Ciena published a WAN infrastructure decision tree to help enterprises choose what type of network they need either for interconnecting data centers or connecting corporate sites.
The infographic helps decide between private infrastructure and a telco service. The decision tree paths lead to (1) OTN mesh, (2) Traditional leased line (OTN, SONET/SDH, DWDM), (3) Layer 2 point-to-point VPN or, (4) Layer 3 VPN.
http://www.ciena.com/connect/blog/Infographic-The-WAN-infrastructure-decision-tree.html
