# File lib/snmp/pdu.rb, line 261
    def sys_up_time
      varbind = @varbind_list[0]
      if varbind && (varbind.name == SYS_UP_TIME_OID)
        return varbind.value
      else
        raise InvalidTrapVarbind, "Expected sysUpTime.0, found " + varbind.to_s
      end
    end