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Guide to Operating Systems, th 5 Edition Chapter 9 Configuring a Network Connection Objectives After completing this chapter, you will be able to: • Explain the fundamentals of network communication • Define common networking terms • Compare and describe network device types • Configure and describe network protocols • Describe the OSI model of networking • Configure networking in an operating system Guide to Operating Systems, 5th Edition © Cengage Learning 2017 2 The Fundamentals of Network Communication • A computer network consists of two or more computers connected by some kind of transmission medium – Such as a cable or air waves • In order to access the Internet, a computer has to be able to connect to a network • The next few slides will cover what is required to turn a standalone computer into a networked computer Guide to Operating Systems, 5th Edition © Cengage Learning 2017 3 Network Components • Hardware components needed – Network interface card (NIC)—an add-on card plugged into an expansion slot that provides a connection between the computer and the network – Network medium—A cable that plugs into the NIC and makes the connection between a computer and the rest of the network • Network media can also be the air waves, as in wireless networks – Interconnecting device—allows two or more computers to communicate on the network without having to be connected directly to one another Guide to Operating Systems, 5th Edition © Cengage Learning 2017 4 Network Components Figure 9-1 A network of computers connected to a switch Guide to Operating Systems, 5th Edition © Cengage Learning 2017 5 Network Computers • Software Components – Network clients and servers • Network client software requests information stored on another network computer or device • Network server software allows a computer to share its resources – Protocols—define the rules and formats a computer must use when sending information across the network – NIC device driver—receives data from protocols and forwards this data to the physical NIC Guide to Operating Systems, 5th Edition © Cengage Learning 2017 6 Steps of Network Communication • 1. Application tries to access a network resource by sending a message • 2. Client software formats the message and passes the message on to the network protocol • 3. Protocol packages the message in a format suitable for the network and sends it to the NIC driver • 4. NIC driver sends data in the request to the NIC card to be converted into necessary signals to be transmitted on the network Guide to Operating Systems, 5th Edition © Cengage Learning 2017 7 Layers of the Network Communication Process • Each step required for a client to access network resources is referred to as a “layer” • Each layer has a task and all layers work together Figure 9-2 Layers of the network communication process Guide to Operating Systems, 5th Edition © Cengage Learning 2017 8 Layers of the Network Communication Process Table 9-1 Layers of the network communication process Guide to Operating Systems, 5th Edition © Cengage Learning 2017 9 How Two Computers Communicate on a LAN • TCP/IP is the most common protocol (language) used on networks • TCP/IP uses 2 addresses to identify devices – Logical address (IP address) – Physical address (MAC address) • Just as a mail person needs an address to deliver mail, TCP/IP needs an address in order to deliver data to the correct device on a network • Think of the Logical address as a zip code and the Physical address as a street address Guide to Operating Systems, 5th Edition © Cengage Learning 2017 10 How Two Computers Communicate on a LAN 1. 2. 3. 4. 5. A user at Comp A types ping 10.1.1.2 at a command prompt Network software creates a ping message The network protocol packages the message by adding IP address of sending and destination computers and acquires the destination computer’s MAC address The network interface software adds MAC addresses of sending and destination computers Comp B receives message, verifies that the addresses are correct and then sends a reply to Comp A using Steps 2 – 4 Guide to Operating Systems, 5th Edition Figure 1-7 Communication Figuretwo 9-3computers Communication between between two computers © Cengage Learning 2017 11 How Two Computers Communicate on a LAN Table 9-2 Saving a file with the network communication process Guide to Operating Systems, 5th Edition © Cengage Learning 2017 12 Network Terminology • Every profession has its own language and acronyms • It is essential to know the language of networks to be able to study them Guide to Operating Systems, 5th Edition © Cengage Learning 2017 13 LANs, Internetworks, WANs, and MANs • Local area network (LAN) – small network, limited to a single collection of machines and connected by one or more interconnecting devices in a small geographic area Figure 9-4 A LAN with computers interconnected by a switch Guide to Operating Systems, 5th Edition © Cengage Learning 2017 14 LANs, Internetworks, WANs, and MANs Figure 9-5 A wireless LAN Guide to Operating Systems, 5th Edition © Cengage Learning 2017 15 LANs, Internetworks, WANs, and MANs • An internetwork is a networked collection of LANs tied together by devices such