in voltage from one state to another within a
predetermined interval is symbolized by a 1.
Manchester encoding: Is a digital transmission encoding
scheme which represents the transition from a positive to a
ground with a 0 and the transition from a ground to a positive
with a 1.




• With serial data transmission, bits are transmitted, one per
clock cycle, across a single transmission medium.
• Synchronization, start/stop, and error correction bits are
transmitted in line with data bits, limiting the overall
throughput of data.
• Serial transmissions can delineate bytes by using either
synchronous or asynchronous techniques.
• The following devices are connected over a serial
transmission port:




• With parallel data transmission, multiple bits are transmitted
across multiple transmission lines.
• Synchronization, start/stop, and error correction bits are
transmitted in line with data bits are mainly sent over
additional transmission lines, improving overall throughput
of data
• The following devices uses the parallel transmission mode:




• In baseband transmissions, digital signaling is used to
send data over a single transmission medium using the
entire bandwidth of that medium.

Sender Receiver

Digital signal




• In broadband transmissions, analog signaling is used to
send data over a transmission medium using a portion of
the bandwidth of that medium.

Sender Receiver

Analog signal



Data Addressing and Delivery

Data to be transferred within the network is packaged and
addressed, so that it can be accurately delivered to its
intended destination.
The various data addressing and delivery mechanisms that
are used are:
MAC Address
Network Address
Network Names
Packets



MAC Address

• A MAC address, also called a physical address, is a
unique, hardware-level address assigned to every
networking device by its manufacturer.
• A MAC address is six bytes long, with :
The first three bytes known as Organizationally Unique
Identifier (OUI)
The last three bytes known as Universal LAN MAC address

Six bytes long

Physical Address. . . . . . . . . : 00-00-86-47-F6-65
OUI Universal LAN MAC
address



Activity 3-1

Activity on Identifying the
Local MAC Address



Network Address

• A network address is a protocol-specific identifier assigned
to a node.
• A network address includes two parts:
Network portion
Node portion
Network portion Node portion

IP Address. . . . . . . . . : 192.168.100.100
Subnet Mask . . . . . . . : 255.255.255.0

Separates network from node



Activity 3-2

Activity on Identifying
the Local Network Address



Network Names

• A network name is a word or phrase assigned to a node to
help users and technicians more easily recognize the
device.
• Naming services are methods that map network names to
network addresses, such as:
Domain Name System (DNS)
NetBIOS
Windows Internet Naming Service (WINS)

Descriptive host name

IP address mapping



Activity 3-3

Local Computer Name



Packets

• A packet, also called a datagram, is a unit of data sent
across the network.
• All packets are made up of three components, such as:
Header
Data
Trailer or footer

Header Data Footer



Activity 3-1

Local MAC Address



Network Connection Mechanisms

A network connection is first established between the two
nodes that want to share data.
The network connection mechanisms are:
Simplex Mode
Half Duplex Mode
Full Duplex Mode
Point-to-Point Connections
Multipoint Connections
Radiated Connections
Connection Services



Simplex Mode

• Simplex mode of communication is the one-way
transmission of information with the full use of bandwidth of
the medium for transmission.



Half Duplex Mode

• Half duplex mode communications permit two-way
communications, but in only one direction at a time.

Sender Receiver



Full Duplex Mode

• Full duplex mode communications permit simultaneous
two-way communications.



Point-to-Point Connections

• A point-to-point connection is a direct connection between
two nodes.



Multipoint Connections

• Multipoint connections are connections between many
nodes. Each multipoint connection has more than two
endpoints.

Receiver Detector Sender Detector



Radiated Connections

• A radiated, or broadcast, connection is a wireless point-to-
point or multipoint connection between devices.
• Wireless LAN, infrared, and Wi-Fi networks are all radiated
connections.

Wireless access point User



Connection Services

• Connection services ensure reliable delivery by detecting
and attempting to correct transmission problems.
• The following connection services are used:
Unacknowledged connectionless service
Acknowledged connectionless service
Connection-oriented service



Reliable Delivery Techniques

• Reliable delivery techniques ensure that the data that is
properly packaged and addressed is transmitted completely
and accurately across the network.
• When the delivery techniques are implemented they
perform the following functions:
Error Detection
Parity checking
Cyclic Redundancy Check
Flow Control



Error Detection

• Error detection is the process of determining if transmitted
data has been received correctly and completely by
attaching extra bits in the form of an error detection code
(EDC) to the original contents.

Data sent with
EDC in footer

Receiver generates an
EDC and compares it with
the one sent in the footer

Do they
Yes match? No

Process data Request data be EDAC attempts to
retransmitted rebuild data



Parity

Parity checking operates on a word-by-word basis and can
only reliably determine if a single bit has been changed or
not. Compare bytes with parity bits

Types of parity checking techniques are:
Even and Odd Parity
Internal Computer Parity Checking




A cyclic redundancy check (CRC) uses a predefined
mathematical operation to calculate a CRC code.

Compare CRCs



Flow Control

• Flow control is a class of techniques for optimizing the
exchange of data between systems.
• The types of flow control techniques commonly used in
computer networking are:
• Buffering
• Data Windows



Flow Control (Contd.)

• Buffering is a flow control technique in which received data
is stored in a temporary high speed memory location, called
a buffer, until the main system components are ready to
work with the data.

Network
cache

High-speed data




• Data windows provides a flow control technique where
multiple packets are sent as a unit called a block or window
and the recipient acknowledges each window rather than
each packet, resulting in higher throughput.
• Types of data windows are:
Fixed length windows
Sliding windows




Fixed and Sliding Windows
Fixed window = Always same size

Fixed window

Buffer
Wasted buffer

Sliding windows = Optimized for
buffer

First window

Optimized buffer



Summary

In this session, you learned that:
• The primary transmission mechanisms that are implemented
on the networks are:
• Unicast transmission
• Broadcast transmission
• Multicast transmission
• The common media access methods are:
Media Access Methods
Polling
Carrier Sense Multiple Access/ Collision Detection (CSMA/CD)
Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA)
Contention Domains



Summary (Contd.)

• The electronic signals that are put onto the communication
media of the networks are categorized as:
Analog Signals
Digital signals
The signaling techniques used in network communication are:



Summary (Contd.)

• The data addressing and delivery mechanisms are:
MAC Address
Network Address
Network Names
Packets
The network connection mechanisms are:
• Simplex Mode
• Half Duplex Mode
• Full Duplex Mode
• Point-to-Point Connections
• Multipoint Connections
• Radiated Connections
• Connection Services



Summary (Contd.)

• The reliable delivery techniques are:
Error Detection
Parity
Flow Control


Comp tia n+_session_02

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