This object counts the number of incoming packets seen for this specific transit tunnel, and as the description notes, is only supported on certain platforms. This counter lets an admin confirm, purely from this mid-path router's perspective, that a transit LSP is actually carrying traffic and roughly how much, which is useful for isolating a traffic drop to a specific transit hop rather than only being able to check counters at the ingress and egress PEs. For example, this counter staying flat over several polling intervals despite the ingress PE showing steady outbound traffic points to a break at or before this specific transit hop.