  Incorrect implementations of network protocol message specifications affect
the stability, security, and cost of network system development. Most
implementation defects fall into one of three categories of well defined
message constraints. However, the general process of constructing network
protocol stacks and systems does not capture these categorical con- straints.
We introduce a systems programming language with new abstractions that capture
these constraints. Safe and efficient implementations of standard message
handling operations are synthesized by our compiler, and whole-program analysis
is used to ensure constraints are never violated. We present language examples
using the OpenFlow protocol.
