Transcript Network Topologies

IT Essentials I v. 3.1
Module 10
Networking Fundamentals
© 2004, Cisco Systems, Inc. All rights reserved.
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Module 10
Networking Fundamentals
10.1 – Introduction to PC Networking
10.2 – Types of Networks
10.3 – Adding a Network Interface Card (NIC)
10.4 – Physical Components of a Network
10.5 – LAN Architectures
10.6 – Networking Protocols and the OSI Model
10.7 – TCP/IP Utilities
10.8 – Connecting to the Internet
Introduction to PC Networking
Defining a Computer Network
• A computer network allows
users to communicate with
other users on the same
network by transmitting data
on the cables used to connect
them.
• A computer network is defined
as having two or more devices
(such as workstations,
printers, or servers) that are
linked together for the purpose
of sharing information,
resources, or both.
Defining a Computer Network
• A network consists of
many overlapping
systems, such as cabling,
addressing schemes, or
applications.
• The layers work together
to transmit and receive
data.
• The Open Systems
Interconnection (OSI)
reference model, was
created to define these
multiple layers.
File, Print, and Application Services
• Computer networks offer file
and print services.
• In networks, different
computers take on specialized
roles or functions.
• Once connected, one or more
computers in the network can
function as network file
servers.
• The server is a repository for
files that can be accessed and
shared across the network by
many users.
File, Print, and Application Services
• All network operating
systems offer file and print
services.
• Sharing information,
collaborating on projects,
and providing access to
input and output devices
are common services of
computer networks.
Mail Services
• E-mail services work like the
postal system, with one computer
taking on the function of post
office.
• The user e-mail account operates
like a post office box, where mail
is held for the user until it is
picked up over the network by an
e-mail client program running in
the user system.
• The e-mail is sent from the client
computer to the server, which
acts as the post office. The server
sends it to the e-mail address.
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.
Directory and Name Services
• Directory and name
services make a network
easier to use.
• After the initial setup of the
directory or name service,
this translation takes place
transparently.
• In addition to their ease of
use, they also make the
network more flexible.
The Internet
• The Internet is a
worldwide public network
of networks,
interconnecting thousands
of smaller networks to
form one large “web” of
communication.
• The Internet functions like
a highway to facilitate
exchange between
geographically separated
users, organizations, and
branches of companies.
The Internet
• The phrase “information
superhighway” describes
the benefit of the Internet to
business and private
communication.
• The Internet breaks down
barriers of time and space,
enabling the sharing of
information around the
globe almost
instantaneously.
Network Administration
• The ongoing task of network administration is to
maintain and adapt the network to changing
conditions.
• Network administrator responsibilities include:
– Setting up new user accounts and services
– Monitoring network performance
– Repairing network failures
Simplex, Half-Duplex,
and Full-Duplex Transmission
• Simplex transmission is a
single one-way baseband
transmission.
• It is also called
unidirectional because
the signal travels in only
one direction.
• An example of simplex
transmission is the signal
sent from the cable TV
station to the home
television.
Simplex, Half-Duplex,
and Full-Duplex Transmission
• This means that only one
side can transmit at a time.
• Two-way radios, such as
Citizens Band (CB) and
police/emergency
communications mobile
radios, work with halfduplex transmissions.
Simplex, Half-Duplex,
and Full-Duplex Transmission
• Traffic can travel in both
directions at the same time.
• A regular telephone
conversation is an example
of full-duplex
communication. Both
parties can talk at the same
time, and the person talking
on the other end can still be
heard by the other party
while they are talking.
Types of Networks
Overview
• By using local-area network (LAN) and wide-area
network (WAN) technologies, many computers are
interconnected to provide services to their users.
• In providing services, networked computers take on
different roles or functions in relation to each other.
• Some types of applications require computers to
function as equal partners. Other types of
applications distribute work so that one computer
functions to serve a number of others in an unequal
relationship.
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 alternately.
Client/Server Networks
• In a client/server network
arrangement, network
services are located in a
dedicated computer whose
only function is to respond to
the requests of clients.
