Is SONET a WAN technology? If not, what WANT technologies does SONET function at?
I will now post a short section of a book that might clarify things even further:
"SONET/SDH equipment was designed to efficiently and reliably transport 64kbps voice cicuits from the customer premises to (and beyond) the nearest exchange; however it was not intended to support the enourmously growing demand for IP bandwidth...With the vast installed base of SONET/SDH infrastructure and the desire to converge both voice and data transport, SONET/SDH was adapted to carry data more efficiently. Since data is not aligned on 64kbps boundaries as are voice signals, a new framing interface is needed at the data link layer to take IP packets and map them efficiently into SONET/SDH payloads. Packet over SONET/SDH (PoS/SDH) is a layer 2 technology that employs a couple of standard techniques to provide very efficient transport of data over SONET/SDH. PoS efficiently encapsulates the IP packets with a low overhead PPP header."
This is from Next-Generation Network Services by Robert Wood, and I hope he doesn't mind me advertising his book :-)