Reinstall Windows. You should reinstall Windows directly over the top of your current

Appendix B ✦ IP Addressing ✦ Simple Mail Transfer Protocol SMTP is for exchanging e-mail. ✦ File Transfer Protocol FTP is for transferring files. FTP enables one computer to trans- fer a file to another computer by using TCP. ✦ Server Message Block SMB enables a computer to use network resources as if they were local. ✦ Network File System NFS enables a computer to use files and peripherals as if they were local. ✦ Telnet is a terminal emulation protocol that enables you to connect to a remote service while in Windows. ✦ Address Resolution Protocol ARP translates 32-bit IP addresses into physical network addresses, such as 48-bit Ethernet addresses. An Ethernet address is also called a MAC address MAC stands for Media Access Control. It’s a number written as 12 hexadecimal digits — 0 through 9 and A through F — as in 0080001021ef. Alternatively, a MAC address might have six hexadecimal numbers separated by periods or colons, as in 0:80:0:2:21:ef. The MAC address is unique to each computer, but it does not iden- tify the location of the computer, only the computer itself. ✦ Reverse Address Resolution Protocol RARP translates physical network addresses into IP addresses. ✦ Internet Control Message Protocol ICMP helps IP communicate error information about the IP transmissions. ✦ Internet Group Management Protocol IGMP enables IP datagrams to be broadcast to computers that belong to groups. Some of the TCPIP protocols are also applications. FTP, Telnet, and SNMP, for example, are programs that you can use over the network because they’re included with the TCPIP suite. Glimpsing the ISOOSI model International Organization for StandardizationOpen Systems Interconnection ISOOSI is a set of standards that defines network functionality. ISOOSI sets standards for cabling, net- work interface cards NICs, protocols, and so on. TCPIP’s layered design works well with the ISOOSI model to transmit network data efficiently and effectively. As the data moves from the network application Layer 7 to the network card Layer 2, one or more of the TCPIP protocols accompanies it every step of the way. The seven-layer model defines computer-to-computer communications. Following is a brief explanation of each layer: ✦ Layer 1 — The physical layer defines the cabling. ✦ Layer 2 — The data link layer controls the flow of data through the network cards. ✦ Layer 3 — The network layer defines the protocols for data routing, to make sure that the data gets to the correct destination. ✦ Layer 4 — The transport layer defines protocols for error checking and message formation. Note Note Appendixes ✦ Layer 5 — The session layer maintains the connection, or session, for as long as it takes to transmit the packets. The session layer also performs security and administration functions. ✦ Layer 6 — The presentation layer identifies the way the data is formatted. ✦ Layer 7 — The application layer defines how the applications interact with the network. Exploring IP Addressing IP addressing was standardized in 1981, with specifications that required each system attached to the Internet be assigned a unique, 32-bit address value. Systems include servers, routers, gateways, and other networking hardware. A router that attaches two network seg- ments, for example, must have two unique IP addresses, one for each network interface. To ensure that IP addresses used on the Internet are unique, the Internet Network Information Center InterNIC must assign any address used on the Internet. InterNIC is the controlling agency for IP addresses and domain names. Examining an IP address An IP address identifies the computer or other node router, printer, server, or other on the network. Each IP address on a network must be unique. An IP address is a binary number written in a series of four decimal digits, which is known as dotted decimal. Four period-delimited octets consisting of up to 12 numerals forms an IP address. For example, Microsoft’s home page IP address is 207.46.131.137 and is a dotted dec- imal. The numbers represent decimal notations for each of the four bytes of the address; the address identifies the computer. The IP address is really made up of two parts: the network number and the host number. ✦ The network number identifies the general location of the computer on the network, and the host number pins it down to the exact computer. In Microsoft’s IP address, 207.46 is the network address. ✦ The host number is represented by 131.137. Each class of address uses a different man- ner of dividing the octets. Microsoft is a Class B network see the following section. The highest value in any octet is 255, because of the way the binary format translates to dot- ted decimal format. Understanding address classes IP addressing is divided into