Packet over
SONET
Synchronous digital hierachies have existed within telcos for years. Now that the demand for high speed datacoms circuits is increasing, the telecoms industry is looking for a way to make the most efficient use of existing technology to deliver broadband services.
Originally, BISDN services such as ATM networks were used for this purpose. The consensus, especially within the US telecoms industry is that the cost-benefit of ATM overhead is not worth it. Then Cisco started to produce network gear that sent raw IP (Internet Protocol) traffic, directly over SONET without bothering about ATM framing. Now many vendors are producing PoS capable gear, and is proving to be a Big Thing.
PoS is really just a high tech version of the same PPP protocol employed by dial-up internet connections.