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8 Network Connectivity Guide to Operating Systems Second Edition Chapter 8 1 8 Objectives After reading this chapter and completing the exercises you will be able to: • Explain basic networking theory, such as network topologies, 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 Chapter 8 2 8 Objectives After reading this chapter and completing the exercises you will be able to: • Explain how bridging and routing are used on networks • Explain LANs and WANs • Describe how network and workstation operating systems are used for remote networking Chapter 8 3 8 Basic Networking • A network is composed of communications media such as communications cable, used to link computers, printers, disk storage, CD-ROM arrays, and network communications equipment • The basic principle of networking is similar to connecting telephones for communications • The hardware components of a computer network are computers, printers, communications cable, and internetworking devices such as bridges, switches, routers, and hubs Chapter 8 4 8 Telephone and Computer Networks Compared Chapter 8 5 8 Basic Networking • Computer networks also have software components consisting of client and server network operating systems • Windows 95, Windows 98, Windows NT 4.0 Workstation, Windows 2000 Professional, and Windows XP Professional are examples of client operating systems • A client operating system is one that enables a workstation to run applications, process information locally, and communicate with other computers and devices over the network Chapter 8 6 8 Basic Networking • A workstation is a computer that has a CPU, and can run applications locally, or obtain applications and files from another computer on the network • Sometimes the term workstation is confused with the term terminal • The difference is that a terminal has no CPU or local storage for running programs independently Chapter 8 7 8 Basic Networking • A network operating system (NOS) is one that enables the coordination of network activities and the sharing of resources – network communications, shared printing, shared access to files, and shared access to software, for example • A server is a computer running a NOS, which provides resources, such as shared files and programs that are accessed by clients Chapter 8 8 8 Reasons for a Network • Networks were invented for three interrelated reasons: to share resources, save money, and increase productivity • Most important, networks allow organizations to save money by sharing resources • Windows NT Server 4.0, Windows 2000 Server, and Windows .NET Server offer several ways to save money and time by centralizing software and client operating system installation through a server Chapter 8 9 8 Sharing Resources in an Office Chapter 8 10 8 Reasons for a Network • In Windows NT Server 4.0, the Network Client Administrator enables you to install the MSDOS and Windows 95 operating systems on any client connected to a network • Windows 2000 Server and Windows .NET Server use Remote Installation Services (RIS) to install pre-configured client operating systems, such as Windows 2000 Professional, on a mass scale Chapter 8 11 8 Reasons for a Network • Both Windows 2000 and Windows .NET Server also enable you to either assign or publish software applications through creating group policies • Assigning applications involves setting up an Active Directory group policy so that a particular version of software, such as Microsoft Word XP, is automatically started through a desktop shortcut or menu selection, or by clicking a file type Chapter 8 12 8 Reasons for a Network • Publishing an application means that the Windows 2000 Professional or Windows XP Professional client can open the Add/Remove Programs (Add or Remove Programs in Windows XP) icon in the Control Panel to install the preconfigured software from a central Windows 2000 or Windows .NET server • Productivity is another reason for networks • Electronic mail (e-mail) is another example of how networking can increase productivity Chapter 8 13 8 Reasons for a Network • With e-mail, you can reach someone on the first try • You also can attach a file, such as a wordprocessing document or spreadsheet, so that the recipient has it right away • Electronic commerce is another network application that increases productivity • Another growing area for networks is electronic conferencing Chapter 8 14 8 The Development of Network Operating Systems • Novell NetWare was one of the first network operating systems, initially demonstrated in 1982 at the National Computer Conference as a groundbreaking PC networking system • Windows 3.1, released in 1992, was one of the first Windows-based operating systems with network capabilities, enabling it to