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Network Connectivity

Network Connectivity. Guide to Operating Systems Second Edition. 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

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Network Connectivity

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  1. Network Connectivity Guide to Operating Systems Second Edition Chapter 8

  2. 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

  3. 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

  4. 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

  5. Telephone and Computer Networks Compared Chapter 8

  6. 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

  7. 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

  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

  9. 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

  10. Sharing Resources in an Office Chapter 8

  11. Reasons for a Network • In Windows NT Server 4.0, the Network Client Administrator enables you to install the MS-DOS 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

  12. 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

  13. 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 pre-configured 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

  14. Reasons for a Network • With e-mail, you can reach someone on the first try • You also can attach a file, such as a word-processing 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. Bus Topology Chapter 8

  21. 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

  22. Ring Topology Chapter 8

  23. Star Topology Chapter 8

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

  33. Devices on a Network With Unique Physical Addresses Chapter 8

  34. 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

  35. 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

  36. 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

  37. 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

  38. 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

  39. 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

  40. 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 high-speed 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

  41. 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

  42. 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

  43. Station with the Token in Token Ring Chapter 8

  44. 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

  45. 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

  46. Implementing a Transport Protocol in an Operating System • Microsoft designed the Network Device Interface Specification (NDIS) and Windows-based 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

  47. 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

  48. 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

  49. 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

  50. 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 connection-oriented communications Chapter 8

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