be a source and a sink of an type a and type b oam segment flow depending on the network architecture it is possible for type a segments to overlap with type b segments for example in the case of point to point architecture segments of type a can overlap with those of type b both segments can operate independently of each other and will thus not have any effect on each other in mpls protection switching however the overlapping can lead to problems a more detailed explanation is given below on the basis of fig3 as to how mpls oam packets can be distinguished from mpls packets bearing payload data two alternative approaches are possible here in a first embodiment of the invention one of the exp experimental bits can be used in the mpls packet header to distinguish mpls oam packets from mpls packets carrying payload data this procedure in particular provides a very simple method of distinguishing the packets this bit can be checked in the sink of an mpls oam segment or at the connection points cp to filter out mpls oam packets before further evaluations are undertaken in a further embodiment of the invention one of the.