connect to NetWare, Microsoft, and other networks • Workgroups (pre-defined groups of member computers) provide the ability to limit resource sharing on the basis of group membership Chapter 8 15 8 The Development of Network Operating Systems • Windows 95 represents yet another major step into networking because it expands peer-to-peer networking and has the ability to connect to more kinds of networks • Windows Me also comes with better networking capabilities for home use • Representing a different Windows operating system track, Windows NT 3.1 was released just a little later than Windows 3.1, but Windows NT 3.1 was intended for industrial strength networking from the beginning Chapter 8 16 8 The Development of Network Operating Systems • The dawning of the millennium brought two new names for Windows NT: Windows 2000 Server and Windows 2000 Professional (Workstation) • Windows 2000 has evolved into two products, Windows XP and Windows .NET Server, both containing the core elements of the Windows 2000 kernel • Both Windows 2000 and Windows XP have built-in options to configure home and small office networks, such as sharing a one modem-based Internet connection between multiple computers connected through a small network Chapter 8 17 8 The Development of Network Operating Systems • Besides the NetWare and Windows-based operating systems, there are several others designed for networking: – UNIX – Banyan Vines – Pathworks – LAN Manager • All three are server operating systems that may be in use on networks, and that run on small to mid-sized computers Chapter 8 18 8 The Basics of Network Topologies • A topology is the design of the network, as if you were looking at it from above in a helicopter, or following the path information takes when it goes from one computer to another • A network that uses a bus topology is designed like a climbing rope with knots tied along the way for a foothold • There is a beginning and end to the rope, and junctures along the way for your feet Chapter 8 19 8 Bus Topology Chapter 8 20 8 The Basics of Network Topologies • A ring topology is one in which the data-carrying signal goes from station to station around the ring, until it reaches the target destination • There is no beginning or end point, so there are no terminators (see Figure 8-4) • The star topology is one in which there is a hub in the middle, with cable segments coming out of the hub in all directions, as shown in Figure 8-5 • The hub sends the signal onto each segment, which has a computer at the end Chapter 8 21 8 Ring Topology Chapter 8 22 8 Star Topology Chapter 8 23 8 The Basics of Network Topologies • Some hubs, called passive hubs, just pass the signal onto a segment without modifying the signal in any way • The disadvantage in using a passive hub is that the signal grows weaker each time it goes through the hub to the next segment • Networks that use active hubs support more computers because the signal is amplified to its original strength each time it goes through the hub Chapter 8 24 8 The Basics of Network Topologies • Switched networks use switches in place of hubs • The switch learns what devices are located on each of the segments attached to it, and only transmits the information on the segment where the destination device resides • Traffic is not transmitted on all segments at once, as happens on hubs Chapter 8 25 8 Packets, Frames, and Cells • Each computer or network device translates data into individual units, and then places the units onto the network cable • Each data unit is called a packet or frame • These terms are sometimes used interchangeably, but they are not the same • Both consist of data and transmission control information contained in a header that is appended to the front of the data Chapter 8 26 8 Packets, Frames, and Cells • The difference is that a packet contains routing information that can be read by specialized devices that are able to forward packets to specific networks • The actual data is placed after the header information, and followed by a footer or trailer that enables detection of a transmission error Chapter 8 27 8 Packets, Frames, and Cells • Older networks transmit at speeds of 4 Mbps (megabits per second), 10 Mbps, and 16 Mbps • Newer networks transmit at 100 Mbps to 10 Gbps and faster, or consist of segments that transmit at 10 Mbps, 100 Mbps, 1 Gbps, or 10 Gbps • Network backbones, which are segments that join main networks, typically run at 100 Mbps or higher Chapter 8 28 8 Packets, Frames, and Cells • A cell is a data unit designed for high-speed communications; it has a control header and a fixed-length payload • The payload is that portion of a frame, packet, or cell that contains the actual data, which might be a portion of an e-mail message or word-processing file