Transcript Chapter 3 Physical Components of a Network

Module 3
Physical Components of a Network
2.1 – Configuring a Network Interface Card
2.2 – Topologies
2.3 – Media Types
2.4 – Devices
2.5 – Connecting to the Internet (WANs)
Configuring a Network Interface Card
What is a NIC?
• A network interface card (NIC) is
a device that plugs into a
motherboard and provides ports
for the network media
connections.
• It is the component that
interfaces with the local-area
network (LAN).
• The following things are
important to consider when
selecting a NIC:
– The type of network
– The type of media
– The type of system bus
Setting the IP Address
• In Windows, the IP address is
manually entered into the
TCP/IP properties dialog box.
• The configuration box is used to
set the address settings, or
configurations that are entered
into the host machine TCP/IP
dialog box, which include:
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An IP address
A subnet mask
Default gateway address
Domain Name System (DNS)
Windows Internet Naming
Service (WINS)
DHCP Servers
• DHCP is a software utility that
automatically assigns IP
addresses to PCs.
• The computer running the
software is known as a DHCP
server.
• DHCP servers assign the IP
addresses and TCP/IP
configuration information to
computers configured as DHCP
clients.
• This dynamic process
eliminates the need for manual
IP address assignments.
Domain Name System
• The Domain Name System
(DNS) is used to translate
the computer names such
as www.cisco.com to the
corresponding unique IP
address.
• Address translations are
used each time the Internet
is accessed.
• The process of translating
names to addresses is
known as name resolution.
Domain Name System
• The DNS server keeps records that map computer
(host) names and their corresponding IP address.
• These record types are combined in the DNS table.
• When a host name needs to be translated to its IP
address, the client contacts the DNS server.
• A hierarchy of DNS servers exists on the Internet
with different servers maintaining DNS information for
their own areas of authority, called zones.
Default Gateway
• A computer located on one
network segment that is
trying to talk to another
computer on a different
segment sends the data
through a default gateway.
• The default gateway is the
near-side interface of the
router.
• It is the interface on the
router to which the local
computer network segment
or wire is attached.
Topologies
The Network Topology
• The network topology
defines the layout of the
network.
• It shows how devices on the
network are interconnected.
• Devices on the network are
termed nodes.
• A network has both a
physical and a logical
topology.
Physical versus Logical Topology
• Physical topology shows
the physical topology of a
network, which refers to the
layout of the devices and
media.
Physical versus Logical Topology
•Logical topology shows the
logical topology of a network,
which refers to the paths that
signals travel from one point
on the network to another.
•These two terminologies can
be confusing, because the
word "logical" in this instance
has nothing to do with the
way the network appears to
be functioning.
Bus Topology
• Commonly referred to as a
linear bus, all the devices
on a bus topology are
connected by one single
cable, which proceeds from
one computer to the next.
• This topology is rarely used
and would only be suitable
for a home office or small
business with only a few
hosts.
Bus Topology
• Advantages of a bus topology:
– The thinnet cabling it uses is quite inexpensive.
– It uses less cable compared to other physical topologies like
star or extended star
– It works well for small networks
– It does not need a central device, such as a hub, switch, or
router
• Disadvantages of a bus topology:
– It results in slower access to the network and less bandwidth
due to the sharing of the same cable by all devices
– It is challenging to identify and isolate problems
– A break at any point in the bus cable can disable the entire bus
network
– It needs terminators
Star Topology
• The star topology is the
most commonly used
architecture in Ethernet
LANs and resembles
spokes in a bicycle wheel.
• A star topology generally
costs more to implement
than the bus topology
because more cable is used
and a central device is
needed, such as a hub,
switch, or router.
Star Topology
• Advantages of a Star Topology:
– It is upgradeable, flexible, and reliable
– It is easy to design and install
– This topology makes diagnosing problems relatively easy
since the problem is localized to one computer or device
– This topology allows for more throughput than any other
topology
• Disadvantages of a Star Topology:
– It requires a lot of cable to connect computers since a cable
is required between each device and the central location.
– It is more expensive to build because of the additional cost
of cables and devices like hubs and switches that are
needed to run between the central device and each
computer
Ring Topology
• A frame, called a token, travels
around the ring and stops at
each node.
