  We introduce a model for synchronizer of marked pairs, which is a node for
joining results of parallel processing in two-branch fork-join queueing
network. A distribution for number of jobs in the synchronizer is obtained.
Calculations are performed assuming that: arrivals to the network form a
Poisson process, each branch operates like an M/M/N queueing system. It is
shown that a mean quantity of jobs in the synchronizer is bounded below by the
value, defined by parameters of the network (which contains the synchronizer)
and does not depend upon performance and particular properties of the
synchronizer. A domain of network parameters is found, where the flow of jobs
departing from the synchronizer does not manifest a statistically significant
difference from the Poisson type, despite the correlation between job flows
from both branches of the fork-join network.
