Check your CMOS settings to make sure they’re correct. See your computer’s documenta-

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