CompTIA Network+ All-in-One Exam Guide in Software

Creation UPC-A Supplement 5 in Software CompTIA Network+ All-in-One Exam Guide

The early days of networking software saw several competing standards that did not work well together Novell NetWare, Microsoft Windows, and Apple Macintosh ran networking software to share folders and printers, while the UNIX/Linux world did crazy things like sharing terminals handy for the UNIX/Linux users, but it made no sense to the Windows folks and there was this new thing called e-mail (like that was ever going to go anywhere) The Internet had just been opened to the public The World Wide Web was just a plaything for programmers and scientists All of these folks made their own software, interpreting (or totally ignoring) the OSI model the way they wanted to, and all trying (arguably) to become THE WAY the whole world was going to network It was an unpleasant, ugly world for guys like me who had the audacity to try to make, for example, a UNIX box work with a Windows computer The problem was that no one agreed on how a network should run Everyone s software had its own set of Rules of What a Network Should Do and How to Do It These sets of rules and the software written to follow these rules were broken down into individual rules called protocols Each set of rules had many protocols lumped together under the term protocol suite Novell NetWare called its protocol suite IPX/SPX, Microsoft called its NetBIOS/NetBEUI, Apple called its AppleTalk, and the UNIX folks used this wacky protocol suite called TCP/IP Well, TCP/IP has won Sure, you may find the occasional network still running one of these other protocol suites, but they re rare these days To get ahead in today s world, to get on the Internet, and to pass the CompTIA Network+ exam, you only need to worry about TCP/IP Novell, Microsoft, and Apple no longer actively support anything but TCP/IP You live in a one-protocol-suite world, the old stuff is forgotten, and you kids don t know how good you got it! TCP/IP fits nicely into the OSI seven-layer model, occupying Layers 3 5: Network, Transport, and Session, respectively (Figure 7-1) Starting from the bottom up, the

Internet Protocol (IP) both version 4 (IPv4), which interests us here, and version 6 (IPv6), which is covered in the chapter of the same name, 13 stands by itself at Layer 3 IP handles all of the logical addressing issues The Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Control Message Protocol (ICMP) operate at the Transport and Session layers These protocols define how the connections take place between two computers All of these individual protocols work together to make the TCP/IP protocol suite

TCP/IP supports simple networks and complex networks You can use the protocol suite to connect a handful of computers to a switch and create a local area network (LAN) TCP/IP also enables you to interconnect multiple LANs into a wide area network (WAN) At the LAN level, all the computers use Ethernet, and this creates a hurdle for WANwide communication For one computer to send a frame to another computer, the sending computer must know the MAC address of the destination computer This begs the question: How does the sender get the recipient s MAC address In a small network this is easy The sending computer simply broadcasts by sending a frame to MAC address FF-FF-FF-FF-FF-FF, the universal MAC address for broadcast Figure 7-2 shows a computer broadcasting for another computer s MAC address Broadcasting takes up some of the network bandwidth, but in a small network it s acceptably small But what would happen if the entire Internet used broadcasting (Figure 7-3) In that case the whole Internet would come to a stop

I need to send this broadcast, but I don t know the MAC address Better broadcast!