Chapter 8 29 8 Packets, Frames, and Cells • One element of the cell header is path information that enables the cell to take the route through the network that is most appropriate to the type of data carried within the cell Chapter 8 30 8 Packets, Frames, and Cells • A protocol is a set of formatting guidelines for network communications, like a language, so that the information sent by one computer can be accurately decoded by another • Protocols also coordinate network communications so that data is transported in an orderly fashion, preventing chaos when two or more computers want to transmit at the same time • A network may use several different protocols, depending on the NOS and the types of devices that are connected Chapter 8 31 8 Connecting to a Network • Computers and internetworking devices connect to a network through a network interface card (NIC) • A NIC is usually a card that goes into a computer’s expansion slot, or that is built into a network device or a computer • Each NIC has a unique hexadecimal address, called a device or physical address, which identifies it to the network • It is also called the Media Access Control (MAC) address Chapter 8 32 8 Devices on a Network With Unique Physical Addresses Chapter 8 33 8 Connecting to a Network • Some NICs also transform data into radio frequency communications, called packet radio, for wireless networks • The software logic consists of one or more programs called firmware because it resides in a programmable chip on the card • Communication between the operating system and its NIC, like communication between the operating system and carious input, output, and storage devices, is controlled by driver software written by the manufacturer of the device Chapter 8 34 8 Networking Protocols • Protocols are used for many types of network communications, including the following: – Coordinating transport of packets and frames among network devices – Encapsulating data and communication control information – Providing communications to accomplish a specific function, such as enabling the destination computer to tell the source computer to slow its transmission speed because it is too fast for the destination computer – Enabling communications over a long-distance network, such as the Internet – Enabling remote users to dial into networks Chapter 8 35 8 Transport Protocols • The commonly used transport protocols are Ethernet and token ring • Ethernet is in more installations than token ring because there are more network equipment options for it, and because modern Ethernet network designs are most easily expanded for high-speed networking • Token ring, an IBM-proprietary protocol, is used because it is reliable, and network problems were initially easier to troubleshoot on token ring networks than on early Ethernet networks Chapter 8 36 8 Ethernet • In Ethernet communications, only one station on the network should transmit at a given moment • If two or more stations transmit at the same time, frames collide • The transmission control method used by Ethernet is called Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • In CSMA/CD, the NICs of computers and devices check the network communications cable for a carrier signal that contains an encoded frame Chapter 8 37 8 Ethernet • If the device’s NIC detects a carrier signal, and if the NIC decodes its own device address within the frame, it forwards that packet to its firmware for further decoding • If the frame does not contain its device address, then the NIC does not process the signal any further • There are two mainstream varieties of Ethernet protocol communications: the IEEE 802.3 standard and Ethernet II • Both are nearly identical, but Ethernet II uses a slightly different frame format for modern network communications Chapter 8 38 8 Ethernet • In IEEE 802.3 and in Ethernet II, frames contain a header that has control information, along with source and destination addressing • The data portion of both frame types contains 576 to 12,208 bytes • Also, both frame formats contain a frame change sequence field as a trailer, which is used to alert the receiving station when a transmission error occurs, by showing that some portion of the received frame contents is not the same as when the frame was sent Chapter 8 39 8 Ethernet • Networks that use Ethernet are designed in a bus topology, or a star topology, in which the internetworking devices simulate a logical bus • Ethernet hybrid star-bus networks are very common in modern network design because they are easier to troubleshoot and expand for highspeed networking than simple bus networks • Fast Ethernet is becoming commonplace, and most NICs are currently designed to handle either 10 or 100 Mbps communications Chapter 8 40 8 Ethernet • All versions of Ethernet