as routers • Reasons for creation: – Two or more groups of users and their computers need to be logically separated but still need to communicate – Number of computers in a single LAN has grown and is no longer efficient – The distance between two groups of computers exceeds the capabilities of most LAN devices Guide to Operating Systems, 5th Edition © Cengage Learning 2017 16 LANs, Internetworks, WANs, and MANs Figure 9-8 An internetwork with two LANs connected by a router Guide to Operating Systems, 5th Edition © Cengage Learning 2017 17 LANs, Internetworks, WANs, and MANs • Wide area networks (WANs) use the services of third-party communication providers to carry network traffic from one location to another • Metropolitan area networks (MANs) use WAN technologies to interconnect LANs in a specific geographic region, such as a county of city Guide to Operating Systems, 5th Edition © Cengage Learning 2017 18 Internet, Intranet, and Extranet • Internet: a worldwide public internetwork – Uses protocols such as TCP/IP and HTTP to transfer and view information • Intranet: a private internetwork in which devices and servers are only available to those users connected to the internal network • Extranet: allows limited and controlled access to internal resources by outside users Guide to Operating Systems, 5th Edition © Cengage Learning 2017 19 Packets and Frames • Computers transfer information across networks in shorts bursts of about 1500 bytes of data • Reasons data is transferred this way: – If an error occurs during transmission of a large file, only the chunks of data involved in the error have to be sent again – Pause between bursts allows other computers to transfer data during pauses – Allows the receiving computer to process received data – Allows the receiving computer receive data from other computers at the same time – Gives the sending computer an opportunity to receive data from other computers and perform other processing tasks Guide to Operating Systems, 5th Edition © Cengage Learning 2017 20 Packets and Frames • Chunks of data sent across the network are usually called packets or frames, with packets being the more well-known term • Packet: a chunk of data with a source and destination IP address added to it • Using the U.S. mail analogy, you can look at a packet as an envelope that has had the zip code added to the address but not the street address Guide to Operating Systems, 5th Edition © Cengage Learning 2017 21 Packets and Frames • Frame: a packet with the source and destination MAC addresses added to it – The packet is “framed” by the MAC addresses on one end and an error-checking code on the other • The process of adding IP addresses and MAC addresses to chunks of data is called encapsulation • Information added to the front of the data is called a header and information added to the end is called a trailer Guide to Operating Systems, 5th Edition © Cengage Learning 2017 22 Clients and Servers • A client can be a workstation running a client OS – Or it can refer to the network software on a computer that requests network resources from a server • The word “client” is usually used in these three contexts: – Client operating system – the OS installed on a computer – Client computer – primary role is to run user applications and access network resources – Client software – software that requests network resources from server software on another computer Guide to Operating Systems, 5th Edition © Cengage Learning 2017 23 Clients and Servers • A computer becomes a server when software is installed on it that provides a network service to client computers • The term “server” is also used in three contexts: – Server operating system – OS installed on a computer designed to share network resources and provide other network services – Server computer – a computer’s primary role in the network is to give client computers access to network resources and services – Server software – responds to requests for network resources from client software Guide to Operating Systems, 5th Edition © Cengage Learning 2017 24 Peer-to-Peer and Client/Server Networks • A network model defines how and where resources are shared and how access to these resources is regulated • Fall into two major types – Peer-to-peer network – most computers function as clients or servers (no centralized control over who has access to network resources) – Server-based network – certain computers take on specialized roles and function mainly as servers, and ordinary users’ machines tend to function mainly as clients Guide to Operating Systems, 5th Edition © Cengage Learning 2017 25 Peer-to-Peer and Client/Server Networks • Computers on a peer-to-peer network can take both a client and a server role • Any user can share resources on his/her computer with any other user’s computer • Every user must act as the administrator of his/her computer – Can give everyone else unlimited access to their resources or grant restricted access to other users – Usernames and passwords (credentials) are used to control that access Guide to Operating Systems, 5th Edition © Cengage Learning 2017 26 Peer-to-Peer and Client/Server Networks • Server-based allow centralized control over network resources • Users log on to the network