Chapter 2
Introduction to Networking
2.1 – Benefits of Networking
2.2 – Types of Networks
2.3 – Network Protocols
2.4 – LAN Architecture
Benefits of Networking
File, Print, and Application Services
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•
•
The desire to share valuable
information was one of the
driving forces behind the
development of computer
networks.
The development of networks
enabled multiple computers to
connect together to share files
and communicate via electronic
mail(e-mail).
Network devices such as
printers connect to the network
so that multiple users can
share one printer.
Mail Services
• E-mail works as a “storageand-retrieval” application.
• Mail messages are stored on
an e-mail server until the
recipient retrieves the e-mail.
• There will also be a post office
box created for the users.
• When e-mail messages are
received, the e-mail server will
redirect the messages to the
users post office box where
the users remain until the user
retrieves them.
Mail Services
• The storage-and-retrieval
nature of e-mail systems
does not require that the
recipient be connected
when the e-mail is sent.
• It can be picked up or
retrieved at a later time.
Directory and Name Services
• To enable users and systems
on the network to find the
services they require, computer
networks make use of
directories and name services.
• The network assigns a name to
users, services, and devices so
that they can be identified and
accessed.
• Knowing the name of a service
on the network enables users to
contact that service without
having to know its physical
location.
Directory and Name Services
• People work easily with names
for services and other entities.
• They can rely on network
directory and name services to
translate those names into the
addresses used to communicate
with the desired service.
• After the initial setup of the
directory or name service, this
translation takes place behind
the scenes, or transparently.
The Internet
• The Internet is a worldwide
public network, interconnecting
thousands of other networks to
form one large "web" for
communication.
• Many private networks, some
with thousands of users of their
own, connect to the Internet by
using the services of Internet
Service Providers (ISPs).
• These linkages enable long
distance access to network
services for information and
device sharing.
Network Administration
• The on-going task of
maintaining and adapting the
network to changing
conditions falls to network
administrators.
• As they evaluate new
technologies and
requirements, administrators
must measure their benefits
against the issues, costs, and
problems the new features
may introduce to the network.
Types of Networks
Overview
• Some networks are designed to interconnect many users
and systems in a limited geographical region and to
enable high-speed communication among them.
• Other networks connect a smaller number of devices that
are separated by large geographical distances.
• To meet the requirements of these two broad categories of
users, different types of networks have been designed.
Local-Area Networks (LANs)
• Local-area networks (LANs)
connect many computers in
a relatively small
geographical area such as
a home, an office, a
building, or a campus.
• The general shape or layout
of a LAN is called its
topology.
• All LANs require the
networked computers to
share the communications
channel that connects them.
Wide-Area Networks (WANs)
• A WAN is usually segmented into
multiple LANs that make up a WAN.
• These lines are called point-to-point
because they connect only two
devices, one on each side of the
line.
• They are called serial lines because
the bits of information are
transmitted one after another in a
series.
• Connections across WAN lines may
be temporary or permanent.
• WANs normally operate at lower
speeds than LANs.
Peer-to-Peer Networks
• In a peer-to-peer network, the
networked computers act as
equal partners, or peers to each
other. As peers, each computer
can take on the client function
or the server function.
• Individual users control their
own resources.
• They may decide to share
certain files with other users.
They may also require
passwords before they allow
others to access their
resources.
Client/Server Networks
• In a client/server
arrangement, network
services are located on a
dedicated computer called
a server, which responds to
the requests of clients.
• The server is a central
computer that is
continuously available to
respond to a client requests
for file, print, application,
and other services.
Client/Server Networks
• The distribution of functions
in client/server networks
brings substantial
advantages, but it also
incurs some costs.
• Although the aggregation of
resources on server
systems brings greater
security, simpler access and
coordinated control,
introduces a single point of
failure into the network.
Networking Protocols
Protocol Suite
• The function of the OSI network model is carried out by the
protocols that are active at each layer.
• When a set of protocols operates in a coordinated way to
deliver a number of functions, they are grouped into a
protocol suite.
• A protocol is a controlled sequence of messages
exchanged between two or more systems to accomplish a
given task.
TCP/IP
• The TCP/IP suite of protocols has become the
dominant standard for internetworking.
• TCP/IP represents a set of public standards that
specifies how packets of information are exchanged
between computers over one or more networks.
