Reference to the value of the EXP bits of the segment
identifier.The value of the MPLS EXP (experimental) or Traffic Class bits that the
SID statistics relate to. Packets received with a MPLS label value
equal to the SID's MPLS label and EXP bits equal to the this value
should be counted towards the associated ingress statistics. Packets
that are forwarded to the destination MPLS label corresponding to the
SID should be counted towards this value. In the egress direction, where
forwarding follows a SID value that requires PHP at the local node,
packets should still be counted towards the egress counters.