five categories, or classes. Three of the classes — Class A, Class B, and Class C — are in use today. The following list describes each of the classes: ✦ Class A is used for large networks. To identify a Class A network address, the first octet uses the numbers from 1 to 126. Class A networks have an 8-bit network prefix; there- fore, they are currently referred to as 8s pronounced “slash eights” or just “eights.” ✦ Class B is mainly used for medium-sized networks, and the first octet values range from 128 to 191. Class B network addresses have a 16-bit network prefix; thus, they are referred to as 16s. Note Appendix B ✦ IP Addressing ✦ Class C is reserved for smaller networks. To identify a Class C network, the values range from 192 to 233. Class C networks have a 24-bit network prefix, and so are referred to as 24s. ✦ Class D addresses aren’t used for networks, because they’re special multicast or broad- casting addresses. ✦ Class E addresses, with values higher than 233 in the first octet, are used only for experimental purposes. All Class A addresses already have been taken by universities and corporations. Class B addresses are assigned to companies and institutions with a minimum of 4,000 hosts. If you apply for an Internet address, you will probably receive a Class C designation. Each class defines its own 32-bit address boundaries. In Class C, the first three octets are for the network address; the last octet represents the host address. If you apply for an Internet address, the InterNIC will give you an address with the first three octets defined. You fill in the last octet with numbers ranging from 1 to 254. The numbers 0 and 255 are reserved. Each number you assign goes to one node on your network, so you can connect up to 254 nodes to the Internet. Looking at the subnet mask A subnet mask is part of the IP addressing system. A subnet mask creates subnetworks that enable a computer in one network segment to communicate with a computer in another seg- ment of the network. The main reason for subnetting or creating subnets on a network is to divide a single Class A, B, or C network into smaller pieces. The subnet mask is a 32-bit address that hides, or masks, part of the IP address so as to add to the number of computers added to the network. All networks must use a subnet mask, even if they don’t connect to another network. If a network isn’t divided into subnets, the default subnet mask is used. The default depends on the IP address class. ✦ Class A networks use a default subnet mask of 255.0.0.0. ✦ Class B uses a default subnet mask of 255.255.0.0. ✦ Class C uses a default subnet mask of 255.255.255.0. Subnetting enables organizations to mix different network technologies across several physi- cal segments. It also enables you to exceed the maximum number of hosts per segment, if you’ve used all your IP addresses. Comprehending the gateway The gateway is a bridge between two segments of a network. Messages travel between net- work segments through the gateway. A gateway is a combination of hardware and software; it creates a shared connection between, say, a LAN and a larger network. Often, you use a gateway to bridge two networks that use different communications proto- cols. A gateway has its own processor and memory that it uses to convert protocols; convert- ing protocols makes the gateway slower than a router or bridge. A gateway must have its own IP address. Appendixes Working with Domain Names Every IP address on the Internet has a corresponding domain name, such as microsoft.com. Domain names make it easy to remember addresses, and you can use them in place of the IP address in the URL text box of your browser. Regarding domain names IP addresses are difficult to remember, so domain names also represent a computer on the Internet. Microsoft’s domain name, for example, is www.microsoft.com. Domain names usu- ally start with www, which stands for World Wide Web; however, www is not always included in an address. The letters www represent a route to a World Wide Web server. Other servers might use a different route, such as w2. If no route is listed, the address takes a default route as listed by the server. Domain names are written from the least specific top-level domain to the most specific host name. Each part is separated by a dot . . The second part of the domain name is the name of the organization, company, product, or another catchy word or phrase. Microsoft, for example, is perfect for the domain name of their Web site. The third part of the domain name identifies the type of organization. The letters com, for example, stand for commercial. Following are other top-level domain identifiers and their meanings: gov Government mil Military net Network providers org Nonprofit organization edu Education Other additions to the domain name include a country