9781111306366_ppt_ch9

Guide to Operating Systems,

4th 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


Networking Basics

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

Combined wireless and cabled network


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


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



• 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



• 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


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


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


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


Network Topologies

Star Topology


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



Networking Hardware

Devices on a network with unique physical (MAC)

addresses


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


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


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



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



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


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)


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


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


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)


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




• 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)



• 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


IP address classes



• 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



Using TCP/IP subnet masksGuide to Operating Systems, 4th ed. 32


• 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



• 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



• 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)



• 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



• Some computers and devices must have an IP address

that is manually assigned and never changes (servers,

switches, routers, etcG)– 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



• In Mac OS X Leopard and Snow Leopard, configurations

are made using the Network option from the System

Preferences windows




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


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


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


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


9781111306366_ppt_ch9

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