The Free On-line Dictionary of Computing (30 December 2018):

transport layer
host-host layer
ISO 8072
ISO 8073
layer 4
X.214
X.224

    (Or "host-host layer") The middle layer in the
   OSI seven layer model.  The transport layer determines how
   to use the network layer to provide a virtual error-free,
   point to point connection so that host A can send messages to
   host B and they will arrive un-corrupted and in the correct
   order.  It establishes and dissolves connections between
   hosts.  It is used by the session layer.

   An example transport layer protocol is Transmission Control
   Protocol (TCP).

   OSI documents: ITU Rec. X.214 (ISO 8072), ITU Rec. X.224
   (ISO 8073).

   (1997-12-07)