On Wed, 9 Jun 2004, Cameron Kerr wrote:
Is this a trick question? The answer, naturally, is money, more specifically, it is far cheaper (essentially free) to serve something from an ISPs local cache than to request it all over again. This way, the ISP `earns' (saves) money, plus it has the very real potential to be faster when hit from cache (though I doubt that is the primary motivation for using transparent proxying in an ISP environment.
Many times however, when you check the bandwidth in vs. the bandwidth out the saving is minimal if you are only doing light cacheing. While it is possible to override "dont cache" headers and expiry times on web sites this will more than likely break dynamic content and requires a lot more work to maintain lists of dynamic pages that break when the cache headers are overridden hence driving up the costs such that the "savings" in bandwidth are artificial. -- Steve.