Transcript CCNA SEMESTER 1 V 3.0

CCNA SEMESTER 1 V 3.0
CHAPTER 2
Students completing this chapter should
be able to:
•Explain the importance of bandwidth in networking.
•Use an analogy from their experience to explain bandwidth.
•Explain the difference between bandwidth and throughput.
•Calculate data transfer rates.
•Explain why layered models are used to describe data communication.
•Explain the development of the Open System Interconnection model
(OSI).
•List the advantages of a layered approach.
•Identify each of the seven layers of the OSI model.
•Identify the four layers of the TCP/IP model.
•Describe the similarities and differences between the two models.
•Briefly outline the history of networking.
•Identify devices used in networking.
•Understand the role of protocols in networking.
•Define LAN, WAN, MAN, and SAN.
•Explain VPNs and their advantages.
•Describe the differences between intranets and extranets.
Networking Fundamentals
Evolution of Networking
Local Area Networks (LAN)
Businesses needed a
solution that would
successfully address the
following three problems:
 How to avoid duplication
of equipment and
resources
 How to communicate
efficiently
 How to set up and
manage a network
Wide-area networks (WANs)
 A way for information
to move efficiently
and quickly
 WANs could connect
user networks over
large geographic
areas
Examples of data Networks
Networking Devices
Equipment that connects directly to a
network segment is referred to as a
device. These devices are broken up into
two classifications.
Network Devices
end-user devices
End user devices
End-user devices that provide users with a
connection to the network are also
referred to as hosts
These devices allow users to share,
create, and obtain information.
Host devices are physically connected to
the network media using a network
interface card (NIC)
Network interface card(NIC)
 A NIC is a printed
circuit board that fits
into the expansion
slot of a bus on a
computer
motherboard, or it can
be a peripheral
device.
Network interface card(NIC)
 Laptop or notebook
computer NICs are
usually the size of a
PCMCIA card.
 Each individual NIC
carries a unique code,
called a Media
Access Control
(MAC) address
End User Devices
Network devices
Network devices provide transport for the
data that needs to be transferred between
end-user devices. Network devices
provide extension of cable connections,
concentration of connections, conversion
of data formats, and management of data
transfers.
Network Devices
Repeater
 A repeater is a network device used to
regenerate a signal. Repeaters regenerate
analog or digital signals distorted by
transmission loss due to attenuation.
Bridges
convert network transmission data formats
as well as perform basic data transmission
management.
provide connections between LANs.
perform a check on the data to determine
whether it should cross the bridge or not.
This makes each part of the network more
efficient
Bridges
Switches
Workgroup switches add more intelligence
to data transfer management.
They can determine whether data should
remain on a LAN or not
They can transfer the data only to the
connection that needs that data.
Switches
Routers
Routers have all the capabilities listed above.
 regenerate signals
 concentrate multiple connections
 convert data transmission formats, and manage data transfers
 They can also connect to a WAN, which allows them to connect
LANs that are separated by great distances
Network topology
 Network topology defines
the structure of the
network. One part of the
topology definition is the
physical topology, which
is the actual layout of the
wire or media. The other
part is the logical
topology, which defines
how the media is
accessed by the hosts for
sending data
Logical topology
 The logical topology of a network is how the
hosts communicate across the medium
- broadcast
Ethernet
- token passing
Token Ring
Fiber Distributed Data Interface (FDDI)
Different topologies
A protocol
 A protocol is a formal
description of a set of
rules and conventions
that govern a particular
aspect of how devices on
a network communicate.
 Protocols determine the
format, timing,
sequencing, and error
control in data
communication
Protocols
Protocols control all aspects of data
communication, which include the following:
(IEEE, ANSI , TIA , EIA , ITU )
 How the physical network is built
 How computers connect to the network
 How the data is formatted for transmission
 How that data is sent
 How to deal with errors
Local-area networks (LANs)
LANs consist of the
following components:
Some common LAN
technologies are:
 Computers
 Network interface
cards
 Peripheral devices
 Networking media
 Network devices
 Ethernet
 Token Ring
 FDDI
LANs technologies
Wide-area networks (WANs)
 WANs interconnect
LANs, which then
provide access to
computers or file
servers in other
locations.
