Open Systems, Standards, and Protocols

Today I start looking at the subject of TCP/IP by covering some background information you will need to put TCP/IP in perspective, and to understand why the TCP/IP protocols were designed the way they are. This chapter covers some important information, including the following:
What an open system is
How an open system handles networking
Why standards are required
How standards for protocols like TCP/IP are developed
What a protocol is
The OSI protocols
You might be eager to get started with the nitty-gritty of the TCP/IP protocols, or to find out how to use the better-known services like FTP and Telnet. If you have a specific requirement to satisfy (such as how to transfer a file from one system to another), by all means use the Table of Contents to find the section you want. But if you want to really understand TCP/IP, you will need to wade through the material in this chapter. It's not complicated, although there are quite a few subjects to be covered. Luckily, none of it requires memorization; more often than not it is a matter of setting the stage for something else I discuss in the next week or so. So don't get too overwhelmed by this chapter!
Open Systems
This is a book about a family of protocols called TCP/IP, so why bother looking at open systems and standards at all? Primarily because TCP/IP grew out of the need to develop a standardized communications procedure that would inevitably be used on a variety of platforms. The need for a standard, and one that was readily available to anyone (hence open), was vitally important to TCP/IP's success. Therefore, a little background helps put the design of TCP/IP into perspective.
More importantly, open systems have become de rigueur in the current competitive market. The term open system is bandied around by many people as a solution for all problems (to be replaced occasionally by the term client/server), but neither term is usually properly used or understood by the people spouting them. Understanding what an open system really is and what it implies leads to a better awareness of TCP/IP's role on a network and across large internetworks like the Internet.
In a similar vein, the use of standards ensures that a protocol such as TCP/IP is the same on each system. This means that your PC can talk to a minicomputer running TCP/IP without special translation or conversion routines. It means that an entire network of different hardware and operating systems can work with the same network protocols. Developing a standard is not a trivial process. Often a single standard involves more than a single document describing a software system. A standard often involves the interrelationship of many different protocols, as does TCP/IP. Knowing the interactions between TCP/IP and the other components of a communications system is important for proper configuration and optimization, and to ensure that all the services you need are available and interworking properly.
What Is an Open System?
There are many definitions of open systems, and a single, concise definition that everyone is happy with is far from being accepted. For most people, an open system is best loosely defined as one for which the architecture is not a secret. The description of the architecture has been published or is readily available to anyone who wants to build products for a hardware or software platform. This definition of an open system applies equally well to hardware and software.
When more than a single vendor begins producing products for a platform, customers have a choice. You don't particularly like Nocrash Software's network monitoring software? No problem, because FaultFree Software's product runs on the Nocrash hardware, and you like its fancy interface much better. You need a more colorful graphical front-end to your Whizbang PC than the one Whizbang provides? Download one from Super Software through the Internet, and it works perfectly. The primary idea, of course, is a move away from proprietary platforms to one that is multivendor.
A decade ago, open systems were virtually nonexistent. Each hardware manufacturer had a product line, and you were practically bound to that manufacturer for all your software and hardware needs. Some companies took advantage of the captive market, charging outrageous prices or forcing unwanted configurations on their customers. The groundswell of resentment grew to the point that customers began forcing the issue. The lack of choice in software and hardware purchases is why several dedicated minicomputer and mainframe companies either went bankrupt or had to accept open system principles: their customers got fed up with relying on a single vendor. A good example of a company that made the adaptation is Digital Equipment Corporation (DEC). They moved from a proprietary operating system on their VMS minicomputers to a UNIX-standard open operating system. By doing that, they kept their customers happy, and they sold more machines. That's one of the primary reasons DEC is still in business today.
UNIX is a classic example of an open software platform. UNIX has been around for 30 years. The source code for the UNIX operating system was made available to anyone who wanted it, almost from the start. UNIX's source code is well understood and easy to work with, the result of 30 years of development and improvement. UNIX can be ported to run on practically any hardware platform, eliminating all proprietary dependencies. The attraction of UNIX is not the operating system's features themselves but simply that a UNIX user can run software from other UNIX platforms, that files are compatible from one UNIX system to another (except for disk formats), and that a wide variety of vendors sell products for UNIX.
The growth of UNIX pushed the large hardware manufacturers to the open systems principle, resulting in most manufacturers licensing the right to produce a UNIX version for their own hardware. This step let customers combine different hardware systems into larger networks, all running UNIX and working together. Users could move between machines almost transparently, ignorant of the actual hardware platform they were on. Open systems, originally of prime importance only to the largest corporations and governments, is now a key element in even the smallest company's computer strategy.
Although UNIX is a copyrighted work now owned by X/Open, the details of the operating system have been published and are readily available to any developer who wants to produce applications or hardware that work with the operating system. UNIX is unique in this respect.
The term open system networking means many things, depending on whom you ask. In its broadest definition, open system networking refers to a network based on a well-known and understood protocol (such as TCP/IP) that has its standards published and readily available to anyone who wants to use them. Open system networking also refers to the process of networking open systems (machaine-specific hardware and software) using a network protocol. It is easy to see why people want open systems networking, though. Three services are widely used and account for the highest percentage of network traffic: file transfer, electronic mail, and remote login. Without open systems networking, setting up any of these three services would be a nightmare.
File transfers enable users to share files quickly and efficiently, without excessive duplication or concerns about the transport method. Network file transfers are much faster than an overnight courier crossing the country, and usually faster than copying a file on a disk and carrying it across the room. File transfer is also extremely convenient, which not only pleases users but also eliminates time delays while waiting for material. A common open system governing file transfers means that any incompatibilities between the two machines transferring files can be overcome easily.
Electronic mail has mushroomed to a phenomenally large service, not just within a single business but worldwide. The Internet carries millions of messages from people in government, private industry, educational institutions, and private interests. Electronic mail is cheap (no paper, envelope, or stamp) and fast (around the world in 60 seconds or so). It is also an obvious extension of the computer-based world we work in. Without an open mail system, you wouldn't have anywhere near the capabilities you now enjoy.
Finally, remote logins enable a user who is based on one system to connect through a network to any other system that accepts him as a user. This can be in the next workgroup, the next state, or in another country. Remote logins enable users to take advantage of particular hardware and software in another location, as well as to run applications on another machine. Once again, without an open standard, this would be almost impossible.

Posted bySumedh at 7:22 AM  


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