Air traffic control service shall be provided:

a) to all IFR flights in airspace Classes D and E;
b) to all VFR flights in airspace Classes D;
c) to all special VFR flights;
d) to all aerodrome traffic at controlled aerodromes

The Above services are provided by

Area Control service :

ACC (Area control center ) , VACC ( virtual area control center) as in our case on VATIND

Approach control service:

APP ( approach  ) on VATIND

Aerodrome control service:

TWR (Tower ) on VATIND

Classification of airspaces

The Indian airspace has the following classfications see section 4.3  in the  following document  Indian AIP , click on the links for detailed information

ATS airspaces in India are classified and designated in accordance with following

Class D:

IFR and VFR flights are permitted and all flights are provided with air traffic control service, IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights. VFR flights receive traffic information in respect of all other flights.Airspaces in terminal areas, control areas,control zones and aerodrome traffic zones have been classified and designated as class D airspace

Class E:

IFR and VFR flights are permitted, IFR flights are provided with air traffic control service and are separated from other IFR flights. IFR flights receive traffic information in respect of VFR flights, VFR flights receive traffic information in respect of all other flights, as far as is practical. Class E is not be used for control zones. Airspaces in designated ATS routes outside terminal areas, control areas and controlzones, where air traffic control service is
provided, have been classified and designated as class E airspace.

Class F:

IFR and VFR flights are permitted. All IFR flights receive an air traffic advisory service and all flights receive flight information service, if requested. Airspaces in designated ATS route segments outside terminal areas, control areas and control zones, where air traffic advisory service is provided, have been classified and designated as class F airspace.

Class G:

IFR and VFR flights are permitted and receive flight information service if requested.Airspaces other than those in Class D, E and F have been classified and designated as class G airspace.