with a single set of credentials maintained by one or more servers running a server OS • In most cases, servers are dedicated to running network services and should not be used to run user applications Guide to Operating Systems, 5th Edition © Cengage Learning 2017 27 Peer-to-Peer and Client/Server Networks • A domain is a collection of users and computers whose accounts are managed by Windows servers called domain controllers • Users and computers in a domain are subject to network access and security policies defined by a network administrator – The software that manages this security is referred to as a directory service. – On Windows servers, the directory service software is Active Directory Guide to Operating Systems, 5th Edition © Cengage Learning 2017 28 Peer-to-Peer and Client/Server Networks • Other network services found on network servers: – Naming services – translate computer names to their address – E-mail services – manage incoming and outgoing email – Application services – grant client computers access to complex applications that run on the server – Communication services – give remote users access to a network – Web services – provide comprehensive Web-based application services Guide to Operating Systems, 5th Edition © Cengage Learning 2017 29 Peer-to-Peer and Client/Server Networks Table 9-3 Peer-to-peer versus server-based networks Guide to Operating Systems, 5th Edition © Cengage Learning 2017 30 Network Device Fundamentals • LANs, WANs, MANs, and internetworks are built with a variety of network hardware • This section covers a wide variety of network devices Guide to Operating Systems, 5th Edition © Cengage Learning 2017 31 Network Hubs • A multiport repeater is just a repeater with several ports to which you can connect cabling – Also referred to as a hub • Receives bit signals generated from a connected computer on one of its ports • Cleans the signal by filtering out electrical noise • Regenerates the signal to full strength • Transmits the regenerated signal to all other ports a computer (or other network device) is connected to Guide to Operating Systems, 5th Edition © Cengage Learning 2017 32 Network Switches • Looks just like a hub – But a switch actually reads data in the message, determines which port the destination device is connected to, and forward the message to only that port • Basic Switch Operation – Data is sent onto the medium one frame at a time – Each frame has the destination MAC address – Switch reads the addresses: • Keeps a record of which computer is on which port (switching table) • Forwards the frame to the port where the destination MAC can be found Guide to Operating Systems, 5th Edition © Cengage Learning 2017 33 Network Switches Figure 9-14 Switches maintain a switching table Guide to Operating Systems, 5th Edition © Cengage Learning 2017 34 Wireless Access Points • The heart of a wireless network is the wireless access point (AP) • APs operate similarly to a hub without wires • All communication passes through the AP • Most small business and home networks use a device typically called a wireless router that combines the functions of an AP, a switch, and a router • Wireless LANs are usually attached to wired networks Guide to Operating Systems, 5th Edition © Cengage Learning 2017 35 Network Interface Cards • Attaching a computer to a network requires a network interface card (NIC) to create and mediate the connection between a computer and the networking medium – Networking medium might be copper wire, fiber-optic cable, or airwaves Guide to Operating Systems, 5th Edition © Cengage Learning 2017 36 Network Interface Cards • The tasks a NIC and its driver perform: – Provide a connection from computer to medium – Incoming messages: Receives bit signals and assembles them into frames • Verifies the destination address • Removes frame header and sends the resulting packet to the network protocol – Outgoing messages: receive packets from network protocol • Creates frames by adding MAC addresses/error check – Converts frame into bit signals suitable for the medium and transmits them Guide to Operating Systems, 5th Edition © Cengage Learning 2017 37 Network Interface Cards Figure 9-15 The NIC handles incoming data from the network medium Guide to Operating Systems, 5th Edition © Cengage Learning 2017 38 Network Interface Cards Figure 9-16 The NIC handles outgoing data to be sent to the network medium Guide to Operating Systems, 5th Edition © Cengage Learning 2017 39 Routers • Most complex device • Connect LANs together to create an internetwork Figure 9-17 Two LANs connected by a router to make an internetwork Guide to Operating Systems, 5th Edition © Cengage Learning 2017 40 Routers • Routers are devices that enable multiple LANs to communicate with one another by forwarding packets from one LAN to another Figure 9-18 Routers interconnect LANs to form the Internet Guide to Operating Systems, 5th Edition © Cengage Learning 2017 41 Routers • The following are the differences between routers and switches – Routers connect LANs, switches connect computers – Routers work with logical (IP) addresses, switches work with physical (MAC) addresses – Routers work with packets, switches with frames – Routers don’t forward