are compatible with popular network operating systems such as: – UNIX – NetWare – Windows NT, 2000, XP, and .NET Server – Windows 3.x – Windows 95/98/Me – Mac OS – Banyan Vines – Pathworks Chapter 8 41 8 Token Ring • In most versions of token ring, only one network station transmits at a time • The sequence of frame and packet transmissions is controlled by the use of a specialized frame, called a token • A token without data is transmitted around the network until it is captured by a station that wants to transmit Chapter 8 42 8 Station with the Token in Token Ring Chapter 8 43 8 Token Ring • Token ring is compatible with the same mainstream network operating systems that are used in Ethernet, including: – UNIX – NetWare – Windows NT, 2000, XP, and .NET Server – Windows 3.x – Windows 95/98/Me – Mac OS – Banyan Vines – Pathworks Chapter 8 44 8 Implementing a Transport Protocol in an Operating System • A transport protocol is interfaced with an operating system through three elements: a network driver specification built into the operating system, a NIC, and a NIC driver • Network operating systems are built to offer special elements, that programmers call “hooks,” in the operating system kernel (program code), which enable the operating system to interface with a network Chapter 8 45 8 Implementing a Transport Protocol in an Operating System • Microsoft designed the Network Device Interface Specification (NDIS) and Windowsbased NDIS drivers for this purpose • When you set up an operating system to work on an Ethernet or token ring network, the first step is to purchase an Ethernet or token ring NIC for the computer running the operating system Chapter 8 46 8 Implementing a Transport Protocol in an Operating System • The NIC cable interface must also match the type of cable used on the network • After the NIC setup is complete, and the computer is connected to the network, the operating system, NIC, and driver handle the work of converting data created at the computer to an Ethernet or token ring format for transport over the network Chapter 8 47 8 Communications Protocols • The development of communications protocols (the protocols that carry data between two communicating stations, and are encapsulated in Ethernet or token ring transport protocols) has been interrelated to the network operating systems in which they are used • The Internet Packet Exchange (IPX) protocol was developed to enable a NetWare file server to communicate with its client workstations Chapter 8 48 8 Communications Protocols • Also, in 1982, researchers implemented and combined two protocols for use on the Advanced Research Projects Agency network, ARPANET, which was the long-distance network that set the foundation for the Internet • The ARPANET protocols now used worldwide over the Internet are Transmission Control Protocol (TCP) and Internet Protocol (IP) Chapter 8 49 8 IPX • IPX is a protocol developed by Novell and modeled after the Xerox Network System (XNS) protocol • IPX encapsulates data and transports it within a host transport protocol format—Ethernet or token ring • When there is a need for more reliable data transport, such as for data from a database, an application running via NetWare can use Sequence Packet Exchange (SPX), a protocol that provides connectionoriented communications Chapter 8 50 8 IPX • IPX relies upon SPX at the transport layer to provide reliable, error-free communication • IPX works with other specialized service and NetWare protocols as follows: – Link Support Layer (LSL) – NetWare Core Protocol (NCP) – NetWare Link Services Protocol (NLSP) – Routing Information Protocol (RIP) – Service Advertising Protocol (SAP) Chapter 8 51 8 NetBEUI • NetBEUI (NetBIOS Extended User Interface) was introduced in the early nineties as the main protocol for LAN Manager, a network server operating system developed by Microsoft and IBM, and the forerunner of Windows NT Server • NetBEUI was developed from the Network Basic Input/Output System (NetBIOS), which is a technique used to interface software with network services Chapter 8 52 8 NetBEUI • NetBIOS should not be confused with a protocol • It acts as a software interface only, providing a way for an application to export data to a network service, such as linking data in a word-processed document to a network mail service that attaches the document to an e-mail • NetBEUI is designed for networks consisting of fewer than 200 stations, and is well suited for Microsoft networks Chapter 8 53 8 NetBEUI • It is particularly compatible with applications that use NetBIOS and computers that run Microsoft operating systems, such as Windows NT, 3.x, 95, 98, and Me • Another advantage of NetBEUI is that later versions of this protocol can handle nearly limitless communication sessions