To define the end of an interconnect mailbag. The interconnect mailbag control number value in the interconnect mailbag trailer (IT) must match the value in the same data element in the corresponding interconnect mailbag header (IH)
This number uniquely identifies the interconnect mailbag to the interconnect entity sender; It is assigned by the interconnect entity sender; Together with the sender ID, it uniquely identifies the interconnect mailbag to the interconnect entity receiver; It is suggested that the interconnect entity sender and the interconnect entity receiver be able to maintain an audit trail of interconnect mailbags using this number; Each interconnect mailbag that is created by the sender should contain a unique control number; Interconnect mailbags that require retransmission should not have their control number changed
A count of the number of interconnect mailbag acknowledgment (IA) segments included in the mailbag
A count of the number of interchanges included in the mailbag