broadcasts, switches do – Routers use routing tables, switches use switching tables Guide to Operating Systems, 5th Edition © Cengage Learning 2017 42 Network Media • Unshielded Twisted Pair (UTP) – the most common media type in LANs – Consists of four pairs of copper wires twisted together and contained in a plastic sheath or jacket – Comes in numbered categories (up to Category 8) • Higher the category, the higher the bandwidth potential – Used in physical star networks – Maximum cable length from NIC to switch is 100 meters Guide to Operating Systems, 5th Edition © Cengage Learning 2017 43 Network Media Figure 9-19 UTP cabling Guide to Operating Systems, 5th Edition © Cengage Learning 2017 44 Network Media • Fiber-Optic Cabling – Uses thin strands of glass to carry pulses of light long distances at high data rates Figure 9-20 Fiber-optic cabling Guide to Operating Systems, 5th Edition © Cengage Learning 2017 45 Network Media • Coaxial Cable – Best known for its use in cable TV – Obsolete as a LAN medium – Used as the network medium for Internet access via cable modem Guide to Operating Systems, 5th Edition © Cengage Learning 2017 46 Network Protocol Fundamentals • Protocols are rules and procedures for communication and behavior – Computers must “speak” the same language and agree on the rules of communication • When a set of protocols works cooperatively it is called a protocol suite (or “protocol stack”) • The most common protocol stack is Transmission Control Protocol/Internet Protocol (TCP/IP) • TCP/IP is composed of more than a dozen protocols operating at different levels of the communication process Guide to Operating Systems, 5th Edition © Cengage Learning 2017 47 Network Protocol Fundamentals Figure 9-21 The TCP/IP layered architecture Guide to Operating Systems, 5th Edition © Cengage Learning 2017 48 Network Protocol Fundamentals The Internetwork layer is where administrators usually do the most network configuration Where the IP protocol operates and is the heart of the TCP/IP protocol suite Responsible for four main tasks: Defines and verifies IP addresses Routes packets through an internetwork Resolves MAC addresses from IP addresses Delivers packets efficiently Guide to Operating Systems, 5th Edition © Cengage Learning 2017 49 Internet Protocol Version 4 • Internet Protocol version 4 (IPv4) or just IP – An internetwork layer protocol that provides source and destination addressing and routing for the TCP/IP protocol suite • IP addresses are 32-bit numbers divided into four 8-bit values called octets, each octet can have a value from 0 to 255 – Four decimal numbers are separated by periods in a format called dotted decimal notation – Example: 172.31.149.10 Guide to Operating Systems, 5th Edition © Cengage Learning 2017 50 Internet Protocol Version 4 • Subnet masks are also 32-bit numbers, that serve to determine how many bits are allocated to a network ID, and how many are allocated to a host ID • When written in binary, 1’s in the subnet mask that correspond to bits in the IP address mean the matching bit locations are part of the network ID Guide to Operating Systems, 5th Edition © Cengage Learning 2017 51 Internet Protocol Version 4 • Example: – 192.168.14.250 = 11000000.10101000.0001110.11111010 255.255.255.0 = 11111111.11111111.11111111.00000000 • Above shows 192.168.14.0 as the network ID, 250 as the host ID Guide to Operating Systems, 5th Edition © Cengage Learning 2017 52 Internet Protocol Version 4 • IP Addresses are categorized in Classes A-E – Only IP addresses in the A, B, and C classes are available for host assignment • Class A – Value of the first octet is between 1 and 127 – IP registry assigns the first octet, leaving the last three octets to be assigned to hosts – Intended for large corporations and government • Class B – Value of the first octet is between 128 and 191 – IP registry assigns the first two octets, leaving the third and fourth octets to be assigned to hosts – Intended for use in medium to large networks Guide to Operating Systems, 5th Edition © Cengage Learning 2017 53 Internet Protocol Version 4 • Class C – Value of the first octet is between 192 and 223 – IP address registry assigns the first three octets – These networks are limited to 254 hosts per network – Intended for small networks • Class D – Value of the first octet is between 224 and 239 – Reserved for multicasting • Class E – Value of the first octet is between 240 and 255 – Reserved for experimental use and can’t be used for address assignment Guide to Operating Systems, 5th Edition © Cengage Learning 2017 54 Internet Protocol Version 4 Table 9-4 IPv4 address class summary Guide to Operating Systems, 5th Edition © Cengage Learning 2017 55 Internet Protocol Version 6 • Originally named IPng (IP next generation), IPv6 was created in 1994 by the Internet Engineering Task Force (IETF) • IPv6 includes the following improvements – – – – – – – Larger address space Hierarchical address space Autoconfiguration Built-in Quality of Server (QoS) support Built-in support for security Support for mobility Extensibility Guide to Operating Systems, 5th Edition © Cengage Learning 2017 56 Internet Protocol Version 6 • IPv6 addresses use128 bits, instead of IPv4’s 32 bits, for an address • IPv6 