One of the divisions in caching is between what I will call transparentand non-transparent caches. Transparent caches are ones where the onlything you are supposed to notice is faster speed; non-transparent cachesrequire you to manage them explicitly, especially cache invalidation.Operating system disk caches are an example of transparent caches, atleast in theory.

(At some level every cache is non-transparent, because it has to bemanaged by someone's code. So this is just a question of how a cache

It's not that complex software systems are inherently fragile for theusual reason, because they have more places and pieces to go wrongthan simple systems do; unlike physical machines, computer softwarehas no mechanical wear and thus doesn't just break on its own (barringintrinsic flaws). Living in a digital world, computer software thatworks keeps working forever until something changes.

The real problem with complex systems is that it's very hard for peopleto keep track of all of the interrelationships, and thus

Using DHCP to assign IP addresses is pretty popular in environments withlots of machines. You'd think that student labs, full of generic machines,would thus be a great environment for DHCP, but actually I disagree; Ibelieve that (normal) DHCP is not a great match for a lab environment.

The problem with DHCP is that it ties the IP address to the wrongthing. In a lab environment you don't want a machine's IP addressto be tied to its hardware; you want

In the spirit of previous cleverness ,here's a simple new technique:

Have your web spider make up random Referer headers.

This wasn't Referer spamming, since the websites in the Referer headerswere completely random URLs, apparently drawn from legitimate sitesaround the Internet (often repeated). Nor were the websites ones thatactually linked to us, or had any relationship to the URLs that werebeing crawled.

Even in low volume this is a sure-fire ticket to our kernel level IPfilters, since it