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too easy to come up with some technical mumbo jumbo if they are ever questioned. If this seems far-fetched, I once attended a meeting where a young engineer was arguing
that a particular router needed to be replaced before it became a bottleneck. He had picked out the ideal replacement, a hot new box that had just hit the market. The problem with all
this was that I had recently taken measurements on the router and knew the average utilization of that bottleneck was less than 5 with peaks that rarely hit 40.
This is an extreme example of why collecting information is the essential first step in network management and troubleshooting. Without accurate measurements, you can easily
spend money fixing imaginary problems.
1.3.2.4 Economic considerations
Solutions to problems have economic consequences, so you must understand the economic implications of what you do. Knowing how to balance the cost of the time used to repair a system
against the cost of replacing a system is an obvious example. Cost management is a more general issue that has important implications when dealing with failures.
One particularly difficult task for many system administrators is to come to terms with the economics of networking. As long as everything is running smoothly, the next biggest issue to upper management
will be how cost effectively you are doing your job. Unless you have unlimited resources, when you overspend in one area, you take resources from another area. One definition of an engineer that I
particularly like is that an engineer is someone who can do for a dime what a fool can do for a dollar. My best guess is that overspending and buying needlessly complex systems is the single most
common engineering mistake made when novice network administrators purchase network equipment.
One problem is that some traditional economic models do not apply in networking. In most engineering projects, incremental costs are less than the initial per-unit cost. For example, if a 10,000-
square-foot building costs 1 million, a 15,000-square-foot building will cost somewhat less than 1.5 million. It may make sense to buy additional footage even if you dont need it right away. This is
justified as buying for the future.
This kind of reasoning, when applied to computers and networking, leads to waste. Almost no one would go ahead and buy a computer now if they wont need it until next year. Youll be able to buy a
better computer for less if you wait until you need it. Unfortunately, this same reasoning isnt applied when buying network equipment. People will often buy higher-bandwidth equipment than they need,
arguing that they are preparing for the future, when it would be much more economical to buy only what is needed now and buy again in the future as needed.
Moores Law lies at the heart of the matter. Around 1965, Gordon Moore, one of the founders of Intel, made the empirical observation that the density of integrated circuits was doubling about every 12
months, which he later revised to 24 months. Since the cost of manufacturing integrated circuits is relatively flat, this implies that, in two years, a circuit can be built with twice the functionality with no
increase in cost. And, because distances are halved, the circuit runs at twice the speed—a fourfold improvement. Since the doubling applies to previous doublings, we have exponential growth.
It is generally estimated that this exponential growth with chips will go on for another 15 to 20 years. In fact, this growth is nothing new. Raymond Kurzweil, in The Age of Spiritual Machines: When
Computers Exceed Human Intelligence, collected information on computing speeds and functionality from the beginning of the twentieth century to the present. This covers mechanical, electromechanical
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relay, vacuum tube, discrete transistor, and integrated circuit technologies. Kurzweil found that exponential growth has been the norm for the last hundred years. He believes that new technologies
will be developed that will extend this rate of growth well beyond the next 20 years. It is certainly true that we have seen even faster growth in disk densities and fiber-optic capacity in recent years, neither
of which can be attributed to semiconductor technology.
What does this mean economically? Clearly, if you wait, you can buy more for less. But usually, waiting isnt an option. The real question is how far into the future should you invest? If the price is
coming down, should you repeatedly buy for the short term or should you invest in the long term?
The general answer is easy to see if we look at a few numbers. Suppose that 100,000 will provide you with network equipment that will meet your anticipated bandwidth needs for the next four years.
A simpleminded application of Moores Law would say that you could wait and buy similar equipment for 25,000 in two years. Of course, such a system would have a useful life of only two
additional years, not the original four. So, how much would it cost to buy just enough equipment to make it through the next two years? Following the same reasoning, about 25,000. If your growth is
tracking the growth of technology,
[4]
then two years ago it would have cost 100,000 to buy four years worth of technology. That will have fallen to about 25,000 today. Your choice: 100,000 now or
25,000 now and 25,000 in two years. This is something of a no-brainer. It is summarized in the first two lines of
Table 1-1 .
[4]
This is a pretty big if, but its reasonable for most users and organizations. Most users and organizations have selected a point in the scheme of things that seems right for them—usually the latest technology they
can reasonably afford. This is why that new computer you buy always seems to cost 2500. You are buying the latest in technology, and you are trying to reach about the same distance into the future.