• If a node wants to transmit data,
it adds that data and the
addressing information to the
frame.
• The frame continues around the
ring until it finds the destination
node, which takes the data out
of the frame.
• The advantage of using this
method is that there are no
collisions of data packets.
Ring Topology
• With single ring all the devices on the network share
a single cable, and the data travels in one direction
only.
• With dual ring two rings allow data to be sent in both
directions.
• This creates redundancy (fault tolerance), meaning
that in the event of a failure of one ring, data will still
be transmitted on the other ring.
• The 802.5 standard is the Token Ring access method
that is used.
• FDDI uses light instead of electricity to transmit data
over a dual ring.
Mesh Topology
• The mesh topology
connects all devices
(nodes) to each other for
redundancy and fault
tolerance.
• It is used in wide-area
networks (WANs) to
interconnect LANs and for
critical networks.
• The mesh topology is
expensive and difficult to
implement.
Hybrid Topology
• The hybrid topology
combines more than one
type of topology.
• When a bus line joins two
hubs of different topologies,
the configuration is called a
star bus.
• The bus line is used to
transfer the data between
the star topologies.
Media Types
Networking Media
• Networking media can be defined simply as the means
by which signals (data) are sent from one computer to
another.
• This includes cable or wireless means.
• There are a wide variety of networking media in the
marketplace.
Coaxial Cable
• Coaxial cable uses copper
shielding to resist interference
from outside electrical
sources.
• A braided copper shield
surrounds the center
conductor and constitutes one
half of the electrical circuit.
• Coaxial cable consists of four
parts:
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Center conductor
Insulation
Shield
Jacket
Coaxial Cable
• There are several types of
coaxial cable, including
thicknet, and thinnet.
• Thicknet has a large diameter,
is rigid, and difficult to install.
• The maximum transmission
rate is only 10 Mbps.
• This is significantly less than
twisted-pair or fiber-optic.
• The maximum length the
cable can be run is 500
meters.
• Thinnet has the same
transmission rate as thicknet.
Coaxial Cable
• The advantages of coaxial cable are the following:
– It can be run for longer distances between nodes than
twisted-pair cable
– It is less expensive than fiber-optic cable
• The disadvantages of coaxial cable are the following:
– The large diameter of Thicknet makes installation
difficult
– Coax needs to be grounded. Otherwise noise problems
will cause data errors
– Bandwidth is limited
Twisted-Pair cable
• Twisted-pair is a type of
cabling that is used for
telephone communications
and most modern Ethernet
networks.
• A pair of wires forms a circuit
that can transmit data.
• The pairs are twisted to
prevent cross talk.
• Pairs of copper wires that are
encased in color-coded
plastic insulation are twisted
together.
Twisted-Pair cable
• Shielded twisted-pair (STP)
cable combines the
techniques of cancellation and
twisting of wires with shielding.
• Each pair of wires is wrapped
in metallic foil to further shield
the wires from noise.
• The four pairs of wires are
then wrapped in an overall
metallic braid or foil.
• STP reduces electrical noise
from cable (crosstalk) and
from outside the cable (EMI
and RFI).
Twisted-Pair cable
• Unshielded twisted-pair
(UTP) has two or four pairs
of wires.
• It relies solely on the
cancellation effect produced
by the twisted wire pairs to
limit signal degradation
caused by electromagnetic
interference (EMI) and radio
frequency interference (RFI).
• UTP is the most commonly
used cabling in Ethernet
networks.
Fiber-Optic Cable
• Fiber-optic cable is a networking
medium that is capable of
conducting modulated light
transmissions.
• To modulate light is to
manipulate it so that it travels in
the way that it transmits data.
• It refers to cabling that has a
core of strands of glass or
plastic (instead of copper),
through which light pulses carry
signals.
Wireless
• Wireless networks use radio
frequency (RF), laser, infrared
(IR), and satellite/microwaves
to carry signals from one
computer to another without a
permanent cable connection.
• Wireless signals are
electromagnetic waves that
travel through the air.
• No physical medium is
necessary for wireless signals.
• Mobile phones are a common
application of wireless.
Devices
Hubs and Repeaters
• Typical LAN devices include
repeaters, hubs, bridges,
switches, and routers.
