[c-nsp] ONSs, DWDM SFPs, and the 3560/3750E

[Justin Shore]

So I'm working on a solution involving a pair of 15454s to transport 
numerous GigE links between a pair of sites over diverse paths and still 
give us a 10G upgrade path someday.  Unfortunately I know little about 
the ONSs at this time even though I've been staring at data sheets, 
presentations and the Dynamic Config Tool for weeks if not months.  Like 
where do I use the filters?

I've been told we could use 15454s to build a fully-redundant chassis 
(PSUs, CPUs, etc) and then buy a pair of Xponder cards for each chassis. 
  Each Xponder card would output a single 10G link and we'd ship that 
link over one path and other 10G link from the other Xponder over the 
other path (for PtP links or use both 10G interfaces for L2 VLAN 
redundancy).  That's the basic plan as laid out in this doc (the only 
Xponder doc I could find):

http://www.cisco.com/en/US/prod/collateral/optical/ps5724/ps2006/product_data_sheet0900aecd805ebef7.html

At one site we meet both of our upstreams with fiber (one provider with 
a Fuji and another with a 15454).  That site also has a data center 
which has numerous links between it and the other site.  And at the 
other site is the core of the ISP and all our offices.

I've been told that the Xponder card can only accept GigE fiber inputs 
using the DWDM SFPs and that we'll have to convert to DWDM optics with 
an external switch if we have to use copper or other fiber links.  Is 
this true?  The one page I found on the Xponder card contradicts what 
this person is telling me.  I haven't had any luck finding good design 
or implementation docs on this card or exactly how it's used.  Both of 
our upstreams hand off as copper.  Fiber is not an option with one of 
the upstreams and with the other it's not something that we've 
discussed.  Either way it wouldn't be with DWDM optics.  The current 
data center hardware can only accept copper, for now.  Our internal 
connections can be fiber.

The first solution that comes to mind is to stack a 3750G-12S with a 
copper 3750G and use that to map VLANs between copper and DWDM ports. 
However I can't find any mention of DWDM SFP support in the 3750G.  Then 
I looked at the 3750E.  However there isn't a SFP-based chassis with the 
3750E.  There is however the 3560E-12D and 12SD.  Since they are the 
exact same switches, sans the stacking interface, why isn't there an 
all-SFP or X2 3750E?  I hate to take a guess.

Then I started thinking I could take the 3560E-12D and put TwinGig 
modules in it.  One side of the TwinGig would be the copper or standard 
fiber SFP and the other side would be the DWDM optic.  Then I read the 
data sheet for the 3560E and found out that DWDM SFPs aren't supported 
in either the 12D or 12SD chassis (but are supported in all the other 
3560Es).  Is there a technical reason behind this?

So I'm rather stuck.  This really isn't making any sense; I think I'm 
missing something here.  I'm short on design and implementation 
information for a DWDM deployment with the 15454s.  What info I do have 
seems to be contradicted by the data sheets, but if it's right is 
difficult to work around due to a lack of support for DWDM SFPs in 
various access switch platforms.  I can't even find the 15454-GE-XP when 
I try to build a 15454 on the Dynamic Config Tool.  I suspect there's 
more to it than what I'd seeing too.

Other solutions are always welcomed too.  I was considering a pure L2 
solution with the 4900Ms but I'd have to double up hardware on each end 
to avoid single-points of failure.  Plus that solution is only useful up 
to 10G of throughput unless I want to burn more fiber for more 10G links 
(something we want to avoid).  I also considered a L3 option with MPLS. 
  However the cost for full-redundancy dwarfs that of the L2 solution 
and should still be considerably more than the DWDM option.

Does anyone have any pointers or tips on any of these problems?  Any 
guidance would be much appreciated.  What am I missing?

Thanks
  Justin