This version includes fixes to better explain the intent of the
transport services architecture and how it differs from the BSD Sockets
API, to clarify the terminology used, and to highlight the flexible
implementation choices given that this is an abstract rather than
concrete API.
It expands the discussion of Connection Groups, the relation between
connections in a connection group, and the use of connection contexts.
It adds a discussion of privacy issues around connection racing to
the security considerations.
And, finally, this version also updates the use of normative language,
and includes a number of minor clarifications and corrections throughout.