Guide to Operating Systems, 4 ed.

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Guide to Operating Systems,

4
th

ed.

Chapter 9: Network Connectivity

Guide to Operating Systems, 4th ed.

2

Objectives

2


Explain networking basics, such as network
topologies, networking hardware, packaging data
to transport, and how devices connect to a network


Describe network transport and communications
protocols, and determine which protocols are used
in specific computer operating systems


Explain how to integrate different operating
systems on the same network

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Networking Basics


Network



a system of computing and
communication devices that are linked together with
cables or wirelessly








Combined wireless and cabled network


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Networking Basics


Networks have hardware and software elements


Hardware components:


Computers


Printers


Communications cable


Networking devices


Software components


Client and server operating systems


Device drivers


Networking protocols

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Client and Server Operating Systems


Client OS


enables a workstation to run
applications, process information locally, and
communicate with other computers and devices
over a network


Workstation


computer that has a CPU and can run
applications locally or obtain applications and files from another
computer on a network


Server OS


coordinates network activities,
authenticates clients to access the network, and
enables client workstations to access shared
network resources such as printers, files, or
software

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Client and Server Operating Systems


Security


important function of a server OS


Can be used to test the credentials of clients before clients are
allowed to access network resources


Basic way to do this: logins and passwords


Certificate services


digital certificates to verify that a user or
entity is trustworthy


Statement of Health (SoH)


certifies that the client is secure
and is current on OS updates (available in Windows Server
2008/R2)


Remote Installation Services (RIS)


used to install client
OSs on a mass scale (Windows Server 2003/R2)


Windows Deployment Services (WDS)


updated version of
RIS that became available in Windows Server 2008/R2


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Client and Server Operating Systems


Publishing an application


Windows Server
2003/R2 and Server 2008/R2 enables Windows
XP/Vista/7 clients to install custom configured
application software


Assigning applications


Windows Server feature
that enables a client to automatically start a
particular version of software through a desktop
shortcut


If user accidentally deletes the shortcut, it is automatically
reinstalled the next time the user logs in

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Local and Wide Area Networks


Networks are often classified by their reach (scope)


Local area network (LAN)



service area is
relatively small, such as a network in an office area
contained on one floor or in one building


Wide area network (WAN)


offers networking
services over a long distance, such as between
cities, states or countries


Often connect LANs over a long distance


Example of a simple WAN


using a cable or DSL modem to
connect to your ISP, which connects you to other networks
worldwide



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Network Topologies


Topology


the physical design of the network
(physical topology) or the path data takes when it
goes from one computer to another (logical topology)


Bus topology


designed as a straight line (central cable) to
which all computers and devices attach with two end points that
must be terminated to keep the signal from reflecting back
along the path




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Network Topologies


Ring topology


the data
-
carrying signal does from
station to station around a logical ring like a circle of
computers connected to one another


No longer used much in LANs


found in some WANs


Star topology


computers or devices (nodes)
connect to a central device such as a switch or
wireless access point


In a cabled network, the switch sends the signal onto the
segment that has the destination computer


Most popular network topology because it has the most
flexibility

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Network Topologies










Star Topology


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Network Topologies


Star
-
bus hybrid topology


combine the logical
communications of a bus with the physical layout of a
star


Each segment radiating from the star (central connecting
device) is like a separate logical bus segment


Networking Hardware


Network interface card (NIC)



an interface card
or an interface that is built into a device that allows
the device to connect to a network


Media Access Control (MAC) address
-

a unique
hexadecimal address, assigned by the manufacturer


Every NIC has one


Another name for this address is physical address


Used much like a postal address because it enables
communications to be sent and received based on the address


Address is stored in
firmware



chip on the NIC that contains
drivers and other software necessary for the NIC to communicate
with OS




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MAC layout


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Guide to Operating Systems, 4th ed.

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Networking Hardware










Devices on a network with unique physical (MAC)
addresses

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Networking Hardware


Cables and Wireless Media


communication medium
is anything through which data is transmitted


Twisted
-
pair cable


consists of one or more pairs
of twisted copper wires bundled together within a
plastic outer coating


Wires are twisted to reduce electromagnetic interference (EMI)
or noise


Two configurations: Unshielded Twisted Pair (UTP) and
Shielded Twisted Pair (STP)


STP is faster and more reliable than UTP but it is more
expensive and less flexible


UTP is the most often used on LANs today


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Networking Hardware


Coaxial cable (coax)


copper wire surrounded by
several layers for insulation


Not often used in LANs today


Mostly used for home Internet connections


Cable television (CATV) uses coax cable


Most connections are made using hybrid fiber/coax (HFC) cable


Fiber
-
optic cable


consists of thin strands of glass
that transmit signals using light


Can transmit faster than copper and is not prone to EMI


Used by businesses on high
-
traffic network
backbones

(main
connecting links between networks)


Wireless transmissions are carried by radio
frequencies or light (infrared) through the air

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Networking Hardware


Network Devices


used to connect computers and
network
-
attached devices like printers to each
other and to connect networks together


Hubs


once were popular network devices (being replaced by
switches)


Communications that go through hubs are broadcast to all
segments attached to the hub


Switch


“intelligent” hub


Only transmits information to the segment where the destination
device is located


Wireless access point


connects wireless devices to a wired
network


Networking Hardware


Network Devices (cont.)