• The server contains the file,
print, application, security,
and other services in a
central computer that is
continuously available to
respond to client requests.
Local-Area Networks (LANs)
• A local-area network (LAN)
can connect many
computers in a relatively
small geographical area
such as a home, an office,
or a campus.
• It allows users to access
high bandwidth media like
the Internet and allows
users to share devices such
as printers.
Local-Area Networks (LANs)
• The general shape or layout
of a LAN is called its
topology.
• Topology defines the
structure of the network.
This includes the physical
topology which is the actual
layout of the wire or media,
and the logical topology
which is how the media is
accessed by the hosts.
Wide-Area Networks (WANs)
• A WAN, as the name implies, is
designed to work over a larger
area than a LAN.
• A WAN uses point-to-point or
point to multipoint, serial
communications lines.
• Point-to-point lines connect only
two locations, one on each side
of the line. Point-to-multipoint
lines connect one location on
one side of the line to multiple
locations on the other side.
Wide-Area Networks (WANs)
• The following are some of the more
common WAN technologies:
–
–
–
–
–
–
Modems
Integrated Services Digital Network (ISDN)
Digital subscriber line (DSL)
Frame Relay
Asynchronous Transfer Mode (ATM)
The T (US) and E (Europe) Carrier series (T1,
E1, T3, E3, and so on)
– Synchronous Optical Network (SONET)
Wide-Area Networks (WANs)
• Connections across WAN lines
may be temporary or
permanent.
• Telephone or dialup lines, might
make a temporary connection to
a remote network from a
computer in a home or small
office.
• In both temporary and
permanent cases, computers
that connect over wide area
circuits must use a modem or
channel service unit/data
service unit (CSU/DSU) at each
end of the connection.
Wide-Area Networks (WANs)
• The public telephone system,
sometimes referred to as plain
old telephone service (POTS), is
a circuit-switched
communications network.
• When a telephone call is placed
in this type of network, only one
physical path is used between
the telephones for the duration
of that call.
• This pathway is maintained for
the exclusive use of the call,
until the connection is ended
and the telephone is hung up.
Wide-Area Networks (WANs)
• In a packet-switched
network, each individual
packet of data can take a
different route and no
dedicated pathway or circuit
is established.
Adding a Network Interface Card (NIC)
What is a NIC?
• A network interface card
(NIC) is a device that plugs
into a motherboard and
provides ports for the
network cable connections.
• It is the computer interface
with the LAN.
• The NIC communicates with
the network through serial
connections and
communicates with the
computer through parallel
connections.
Setting the IP Address
•
•
•
In a (TCP/IP)-based LAN, PCs
use an IP address to identify
each other.
These addresses allow
computers that are attached to
the network to locate each
other.
IP addresses for hosts on a
LAN can be assigned in two
ways:
1. Manually assigned by the
network administrator
2. Assigned by a Dynamic Host
Configuration Protocol (DHCP)
server
DHCP Servers
• The most common and efficient
way for computers on a large
network to obtain an IP address
is through a Dynamic Host
Configuration Protocol (DHCP)
server.
• DHCP is a software utility that
runs on a computer and is
designed to assign IP addresses
to PCs.
• When the DHCP server receives
a request from a host, it selects
IP address information from a set
of predefined addresses that are
stored in its database.
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, the interface on the
router to which the network
segment or wire of the local
computer is attached.
Domain Name System
• Most hosts are identified on the
Internet by friendly computer
names known as domain
names.
• The Domain Name System
(DNS) is used to translate
computer names such as
cisco.com to their
corresponding unique IP
address.
• The DNS server keeps records
that map computer (host)
names and their corresponding
IP address. These record types
are all combined in the DNS
table.
Physical Components of a Network
Network Topologies
• The network topology
defines the way in which
computers, printers, and
other devices are connected.
A network topology describes
the layout of the wire and
devices as well as the paths
used by data transmissions.
• Commonly referred to as a
linear bus, all the devices on
a bus topology are
connected by one single
cable.
Network Topologies
• The star topology is the most
commonly used architecture in
Ethernet LANs.
