GlobalSim::v1::Tower Node1 GlobalSim::v1::Tower + ptt + eta + phi + flag_et_overflow + flag_error + flag_next_tob_same_et + flag_truncate + DECLARE_FIELDS() Node2 GlobalSim::BitSpec < Tower, 64 > + width + field() + numFields() + forEachField() + json() + packFields() # makeFields() # allFields() # validateFields() - validateFieldList() - validateField() - checkOverlap() Node2->Node1 Node3 GlobalSim::NoBase   + allFields() Node3->Node2