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<HTML><HEAD><TITLE>Chapter 11 -- How Converting IPX Networks to an Intranet Works</TITLE><META></HEAD><BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#0000EE" VLINK="#551A8B" ALINK="#CE2910"><H1><FONT SIZE=6 COLOR=#FF0000>Chapter 11</FONT></H1><H1><FONT SIZE=6 COLOR=#FF0000>How Converting IPX Networks toan Intranet Works</FONT></H1><HR><P><CENTER><B><FONT SIZE=5><A NAME="CONTENTS">CONTENTS</A></FONT></B></CENTER><UL><LI><A HREF="#HowConvertingIPXtoanIntranetWorks">How Converting IPX to an Intranet Works</A></UL><HR><P>It's rare that an entire intranet will be built completely fromscratch. It is more likely that an existing network, such as aNovell NetWare network, will be converted to an intranet. At acorporation there can be many networks already in existence beforean intranet comes in, often connected in a company-wide Wide AreaNetwork (WAN). There may be a variety of different network technologiesconnected to the WAN. One way of converting a network to an intranetis to take it piece by piece and convert individual departmentLANs to an intranet, and then build from there.<P>Often, the single most important factor in convincing a corporationto start an intranet is that people within the company will gainaccess to the Internet and its resources. So the first step increating the intranet will often be giving easy access to theInternet from an existing corporate network. It's much fasterfor people to get at the Internet over a network instead of havingto dial in via modem-and it also saves money in the long run.But when that Internet access is provided, it's also importantthat all the existing network services be maintained as well.<P>A simple solution is to have people run software needed both forthe existing network as well as for the Internet. Let's take aNetWare network as an example. In order to use NetWare and getaccess to its services such as electronic mail and others, computerson the network need to run the IPX (Internet Packet Exchange)protocol. Don't be confused about the name-IPX doesn't allow accessto the Internet, but instead to a NetWare network's resources.<P>When people want access to the Internet as well, they can runa <I>TCP/IP stack</I>-software that will allow them to accessthe Internet. The TCP/IP stack and IPX will both be running simultaneouslyon their computers. When they need to access a NetWare resource,IPX allows them to do it. When they want to access the Internet,TCP/IP does the job. The problem with this is that it is not assimple as it sounds because the protocol stacks take up considerablememory and sometimes there is not enough memory left to startapplications without unloading one of the protocols.<P>Internet requests go via TCP/IP to an intranet router, which isconnected to an Internet Service Provider via a Channel ServiceUnit/Data Service Unit (CSU/DSU). Especially in large companieswith many people on a network, this connection will be made viaa leased high-speed digital line, such as a T1 line. There needsto be a CSU/DSU and a router on the other end, and the requeststravel through them in reverse order, that is into the CSU/DSUand then to the router. The CSU/DSU units are used to assure qualitydigital signals over digital phone lines.<P>In this kind of setup, people can access an intranet as well asthe Internet. In this way, a company can slowly build up an intranetwhile keeping an existing Novell network. People on the networkwill be able to access intranet resources since they're runningTCP/IP stacks, and NetWare resources, since they're running IPX.<H2><A NAME="HowConvertingIPXtoanIntranetWorks"><FONT SIZE=5 COLOR=#FF0000>How Converting IPX to an Intranet Works</FONT></A></H2><P>Most intranets aren't built from scratch-many are existing networks,such as Novell NetWare, that have to be converted into an intranet.Often, the first step in moving toward an intranet is to giveInternet access to users on an existing network. At some laterpoint, intranet technology can then be brought inside the networkitself and it can be turned into an intranet. This illustrationshows that first step: how an existing network, such as a NetWare-basedone, can be given access to the Internet, yet still keep accessto the NetWare architecture.<OL><LI>When a computer on the network wants to connect to the Internetand request information from it, a request is sent to a routeron the intranet. This router will send the request to the properInternet destination.<LI>On a NetWare network, the NetWare operating system is usedto handle network traffic and administration. As a way to routepackets across the network, NetWare uses the IPX (Internet PacketExchange) protocol. Note that although IPX is called InternetPacket Exchange, it doesn't actually provide Internet access ortransport Internet information. Workstations attached to the NetWarenetwork-and servers on the network-need to have IPX loaded inmemory in order to use the network.<LI>In order for workstations on the Novell network to gain accessto the Internet or intranet, they need to run the TCP/IP protocolsthat form the basis of the Internet. To do that, a <I>TCP/IP stack</I>must be installed on each computer that will allow it to accessthe Internet. That means that each computer will have both IPXand a TCP/IP stack installed on it, to allow it to access theInternet as well as the Ethernet network. Basically, this resultsin "RAM cram" and is one of the biggest headaches foranyone trying to run both protocol stacks.<LI>A Channel Service Unit/Data Service Unit (CSU/DSU) makes thephysical connection between the intranet router and an InternetService Provider (ISP). The ISP provides the actual Internet connectionand services. A variety of digital lines can connect the CSU/DSUto the ISP, including a 56 Kbps leased line, a high-speed T1 line,or an even higher-speed T3 line.<LI>The requested information is sent back through the CDU/DSUand router, and is then routed to the computer that requestedthe information.<LI>If the information is instead located on an intranet insidethe company, the router will send the request to the proper host,which will then send the information back to the requester.<LI>Some products such as NetWare/IP will allow computers on aNetWare network to access both NetWare services and servers andthe Internet. That means they don't have to run both the IPX andTCP/IP protocols, eliminating the memory problems resulting fromthe multiple stacks.</OL><HR><CENTER><P><A HREF="ch10.htm"><IMG SRC="PC.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><A HREF="#CONTENTS"><IMG SRC="CC.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><A HREF="contents.htm"><IMG SRC="HB.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><A HREF="ch12.htm"><IMG SRC="NC.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><HR WIDTH="100%"></P></CENTER></BODY></HTML>?? 快捷鍵說明
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