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Not to beat a dead horse but a few more thoughts on bandwidth
From: David Farber <dave () farber net>
Date: Tue, 3 Jan 2006 19:45:02 -0500
Begin forwarded message: From: "Jonathan M. Smith" <jms () central cis upenn edu> Date: January 3, 2006 7:08:37 PM EST To: dave () farber net Cc: "Jonathan M. Smith" <jms () central cis upenn edu> Subject: Not to beat a dead horse but a few more thoughts on bandwidth Dave: I really enjoyed that discussion and it brought a few more thoughts. First, an old rule of thumb in systems design (I may have learned this from you): accountants care about throughput, users care about response time. Second, something we thought about in the Gigabit Testbed effort quite explicitly (e.g., in John Shaffer's PhD thesis) was the relationship between these two things, which is roughly that the response time (to get an object) is propagation time + (object size) / throughput. Third, the object sizes, due to both Moore's Law (memory sizes are typically the fastest-rising exponential) and consumer demand (e.g., Mpixels on digital cameras), are increasing rapidly. The speedups we achieved with the testbed program achieved usability, as I mentioned in a previous e-mail on this topic. The takeaway from the response time relationship however, is that an increase in throughput commensurate with increases in memory and object sizes will be necessary to maintain the present state of affairs, and a trajectory of even greater throughput improvements will be necessary for increased usability. Best, -JMS------------------------------------------------------------------------ -
Jonathan M. Smith Olga and Alberico Pompa Professor of Engineering and Applied ScienceProfessor of Computer and Information Science, University of Pennsylvania
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- Not to beat a dead horse but a few more thoughts on bandwidth David Farber (Jan 03)