[c-nsp] SFP+ modules in Catalyst switches (was: Nexus 7000)

[Richard A Steenbergen]

On Wed, Jan 30, 2008 at 10:05:07AM +0100, Marian ??urkovi?? wrote:
> Unfortunately it seems Cisco now tries to completely avoid XFPs on 
> ethernet linecards for Catalyst switches.
> 
> In the past they were too conservative and selected X2s because of LX4 and CX4
> support. Ironically, just a few months after X2 linecards appeared, the XFP
> camp released CX4 XFPs and eliminated the need for LX4 by LRM. So at present,
> XFP platforms enjoy full range of optical interfaces at much lower cost,
> while X2 product line is expensive and still not complete - no ZR/DWDM,
> tunables may not appear at all.
> 
> Despite of this, new linecards are still released with X2 slots - e.g.
> the most recent WS-X6716-10GE.
> 
> Now what matters is which formfactor will get onto the next-generation
> ethernet linecards for 80 Gbps/slot Supervisor2080 - if SFP+, there will
> be again the same problem with lack of long reach / DWDM optics...

There are major advantages for Cisco to go with X2 (at the expense of 
their customers) on enhancements to existing designs, even outside of the 
old "supports ?X4" mantra (which as you point out is becoming rather 
dated). Switching to XFP or SFP+ requires a major redesign and new ASICs, 
whereas using X2 lets them use their existing chips with only relatively 
minor physical modifications. This is probably why you see SFP+ only on 
"new" products from Cisco, and X2 on the "old" products (i.e. 6716 is 
still mostly just the same thing as a 6708 and 6704).

You could also look for sinister motives behind the choice of SFP+, for 
example right now there are a huge number of manufacturers producing cheap 
XFPs for the entire spectrum of media types and reaches, and Cisco 
controls almost none of that market. Moving to SFP+ lets them force their 
customers into buying all new $4000 LR optics from Cisco only, and 
effectively stops people from using the cheap enterprise-grade boxes in 
long reach applications (competing against 15454 type metro transport 
products, etc, the way you could with a high-density XFP box and DWDM 
optics). Of course you could also just argue that since Nexus is clearly 
an enterprise and enterprise ONLY product, there is very little need for 
exotic media types outside of standard SR/LR and thus port density was 
more important. Either way, SFP+ (and thus Nexus) is still a bad choice 
for a lot of service providers and power users.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
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