From tony1@home.net Tue Oct 26 05:39:16 1999 Date: Mon, 25 Oct 1999 22:13:35 -0700 From: Tony Li <tony1@home.net> To: Alex P. Rudnev <alex@virgin.relcom.eu.net> Cc: Vadim Antonov <avg@kotovnik.com>, abender@tns-inc.com, akyol@pluris.com, nanog@merit.edu Subject: Re: Traffic engineering tools
Alex,
You are absolutely correct. A critically damped, dynamic traffic engineering system would provide benefits above and beyond that which can be derived in a static system.
However, the dynamic system is non-trivial to construct. As has been shown with routing protocols that react to dynamic changes, it is very easy to underdamp the system, with catastrophic results.
I certainly believe that such dynamic systems are possible, and certainly folks with enough background in control theory could contribute wonderfully here. However, the state of the art isn't quite there yet. Sigh.
"And that's the way it is..." - Walter Cronkite
Hear, hear! Beside simply solving the static minimization problem, decentralized computation, and consideration of disjoint restoration paths are what I see to be necessary prerequisites ( and arguably quite "interesting" ones ) for the realization of dynamic TE. Evading these is something that we seem to have succeeded at, as engineers. As "easy" as it may be to prove the computational complexity of a problem, I find offense instead in equating such a result with a decisive judgement on practical tractability. I agree with Mr. Li that this is an approachable domain, although many of its challenges remain areas of active interest. The design of contemporary network elements suggests the unfortunate level of attention this topic receives. Despite impressive improvements in datapath, equipment control planes still seem to be sized / designed for maintenance of traditional topologies with established methods. 1000MIPS* integer cores are readily available in general purpose, commodity devices, and higher performance is neither impractical nor unknown. The possibilities this suggests for performance headroom of control systems should permit more serious consideration of practical solutions for dynamic TE than is observed today, dispensing with easy reasons not to implement path otimization or TE as a (semi-) automated, online function. Regards, Andrew Bender Total Network Solutions, Inc. (* Yes, this metric is an arbitrary and somewhat bogus oversimplication)