Bridge (being replaced by switches)
-

used to extend segments
or link segments that use different cable types


Router used to connect networks


Can be programmed to act as a
firewall

(hardware or software
that secures data from being accessed outside a network and can
prevent data from leaving the network)


Router keep tables of network addresses along with the best
“routes” to other network addresses

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Packets, Frames, and Cells


Each network device translates data into individual
units and then places the units onto network media
for transmission


Each data unit is called a packet or frame


Packet


contains routing information that allows the packet to
be forwarded to specific networks


Frame


contains information about the specific sending or
receiving device





Basic packet format

Packets, Frames, and Cells


Cell


data unit designed for high
-
speed
communications


Has a control header and a fixed
-
length payload


Payload


portion of a frame, packet, or cell that contains the
actual data


One element of the cell header is path information that enables
the cell to take the route through the network that is most
appropriate for the type of data



Exact format of a frame, packet, or cell is
determined by the type of protocol used on a
network

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Networking Protocols


Protocol


set of formatting guidelines for network
communications (like a language), so that data
sent by one computer can be read by another


Protocols are used for:


Communicating transport of packets and frames among network
devices


Encapsulating data and communication control information


Providing communications to accomplish a specific function


Such as, flow control


Enabling communications over a long
-
distance network


Enabling remote users to dial into networks


Transporting test, network status, and other network management
information

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Transport Protocols


Standards for network communication were
established by the Institute of Electrical and
Electronics Engineers (IEEE) through its 802
standards committee


802 standards are followed by network administrators and
manufacturers to ensure all network devices will be able to
communicate with each other


Ethernet


only one station on a network segment
can transmit at a time


If two or more devices transmit at the same time, frames collide


Uses carrier sense multiple access with collision detection
(CSMA/CD)

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Transport Protocols


Ethernet (cont.)


In CSMA/CD


NIC listens to see if another device is
transmitting, if it does not hear a transmission then it will
transmit


If two devices on the same segment try to transmit at the same
time, a collision occurs and both transmission are dead


A “jam” signal is sent to warn all other stations


Each device waits a different amount of time before attempting to
transmit again


Typical speeds supported today are 100 Mbps (Fast Ethernet)
and 1 Gbps (Gigabit Ethernet)


10 and 100 Gbps Ethernet are mostly used on Ethernet
backbones

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Transport Protocols


Wireless


uses carrier sense multiple access with
collision avoidance (CSMA/CA)


A variation of CSMA/CD


Four main IEEE wireless specifications today:









Summary of 802.11 wireless communications technologies

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Transport Protocols


A transport protocol is interfaced with an OS
through:


Network driver specification built into the OS


A NIC


A NIC driver


Microsoft and 3COM designed the Network Device
Interface Specification (NDIS) drivers


UNIX and Linux are compatible with NDIS driver through open
source software, such as NDISwrapper


Mac OS X is compatible with NDISwrapper when using a
nonproprietary NIC (Intel)


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Transport Protocols


When purchasing a NIC:


The NIC cable interface must match the type of cable used on
the network


Choose a wireless NIC if no cable is needed


Make sure the current driver is installed to support
the NIC


After NIC setup is complete, the OS, NIC, and
driver handle the work of converting data to an
Ethernet or wireless format for transport over a
network (same three elements enable receiving
and interpreting data as well)

Communications Protocols


Communications protocols


carry data between
two communicating devices


Today, all OSs discussed in this book use TCP/IP family of
protocols (protocols developed for the Internet)


Developed in early 1980’s for use on the US Dept. of Defense
Advanced Research Projects Agency Network (ARPANET)


Transmission Control Protocol (TCP)


Establishes the communication session between two
computers


Ensures that data transmissions are accurate


Encapsulates, transmits, and receives the payload data


Closes the communication session between two computers



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Communications Protocols


Internet Protocol (IP)


Handles packet addressing


Handles packet routing


Fragments packet, as needed, for transport across different
types of networks


Provides simple packet error detection in conjunction with the
more thorough error detection provided by TCP


TCP/IP comes in two version IPv4 and IPv6


IPv4 is most commonly used today but has a limitation of
address allocation (world is nearly out of new IP addresses)


IPv4 uses a dotted decimal notation that consists of four 8
-
bit
binary numbers separated by periods (known as
IP address
)

