On Sun, 21 Apr 2024 at 09:05, Mark Tinka <mark@tinka.africa> wrote: > Technically, what you are describing is EoS (Ethernet over SONET, Ethernet > over SDH), which is not the same as WAN-PHY (although the working groups that > developed these nearly confused each other in the process, ANSI/ITU for the > former vs. IEEE for the latter). > > WAN-PHY was developed to be operated across multiple vendors over different > media... SONET/SDH, DWDM, IP/MPLS/Ethernet devices and even dark fibre. The > goal of WAN-PHY was to deliver a low-cost Ethernet interface that was > SONET/SDH-compatible, as EoS interfaces were too costly for operators and > their customers. > > As we saw in real life, 10GE ports out-sold STM-64/OC-192 ports, as networks > replaced SONET/SDH backbones with DWDM and OTN.
Key difference being, WAN-PHY does not provide synchronous timing, so it's not SDH/SONET compatible for strict definition for it, but it does have the frame format. And the optical systems which could regenerate SONET/SDH framing, didn't care about timing, they just wanted to be able to parse and generate those frames, which they could, but they could not do it for ethernet frames. I think it is pretty clear, the driver was to support long haul regeneration, so it was always going to be a stop-gap solution. Even though I know some networks, who specifically wanted WAN-PHY for its error reporting capabilities, I don't think this was majority driver, majority driver almost certainly was 'thats only thing we can put on this circuit'. -- ++ytti
