It could also just be a direct Ethernet path over a SONET circuit without the inherent 802.17 resiliency. You should ask them for more information about their infrastructure. Are they using 802.17? Is it path-protected on the SONET side?
Sorry for the delay in posting, but I thought I would add couple of
Ethernet transport over SONET/SDH can be done in several ways.
- Frame mapped GFP encapsulation (ITU-T G.7041). Here is a white paper
that is pretty detailed
- You can also do it using X.86 (LAPS)
As far RPR goes, RPR is a MAC (802.17) and it is pretty much agnostic of
the PHY layer. RPR can run on dark fiber or on a SONET/SDH path layer.
RPR is not an encapsulation mechanism for Ethernet packets over SONET.
It is at the MAC layer and provides additional functionality like
running the nodes in a ring, oversubscription, fairness, QoS and
resiliency against node and fiber failures. Here is a tutorial about