Abstract
This chapter provides TCP/IP foundational knowledge including TCP/IP definitions, Microsoft’s implementation of TCP/IP, detailed analysis of TCP and IP, definition and application of Windows Sockets, and NT Server basic routing.
In This Chapter Defining TCP/IP Microsoft’s implementation of TCP/IP A detailed analysis of TCP A detailed analysis of IP Windows Sockets—definition and application Windows NT Server basic routing
Did you ever wonder what the payoff was from years of US military expenditures? Was it $200 wrenches and other doo-dads publicly highlighted by former Senator William Proxmire and his “Golden Fleece” awards? No, two of the great payoffs from the huge military buildup that spanned generations were Transmission Control Protocol/Internet Protocol (TCP/IP) and the Internet itself. Not only has TCP/IP become a de facto standard for internetworking, it is also the default protocol for Windows NT Server.
As I prepared this chapter, I promised myself that I wouldn’t drone on about the history of the Internet, Request for Comments, and other historical hooey that have been covered in far too many books. In fact, I made two assumptions in designing this chapter. First, that you are not a newbie, you know the definition of TCP/IP and have other thicker and more technical resources dedicated specifically to TCP/IP. Second, that perhaps like I, you have trouble sitting still when the going gets boring, so if the presentation of TCP/IP (which can be very dry) isn’t exciting, then you will drift away and miss the finer points about TCP/IP that are important to catch. Call it attention deficit disorder, but you have my assurance that I’ll cut to the chase and tell you what you need to know about using TCP/IP with Windows NT Server 4.0. That said, may I take just a few pages to set the foundation for our TCP/IP discussion?
ABOUT TCP/IP
Although TCP/IP’s popularity can in part be traced to darn good publicity, it is also an efficient routable protocol robust enough to perform well on large corporate networks. Network engineers now favor TCP/IP because it is scalable from the smallest node (a single workstation running TCP/IP for dial-up Internet access) to a LAN and even a worldwide enterprise WAN. Developers know that TCP/IP has an important role in their lives as they develop client/server WinSock-compliant applications at the upper layers of the OSI model.
Remember the golden rule of TCP/IP: It’s a good fit and truly you could say one size fits all when discussing protocols.
So important is TCP/IP area that a grassroots movement has arisen within the MCSE certification community to have it included as a “core” exam for the MCSE track. And with good reason. Perhaps no greater paradigm shift has occurred in network computing than the early/mid-90s shift to the Internet and use of the TCP/IP protocol. Not only did the move to the Internet catch many (including Microsoft) off guard, but the rapid acceptance of the TCP/IP protocol left more than one from the Novell camp (and the IPX world) briefly concerned about their job prospects.
The standard-bearer
Transmission Control Protocol/Internet Protocol (TCP/IP) has emerged as the standard protocol for not only networked personal computers but also stand-alone computers that access the Internet. Close to celebrating its thirtieth birthday, TCP/IP was developed in 1969 at the height of the antiwar protests by the Department of the Defense. It was part of the experiment that created ARPANET, which became the Internet as we know it.
Tip: The key point to remember about TCP/IP is that it is routable, is scalable, connects unlike systems via FTP and Telnet, and was designed for use with wide area networks (or internets). Equally important today, don’t forget that TCP/IP was designed for use with the Internet.
Additionally, TCP/IP is an “enabling” or foundation technology that not only supports Internet connectivity but also Point to Point Protocol (PPP), Point to Point Tunneling Protocol (PPTP) and Windows Sockets. PPP and PPTP will be discussed later in this section of the book.
Note: Uppercase “Internet” refers to the global Internet that millions use and enjoy. Lowercase “internet” refers to a private wide area network connected via routers.
Developers can rejoice because Microsoft’s implementation of TCP/IP supports the Windows Sockets interface, a Windows-based implementation of the Berkeley Sockets interface for network programming (a widely used standard). Thus, developers (in general) find Microsoft’s TCP/IP to be a robust, scalable cross-platform client/server framework that they can achieve success with.
By committee: Requests for Comments (RFCs)
A popular moniker in professional basketball in the late 1990s is to say “we win by committee.” That is, everyone contributed to the effort. Well, you could say everyone contributed to the effort to develop the TCP/IP protocol suite, but more important, everyone has contributed to effort to maintain it. These contributions come in the form of Requests for Comments (RFCs). These documents go a long way toward helping both developers and network engineers alike understand both the TCP/IP protocol suite and the Internet itself. Indeed, unlike the media shy, those of us that spend significant time in the TCP/IP community are very interested in “comments” related to implementing TCP/IP.
The standards setting process is managed by the Internet Activities Board (IAB). This is a committee that is responsible for not only setting Internet standards but controlling the publication of RFCs. Two groups are governed by the IAB: the Internet Engineering Task Force (IETF) and the Internet Research Task Force (IRTF). Whereas the IRTF coordinates all TCP/IP research projects and the like, the IETF focuses on Internet problems and solutions. RFCs are officially published by the IETF with input from the parent organization (IAB), the IRTF, and contributors like you and me.
