message sequence chart (signaling) (MSC)
The Message Sequence Chart (MSC) is an ITU-T standard for the graphical representation of signal sequences in switching technology.
The Message Sequence Chart is described as a standardized protocol test in ITU Recommendation Z.120 of 1999 and in its annexes "Formal Semantics of Message Sequence Charts" and "Static Semantics of Message Sequence Charts".
The Message Sequence Chart can be used to describe the communication behavior of switching systems. An MSC chart represents the temporal flow of information between the switching components and the connected networks and devices.