TCP/IP
• The following protocols function at the application
layer of the OSI model:
– File Transfer Protocol (FTP)
– Simple Mail Transport Protocol (SMTP)
– Domain Name System (DNS)
• The following protocols are seen at the transport
layer of the OSI model:
– Transmission Control Protocol (TCP)
– User Datagram Protocol (UDP)
TCP/IP
• The following protocols are seen at the network layer
of the OSI model:
–
–
–
–
–
Internet Protocol (IP)
Internet Control Message Protocol (ICMP)
Routing Information Protocol (RIP)
Open Shortest Path First (OSPF)
Address Resolution Protocol (ARP)
Proprietary versus Open Standards
• Proprietary technologies are owned
by one company and are generally
not compatible with equipment sold
by other vendors.
• Open source software is free and
users are not bound to the
copyright laws that might be broken
when using proprietary software.
• The core code of open software
can be easily studied by other
programmers and improved.
• The only provision is that these
improvements must be revealed
publicly and distributed freely in a
process that encourages continual
innovation.
LAN Architectures
Ethernet
• The Ethernet architecture is the
most popular type of LAN link
used today.
• It is based on the 802.3 standard.
• This specifies that a network that
implements the Carrier Sense
Multiple Access/Collision
Detection (CSMA-CD) access
control method must use a
baseband transmission over
coaxial or twisted-pair cable that
is laid out in a bus topology.
• Standard transfer rates are 10
megabit per second (Mbps), 100
Mbps, or 1000 Mbps.
Ethernet
• Currently, 10BASE-T is one of the most popular
Ethernet implementations. It uses a star bus
topology.
• Advantages of 10BASE-T is that it is relatively
inexpensive and has the ability to upgrade.
• The disadvantages of 10BASE-T are that the
maximum length for a 10BASE-T segment (without
repeaters) is only 100 meters (about 328 feet).
• UTP is more vulnerable to electromagnetic
interference (EMI) and attenuation than other cable
types.
• Attenuation is the decreasing of the signal, as it
gets further away from the source.
Ethernet
• 100BASE-X comes in several different flavors. It
can be implemented over Category 5 UTP
(100BASE-T), over 2-pair Category 5 UTP or STP
(100BASE-TX) or as Ethernet over 2-strand fiberoptic cable (100BASE-FX).
• Advantages are high-speed performance. At 100
Mbps, transfer rates are 10 times that of 10BASE-T.
• 100BASE-X shares the disadvantages of 10BASET, which are inherent to twisted-pair cabling, such
as susceptibility to EMI and attenuation.
Ethernet
• 1000BASE-T is called Gigabit Ethernet.
• This architecture supports data transfer rates of 1
gigabit per second (Gbps), which is many times
faster than a T-1 line.
• The greatest advantages of 1000BASE-T is
performance.
• The only disadvantages associated with
1000BASE-T are those common to all UTP
networks.
Ethernet
• Half duplex allows for only
one direction that can be
used at a time when data is
being transmitted over the
lines.
• Data can only be sent and
received at separate times.
• An intercom is a good
example of how half duplex
transmission occurs
• Full duplex allows for two
simultaneous directions of
data flow.
• A telephone conversation
between two people is a
good example of how fullduplex transmission occurs.
DSL
• Asymmetric DSL (ADSL) currently is the most common
implementation. It has speeds that vary from 384 kbps to more than
6 Mbps downstream. The upstream speed is typically lower.
• High Data Rate DSL (HDSL) provides bandwidth of 768 kbps in
both directions.
• Symmetric DSL (SDSL) provides the same speed, up to 3 Mbps, for
uploads and downloads.
• Very High Data Rate DSL (VDSL) is capable of bandwidths
between 13 Mbps to 52 Mbps.
• ISDN DSL (IDSL) has a top speed of 144 kbps but is available in
areas that do not qualify for other DSL implementations. IDSL is
actually DSL over ISDN lines.
Cable Modems
• A cable modem acts like a LAN
interface by connecting a
computer to the Internet.
• The cable modem connects a
computer to the cable company
network through the same coaxial
cabling that feeds Cable TV
(CATV) signals to a television set.
• The cable modem service, similar
to DSL, is also an "always-on"
technology.