TCP Transport Connections shall be closed using the “don't linger” option.

A TCP Transport Connection is closed under a number of situations. These are described in the DICOM Upper Layer Protocol State Machine. Some typical cases are discussed below:

a) After an A-RELEASE-RQ has been sent and the A-RELEASE-RP PDU is received

b) When a Transport Connection has been established by the DICOM remote UL Entity and no A-ASSOCIATE-RQ is received before the ARTIM Timer expires

c) When an A-ABORT PDU has been received

d) When an A-ABORT PDU has been sent and the ARTIM Timer expires before the Transport Connection is closed

e) When a TCP connection is being disconnected by the Transport Service Provider (e.g. network failure)

f) When a TCP connection is being disconnected by the remote DICOM UL Entity

Notes 1. Except following the normal completion of an association reject, release or abort and in specific situations such as temporary lack of resources, an Upper Layer State Machine should not disconnect a TCP connection or reject its establishment. The appropriate behavior is to use the Association Reject or Abort services.

2. The ARTIM Timer should not be used to oversee the Association Establishment or Release. Such a mechanism falls under the protocol definition of the layer above the DICOM Upper Layer (i.e. DICOM Application Entity, see PS 3.7).