- interfaces more connection/transfer oriented with links + sessions
    as views on the total ordering of messages on the connection
    + circular buffer of transfers with pointers to the next session and link transfers?
  - who allocates transfers?
    + probably engine can manage the transfers themselves
  - who allocates message data?
    + if engine then this forces another copy
    + if user then we need to be able to pass back an empty transfer
      and have the bytes pointer be supplied by the user
  - expanded or additional low level interface that would cover
    creation of multiple network connections, and/por accepting of
    incoming connections
  - change sessions and links to be fully contained by connections
    without independent lifecycle