The disclosed methods for reducing the port setup time for a large number of TWAMP test sessions for performance measurement testing of telecommunication transport networks include parsing a configuration file to populate an accept-port data structure with proposed receiver ports for communication from a session-sender to session-reflectors; repeatedly and in parallel, from a control client, communicating with receiving servers to set up pairwise test sessions using receiver port allocations from the accept-port data structure, and receiving and checking blocks of Accept-Session messages from the receiving server and handling either case of acceptance of the proposed receiver port or of counter proposal of an alternate-and-available port to be used for the measurement session; and allocating the alternate-and-available port and updating the accept-port data structure by storing the alternate-and-available port received in the particular Accept-Session message; and using the stored ports to initiate TWAMP messages in the pairwise test sessions.