IA is (Initial Attach) …
Here are the main types in more detail:
- Default (the default)
Function:
This is the most important type. It is used for all general internet traffic.
When used:
When you visit websites, use apps, stream videos or sync data in the background.
Important:
An APN must have this type for the cell phone to even get on the Internet. Without default, there is no normal data connection.
- MMS (Multimedia Messaging Service)
Function:
Specifically for sending and receiving MMS (image, audio or video messages).
When used:
Only if you send or receive an MMS.
Special feature:
These APNs often have different server settings (MMSC URL) or require special authentication that deviates from the normal Internet APN.
The phone automatically switches to this APN as soon as an MMS is sent, and then immediately switches back to the default APN.
- SUPL (Secure User Plane Location)
Function:
Used for GPS location services. It allows the cell phone to quickly charge satellite data (A-GPS) over the mobile network to determine the position faster.
When used:
Whenever an app (like Google Maps, Uber or Weather Apps) gets your location.
Special feature:
This type is often combined with default in an APN (e.g. Default,SUPL) so that location and Internet run over the same channel.
- Dun (Dial-Up Networking)
Function:
Allows you to use your phone as a hotspot (tethering) for other devices (laptops, tablets).
When used:
When you activate the mobile hotspot and another device connects.
Special feature:
Some providers separate hotspot data from the normal mobile phone tariff. A separate APN with Dun can be used to book or limit hotspot usage separately. This type is also often integrated into default if no separate hotspot APN is required.
- IMS (IP Multimedia Subsystem)
Function:
Critical to modern voice services such as Voice over LTE and Wi-Fi calling.
When used:
During a voice call via the 4G/5G network or WLAN.
Special feature:
This traffic is often prioritized and routed via a secure network segment to guarantee quality and encryption.
It is strictly separated from the normal Internet (default) so that a call does not cancel when the Internet is full.
- HiPRI (High Priority)
Function:
For high priority traffic, often for emergency services or special enterprise applications.
When used:
rarely in the private sector.
Can be used for emergency calls (emergency apps) or special carrier services that must have priority over normal traffic.
- FOTA (Firmware Over-the-Air)
Function:
Specifically for device system updates.
When used:
When the cell phone downloads an update for the operating system (Android) or the firmware.
Special feature:
Some providers use this to deliver updates via a separate, stable channel that is not influenced by the normal Internet load.
- CBS (Cell Broadcast Service)
Function:
For cell broadcast messages (e.g. warnings of natural disasters, Amber Alerts).
When used:
Very rarely active in the APN menu, as this is often controlled directly by the network.
- IA (Initial Attach)
Function:
Used when the device first logs into a network before a specific service is requested.
When used:
when turning on the cell phone or changing the location (roaming) to establish a basic connection.
- Emergency
Function:
Especially for emergency calls (112, 911 etc.) if no normal SIM card is detected or there is no credit.
When used:
only in an emergency to establish a connection even without a regular contract.
— What do these types look like in practice?
In the Android settings, you often see these types as a comma-separated list in a single APN entry.
This means that one APN can take over several functions at the same time.