addresses are written as eight 16-bit hexadecimal numbers separated by colons: – Fe80:0:0:0:18ff:0024:8e5a:60 – Things to note about IPv6 addresses: • One or more consecutive 0 values can be written as a double colon, but only one double colon can exist in an IPv6 address • Leading 0s are optional • Hexadecimal numbers are easier to convert to binary Guide to Operating Systems, 5th Edition © Cengage Learning 2017 57 Introducing the OSI Model of Networking • Open Systems Interconnection (OSI) reference model proposed by the International Organization for Standardization (ISO) provides a common framework for developers and students of networking to work with and learn from • OSI model is not specific to any protocol suite and can be applied to most networking protocols • OSI model is a seven-layer organization of how data travels from place to place on any given network Guide to Operating Systems, 5th Edition © Cengage Learning 2017 58 Structure of the OSI Model Figure 9-23 The seven layers of the OSI reference model Guide to Operating Systems, 5th Edition © Cengage Learning 2017 59 Structure of the OSI Model • Each layer in the OSI model has its own set of welldefined functions – The functions of each layer communicate and interact with the layers immediately above and below it – Example: The Transport layer works with the Network layer below it and the Session layer above it Guide to Operating Systems, 5th Edition © Cengage Learning 2017 60 Structure of the OSI Model • The Application layer (Layer 7) provides interfaces for applications to access network services – File sharing, message handling, and database access – Common protocols found at Layer 7 include HTTP, FTP, SMB/CIFS, TFTP, and SMTP Guide to Operating Systems, 5th Edition © Cengage Learning 2017 61 Structure of the OSI Model • The Presentation layer (Layer 6) handles data formatting and translation • For outgoing messages – Converts data into a format specified by the Application layer • For incoming messages – Reverses the conversion if required by the receiving application • A software component known as a “redirector” operates at this layer – Intercepts requests for service from the computer, requests that can’t be handles locally are redirected across the network to a network resource that can handle the request Guide to Operating Systems, 5th Edition © Cengage Learning 2017 62 Structure of the OSI Model • Session layer (Layer 5) permits two computers to hold ongoing communications, called a “session” • This layer handles communication setup ahead of data transfers and session teardown when the session ends • Common network functions at this layer: – Name lookup, user logon and logoff Guide to Operating Systems, 5th Edition © Cengage Learning 2017 63 Structure of the OSI Model • Transport layer (Layer 4) manages data transfer from one application to another across a network – By breaking data down into smaller chunks called “segments” • Segmenting data is important because every network technology has a maximum frame size called the maximum transmission unit (MTU) • Includes flow control and acknowledgements to ensure reliability • Handles resequencing segments into the original data on receipt Guide to Operating Systems, 5th Edition © Cengage Learning 2017 64 Structure of the OSI Model • The Network layer (Layer 3) handles logical addressing, translates logical network addresses (IP addresses) into physical addresses, and performs best path selection and routing in an internetwork • Software working at this layer include IP, ARP and ICMP • Routers operate at this layer – As well as switches with routing capabilities, known as a Layer 3 switch Guide to Operating Systems, 5th Edition © Cengage Learning 2017 65 Structure of the OSI Model • The Data Link layer (Layer 2) works with frames and is the intermediary between the Network layer and Physical layer • Defines how computers access the network medium (also called media access control) – MAC address is defined at this layer • The software component operating at this layer is the NIC driver and hardware components include NICs and switches Guide to Operating Systems, 5th Edition © Cengage Learning 2017 66 Structure of the OSI Model • The Physical layer (Layer 1) converts bits into signals for outgoing messages and signals into bits for incoming messages – Wire media uses electrical pulses, fiber-optic uses light pulses and wireless media uses radio waves • Details for creating a physical network connection are specified at this layer – Example: type of connectors used to attach the medium to the NIC Guide to Operating Systems, 5th Edition © Cengage Learning 2017 67 Structure of the OSI Model Table 9-5 OSI model summary Guide to Operating Systems, 5th Edition © Cengage Learning 2017 68 Configuring Networking in an Operating System • Network configuration in an OS follows a similar pattern as the steps in the network communication process • All functions of the network model must be accounted for Guide to Operating Systems, 5th Edition © Cengage Learning 2017 69 Configuring the Network Interface • In most cases, you don’t have to configure the NIC – If a NIC is installed, the OS will usually install the proper driver – May need to install a new or different driver