Some common WAN
technologies are:
 Modems
 Integrated Services
Digital Network (ISDN)
 Digital Subscriber Line
(DSL)
 Frame Relay
 US (T) and Europe (E)
Carrier Series – T1, E1,
T3, E3
 Synchronous Optical
Network (SONET)
WANs and WAN Devices
Metropolitan-area networks (MANs)
 A MAN is a network
that spans a
metropolitan area
such as a city or
suburban area. A
MAN usually consists
of two or more LANs
in a common
geographic area .
Storage-area networks (SANs)
A SAN is a dedicated, high-performance network used to
move data between servers and storage resources
SANs offer the following features:
 Performance – SANs enable concurrent access of disk
or tape arrays by two or more servers at high speeds.
 Availability – SANs have disaster tolerance built in,
because data can be mirrored using a SAN up to 10
kilometers (km) or 6.2 miles away.
 Scalability – Like a LAN/WAN, it can use a variety of
technologies. This allows easy relocation of backup data,
operations, file migration, and data replication between
systems.
Storage-area networks (SANs)
Virtual private network (VPN)
 A VPN is a private network that is constructed within a
public network infrastructure such as the global Internet.
Using VPN, a telecommuter can access the network of
the company headquarters through the Internet by
building a secure tunnel between the telecommuter’s PC
and a VPN router in the headquarters
Types of VPNs
 Access VPNs – Access VPNs provide remote
access to a mobile worker and small office/home
office (SOHO) to the headquarters of the
Intranet or Extranet over a shared infrastructure.
 Intranet VPNs – Intranet VPNs link regional and
remote offices to the headquarters of the internal
network over a shared infrastructure using
dedicated connections
 Extranet VPNs – Extranet VPNs link business
partners to the headquarters of the network over
a shared infrastructure using dedicated
connections
Benefits of VPNs
 A VPN is a service that offers secure, reliable
connectivity over a shared public network
infrastructure such as the Internet.
 They are the most cost-effective method of
establishing a point-to-point connection
between remote users and an enterprise
customer's network
Intranets and extranets
 Intranets are designed to
permit access by users
who have access
privileges to the internal
LAN of the organization.
 Extranets refer to
applications and services
that are Intranet based,
and use extended, secure
access to external users
or enterprises.
Importance of bandwidth
 Bandwidth is defined as the amount of
information that can flow through a network
connection in a given period of time.
Pipe Analogy for Bandwidth
Highway Analogy for Bandwidth
Measurement
 In digital systems, the basic unit of bandwidth is
bits per second (bps). Bandwidth is the measure
of how much information, or bits, can flow from
one place to another in a given amount of time,
or seconds.
Limitations
Bandwidth varies depending upon the type
of media as well as the LAN and WAN
technologies used. The physics of the
media account for some of the difference.
The actual bandwidth of a network is
determined by a combination of the
physical media and the technologies
chosen for signaling and detecting network
signals.
Distance and bandwidth
File Transfer Time Calculations
Throughput
 Throughput refers to actual measured
bandwidth, at a specific time of day, using
specific Internet routes, and while a specific set
of data is transmitted on the network
Digital versus analog
 Electromagnetic waves are called analog because they
have the same shapes as the light and sound waves
produced by the transmitters
 Analog bandwidth is measured by how much of the
electromagnetic spectrum is occupied by each signal. The
basic unit of analog bandwidth is hertz (Hz), or cycles per
second.
 In digital signaling all information is sent as bits, regardless
of the kind of information it is. Voice, video, and data all
become streams of bits when they are prepared for
transmission over digital media.
 Unlimited amounts of information can be sent over the
smallest or lowest bandwidth digital channel.
