The simple data link (SDL) is a new framing protocol for variable/fixed length packets over a general-purpose point-to-point communications channel. SDL extends the HEC-like framing mechanism used in ATM to variable-length data. Its low implementation complexity makes it particularly suitable for high-speed transport links in wavelength channels and dark fiber applications. SDL is a very attractive alternative to conventional solutions such as ATM and PPP-over-SONET (POS) for high data rate environments. SDL has also been designed to facilitate many OAM&P functions needed in next generation multiservice optical packet networks including multiprotocol encapsulation, virtual links, quality-of-service (QoS) differentiation, link management, and control. We describe framing and data link synchronization procedures in SDL, and evaluate its performance over octet and bit synchronous transport facilities.