if an update becomes available • Linux and Mac OS X offer configuration settings for the network interface – Use the command-line tool ethtool to display and change network interface settings – In Mac OS X, use the advanced settings in the Network dialog box Guide to Operating Systems, 5th Edition © Cengage Learning 2017 70 Configuring IPv4 Addresses • Configuration of an IP address consists of the following parts: – – – – – IP address Subnet mask Default gateway Preferred DNS server Alternate DNS server Guide to Operating Systems, 5th Edition © Cengage Learning 2017 71 Configuring IPv4 Addresses • Rules for IP address assignment – A host can be assigned only a Class A, Class B, or Class C address – Every IP address configuration must have a subnet mask – All hosts on the same physical network must share the same network ID in their IP addresses – All host IDs on the same network must be unique – You can’t assign an IP address in which all the host ID bits are binary 0 Guide to Operating Systems, 5th Edition © Cengage Learning 2017 72 Configuring IPv4 Addresses • Rules for IP address assignment (cont’d) – You can’t assign an IP address in which all the host ID bits are binary 1 – Computers assigned different network IDs can communicate only if a router is present to forward packets – The default gateway address assigned to a computer must have the same network ID as that computer Guide to Operating Systems, 5th Edition © Cengage Learning 2017 73 Configuring an IPv4 Address in Windows • Windows is configured to obtain an IP address automatically by default – Using Dynamic Host Configuration Protocol (DHCP) – Requests an IP address configuration from a DHCP server • If no DHCP server responds to the request the computer assigns an automatic private IP addressing (APIPA) address – Always begins with 169.254 with 255.255.0.0 subnet mask Guide to Operating Systems, 5th Edition © Cengage Learning 2017 74 Configuring an IPv4 Address in Windows • Sometimes you may need to configure a static IP address, which is manually configured • Configure a static IPv4 address in Windows using a GUI or the command line – Use netsh to configure from a command line • To configure an interface named Ethernet0: – netsh interface ipv4 set address “Ethernet0” static 10.1.1.1 255.255.0.0 – Can include the default gateway by adding the address to the end of the command Guide to Operating Systems, 5th Edition © Cengage Learning 2017 75 Configuring an IPv4 Address in Linux and Mac OS X • To configure an IP address to an interface named eth0, use the following command from the shell prompt: – ifconfig eth0 10.1.1.1 netmask 255.255.0.0 • To configure a default gateway in Linux, use the route command: – route add default gw 10.1.1.250 • Most Linux installations have a GUI tool for configuring the IP address settings Guide to Operating Systems, 5th Edition © Cengage Learning 2017 76 Configuring an IPv4 Address in Linux and Mac OS X Figure 9-28 Configuring an IP address in Linux Guide to Operating Systems, 5th Edition © Cengage Learning 2017 77 Configuring IPv6 Addresses • A computer with IPv6 enabled is always automatically assigned a link-local IPv6 address – Always begins with fe80 and is self-configuring • IPv6 autoconfiguration occurs by two methods: – Stateless autoconfiguration - the node listens for router advertisement messages from a local router – Stateful autoconfiguration - the node uses an autoconfiguration protocol, such as DHCPv6, to obtain its IPv6 address and other configuration information Guide to Operating Systems, 5th Edition © Cengage Learning 2017 78 Configuring IPv6 Addresses Figure 9-30 The ipconfig command in Windows showing the link-local IPv6 address Guide to Operating Systems, 5th Edition © Cengage Learning 2017 79 Summary • Components needed to make a stand-alone computer a networked computer include a NIC, a network medium, and usually an interconnecting device • The layers of the network communication process can be summarized as user application, network software, network protocol, and network interface • The terms used to describe networks of different scope are LAN, Internetwork, WAN, and MAN Guide to Operating Systems, 5th Edition © Cengage Learning 2017 80 Summary • Packets and frames are the units of data handled by different network components • A client is the computer or network software that requests network data and a server is the computer or network software that makes the network data available to requesting clients • A peer-to-peer network model has no centralized authority over resources while a server-based network usually uses as directory service to provide centralized resource management Guide to Operating Systems, 5th Edition © Cengage Learning 2017 81 Summary • LANs, WANs, MANs, and internetworks are built with a variety of network hardware • TCP/IP is the main protocol suite used in networks • The Open Systems Interconnection (OSI) reference model for networking explains how networks behave within an orderly, seven-layered model for communication • Network configuration in an OS follows a similar pattern as the steps in the network communication process, the TCP/IP model, and the OSI model Guide to Operating Systems, 5th Edition © Cengage Learning 2017 82