APN - Access Point Name

• It is a setting that enables you to access data (internet service) on your mobile [common man meaning]
• It identifies an access point on the far side of a GGSN, it acts as a reference to GGSN [technical meaning]

In addition to identifying a Packet Data Network, an APN may also be used to define the type of service (e.g. connection to WAP server, MMS) that is provided by the PDN

An APN resembles to a DNS name of a GGSN and has a maximum length of 100 octets. An APN consists of one more labels. 

Structure of APN

Network Identifier 

• Defines to which external network the GGSN is connected to. [required field]
• It will contain atleast one label and have a maximum length of 63 octets. 
• It will not start with the strings 'rac' 'lac' or 'sgsn'; not end in '.gprs' and not take the value '*'.

Operator Identifier 

• Defines in which PLMN GPRS backbone the GGSN is located
• It is composed of three labels. The last label be 'gprs'. The first two labels together identify the GPRS PLMN. 
• For each service provider (operator), there is a default Operator Identifier that is derived from IMSI 
• mnc<MNC>.mcc<MCC>.gprs
• 
  

NOTE - To support inter-PLMN roaming, the internal GPRS DNS functionality is used to translate the APN into the IP address of the GGSN.

How to configure APN manually ?? [DIY]

Go to Settings --> Wireless & Networks --> Mobile Networks --> Access Point Names --> Create New APN and Edit the fields you get from the service provider

Look !! how i did in my mobile

** You just need to set Name and APN fields only **

• Proxy, Port, Username, Password & Server not required to be set
• MMSC, MMS Proxy and MMS Port are related to MMS functionality
• MCC & MNC will already be set when you create a new APN (depending on your operator)
• Authentication Type is not needed to be set, but you can check about the two types here
• APN Type can be set as default or not needed to be set
• APN & APN roaming protocol is also set as IPv4 once you create a new APN
• Bearer field must by set Unspecified
• MVNO - Mobile Virtual Network Operator 
• It is the network operator who doesn't have the frequency spectrum or infrastructure to provide internet service. 
• Three types are SPN (Service Provider Name); IMSI (International Mobile Subscriber Identity & GID (Group Identifier).
• So, MVNO type and value are not needed to be set. You can try if you wish to know the SPN, IMSI and GID of your mobile

After you set the APN, just restart your phone and surf internet.

OR

Call your operator's customer care and tell him to send internet settings for your phone. Once received, just save it and make it as default settings

Example:

internet.mnc852.mcc405.gprs ; Set APN as internet and Name as specified by your operator

** Now-a-days, service providers are using star APN or default APN, you must save the settings sent by them. Rest you can make any changes in name or other fields but data surfing wont get affected **

Add-ons

• Watch this 2 minute video if you face any difficulty in setting APN
• List of APNs of leading service operators in India - Check this link
• Find APN list for US, Canada, UK & Australia here

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Satya Sravan