Table 1-1. Cost estimates Year 1
Year 2 Year 3 Year 4 Total
Four-year plan
100,000 0 0 0 100,000 Two-year
plan 25,000
0 25,000 0 50,000
Four-year plan with maintenance 112,000 12,000 12,000 12,000 148,000
Two-year plan with maintenance 28,000 3,000 28,000 3,000 62,000
Four-year plan with maintenance and 20 MARR 112,000 10,000 8,300 6,900 137, 200
Two-year plan with maintenance and 20 MARR 28,000 2,500 19,500 1,700 51,700
If this argument isnt compelling enough, there is the issue of maintenance. As a general rule of thumb, service contracts on equipment cost about 1 of the purchase price per month. For 100,000, that is
12,000 a year. For 25,000, this is 3,000 per year. Moores Law doesnt apply to maintenance for several reasons:
•
A major part of maintenance is labor costs and these, if anything, will go up.
•
The replacement parts will be based on older technology and older and higher prices.
•
The mechanical parts of older systems, e.g., fans, connectors, and so on, are all more likely to fail.
•
There is more money to be made selling new equipment so there is no incentive to lower maintenance prices.
Thus, the 12,000 a year for maintenance on a 100,000 system will cost 12,000 a year for all four years. The third and fourth lines of
Table 1-1 summarize these numbers.
TE AM
FL Y
Team-Fly
®
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Yet another consideration is the time value of money. If you dont need the 25,000 until two years from now, you can invest a smaller amount now and expect to have enough to cover the costs later. So
the 25,000 needed in two years is really somewhat less in terms of todays dollars. How much less depends on the rate of return you can expect on investments. For most organizations, this number is
called the minimal acceptable rate of return MARR. The last two lines of
Table 1-1 use a MARR of
20. This may seem high, but it is not an unusual number. As you can see, buying for the future is more than two and a half times as expensive as going for the quick fix.
Of course, all this is a gross simplification. There are a number of other important considerations even if you believe these numbers. First and foremost, Moores Law doesnt always apply. The most
important exception is infrastructure. It is not going to get any cheaper to pull cable. You should take the time to do infrastructure well; thats where you really should invest in the future.
Most of the other considerations seem to favor short-term investing. First, with short-term purchasing, you are less likely to invest in dead-end technology since you are buying later in the life cycle and will
have a clearer picture of where the industry is going. For example, think about the difference two years might have made in choosing between Fast Ethernet and ATM for some organizations. For the
same reason, the cost of training should be lower. You will be dealing with more familiar technology, and there will be more resources available. You will have to purchase and install equipment more
often, but the equipment you replace can be reused in your networks periphery, providing additional savings.
On the downside, the equipment you buy wont have a lot of excess capacity or a very long, useful lifetime. It can be very disconcerting to nontechnical management when you keep replacing
equipment. And, if you experience sudden unexpected growth, this is exactly what you will need to do. Take the time to educate upper management. If frequent changes to your equipment are particularly
disruptive or if you have funding now, you may need to consider long-term purchases even if they are more expensive. Finally, dont take the two-year time frame presented here too literally. Youll
discover the appropriate time frame for your network only with experience.
Other problems come when comparing plans. You must consider the total economic picture. Dont look just at the initial costs, but consider ongoing costs such as maintenance and the cost of periodic
replacement. As an example, consider the following plans. Plan A has an estimated initial cost of 400,000, all for equipment. Plan B requires 150,000 for equipment and 450,000 for infrastructure
upgrades. If you consider only initial costs, Plan A seems to be 200,000 cheaper. But equipment needs to be maintained and, periodically, replaced. At 1 per month, the equipment for Plan A would
cost 48,000 a year to maintain, compared to 18,000 per year with Plan B. If you replace equipment a couple of times in the next decade, that will be an additional 800,000 for Plan A but only 300,000
for Plan B. As this quick, back-of-the-envelope calculation shows, the 10-year cost for Plan A was 1.68 million, while only 1.08 million for Plan B. What appeared to be 200,000 cheaper was really
600,000 more expensive. Of course, this was a very crude example, but it should convey the idea.
You shouldnt take this example too literally either. Every situation is different. In particular, you may not be comfortable deciding what is adequate surplus capacity in your network. In general, however,
you are probably much better off thinking in terms of scalability than raw capacity. If you want to hedge your bets, you can make sure that high-speed interfaces are available for the router you are
considering without actually buying those high-speed interfaces until needed.
How does this relate to troubleshooting? First, dont buy overly complex systems you dont really need. They will be much harder to maintain, as you can expect the complexity of troubleshooting to grow
with the complexity of the systems you buy. Second, dont spend all your money on the system and
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forget ongoing maintenance costs. If you dont anticipate operational costs, you may not have the funds you need.
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Chapter 2. Host Configurations
