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.


Ps: ATM, what's that?