Abstract: The invention relates to a method for controlling the flow of data messages exchanged between asynchronous digital stack processes in an unreliable distributed multiprocessor system, such as an SDH (Synchronous Digital Hierarchy) node. In accordance with the invention, the inter-process flow control algorithm is based on a credit mechanism. According to that mechanism, a sending process (P1) must receive credit from the receiving process (P2, P3, P4) before the sending process (P1) can send messages (Q) to the recipient. The sending process (P1) uses in the account (account P2, account P3, account P4) of each receiving process the process's own pool (V2, V3, V4) and, in addition, a common pool (Y1) for all the receiving processes, so that a pool at each given moment represents the unused amount of credit obtained from the receiving processes (P2, P3, P4) and so that the free portion in the pool indicates how much there is room left in the message buffer for messages (Q) sent to the receiving process.