Portals is based on the concept of elementary building blocks that can be combined to support a wide variety of upper-level network transport semantics.
In particular, Portals is aimed at providing the fundamental operations necessary to support a high-performance and scalable implementation of the Message Passing Interface (MPI) standard.
All incoming messages would first pass through a match-list that allowed individual portals to respond to specific groups, ranks, and a set of user specified match-bits.
[2] This standard was designed for systems where the work required to prepare, transmit, and deliver messages is longer than the round-trip to the Portals data structures.
The standard has been revised since the initial release to make it more suited for modern high performance, massively parallel computers.