On 26 February 2020 5:30:56 pm GMT+01:00, Warren Kumari <warren@kumari.net> wrote:

On Wed, Feb 26, 2020 at 11:20 AM Coy Hile <coy.hile@coyhile.com> wrote:

 On 2020-02-26 11:14, Randy Bush wrote:
We use plenty of multi-mode, but only in the data centre, between our
own kit, for racks within the same cage.

 so you have to stock both single and multi?  hmmm

 randy

 I'd expect that from the ToR -> Servers would be MMF, but that other
 infrastructure cabling would be SMF.
 Even using aftermarket optics, putting single-mode transceivers in every
 server and access port would quickly become cost-prohibitive, would it
 not?

Cisco GLC-SX-MM Compatible 1000BASE-SX SFP 850nm 550m DOM Transceiver
Module - $6.00 - https://www.fs.com/products/11774.html
Cisco SFP-GE-L Compatible 1000BASE-LX/LH SFP 1310nm 10km DOM
Transceiver Module - $7.00 - https://www.fs.com/products/12622.html

Yup, it is $1.00 more for SM, and you need 2 per link, but unless you
are doing *lots* that's likely not cost-prohibitive. The delta on 10G
is a bit more ($21 vs $18), but still not crazy-pants territory...

Of course, sometimes you don't have the option of SM - you are
connecting some someone else than they only do MM, or you are
connecting to a piece of kit which doesn't have replaceable optics, or
you have legacy cabling which is MM, or... but, the cost of the optics
these days is not really the limiting factor.


 --
 Coy Hile
 coy.hile@coyhile.com