• When installed, the star topology
resembles spokes in a bicycle
wheel.
• Larger networks use the
extended star topology. When
used with network devices that
filter frames or packets, like
bridges, switches, and routers,
this topology significantly
reduces the traffic on the wires
by sending packets only to the
wires of the destination host.
Network Topologies
• A frame travels around the ring,
stopping at each node. If a node
wants to transmit data, it adds
the data as well as the
destination address to the frame.
• The frame then continues
around the ring until it finds the
destination node, which takes
the data out of the frame.
– Single ring – All the devices on the
network share a single cable
– Dual ring – The dual ring topology
allows data to be sent in both
directions although only one ring is
used at a time.
Network Topologies
• The mesh topology
connects all devices
(nodes) to each other for
redundancy and fault
tolerance.
• It is used in WANs to
interconnect LANs and for
mission critical networks
like those used by
governments.
• Implementing the mesh
topology is expensive and
difficult.
Physical versus Logical Topology
• Networks have both a
physical and logical
topology:
– Physical topology –the
layout of the devices and
media.
– Logical topology – the
paths that signals travel
from one point on the
network to another.
– The way in which data
accesses media and
transmits packets across it.
Networking Media
• Networking media can be
defined simply as the means by
which signals (data) are sent
from one computer to another
(either by cable or wireless
means).
• Coaxial cable is a copper-cored
cable surrounded by a heavy
shielding and is used to connect
computers in a network.
• There are several types of
coaxial cable, including thicknet,
thinnet, RG-59 (standard cable
for cable TV), and RG-6 (used in
video distribution).
Networking Media
• 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 provide protection
against crosstalk, the noise
generated by adjacent pairs.
• There are two basic types,
shielded twisted-pair (STP) and
unshielded twisted-pair (UTP).
Networking Media
• UTP comes in several categories that are based on
the number of wires and number of twists in those
wires.
• Category 3 is the wiring used primarily for telephone
connections.
• Category 5 and Category 5e are currently the most
common Ethernet cables used.
Networking Media
• Fiber-optic cable is a
networking medium capable
of conducting modulated
light transmissions.
• Fiber-optic refers to cabling
that has a core of strands of
glass or plastic (instead of
copper), through which light
pulses carry signals.
• Signals that represent data
are converted into beams of
light.
Networking Media
• If the cost of running cables is
too high or computers need
to be movable without being
tethered to cables, wireless is
an alternative method of
connecting a LAN.
• 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.
Common Networking Devices
• A hub is a device that is
used to extend an Ethernet
wire to allow more devices
to communicate with each
other.
• Hubs are most commonly
used in Ethernet 10BASE-T
or 100BASE-T networks,
although there are other
network architectures that
use them.
Common Networking Devices
• Bridges connect network
segments.
• The basic functionality of the
bridge resides in its ability to
make intelligent decisions about
whether to pass signals on to
the next segment of a network.
• A switch is a more sophisticated
device than a bridge, although
the basic function of the switch
is deceptively simple.
• Ethernet switches are becoming
popular connectivity solutions
because they increase network
performance.
Common Networking Devices
• Routers are slower than
bridges and switches, but
make “smart” decisions on
how to route (or send)
packets received on one
port to a network on
another port.
• Routers contain tables of
network addresses along
with optimal destination
routes to other networks.
Server Components
• Server components are
those components that are
used exclusively with the
network server. End users
depend on the server to
provide the services
required.
• To keep the server running
at it is optimal performance,
a higher level of preventive
maintenance must be
maintained.
LAN Architectures
Ethernet
• The Ethernet architecture is based on the IEEE 802.3
standard. The IEEE 802.3 standard specifies that a
network implements the Carrier Sense Multiple
Access with Collision Detection (CSMA/CD) access
control method.
• Standard transfer rates are 10 Mbps or 100 Mbps,
but new standards provide for gigabit Ethernet, which
are capable of attaining speeds up to 1 Gbps over
fiber-optic cable or other high-speed media.
Ethernet
• 10BASE-T uses a star
topology.
