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 masks



• 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, 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



• 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

Education

Transcript of 9781111306366 ppt ch9