OK, it is well understood that there are tons of circuits out there, and they will probably not disappear in the short term. Ethernet/MPLS/IP is indeed taking over but the very large SONET/SDH installed base will continue to enable TDM leased lines as long as it is profitable.
If we put voice aside, those TDM leased lines are many times Ethernet-over-SONET (or Ethernet-over-SDH) point to point secure and reliable service to enterprise customers. So in this example I would say that EoS service migration to packet solutions is simpler than OTN solutions. Packet solutions today present CoS/QoS as good as SONET/SDH solutions.
- Packet does TDM: with standard circuit emulation protocols (also for high capacity). At mobile networks, Packet does TDM (with SAToP/CESoP/etc.) as common practice
- OTN does packet: true, natively. But… native TDM support is built-in and therefore scaling up packet in OTN is challenging. Enabling 90% packet traffic over OTN – not so cheap and not so easy…