Donald Neal wrote:
Alastair, you know that telco "five nines" tends to apply to a subset of the network, not necessarily to a single customer connection.
Yes, that's correct. Although there are many telcos that define explicitly how their SLA is measured, and on what components it affects. I've personally signed contracts with a few telcos that make mention of access SLAs vs. the core SLAs.
Are you sure there's a good reason to deploy 48V DC to customer premises beyond that being needed for the SDH kit? A chain of devices with customer premises mains supply at one end adds single points of failure for the connection. Is the improvement in power quality worth it?
I never suggested it was a good reason or should be done - but that perhaps the MetroE providers should look at how telcos have delivered high availability (whether it's five nines or not) in high value services. Whether MetroE costs a little or a lot, many people are placing high *value* on it - and part of that value should be around "how do we make sure it works as close to all the time as possible". It's been said that UPS' don't scale (even I agree with this), yet somehow the telcos have managed to deploy many services with active electronics at the customer end, where they have also deployed their own power protection systems. Perhaps there's a market for Cisco and other vendors to introduce MetroE switches/NTUs with batteries built in. aj