• A repeater receives the
signal, regenerates it, and
passes it on.
• Repeaters are used mainly
at the edges of networks to
extend the wire so more
workstations can be added.
Hubs and Repeaters
• Using a hub changes the
network topology from a linear
bus, where each device plugs
directly into the wire, to a star.
• Data arriving over the cables to
a hub port is electrically
repeated on all the other ports
connected to the same Ethernet
LAN, except for the port on
which the data was received.
• Hubs come in three basic types:
– Passive
– Active
– Intelligent
Bridges and Switches
• Bridges and switches operate
at the data link layer of the OSI
model.
• The function of the bridge is to
make intelligent decisions about
whether or not to pass signals
on to the next segment of a
network.
• When a bridge sees a frame on
the network, it looks at the
destination MAC address and
compares it to the forwarding
table to determine whether to
filter, flood, or copy the frame
onto another segment.
Bridges and Switches
• Switches learn certain
information about the data
packets that they receive from
computers on the network.
• They use this to build forwarding
tables to determine the
destination of data being sent by
one computer to another on the
network.
• They help segment a network
and reduce network traffic
congestion by limiting each port
to its own collision domain.
Routers
• Routers operate at the Network
layer of the OSI model.
• They are slower than bridges
and switches but make "smart"
decisions on how to route
packets received on one port to
a network on another port.
• Routers are capable of
segmenting the network.
• Routers are capable of
segmenting a network into
multiple collision domains as well
as into multiple broadcast
domains.
Routers
• Routers can be computers
with special network
software installed on them
or they can be other
devices built by network
equipment manufacturers.
• Routers contain tables of
network addresses along
with optimal destination
routes to other networks.
Connecting to the Internet (WANs)
Synchronous and Asynchronous Serial Lines
• Synchronous serial transmission – Data bits are
sent together with a synchronizing clock pulse.
• A built-in timing mechanism coordinates the clocks of
the sending and receiving devices.
• Asynchronous serial transmission – Data bits are
sent without a synchronizing clock pulse.
• It uses a start bit at the beginning of each message.
• When the receiving device gets the start bit, it can
synchronize its internal clock with the sender clock.
Modems
• The modem is an electronic device
that is used for computer
communications through telephone
lines.
• It allows data transfer between one
computer and another.
• Modems convert digital data to
analog signals and analog signals
back to digital data.
• There are four main types:
– Expansion cards are the most
common.
– PCMCIA modems
– External modems
– Built-in modems
Dialup Networking, Modem Standards, AT
Commands
• When computers use the public
telephone system or network to
communicate, it is called Dial-Up
Networking (DUN).
• DUN actually creates a Point-toPoint Protocol (PPP) connection
between the two computers over
a phone line.
• In this process, PPP causes the
modem to act like a network
interface card.
• The modem must operate in the
following two states to enable
DUN:
– Local command state
– Online state
ISPs and Internet
Backbone Providers
• Services of an Internet
service provider (ISP) are
needed to surf the Internet.
• An ISP connects computers
to the Internet and World
Wide Web.
• When connecting to an ISP,
the computer becomes a
remote client on the ISP
local network.
ISPs and Internet
Backbone Providers
• The current U.S. Internet
infrastructure consists of a
commercial backbone and
a high-speed service
known as the Very HighSpeed Backbone Network
Service (vBNS).
ISPs and Internet
Backbone Providers
• The ISP that cannot connect
directly to the national backbone is
charged a fee to connect to a
regional provider
• In turn, this links to the national
backbone through a Network
Access Point (NAP).
• A NAP is the point at which access
providers are interconnected.
• Some ISPs that are in the same
geographic area make their own
interconnections and peering
agreements called Metropolitan
Area Exchange (MAE).
DSL
• Digital Subscriber Line (DSL) is
an always-on technology. This
means that there is no need to
dial up each time when
connecting to the Internet.
• Transfer rates are often broken
down into upstream and
downstream rates.
• Upstream is the process of
transferring data from the end
user to the server.
• Downstream is the process of
transferring data from the
server to the end user.
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.
Cable Modem versus
DSL Internet Technologies
• When it comes to
comparing cable modem
and DSL Internet
technologies both have their
pros and cons.