Guide to Operating Systems, 4 ed.

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Guide to Operating Systems,



Chapter 9: Network Connectivity

Guide to Operating Systems, 4th ed.




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

Guide to Operating Systems, 4th ed.


Networking Basics


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

Combined wireless and cabled network

Guide to Operating Systems, 4th ed.


Networking Basics

Networks have hardware and software elements

Hardware components:



Communications cable

Networking devices

Software components

Client and server operating systems

Device drivers

Networking protocols

Guide to Operating Systems, 4th ed.


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


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

Guide to Operating Systems, 4th ed.


Client and Server Operating Systems


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

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

Guide to Operating Systems, 4th ed.


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

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

Guide to Operating Systems, 4th ed.


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

Guide to Operating Systems, 4th ed.


Network Topologies


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

Guide to Operating Systems, 4th ed.


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

Guide to Operating Systems, 4th ed.


Network Topologies

Star Topology

Guide to Operating Systems, 4th ed.


Network Topologies

bus hybrid topology

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

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

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

Guide to Operating Systems, 4th ed.


MAC layout

Guide to Operating Systems, 4th ed.


Guide to Operating Systems, 4th ed.


Networking Hardware

Devices on a network with unique physical (MAC)

Guide to Operating Systems, 4th ed.


Networking Hardware

Cables and Wireless Media

communication medium
is anything through which data is transmitted

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

Guide to Operating Systems, 4th ed.


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

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

connecting links between networks)

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

Guide to Operating Systems, 4th ed.


Networking Hardware

Network Devices

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


once were popular network devices (being replaced by

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


“intelligent” hub

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

Wireless access point

connects wireless devices to a wired

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

(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

Guide to Operating Systems, 4th ed.


Guide to Operating Systems, 4th ed.


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


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


contains information about the specific sending or
receiving device

Basic packet format

Packets, Frames, and Cells


data unit designed for high

Has a control header and a fixed
length 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

Guide to Operating Systems, 4th ed.


Guide to Operating Systems, 4th ed.


Networking Protocols


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

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

Guide to Operating Systems, 4th ed.


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


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

Guide to Operating Systems, 4th ed.


Transport Protocols

Ethernet (cont.)


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

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

Guide to Operating Systems, 4th ed.


Transport Protocols


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

Guide to Operating Systems, 4th ed.


Transport Protocols

A transport protocol is interfaced with an OS

Network driver specification built into the OS


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)

Guide to Operating Systems, 4th ed.


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

Ensures that data transmissions are accurate

Encapsulates, transmits, and receives the payload data

Closes the communication session between two computers

Guide to Operating Systems, 4th ed.


Guide to Operating Systems, 4th ed.


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
binary numbers separated by periods (known as
IP address

Guide to Operating Systems, 4th ed.


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

Class B

assigned to medium networks

can have up to
65,536 nodes

Class B network address example

Class C

assigned to small networks

can have up to 256

Class C network address example

Class D

used for multicasts (sent to multiple nodes)

Class E

used for experimentation

Broadcast address:

sent to all nodes on a

Communications Protocols

IP address classes

Guide to Operating Systems, 4th ed.


Communications Protocols

Classless interdomain routing (CIDR)

newer way
of addressing that ignores address class

CIDR provides more IP address options for medium

Example :

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

Guide to Operating Systems, 4th ed.


Communications Protocols

Using TCP/IP subnet masks

Guide to Operating Systems, 4th ed.


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


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

Guide to Operating Systems, 4th ed.


Communications Protocols

Guide to Operating Systems, 4th ed.


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


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

Guide to Operating Systems, 4th ed.


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)

Guide to Operating Systems, 4th ed.


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

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

Guide to Operating Systems, 4th ed.


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


Guide to Operating Systems, 4th ed.


Communications Protocols

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

Guide to Operating Systems, 4th ed.


Communications Protocols

Guide to Operating Systems, 4th ed.


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

Guide to Operating Systems, 4th ed.


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
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

Guide to Operating Systems, 4th ed.


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

Guide to Operating Systems, 4th ed.


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

Guide to Operating Systems, 4th ed.