Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Part One
Introduction to the TCP/IP Protocol

Chapter 1
Transmission Control Protocol/Internet Protocol

The TCP/IP protocol suite is being used for communications, whether for voice, video, or data. There is a new service being brought out for voice over IP at a consumer cost of 5.5 cents per minute. Radio broadcasts are all over the Web. Video is coming, but the images are still shaky and must be buffered heavily before displaying on the monitor. However, give it time. All great things are refined by time, and applications over TCP/IP are no exception.

Today, you will not find too many data communications installments that have not implemented or have not thought about the TCP/IP protocol. TCP/IP is becoming so common that it is not so much a matter of selecting the TCP/IP protocol stack as it is selecting applications that support it. Many users do not even know they are using the TCP/IP protocol. All they know is that they have a connection to the Web, which many people confuse with the Internet. We’ll get into the details of the differences later, but for now, you just need to understand that the Web is an application of the Internet. The Web uses the communications facilities of the Internet to provide for data flow between clients and servers. The Internet is not the Web and the Web is not the Internet.

In the 1970s, everyone had some type of WANG machine in their office. In the 1980s and early 1990s, Novell’s NetWare applications consumed every office. Today, NetWare continues to dominate the network arena with its installed based of client/server network applications. However, the TCP/IP protocol and Internet browsers, such as NetScape’s Navigator and Microsoft’s Internet Explorer, and Web programming languages are combining to produce powerful corporate networks known as intranets, which mimic the facilities of the Internet but on a corporate scale. Intranets from different companies or simply different sites can communicate with each other through the Internet. Consumers can access corporate intranets through an extranet, which is simply part of the corporate intranet that is available to the public. A great example of this is electronic commerce, which is what you use when you purchase something via the Internet. Directory services are provided through Domain Name Services (DNSs) Microsystems. File and print services are provided in many different ways. Finally, the ultimate in full connectivity is the Internet, which allows the corporate intranets to interconnect (within the same corporation or different corporations), providing global connectivity unmatched by any network application today. Therefore, within a short time (possibly 1998), very powerful applications will be built that utilize the TCP/IP software suite that will eventually rival NetWare at the core.

Another key factor of TCP/IP is extensibility. How many people can you name that use NetWare out of their house to allow for corporate connectivity or for commercial connectivity? Yes, programs such as remote node and remote control allow for NetWare clients to be accessed remotely, but not as seamlessly as with TCP/IP. TCP/IP allows you to move your workstation to any part of the network, including dialing in from any part of the world, and gain access to your network or another network. This brings up another point: How many networks interact using NetWare? Theoretically, with TCP/IP you can access (excluding security mechanisms for now) any other TCP/IP network in the world from any point in the world. Addressing in TCP/IP is handled on a global scale to ensure uniqueness. Novell attempted global addressing but failed. Novell addresses are unique to each private installation, such as a single company, but are probably massively duplicated when taken as a whole (all installations). I know many installations with the Novell address of 1A somewhere in their network. Not everyone is going to renumber their network for uniqueness, but one trick is to match the 32–bit address of TCP/IP subnets to your Novell network. Convert each octet of the 32–bit address of TCP/IP into hex and use that as your NetWare address.

Novell has entered the TCP/IP fray with its IntranetWare and support for native IP. IntraNetWare allows NetWare workstations to access TCP/IP resources. As of version 5.0, IntraNetWare is going away in name only and another version of NetWare is supposed to allow for NetWare to run directly on top of TCP/IP (this is known as native TCP/IP support).

Microsoft and its emerging NT platform can also use TCP/IP as a network protocol. Two flavors are available:

•  Native TCP/IP and its applications (TELNET, FTP, etc.)

•  RFC compliant (RFC 1001 and 1002) TCP, which allows file and print service

This enables the ability to telnet from an NT server or workstation and transfer files to that workstation or server using native TCP/IP. For file and print services in a TCP/IP environment, NT can be configured to use NetBIOS over TCP/IP. This enables NT to be involved in a routed network. NT can run many other protocols as well, but that is beyond the scope of this book.

However, this does not mean that the other protocols (beyond TCP/IP) are being disbanded. Novell NetWare continues to run with the IPX protocol. As of this writing, NetWare is still the best constructed client server platform available. Tens of thousands of programs have been written directly to the NetWare interface and it is used in corporate networks, schools, and state, local, and federal governments. These users are not going to disconnect their NetWare networks and move to TCP/IP over night. NetWare will be around for a great length of time, albeit in a diminishing role (start the arguments!).

Most Fortune 1000 companies still depend on large mainframes for their day–to–day processing. The early 1990s and late 1980s were interesting times when many corporations were convinced that smaller Unix platforms using a distributed (client/server) architecture could replace their “antiquated” SNA networks. Wrong! Although some networks have converted to this architecture, many have not. There are many factors involved here. Time and money play an important role, but the rule continues to be, “if it ain’t broke, don’t fix it.” Huge applications such as the airline reservation system and the banking system are built using the SNA architecture, and even if a perfect solution is found, it will take years to convert these programs over to a new system. SNA is still being used, and I have even supported some sites that have reverted back to SNA mainframes, which were best suited to their particular situation. Today, there are Web servers that front IBM mainframes as well. IBM fully supports the TCP/IP protocols and there is a 3270 terminal emulation program known as TN3270 that allows for 3270 terminal emulation over the TCP/IP protocol. All of this is beyond the scope of this book, but remember, TCP/IP is very popular; however, protocol schemes are still in existence, still provide many benefits, and will continue to be used for years to come.

From this, one would tend to think that the TCP/IP protocol was developed by a large–scale R&D center like that of IBM or DEC. It wasn’t. It was developed by a team of research–type people, comprised of college professors, graduate students, and undergraduate students from major universities. This should not be hard to believe. These individuals are the type who not only enjoy R&D work, but also believe that, when problems occur, the fun starts.

Many years from now we will look back on the TCP/IP protocol as the protocol that provided the building blocks of future data communications. However, take notice: TCP/IP is an extensible protocol. It is fully functional today, but the work on the project continues. There are over 75 working groups of the Internet Engineering Task Force (IETF, explained in a moment), and as new needs continue to arise for the Internet, new working groups are formed and new protocols will emerge. In fact, the IP version of the existing protocol (known as IPv4, or IP version 4) will be replaced. IP version 6 (IPv6) is currently being implemented around the Internet. It will be a few years before a complete switchover takes place, but it is a great example of the extensible protocol.