Traffic Engineering

pkavi at pkavi at
Wed Sep 17 20:33:06 UTC 1997

     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.

______________________________ Reply Separator _________________________________
Subject: Re: Traffic Engineering
Author:  "Kent W. England" <kwe at> at smtplink
Date:    9/17/97 10:19 AM

At 09:59 AM 9/17/97 -0500, pkavi at 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.
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.  :-)

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