Hi,
RPR will be a new Layer 2 technology standard which is ring-based & similar to Sonet-ring but very far different in operation. It is packet ring technology. But as far as I know that RPR standard is not ready now.
DTP is the ring technology which uses SRP protokol in it. It is Cisco specific protokol & tech. We can say that DTP is the RPR method which Cisco wants to push.
Regards