Chapter 8 54 8 NetBEUI • An important limitation of NetBEUI is that it is not designed to carry routing information, which means that it is not a good choice for medium and large networks • Other advantages of NetBEUI are: – Low use of memory resources – Quick transport of information on small networks – Strong error detection and recovery – Relatively easy configuration in the host operating system Chapter 8 55 8 NetBEUI Flooding All Networks with a Large Network Setup Chapter 8 56 8 TCP/IP • TCP/IP is one of the oldest protocols, initially developed for long-distance networking on ARPANET, and now used on most networks • One of the strongest influences on TCP/IP use has been the growth of the Internet • UNIX has always used TCP/IP as its main network communications protocol • TCP was developed for extremely reliable pointto-point communications between computers on the same network Chapter 8 57 8 TCP/IP • TCP/IP is also compatible with the following operating systems: – Windows 3.1 and 3.11 – Windows 95/98/Me – Windows NT 3.0, 3.5, 3.51, and 4.0 – Windows 2000/XP/.NET Server – Mac OS – Banyan Vines Chapter 8 58 8 TCP/IP • Some of the communication functions performed by TCP are: – 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 Chapter 8 59 8 TCP/IP • The IP portion of TCP/IP is used to make sure that a frame or packet reaches the intended destination • IP performs the following complementary functions with TCP: – Handles packet addressing – Handles packet routing – Fragments packets, 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 Chapter 8 60 8 TCP/IP • IP addressing uses the dotted decimal notation that consists of four 8-bit binary numbers (octets) separated by periods • There are five IP address classes, Class A through Class E, each used with a different type of network • The address classes reflect the size of the network, and whether the packet is unicast or multicast Chapter 8 61 8 TCP/IP • In the unicast method of transmission, one copy of each packet is sent to each target destination • In the multicast method, the recipients are placed in a group, such as a group of all eight workstations since they are on the same network • Classes A through C are intended as unicast addressing methods, but each class represents a different network size • Class A is used for the largest networks composed of up to 16,777,216 nodes Chapter 8 62 8 TCP/IP • Class A networks are identified by a value between 1 and 126 in the first position of the dotted decimal address • The network ID is the first eight bits, and the host ID is the last 24 bits • Class B is a unicast addressing format for medium-sized networks composed of up to 65,536 nodes, and it is identified by the first octet of bits ranging from decimal 128 to 191 Chapter 8 63 8 TCP/IP • The first two octets are the network ID, and the last two are the host ID • Class C addresses are used for unicast network communications on small networks of 256 nodes or less • The first octet translates to a decimal value in the range of 192 to 223, and the network ID is contained in the first 24 bits, while the host ID is contained in the last eight bits Chapter 8 64 8 TCP/IP • Class D addresses do not reflect the network size, only that the communication is a multicast • Unlike Classes A through C, the four octets are used to specify a group of nodes to receive the multicast, which consists of those nodes that are multicast subscription members • Class D addresses are in the range from 224.0.0.0 to 239.255.255.255 • A fifth address type, Class E, is used for experimentation, and addresses range from 240 to 255 in the first octet Chapter 8 65 8 TCP/IP • Besides class addressing, there are some specialpurpose IP addresses, such as 255.255.255.255, which is a broadcast packet sent to all network locations • A new way to ignore address class designations is by using Classless Interdomain Routing (CIDR) addressing that puts a slash (/) after the dotted decimal notation • CIDR provides more IP address options for mediumsized networks because there is shortage of Class B and Class C addresses Chapter 8 66 8 TCP/IP • Computers and devices that use IP addressing actually have two addresses: a physical address and an IP address • The use of two addresses provides better insurance that a packet will reach the right destination, while expending the fewest network resources • TCP/IP works with a range of associated protocols that make this a powerful combination for networks of all sizes and types Chapter 8 67 8 Using TCP/IP Subnet Masks Chapter 8 68 8 TCP/IP • Some protocols include the following: – Routing Information Protocol (RIP) – Simple Mail Transfer Protocol (SMTP) – File Transfer Protocol (FTP) – Telnet – Hypertext Transfer Protocol (HTTP) – Point-to-Point Protocol (PPP) – Simple Network Management Protocol (SNMP) – Internet Control Message Protocol (ICMP) – Domain Name Service (DNS) – Dynamic Host Configuration Protocol (DHCP) Chapter 8 69 8 AppleTalk • AppleTalk is a network communications protocol used between Macintosh computers • It is designed primarily as a peer-to-peer protocol, rather than for combined peer-to-peer and client-to-server communications • As a peer-to-peer protocol, AppleTalk establishes equal communications between networked Macintosh computers, without the need for a server • AppleTalk performs three essential services: remote access to files over a network, network print services, and access to computers running MS-DOS or Windows operating systems Chapter 8 70 8 Peer-to-Peer Networking Using AppleTalk and No Server Chapter 8 71 8 AppleTalk • Examples of protocols designed for use with AppleTalk are as follows: – AppleTalk Address Resolution Protocol (AARP) – AppleTalk Data Stream Protocol (ADSP) – AppleTalk Session Protocol (ASP) – Datagram Delivery Protocol (DDP) – Name-Binding Protocol (NBP) – Printer Access Protocol (PAP – Routing Table Maintenance Protocol (RTMP) Chapter 8 72 8 Implementing Communications Protocols in an Operating System • Most computer operating systems are designed to support one or more communications protocols • In general, there are two steps involved in setting up a communications protocol in an operating system • The first is to install the protocol software that is written for that operating system • Step two is to bind the protocol with the NIC Chapter 8 73 8 Implementing Communications Protocols in an Operating System • Binding the protocol enables the NIC to format data for that protocol, and identify the most efficient methods for transporting it within Ethernet or token ring • When two or more protocols are used, binding also enables the NIC to set a priority for which protocol to process first Chapter 8 74 8 Implementing Communications Protocols in an Operating System • The Mac OS up through version 9.x provides one of the easiest methods for setting up communications protocols • In the Mac OS, you use a Control Panel to designate a port for network communications associated with the NIC • In Mac OS X, setting up network communications is also simplified, but with more options than in Mac OS 9.x Chapter 8 75 8 Implementing Communications Protocols in an Operating System • Through the Mac OS X Network panel, you can fully configure your Mac to use TCP/IP and TCP/IP network services, including the following: – Manual configuration of IP address and subnet mask – Automatic configuration of the IP address using DHCP – Identification of the nearest router by IP address – Identification of Domain Name Service (DNS) servers by IP address – Identification of search domains by IP address Chapter 8 76 8 Implementing Communications Protocols in an Operating System • Most UNIX systems have TCP/IP networking support built in, and some of these automatically run a network configuration program when you first boot the computer with an installed NIC • For some versions of UNIX, including Red Hat Linux, you must configure a loopback device, which is used to provide your computer with an internal IP address, even when it is not connected to the network Chapter 8 77 8 Implementing Communications Protocols in an Operating System • In the Red Hat Linux GNOME interface, you can configure a network connection by clicking the Start icon on the panel, pointing to Programs, pointing to System, and clicking Network Configuration • Communications protocols in NetWare, such as IPX and TCP/IP, can be set up in a window that appears when NetWare is installed • In Windows 3.1 and 3.111, communications protocols are set up through the Main program group by opening the Windows Setup icon and the Options menu Chapter 8 78 8 Implementing Communications Protocols in an Operating System • Communications protocols are set up in Windows 95/98/Me and Windows NT 4.0 through the Network icon in the Control Panel Chapter 8 79 8 Implementing Communications Protocols in an Operating System Chapter 8 80 8 Integrating Different Operating Systems on the Same Network • The key to implementing multiple operating systems on one network is to select a transport protocol and communications protocols that are supported in all of the operating systems that must be connected • Ethernet is particularly well suited to a network that has different operating systems • In situations where TCP/IP is not supported by all operating systems, then multiple protocols can be configured, such as a combination of AppleTalk, TCP/IP, and IPX/SPX Chapter 8 81 8 Bridging and Routing • One or more networks or segments can be linked by using internetworking devices such as bridges and routers • Bridges are used to link segments that are close together, such as on different floors in the same building • Another use for bridges is to extend segments, such as when more stations must be added, but the primary segment already contains the maximum length of cable or number of stations permitted by network standards Chapter 8 82 8 Bridging and Routing • Bridges operate in what network administrators call promiscuous mode, which means that they examine the physical destination address of every frame that passes through them • Bridges are protocol independent, a characteristic that permits them to forward all kinds of frame formats • Bridges are not designed to route packets from one network to another because they ignore routing information Chapter 8 83 8 Using a Bridge Filter to Direct Segment A Frames to Segment D Chapter 8 84 8 Bridging and Routing • Switches operate in promiscuous mode like bridges, but they provide additional logic that enables them to move network traffic more efficiently than the old-style bridges • Routers are used to join networks, either locally or remotely • Unlike bridges, routers are designed to look at routing information in packets before forwarding those packets to another network • Routers also make excellent firewalls because networks connected to a router can be divided into subnets as a way to control incoming and outgoing traffic to each subnet Chapter 8 85 8 Router Linking Different Types of Networks and Protocols Chapter 8 86 8 Local and Wide Area Networks • A local area network (LAN) is one in which the service area is relatively small, such as a network in an office area, or one spread through a floor in a building • A wide area network (WAN) is one that offers networking services over a long distance, such as between cities, states, or countries • There are several interrelated elements that can be used to determine the intersection of a LAN with a WAN • One element is that the network topology may change between the two, such as a LAN that uses a ring topology and a WAN that uses a star • Another factor is a change in cable type Chapter 8 87 8 Using Operating Systems for Dial-Up Access • Windows NT/2000/.NET Server offer a similar option for dialing into a LAN through a Remote Access Services (RAS) server • RAS is a set of network services that can be installed on any Windows NT/2000/.NET server connected to one or more modems • Besides setting up a RAS server, there must be a way to set up remote access capability on client workstations Chapter 8 88 8 Using Operating Systems for Dial-Up Access • Windows 95/98/Me and Windows NT/2000/XP all have a dial-up networking service that can be configured to access a remote network • Security for dial-up remote access is a very important topic because of potential threats from viruses or hackers Chapter 8 89 8 Using Operating Systems for Dial-Up Access • Two ways to enhance the security surrounding the use of remote access is with authentication and encryption • Authentication is the way you identify and validate who you are to the server • Encryption is the encoding of the data between you and the server so that only you and the server can decode the information Chapter 8 90 8 Summary • A network is a system of information resources and productivity tools that facilitates our human need to communicate • Networks were invented because they enable users to share information and information resources over short and long distances • Networks are designed in standardized topologies (bus, star, and ring) and use standardized communication means, such as frames, packets, and protocols, with the end result that a network in Jackson, Wyoming can be connected to another in Denver, Colorado or Montreal, Canada Chapter 8 91 8 Summary • Protocols are particularly important to networking because they act as a common language for communications • Modern computer operating systems use a variety of network protocols for communications, such as TCP/IP, IPX/SPX, and NetBEUI • Table 8-1, 8-2, and 8-3 provide a summary of the transport, communications, and remote protocols introduced in this chapter, and the operating systems that support those protocols Chapter 8 92 8 Summary Chapter 8 93 8 Summary • Bridges, switches, and routers can be employed for network security and to control network traffic patterns • LANs are smaller networks that run throughout an office area or a floor in a building • WANs are long-distance networks that can span states and continents to join LANs and individual users • Also called dial-up access, modem communications with a LASN are made possible through remote communications protocols, such as SLIP and PPP • PPP is most commonly used because it can transport a combination of protocols, such as TCP/IP and IPX/SPX Chapter 8 94