North American Network Operators Group

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RE: DWDM interconnects

  • From: David Diaz
  • Date: Mon Jan 06 23:59:58 2003


Ive had an interesting offline thread.

Someone was asking how come carriers would need to stock so many lasers. If they have an 8 wave network he could not see why they would have to have a spare for each wave length in each region. I explained that without tunable lasers this was necessary. Usually the customer includes it in their contract with the vendor. The vendor stocks each card in a region such that they could have it onsite within 24hrs. The vendor then can have 1 space covering all customers in the region.

I was asked why could the carrier not just reroute the lost wave onto another one. Generally that was the question.

1st, yes with sonet, the carrier might have a traffic protected in a ring fashion. I would say this is a waste. Many customers may also have protection at a higher layer.

2nd, DWDM does not imply switching capability. So that you could not have traffic from one way just "move" over to another. DWDM transport gear just creates the waves and shots them down the line. Now, most next-gen gear coming out does have switching capabilities, OR the switch companies are including DWDM into the same box. That means yes, if u have DWDM fed (or combined) into a switch at most big points, you could remap the traffic onto a spare wave.

The only problem is, this protects ONLY a failure of a card or particular laser. Truth is it's far more likely we would see a fiber cut. In which case ALL those waves would have to be moved to spare capacity.

At this point it's pretty clear that unless you have 1 to 1 spare capacity someone is going to have to see an outage. Prioritizing kicks in at this point. Different service levels (ie Platinum, Gold, Lead) kick in. Most lead customers would likely not be protected at this point. But these may be simple backup links for those customers.

I got flamed last time, but I will just say: Good, Fast, Cheap... pick any 2.

I would love to see a Bill Norton type white paper on DWDM peering. What it would take etc. I know DWDM may not be up Bill's ally but I really thing we need to start hypothesizing about where we see this scaling.

David



At 21:17 -0700 1/6/03, brett watson wrote:
 -----Original Message-----
 From: [email protected] [mailto:[email protected]] On
 Behalf Of David Diaz
 Sent: Monday, January 06, 2003 5:24 PM
 To: [email protected]
 Subject: Re: DWDM interconnects

 Actually I forgot to mention.  Since we have different frequencies
 for the lasers, you and your peer would have to agree ahead of time
 and stock that particular frequency or "color."  IT's a major
 stocking nightmare especially for spares.  The real explosion may
 occur as tunable lasers drop in price that can allow 8 or more
 different frequencies.
there are nifty boxes out (have been for 8 months or so) that do
wavelength conversion.  so the box-operator in the middle handles the
wavelength map, and users on each end can all use the same lasers
(colors).  they were expensive at the time I looked but I would think
prices would have come down.

but yes, cheap tunables would be great.

-b

--

David Diaz
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www.smoton.net [Peering Site under development]
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