• The 10 stands for the
common transmission
speed of 10 MBps, the
"BASE" stands for
baseband mode, and the
"T" stands for twisted pair
cabling.
Ethernet
• 100BASE-X comes in
several different varieties.
• It can be implemented over
4-pair Category 3, 4, or 5
UTP (100BASE-T).
• It can also be implemented
over 4-pair Category 5 UTP
or Shielded Twisted Pair
(STP) (100BASE-TX), or as
Ethernet over 2-strand fiberoptic cable (100BASE-FX).
Ethernet
• 1000BASE-T is Gigabit Ethernet.
• This architecture supports data transfer rates of 1
Gbps.
Token Ring
• The Token Ring standards are
defined in IEEE 802.5.
• A Token Ring network uses a
token (that is, a special signal)
to control access to the cable.
– A token is initially generated
when the first computer on the
network comes online.
– When a computer wants to
transmit, it waits for and then
takes control of the token when
it comes its way.
– The token can travel in either
direction around the ring, but
only in one direction at a time.
Fiber Distributed Data Interface (FDDI)
• FDDI is a type of Token
Ring network.
• It runs on fiber-optic cable,
and thus combines highspeed performance with the
advantages of the tokenpassing ring topology.
• It runs at 100 Mbps, and its
topology is a dual ring.
• The outer ring is called the
primary ring and the inner
ring is called the secondary
ring.
Networking Protocols and the OSI Model
OSI Model Overview
• The Open Systems
Interconnection (OSI)
reference model is an
industry standard
framework that is used to
divide the functions of
networking into seven
distinct layers.
• Each layer provides
specific services to the
layers above and below it
in order for the network to
work effectively.
OSI Model Overview
• A message begins at the top
application layer and moves
down the OSI layers to the
bottom physical layer.
• As the message descends,
each successive OSI model
layer adds a header to it.
• A header is layer-specific
information that basically
explains what functions the
layer carried out.
• Conversely, at the receiving
end, headers are striped from
the message as it travels up the
corresponding layers.
What is a Protocol?
• Protocol is a controlled
sequence of messages that
is exchanged between two
or more systems to
accomplish a given task.
• Protocol specifications
define this sequence
together with the format or
layout of the messages that
are exchanged.
Transmission Control Protocol/Internet
Protocol
• The Transmission Control
Protocol/Internet Protocol
(TCP/IP) suite of protocols
has become the dominant
standard for internetworking.
• TCP/IP represents a set of
public standards that
specify how packets of
information are
exchanged between
computers over one or
more networks.
Transmission Control Protocol/Internet
Protocol
Internetwork Packet
Exchange/Sequenced Packet Exchange
• Internetwork Packet
Exchange/Sequenced
Packet Exchange
(IPX/SPX) is the
protocol suite employed
originally by Novell®.
• It delivers functions
similar to those included
in TCP/IP.
NetBEUI
• NetBIOS Extended User Interface (NetBEUI) is a
protocol used primarily on small Windows NT
networks.
• NetBEUI is a simple protocol that lacks many of the
features that enable protocol suites such as TCP/IP
to be used on networks of almost any size.
AppleTalk
• AppleTalk is comprised of
a e set of protocols that
span the seven layers of
the OSI reference model.
• AppleTalk protocols were
designed to run over the
major LAN types, notably
Ethernet and Token Ring,
and also Apple's own
LAN physical topology,
LocalTalk.
TCP/IP Utilities
Overview
• TCP/IP is a complex
collection of protocols.
• Most vendors implement
the suite to include a variety
of utilities for viewing
configuration information
and troubleshooting
problems.
Ping
• Ping works by sending an ICMP echo request to the
destination computer.
• The receiving computer then sends back an ICMP
echo reply message
• It is also possible to use Ping to find the IP address of
a host when the name is known.
ARP, RARP, NSLOOKUP
• Address Resolution Protocol
(ARP) is the means by which
networked computers map
Internet Protocol (IP)
addresses to physical
hardware (MAC) addresses
that are recognized in a local
network.
• Machines that do not know
their IP addresses use
Reverse Address Resolution
Protocol (RARP).
