9781111306366_ppt_ch9
TRANSCRIPT
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
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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
Guide to Operating Systems, 4th ed. 6
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
Guide to Operating Systems, 4th ed. 9
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
Guide to Operating Systems, 4th ed. 11
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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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
Guide to Operating Systems, 4th ed. 16
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
Guide to Operating Systems, 4th ed. 17
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
Guide to Operating Systems, 4th ed. 22
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)
Guide to Operating Systems, 4th ed. 23
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
Guide to Operating Systems, 4th ed. 24
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)
Guide to Operating Systems, 4th ed. 26
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)
Guide to Operating Systems, 4th ed. 29
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 masksGuide to Operating Systems, 4th ed. 32
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
Guide to Operating Systems, 4th ed. 37
Communications Protocols
• 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
Guide to Operating Systems, 4th ed. 38
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
Guide to Operating Systems, 4th ed. 41
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
Guide to Operating Systems, 4th ed. 42
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. 43
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. 44