I've been doing a lot reading the last few days on the advantages of "PPP over SONET/SDH" vs "IP over ATM AAL5". The available information bandwidth of roughly 150 Mbps out of 155.5 Mbps with STS-3c/STM-1 makes the PPP over SONET solution very attractive.
Speaking SDH, it's VC4, so payload is 139.264Mbit (STS-3c SPE)
I understand that SONET facilities are widely deployed throughout the carriers' broadband infrastructures but when will it become practical to run packet data over these facilities? I am aware that Cisco is planning to provide an OC-3/STM-1 interface in the 3d quarter but what about other hardware vendors?
When will carriers be ready to support this service?
It's possible today, it's a matter of tariff, any SDH/Sonet network is capable of doing this.
Are multiplexers available or planned for the near future?
You can't do subrates, the rest is standard tranmission gear avaliable from a variety of vendors.
Are there carrier-to-carrier issues that need to be worked out?
It depends if you are buying this as a circiut within a network or as two half circiuts. If you are obtainging two half-circiuts the two corresponding carriers have to work out the maintenence procedures. --Peter Ps: ATM, what's that?