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Communications Protocols


5 classes of IPv4 IP addresses


Class A


assigned to large networks


can have up to
16,777,216 nodes


Class A network address example


122.0.0.0


Class B


assigned to medium networks


can have up to
65,536 nodes


Class B network address example


132.155.0.0


Class C


assigned to small networks


can have up to 256
nodes


Class C network address example


220.127.110.0


Class D


used for multicasts (sent to multiple nodes)


Class E


used for experimentation


Broadcast address: 255.255.255.255


sent to all nodes on a
network

Communications Protocols










IP address classes

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Communications Protocols


Classless interdomain routing (CIDR)


newer way
of addressing that ignores address class
designation


CIDR provides more IP address options for medium
-
sized
networks


Example : 165.100.0.0/14


Subnet mask


used to identify networks or
subnetworks (subnet) within a larger network setup


On large networks, subnets allow an administrator to create
smaller networks to limit network traffic and congestion on
network segments

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Communications Protocols










Using TCP/IP subnet masks

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Communications Protocols


Computers and network devices that use TCP/IP
protocol have two addresses


MAC address


address burned into the NIC


IP address


assigned by network administrator


IPv6


new TCP/IP version uses 128 bit addresses
(to solve the shortage of IPv4 addresses)


Provides more specialized networking implementations, such
as voice, video, and multimedia applications


All new OSs support IPv6

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Communications Protocols

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Communications Protocols


Three steps involved in setting up a
communications protocol in an OS


Installing the protocol in the OS


Binding the protocol to the NIC


Configuring protocol communications parameters


Installing and Binding a Protocol


Combined into one procedure


Usually automatic when you install the OS


Binding


enables the NIC to format data for that protocol and
identify the most efficient methods for transporting it

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Communications Protocols


Configuring a Protocol


parameters to configure
include some or all of the following:


Configuring an IPv4 address


Configuring an IPv6 address


Specifying the subnet mask (also called the netmask)


Designating a default gateway (the device that links the
network to other networks, such as the Internet)


Specifying a preferred DNS server (provides lookup of IP
addresses and computer/device names)


Specifying an alternate DNS server (used when preferred
server is busy or cannot be reached)

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Communications Protocols


Dynamic Host Configuration Protocol (DHCP)


used to automatically assign IP address
information to computers


Two advantages:


Not necessary to assign addresses manually


Ensures that no two computers are assigned the same IP address


Automatic Private IP Addressing (APIPA)


Available in Windows XP/Vista/7, Server 2003/R2, Server
2008/R2


If automatic addressing is selecting but there is no DHCP
server on the network, the OS assigns the IPv4 address from a
reserved range of 169.254.0.1


169.254.255.254

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Communications Protocols


Some computers and devices must have an IP
address that is manually assigned and never
changes (servers, switches, routers, etc…)


Called a static IP address


Important for devices that will be well known and used by other
devices for services


Most UNIX/Linux OSs have TCP/IP networking
support built in


Some automatically run a network configuration program when
you first boot the computer


If not, it can be configured later by using the
ifconfig

command

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Communications Protocols


In Mac OS X Leopard and Snow Leopard,
configurations are made using the Network option
from the System Preferences windows







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Communications Protocols

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Configuring a wireless network connection
in Mac OS X Snow Leopard

Integrating Different Operating
Systems on the Same Network


Key to implementing multiple OSs on one network:


Select a transport and communications protocol that are
supported in all of the OSs


Ethernet and TCP/IP are supported by most
operating systems

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Chapter Summary


A network is a system of resources and productivity tools
that communicate with each other enabling us to share
information over short and long distances


Networks are roughly categorized as LANs or WANs,
depending on their areas of service (LANs typically cover a
building or floor of a building and WANs are long
-
distance
networks that join LANs and individual users)


Networks are designed in standardized topologies (bus, star,
ring, star
-
bus hybrid) and use standardized communications
means, such as frames, packets, and protocols


Protocols are important to network because they act as a
common language for communication between devices and
provide reliability, delivery of data and monitor networks for
problems

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Chapter Summary


Modern computer operating systems use TCP/IP, which is
the communications protocol preference for networks and
the Internet


IPv4 is in greatest use today, but networks will eventually
convert to IPv6 because it offers a greater range of
addresses, better security, and other network improvements


Networking devices such as hubs, bridges, switches, and
routers enable network connectivity (hubs and bridges are
becoming obsolete) Each device is used to achieve different
connectivity goals based on its capabilities


Cabled Ethernet and wireless networks are used separately
and also combine to enable flexible networking

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Chapter Summary


Windows operating systems, UNIX, Linux, and Mac OS X all
offer tools for configuring TCP/IP communications, including
IP address, subnet mask, gateway, and DNS parameters


Current Windows operating systems, UNIX, Linux, and Mac
OS X Leopard and Snow Leopard can be integrated on the
same network, in part because they all support TCP/IP as
their default communications protocol and are compatible
with Ethernet

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