Good point re the changing patterns over time. Traffic engineering is not a one time activity, but something you should expect to do once a quarter. Measurement, trendline analysis, projections, and verifying the accuracy of the projections, and determining the reasons for inaccurate projections are all important parts of the process. In this way, traffic engineering is akin to writing a company's business plan--a dynamically changing document that helps you make decisions, rather than set in stone and oblivious to the outside world. Prabhu ______________________________ Reply Separator _________________________________ Subject: Re: Traffic Engineering Author: "Kent W. England" <kwe@geo.net> at smtplink Date: 9/17/97 10:19 AM At 09:59 AM 9/17/97 -0500, pkavi@pcmail.casc.com wrote:
As a former network design guy who's done traffic engineering and design (and redesign) on many networks (Internet and otherwise), I disagree that traffic engineering doesn't work for the Internet.
Prabhu; Thanks for the treatise on network engineering. I agree that network engineering is useful and that there should be traffic engineers. However, the engineering managers must not forget to see the forest for the trees and must heavily discount the traffic engineering studies, when faced with out-of-the-box data. Here are some examples:
2. Identify which % of traffic, if any, has regional locality. For pure Internet traffic, the probability that the source and destinatino of traffic are within the same metropolitan area tends to be low (10% or lower for metros within the US).
This is true only so long as the density of the Internet is low. This is so because so long as the density is low, few of your neighbors will be on the Internet and therefore local issues are irrelevant. However, at some point, the density of the Internet gets to a critical point, say 30% to 40%. At that point a pizza parlor owner says to himself "two out of every five of my customers are on the Internet. Perhaps I need a web page." And, suddenly, pizza on the Net makes a lot of sense and the traffic patterns shift. As the density grows to 90%, local traffic becomes dominant over distant traffic. Another example is distributed web hosting. When distributed web hosting takes off, your backbone will be heavily discounted and your peripheral interconnect bandwidth will be woefully short. Web traffic will zoom as performance dramatically improves, but your backbone bandwidth will drop. That breaks your traffic model. So, by all means, do your traffic studies, but be prepared to throw them out or re-write them when the environment changes. Then throw bandwidth where it will do the most good. :-) --Kent