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Re: Do ATM-based Exchange Points make sense anymore?

  • From: David Diaz
  • Date: Sun Aug 11 18:28:27 2002


Paul just hit on it. At how many layers do you want protection, and will they interfere with each other. Granted not all protection schemes overlap. If there if not a layer 1 failure, and a router maintains link0 but the card or routers has somehow failed and is no longer passing packets, I suppose that would have to be caught at layer 3.

At an (MAN) exchange pt based in S. Fl, the technology is a multi-node area exchange point (layer 1 technology) based on dwdm and optical switches. The detection of nodes and failures is done with enhanced-OSPF. On testing, failure between the farthest two nodes and recovery took 16ms (approx 95miles dist btw nodes).

Each individual circuit has a choice of protection level. This allows for no protection for any of a number of reasons. One may be to not interfere with a protection scheme at a higher level. While the switches do use OSPF for detection and recovery, they also use MPLS for reservation of bandwidth. None of this information is passed onto the customer routers however.

It seems there should be a clear delineation btw the layers and what protection schemes should run at each. I also believe in separation of church and state if u will, router companies should play in their space while optical companies show stay in theirs. While it makes sense for some information to pass btw differing types of equipment (such as ODSI protocol or UNI 1.0) integration of the protection schemes runs a high degree of a cascade failure, or susceptibility to an exploit attach.

As an added thought, the same MAN exchange point can do intranode connections (hairpinning). So that the same node that is used in internodal transport and peering, can also be used within a colo as an intelligent cross-connect box. This would allow for visibility and monitoring within the colo and even customer network management of their cross connects.

I suppose the discussion is what do you want from your exchange pt operator and what do you NOT want. Many people would not feel comfortable that circuit operators have visibility and maintain stats on even NUMBER of packets passed....

dd

At 9:21 +0000 8/10/02, Paul Vixie wrote:
warning: i've had one "high gravity steel reserve" over my quota.  hit D now.

The issue I'm trying to address is to figure out how to extend the robustness
that can be achieved with tuned IGP's with subsecond convergence across
an exchange point without suffering a one to five minute delay blackholing
packets.
why on god's earth would subsecond anything matter in a nonmilitary situation?

are you willing to pay a cell tax AND a protocol complexity tax AND a device
complexity tax to make this happen?  do you know what that will do do your
TCO and therefore your ROI?  you want to pay this tax 100% of the time even
though your error states will account for less than 0.001% of the time?  you
want to have the complexity as your most likely source of (false positive)
error?

 As far as I understand, this "complexity" just got added with Neighbor
 Discovery on IPv6.
if so, then, you misunderstand.
--
Paul Vixie
--

David Diaz
dave@smoton.net [Email]
pagedave@smoton.net [Pager]
Smotons (Smart Photons) trump dumb photons






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