Networking Models
 The concept of layers is used to describe
communication from one computer to another
 As the data passes between layers, each layer
adds additional information that enables
effective communication with the corresponding
layer on the other computer
 The OSI and TCP/IP models have layers that
explain how data is communicated from one
computer to another.
Network Comparisons
Layer Communication
 Layer 4 on the source computer communicates
with Layer 4 on the destination computer. The
rules and conventions used for this layer are
known as Layer 4 protocols.
OSI model
OSI layers
The OSI reference model explains how packets travel through the
various layers to another device on a network
Dividing the network into seven layers provides the following
advantages:
 It breaks network communication into smaller, more manageable
parts.
 It standardizes network components to allow multiple vendor
development and support.
 It allows different types of network hardware and software to
communicate with each other.
 It prevents changes in one layer from affecting other layers.
 It divides network communication into smaller parts to make learning
it easier to understand.
The OSI Model - Layer 1
The OSI Model - Layer 2
The OSI Model - Layer 3
The OSI Model - Layer 4
The OSI Model - Layer 5
The OSI Model - Layer 6
The OSI Model - Layer 7
Peer-to-peer communications
 Each layer of the OSI model at the source
communicate with its peer layer at the
destination
 The protocols of each layer exchange
information, called protocol data units (PDUs).
 Each layer depends on the service function of
the OSI layer below it.
 The lower layer uses encapsulation to put the
PDU from the upper layer into its data field; then
it adds whatever headers and trailers the layer
needs to perform its function.
Peer-to-peer communications
TCP/IP model
 Application layer handles
issues of representation,
encoding, and dialog control.
 The transport layer deals with
the quality of service issues of
reliability, flow control, and
error correction
 Internet layer divides TCP
segments into packets and
send them from any network
 Network layer is concerned
with all of the components,
both physical and logical, that
are required to make a
physical link
Common TCP/IP Protocols
The relationship
between IP and TCP is
an important one. IP
can be thought to point
the way for the packets,
while TCP provides a
reliable transport
Comparing TCP/IP with OSI
TCP
IP
Ethernet
Detailed encapsulation process
If one computer (host A) wants to send
data to another computer (host B), the
data must first be packaged through a
process called encapsulation.
Encapsulation wraps data with the
necessary protocol information before
network transit.
Data Encapsulation
Data Encapsulation example
An understanding of the following key
points should have been achieved:
 Understanding bandwidth is essential when studying networking
 Bandwidth is finite, costs money, and the demand for it increases
daily
 Bandwidth is measured in bits per second, bps, kpbs, Mbps, or
Gbps
 Limitations on bandwidth include type of media used, LAN and WAN
technologies, and network equipment
 Throughput refers to actual measured bandwidth, which is affected
by factors that include number of users on network, networking
devices, type of data, user’s computer and the server
 The formula T=S/BW (transfer time = size of file / bandwidth) can be
used to calculate data transfer time
 Comparison of analog and digital bandwidth
An understanding of the following key
points should have been achieved:
 Network communication is described by layered models
 The OSI and TCP/IP are the two most important models of network
communication
 The International Organization for Standardization developed the OSI model
to address the problems of network incompatibility
 The seven layers of the OSI are application, presentation, session,
transport, network, data link, and physical
 The four layers of the TCP/IP are application, transport, internet, and
network access
 The TCP/IP application layer is equivalent to the OSI application,
presentation, and session layers
 Fundamental networking devices are hubs, bridges, switches, and routers
 The physical topology layouts include the bus, ring, star, extended star,
hierarchical, and mesh
 A WAN consists of two or more LANs spanning a common geographic area
An understanding of the following key
points should have been achieved:
 A SAN provides enhanced system performance, is
scalable, and has disaster tolerance built in
 A VPN is a private network that is constructed within a
public network infrastructure
 Three main types of VPNs are access, Intranet, and
Extranet VPNs
 Intranets are designed to be available to users who have
access privileges to the internal network of an
organization
 Extranets are designed to deliver applications and
services that are Intranet based, using extended,
secured access to external users or enterprises