code, if the server is located outside of the United States. UK stands for United Kingdom, for example, and IT stands for Italy. Domain names are listed in the Uniform Resource Locator URL to a site. The URL is the full address, or computer identifier, on the Web. URLs contain numerous slashes and dots that separate the parts of the address, similarly to the way you separate folders in a path. Microsoft’s complete URL is http:www.microsoft.com. If you want a particular docu- ment on a site, you must use a longer URL, such as http:support.microsoft.comsup- portindex.html. The letters http stand for Hypertext Transfer Protocol; this is the protocol your computer uses to attach to the server computer. HTTP defines the language the computers will use to transfer pages and hypertext links. With most newer browsers, you don’t have to type the http in the address, but it doesn’t hurt to add it. In the sample URL, no www is used, but the address of the server is identified as support. microsoft.com. The support between forward slashes represents a folder, or directory. Tip Appendix B ✦ IP Addressing The HTML document is the one you view in that folder. There are no rules as to when to use www or http. The best practice is to copy the exact URL from literature or documentation about the Web site. Understanding the domain name system The Domain Name System DNS is a method of matching IP addresses with domain names. When you type a domain name in the URL address area of your browser, that query is trans- mitted to a DNS server. A DNS server maintains a database of domain names and IP addresses. The DNS server finds the IP address that matches the domain name and then sends your request on to that server. The process is called name resolution. You might find a DNS server in a university or college, on a corporate LAN, or even on a smaller LAN. Most primary ISPs also have DNS servers. Local ISPs connect to larger, or sec- ondary, ISPs, and those ISPs connect to much larger, primary ISPs that make up the Internet. DNS, or name, servers are grouped into domains, which identify different levels of authority. At the top of this hierarchical structure is the root domain, or top-level domain, such as com, edu, org, and so on. Within the top-level domains are second-level domains. Second-level domains contain hosts and subdomains. Going back to the microsoft.com example, microsoft.com is a second-level domain. A subdomain of microsoft.com might be ftp.microsoft.com. support.microsoft.com then would be a host name within the domain. Each Domain Name Server has a specific area for which it stores addresses and domain names. Called the zone of authority, the Domain Name Server can resolve only addresses within its zone. If a Domain Name Server doesn’t contain the IP address for the queried domain name, it forwards the query to another Domain Name Server. Recognizing DHCP Dynamic Host Configuration Protocol DHCP is a utility for assigning TCPIP addresses to work- stations automatically. DHCP servers are used mainly by corporations and large TCPIP networks to configure their clients, although they are also used by some Internet service providers. When a client accesses a TCPIP network, the DHCP server assigns the client an IP address, a subnet mask, and a gateway, if needed. The DHCP server has a range of possible IP addresses from which to choose. Each time the client logs off of the network, the IP address goes back into a pool and might be assigned to another client logging on to the network. Letting the DHCP server configure clients when they attach to the network saves the administrator of a large IP net- work a lot of time and effort. A DHCP server can grant a lease to a DHCP client. The lease provides one IP address for use by the client for up to 30 days. Each time the client logs on to the IP network, the lease is updated, so the lease doesn’t run out unless the client doesn’t log on within the 30 days of the lease. A lease is important for some networks, because to communicate with other corporate programs over the network, the client might need a stable IP address. The DHCP protocol requires a client ID for each computer. By default, the DHCP server uses the client computer’s MAC address. DHCP works with Mac OS; Microsoft Windows 95, 98, NT, 2000, XP; Novell NetWare; Novell LAN Workplace for DOS for attaching to a Unix workbox, or terminal; and Linux. Appendixes Why Use TCPIP? You can use TCPIP to connect your LAN to the Internet or to create an intranet or simply to speed up your local area network. You might want to use TCPIP because it’s so compatible with many different hardware and software products, or simply because you want to experiment with it. In addition, most newer operating systems — Windows 98 Second Edition, 2000, and XP; Mac OS X 10; and Linux distributions — come with TCPIP