For the NetIron CES and NetIron CER devices:
There are 20 Bidirectional Sessions per LP and 40 Bidirectional sessions system-wide
For the Netiron XMR series, MLX series, and the MLXe series:
The devices have a set limit of 250 BFD sessions per system with a maximum number of 40 sessions per Interface Module. This number is inclusive of the fact that IS-IS and OSPF sessions on an Interface Module will include both Tx and Rx sessions. Consequently, the 40 sessions per Interface Module actually corresponds to 80 sessions where each OSPF and IS-IS session consumes 2 sessions (1 Tx and 1 Rx).
Unlike IS-IS and OSPF however, the Tx and Rx sessions for MPLS BFD can reside on different interface modules. This means that when counting MPLS BFD sessions against the Interface Module maximum, the Tx and Rx sessions must be counted separately. In practice this means that the maximum number of sessions per-Interface Module is 80; where each Tx and Rx session for MPLS BFD is counted as 1 and IS-IS and OSPF BFD sessions are counted as 2 towards a per-Interface Module maximum number of sessions of 80.