• It is used to obtain IP address
information based on the
physical or MAC address.
ARP, RARP, NSLOOKUP
• Nslookup returns the IP address for a given
hostname.
• It will also do the reverse and find the host name
for a specified IP address.
Netstat/tpcon
• The netstat command is used in Windows and
UNIX/Linux to display TCP/IP connection and protocol
information.
• The netstat command provides a list of connections
that are currently active.
• Netstat statistics can be useful in troubleshooting
TCP/IP connectivity problems.
Nbtstat
• The Microsoft TCP/IP
stacks included in
Windows operating
systems provide the
nbtstat utility, which is
used to display NetBIOS
information.
Ipconfig, winipcfg, config, and ifconfig
• TCP/IP configuration
information can be
displayed using different
utilities
• Ipconfig – Windows NT
and Windows 2000
(command-line)
• Winipcfg –- Windows 95,
98, and ME (graphical
interface)
• Ifconfig – UNIX and Linux
(command-line
Tracert, iptrace, and traceroute
• It is often useful to trace the
route a packet takes on its
journey from source
computer to destination
host.
• TCP/IP stacks include a
route tracing utility that
enables users to identify the
routers through which the
message passes.
• The options depend on the
operating system:
– Tracert
– Iptrace
– Traceroute
Connecting to the Internet
Synchronous and Asynchronous Serial
lines
• Synchronous serial
transmission – Data bits are
sent together with a
synchronizing clock pulse. Builtin timing mechanism
coordinates the clocks of the
sending and receiving devices.
• Asynchronous serial
transmission – Data bits are
sent without a synchronizing
clock pulse. 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.
• There are four main types
of modems:
–
–
–
–
Expansion cards
PCMCIA
External modems
Built-in modems
Dial-Up Networking,
Modem Standards, AT Commands
• When computers use the
public telephone system or
network to communicate, it is
called Dial-Up Networking
(DUN).
• All modems require software to
control the communication
session.
• The set of commands that
most modem software uses
are known as the Hayescompatible command set. The
Hayes command set is based
on a group of instructions that
always begins with a set of
attention characters (AT).
ISPs and Internet Backbone Providers
• Services of an Internet Service Provider (ISP) are
required to surf the Internet.
• An ISP is a company that connects computers to
the Internet and World Wide Web.
• The actual connection to the Internet is tiered.
• The ISP may link to a larger regional ISP, which in
turn might connect to one of a number of
nationwide computer centers.
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 High-Speed Backbone
Network Service (vBNS).
• The vBNS connects five
supercomputer networks across
the country:
– UUNET - a division of
WorldCom
– Cable & Wireless USA
– Sprint
– AT&T
– BBN Planet
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 that links to the
national backbone through a
Network Access Point (NAP).
• Not all the Internet traffic
goes through NAPs.
• Some ISPs that are in the
same geographic area make
their own interconnections
and peering agreements.
Digital Subscriber Line (DSL)
• Digital Subscriber Line (DSL) is an always-on
technology. This means there is no need to dial up
each time to connect to the Internet.
• DSL comes in several varieties:
–
–
–
–
Asymmetric DSL (ADSL)
High Data Rate DSL (HDSL)
Symmetric DSL (SDSL)
Very High Data Rate DSL (VDSL)
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.
Cable Modem versus
DSL Internet Technologies
• When it comes to
comparing cable modem
and DSL Internet
technologies, both have
their pros and cons.
ISDN
• Another alternative to using
analog telephones lines to
establish a connection is ISDN.
• Speed is one advantage ISDN
has over telephone line
connections.
• ISDN uses a pair of 64Kbps
digital lines to connect, which
provides a total of 128Kbps
throughput.
• A telephone line connects at a
maximum speed of 56Kbps, and
in some areas, doesn’t even
reach that.
Satellite
• Satellite is an option for users in
rural areas or with no other
access to high speed Internet
service.
• Satellite Internet does not require
a phone line or cable. Two-way
communication, for upload and
download, is achieved with the
use of a satellite dish.
• Download speed is up to 500
kbps while the upload speed is
one-tenth of that of that.