What is an APN? | how do I change it? | What is the APN format?

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 APN is short of Access Point Name and provides a phone with the information needed to connect to wireless service. It can be changed by adding a new APN profile with information from the carrier in the phone's settings.

What is an APN?

The Access Point Name (APN) is the name for the settings your phone reads to set up a connection to the gateway between your carrier's cellular network and the public Internet.

Your carrier reads these settings in order to generate an IP address, connect to the correct secure gateway, and see the carrier needs to connect you to a private network like a VPN. All the heavy lifting is done on the carrier side, but we need to make sure the right settings are in place to get on the network we need, in the way we need to connect.

An APN has the network setting your phone needs to connect to your provider.

Depending on how your carrier's network is structured, different settings are mandatory. The rest can be slightly altered to change some of the parameters, but for most of us, we will need to use the exact settings provided by our carrier.

The good news is that most of the time, your phone has several APN settings already programmed in and one will work for phone calls automatically. Very handy if you need to call support for help if one of the built-in settings does not work correctly and you'll need to add an APN yourself.

The bad news is that carriers can customize the software on any phone they sell, and that includes blocking the ability to change the APN. Even if your phone is unlocked. You might be able to find a workaround online, but there is also a good chance that you're just not going to be able to use any other network. We suggest buying your next phone from someone else.

Why would you change your APN?

Unlocked phones and alternative carriers are more popular now than ever before. Most companies make an unlocked model or two that you can buy directly from their website or a retailer like Amazon with the necessary parts and software to use on any GSM network around the world. And when you don't have a phone that's tied to a carrier through financing you're free to try other carriers and see who offers what's best for you.

Shifting things around and trying someone new for phone service is pretty simple and pain-free, but you might need to know how to set the APN on your phone. Let's take a look at what an APN is and how you go about changing or adding one.

How to change your APN?

The first thing you'll need to do is find the right APN settings for the network you want to use. You'll be able to find these on the support pages on the carrier website. The settings will look like this example for Mint Mobile:

These are the settings you'll need to enter for a new APN that can use Mint Mobile's service for data and MMS. Now we just need to find where to enter it.

This is going to be different depending on who made your phone, but it's always going to be in the Wireless & networks section of the settings. You're looking for a setting for Access Point Names and it might be nested in another setting like Cellular Networks. That's where you'll find it on the Pixel or Moto Z, and it should be similar to your phone. Don't worry, you can't mess anything up by tapping the settings and looking inside. Just try not to make any changes while you're looking.

Once you've found the "Access Point Names" section. Tap to open it.

You should see a list with at least one APN on it. If things aren't working with the current APN, you need to add another. Don't modify or delete the one you see, instead make a new one and we can choose it when we're done. At the top of the page, press the plus sign to bring up the "Edit access point" screen.

This is where you will enter the settings you got from your carrier's website. Two very important things here:

Once you have the settings provided by your carrier entered, you need to save the APN. You do that by pressing the three dots in the upper right and selecting the "Save" option.

Once your APN information is saved, go back one screen to the list we saw earlier. On this screen, tap the new APN settings you just entered to make them active. Your phone will lose its data connection for a little while as it connects to the new network using the new network settings. If you can't get a connection after a few minutes, you might need to restart your phone.

On rare occasions, your provider may have two APNs that need entering. This is because they use a separate gateway for MMS or other data that are separate from your data plan. If this is the case, you'll find a full explanation of both APN settings on your carrier's support site. Most times, one APN is all you need, though.

And that's it! Now your phone should work for calls, SMS, MMS, and data. Now be sure to set up any Data Saver or warning settings your phone might have to monitor how much data you use and if you are getting close to your allotment.

What is the APN format? 

The format is a string type that may consist of alphabets, numbers, and other characters.  The roaming network needs to do a DNS lookup to get the IP address of the GGSN/PGW, before starting any signaling. The string may contain operator information by including MCC and MNC digits or just a plain string with no such information.

For Example:

Few examples of Apn names: 

internet – This name has no information for the serving mobile operator or company.

internet.co.uk – This name belongs to a UK-based mobile company.

Airtel.in – This name belongs to the Indian mobile operator Airtel.

internet.mnc234.mcc345.GPRS – This belongs to the mobile operator with MCC as 345 and MNC as 234.  A mobile operator may have multiple MNC within a country. Multiple MNCs lead to having multiple APNs by the same operator in the same country.

How does an APN string encode in the network protocol messages?

During the location update procedure, while attaching, HLR sends the APN to the roaming network as part of the subscription data. Over the wire, the APN string needs to convert to bytes in protocol format as per the 3GPP specification. 

Each character converts to its equivalent ASCII value. If APN contains dots(.), the first byte contains the length of the immediate string till the next dot (.).  Following are a few examples of APN encoding with dots and no dot.

internet –   0x08, ASCII(i), ASCII(n), ASCII(t), ASCII(e), ASCII(r), ASCII(n), ASCII(e), ASCII(t)

internet.co.uk – 0x08, ASCII(i), ASCII(n), ASCII(t), ASCII (e), ASCII(r), ASCII(n), ASCII(e), ASCII(t), 0x02, ASCII(c),ASCII(o), 0x02, ASCII(u),ASCII(k)

How to configure APN settings?

The mobile operator configures the setting of the APN in the device during the attach procedure. Still, if data is not working, there are other options you may use to do settings manually. The following section will describe how you can change APN settings in iPhone and Android devices.

How to change APN Settings in iPhone?

To set the manually following are the steps.

• Go to settings and click on cellular.
• Select the data network.
• Change your settings for APN parameters.
• After the change, come back to the home screen, the changes will be saved.

Apn settings in Android or what is my APN:

Go to settings -> Connections->Mobile Networks-> Access Point Names. Here one can edit or add a new APN.

What are MCC and MNC in the APN setting?

HLR sends a list of APNs in the subscription profile during camping on a network. The phone selects only one of them for data. Which one it will select, is determined by the data requirements. You do not need to worry.

But while selecting APN manually, you see that it has many settings, MCC and MNC are two of them.  Till now you may never worried about what is MCC and MNC in APN? 

When mobile phones roam, it comes under a PLMN, which is identified by the MCC and MNC pair.  If the user sets the MCC and MNC value, the phone will allow getting data service in PLMN which has configured MCC and MNC values only.

For example, if you are carrying a sim card from TMobile USA and roam in India. If you set the MCC and MNC of Airtel, The phone can use data only when the Airtel network is selected.  It is not advisable to set MCC and MNC in and by the mobile subscriber.

How does a device know what APN to use? 

Besides the GGSN, the GPRS network has an additional component(HLR) to enable data roaming. Before setting up a data connection,  the SIM card does registration with the HLR and downloads the subscription profile.

When a subscriber roams, it attaches to the home network for services(voice, SMS, and data). For accessing data service,  SGSN in the roaming network does the signaling with the HLR for GPRS registration. After getting GPRS access, it attaches to the GGSN and sets up a tunnel for the internet by using a GTP to create PDP context.

Subscriber subscription and APN:

HLR provisions the list of APNs and QoS profiles for 3G subscribers. On network attach, SGSN downloads APN and QoS profiles for the subscriber.

In the case of 4G, HSS stores the APN profiles. Each SIM has an EPC profile that contains the APN name and quality of service. Subscriber attaches to the HSS via MME.  During attach, Mme downloads the EPS-Subscribed QoS profile. There can be multiple APNs for a subscriber. HSS marks one of the APN as default.