installed. Many OSs use only TCPIP. Although TCPIP seems severe and awkward, it’s really not that difficult to get the hang of it. You might start by configuring your computers for dialing up the Internet and then decide you want to try a TCPIP network in your own home. For information about intranets, see Chapter 19. For information about using the Internet, see Chapter 16. For instructions on setting up dial-up networking, see Appendix C. Looking at advantages of TCPIP Using TCPIP has many advantages. It’s more efficient and faster than NetBEUI. Additionally, many hardware and software vendors support TCPIP. You can use it with a variety of pro- grams and products. If the computers on your network use different operating systems, such as Macintosh and PCs, TCPIP enables those computers to communicate. The following sections discuss some more advantages of using TCPIP. Intranet Using TCPIP, you can create a private internet intranet on your home network. Publish documents for your family to view on their Web browsers by using Internet technologies, including HTTP, HTML, and more. If you create an intranet for your employees to contribute to and use, you can easily connect it to the Internet and extend its purpose to clients and vendors, as well. Following are some other reasons to create an intranet on your home network: ✦ Create an intranet so that you can share family stories, pictures, and play games over the network. ✦ Familiarize yourself and your family with Internet technology and the use of TCPIP, as well. ✦ If you’re thinking about creating a Web page for the Internet, experiment with designs on your intranet before you publish to the Web. ✦ If you’re thinking about starting a small home business, you can use your intranet to set up a home page and an index, create links to your pages, and test the site before you put it up on the Internet. ✦ If you’re planning to start an Internet business, set up the e-commerce site on your intranet before taking it to the Web. Internet You need TCPIP to connect to the Internet. Realize that there is a difference between installing TCPIP on your network and installing it for dial-up networking use; these are two separate installations and uses for the protocol. Small Business Tip Cross- Reference Appendix B ✦ IP Addressing You install TCPIP to use with the dial-up networking feature. This installation enables you to connect to the Internet by means of a modem. The TCPIP communicates with Web servers on the Internet. If you install TCPIP on your network, you use it to connect to the other com- puters on your LAN. One installation has nothing to do with the other. For more information, see the section “Installing and Configuring TCPIP” later in this appendix. Using TCPIP to connect to the Internet provides you with all the Internet features and advan- tages, including e-mail, Web browsers, and file transfer. Also, TCPIP includes various pro- grams which are also protocols that you can use to access information on the Internet. If you have special needs for FTP or Telnet, for example, TCPIP provides those programs for you to use. If you plan to expand your network to the Internet someday, your knowledge and use of TCPIP will help you tremendously. Knowing how to configure TCPIP will make it easier for you to transfer your Web sites and pages to the Web and to configure clients and servers for the Internet. Having TCPIP in place means less configuring when you move to the Internet. Dial-Up Networking You also can use TCPIP to connect to your home or work computer. If you’re on the road, for example, and want to call your home network to retrieve some information or your schedule, you can use Windows dial-up networking to accomplish this. You use TCPIP in Terminal Services as well. Terminal Services is a method of communication between a remote computer and a server using Windows 2000 Server. For more information, see Appendix C. If your work network uses TCPIP, you can call in to that network from home or while you’re on the road. Additionally, if your office network includes DHCP server, calling from a remote computer becomes even easier. The DHCP server configures your computer so that all you need to do is dial and connect. Creating your own TCPIP network When setting up your own TCPIP network, you need to choose IP addresses for your com- puters. Remember, each computer on the network needs a unique IP address. You also need to set a specific subnet mask for your network to use. Several IP addresses are reserved for private use. Following are the three blocks reserved for IP addresses: 10.0.0.0 to 10.255.255.255 172.16.0.0 to 172.31.255.255 192.168.0.0 to 192.168.255.255 For your home network, for example, you could use the following IP addresses for five com- puters on the network: 172.16.0.1 172.16.0.2 172.16.0.3 172.16.0.4 172.16.0.5 Note