In fact, anyone in the networking and development communities can contribute to the TCP/IP standard-making process. Just submit a document as an RFC to the Internet Engineering Task Force (IETF). Crazy? You bet. But it’s true. The RFC that you submit might just cut the mustard and become “published” after extensive editorial review, testing, and consensus among the powers that be.
Secret: Many companies in the software and technology field contribute significant resources to having their implementations of protocols and other networking and developer features adapted as standards by industry boards like the IETF. Although it is “possible” to contribute to the TCP/IP RFC process, in reality, this is the world of corporate-level software engineers from companies like HP, IBM, and Microsoft. Standards implemented via the consensus method in place for TCP/IP RFCs have survived a very political process (and not necessarily of the Justice Department variety).
Likewise, a manufacturer may elect to implement certain RFCs and ignore others. Table 4-1 shows the full set of RFCs that make up the Microsoft’s implementation of the TCP/IP protocol suite.
Tip: If you want to track RFC activity in the TCP/IP and Internet communities, point your browser to review the IAB-published quarterly memo titled “IAB Official Protocol Standard.” Here you will receive the current RFC status for each “protocol” in the TCP/IP protocol suite. You may also download the RFCs from this site.
Note that the IAB home page is now housed within the School of Engineering at the University of Southern California (see Figure 4-1). To be honest, those who are newer to Windows NT Server may not be as interested in RFC and visiting the IAB home page as those who have worked in the industry for longer periods of time. Why? My observation is that the longer you’ve been working with networks, the more interested you are in expanding your horizons beyond just the Windows NT Server NOS. If that is true, then RFCs are a great place to start that expansion.
To obtain RFCs via FTP or e-mail, send an e-mail message to with the subject “getting rfcs” and the message body “help: ways_to_get_rfcs.” You may also obtain RFCs via FTP at the following FTP sites:
NIS.NSF.NET
NISC.JVNC.NET
VENERA.ISI.EDU
WUARCHIVE.WUSTL.EDU
SRC.DOC.IC.AC.UK
DS.INTERNIC.NET
NIC.DDN.MIL
It’s a suite, not just a protocol
It’s essential to understand that TCP/IP is a protocol suite that spans several layers of the OSI model. It is incorrect to think of TCP/IP as a protocol in a singular sense; for example, it’s not just a networking layer protocol. In fact, TCP/IP doesn’t even map well to the OSI model; it’s based on an alternate networking model called the DOD model (that’s for Department of Defense). It is also known as the Internet Protocol Suite. Whereas the OSI model has seven layers, the DOD model has four layers that map to the seven layers of the OSI model as shown in Figure 4-2.
It is interesting to note that:
The DOD application layer maps to the upper three layers of the OSI model (application, presentation, session). This is where you find TCP/IP applications such as Telnet. It is also the home of Windows Sockets and NetBIOS.
The transport layer is simple. The DOD model and the OSI model map directly to each other. Here is where TCP and UDP reside. Tip: Remember that TCP is connection-oriented and guaranteed. UDP is connectionless and doesn’t guarantee delivery.
The DOD “Internet” layer maps directly to the OSI network layer. Here you find IP, ARP, ICMP, and so on.
At the bottom of the DOD model, we have the network interface. This layer maps to the OSI’s data link and physical layers.
The DOD model provides a comparative framework for understanding TCP/IP in other contexts than the OSI model. That is clearly understood from the points just covered. But, as an MCT instructor, I still enjoy the predictable question of “How does it apply to me” from my MCSE students. Granted, certification students quickly lose interest in a subject if they can’t see its relevance. Regarding the DOD discussion, you can see that TCP/IP packets captured on a Windows NT Server network reference the DOD model (see the Ethernet Type line in Figure 4-3).
Basically it is important to understand the underlying models that can be used to describe the TCP/IP protocol suite and how it is implemented. When working with peers from the Windows NT Server community, you will find that it is assumed you know this stuff. If you don’t at least understand the basics, you’ll quickly be lost in the proverbial ether.
Comparing TCP/IP to operating systems
Unfortunately, one thing neither the OSI or DOD model will do for you is conceptually map TCP/IP to the underlying operating system on your computer. That is because both the OSI and DOD models are oriented toward explaining communications models via a layering approach. A ring model describes the world of operating systems starting basically with the Kernel (see Figure 4-4).
With the operating system “ring” model, note that the Kernel is in Ring 0 and applications run in Ring 3. Do you know what the difference between running code in Ring 0 and Ring 3 is? Hint: Ring 3 has protected memory space for applications; Ring 0 is very fast!
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Defining TCP/IP
is now housed within the School of Engineering at the University of Southern California (see 