### Introduction Verizon employs numerous identifiers to name the devices on its network, which can be confusing when you are configuring an M2M deployment. This article shows where IDs originate, from manufacturer to the point when they are provisioned on the Verizon network. It then explains the IDs used for 2G/3G M2M devices vs. 4G M2M devices. ### What’s My Name? Helping to Clear Up Device ID Confusion  ### 2G/3G Device Identifiers Defined **Electronic Serial Number (ESN)** ESNs were assigned to CDMA devices by their manufacturers up to about 2006. An ESN uniquely identifies a device. It is transmitted to the network each time the device is used to verify that the device has not been reported lost or stolen and that all subscriber bills are current. ESNs were administered by the Telecommunications Industry Association (TIA), which assigned a code to each device manufacturer to prepend to the actual serial number, which the manufacturer controlled. An 11-digit ESN is composed of the manufacturer’s code, represented in the first 3 digits, and serial number of the device, which makes up the remaining eight digits. As manufacturers produce certified Verizon devices, they upload identifiers, including ESNs, to the Verizon Device Management Database (DMD), where they await activation by an approved account. **Mobile Equipment Identifier (MEID)** After the ESN supply was exhausted, the TIA devised the MEID system for CDMA device manufacturers to use to identify 3G devices. Like the ESN, an MEID is transmitted to the network each time its device is used to verify that the device has not been reported lost or stolen and that all subscriber bills are current. The following three pieces of data are represented in the 14 hexadecimal characters of an MEID: - Regional code - Manufacturer code - Serial number As manufacturers produce certified Verizon devices, they upload identifiers, including MEIDs, to the DMD, where they await activation by an approved account. **Mobile Directory Number (MDN)** MDN is the unique 10-digit phone number Verizon assigns to a CDMA device at activation. It is composed of the area code (3 digits), exchange (3 digits) and number (4 digits). **Mobile Identification Number (MIN)** Verizon uses a 10-digit MIN to internally track and route traffic to/from a device. The MIN of a device is transmitted to the network each time the device is used to verify that the phone has not been reported lost or stolen and that all subscriber bills are current. Traditionally, only 3G devices are assigned MINs; however, because 4G devices contain components to also allow 3G traffic, they too have MINs. ### 4G Device Identifiers Defined **International Mobile Equipment Identity (IMEI)** All 4G M2M devices include radio modules that allow wireless communication. These radio modules are assigned unique IMEIs by their manufacturers. Think of IMEIs as the main 4G device identifiers. Most 4G devices also have a 3G modem to allow communication when a 4G connection isn’t available. These devices have both MEID and IMEI identifiers that are recognized by the Verizon network; however, the IMEI is the primary identifier. As manufacturers produce certified Verizon devices, they upload identifiers, including IMEIs, to the Verizon DMD, where they await activation by an approved account. In some circumstances, these devices may never be activated on the Verizon network. **Subscriber Identity Module (SIM)** Every 4G M2M device requires a SIM card, which enables it to communicate on a wireless network. SIM cards are made to operate on a certain carrier’s network. Therefore, SIM cards manufactured to enable communication on the Verizon network differ from those built to communicate on other carriers’ networks. A SIM card identifies a device to the network by carrying two identities: ICCID and IMSI. **Integrated Circuit Card Identifier (ICCID)** This identifier is the unique serial number assigned to and physically imprinted on a SIM card by the manufacturer. An ICCID is stored in a SIM card’s memory and never changes over the life of the card. You can remove a SIM card from a device and insert it into another device. When you decouple a SIM card from a device, the ICCID and IMSI remain with the SIM, but the IMEI associated with the SIM changes. **International Mobile Subscriber Identifier (IMSI)** This identity is stored on a 4G device’s SIM card. It Identifies and authenticates the user of the network, which Verizon also calls the subscriber. The IMSI is only revealed to and known by the carrier. The following components comprise the IMSI: - MCC = Mobile Country Code (311) - MNC = Mobile Network Code (480) - MSIN = Mobile Subscription Identification Number – unique number for the subscriber on the Verizon network **Mobile Station International Subscriber Directory Number (MSISDN)** MSISDN is the unique 11-digit phone number Verizon associates with a 4G device at activation. It is functionally equivalent to a 3G device’s MDN. ### Other Ways to Reference Devices You must use device identifiers to add devices to your account, but once they are added you may find it easier to manage devices by putting them in device groups or by assigning values to custom fields. ### Create Device Groups You can put devices in groups in order to perform operations on multiple devices at one time. - Device groups can contain an unlimited number of devices. - All devices in a group must be associated with the same Billing Account. - Each Device can belong to only one group at a time. - Initially, all devices belong to the Default device group. When you create your own device group and add devices to it, the devices move from the Default group into your device group. - You can group 2G, 3G, and 4G devices together. ### Use Custom Fields Custom fields for devices are optional. They are usually used to categorize, identify and track devices. These fields can represent regions, business units, device types and models, or any other information that is helpful in categorizing, identifying, sorting and monitoring devices. - Each device has five custom fields, named CustomField1 through CustomField5. - It is important to use each custom field in the same way for all devices, such as always putting device location in CustomField1 and device type in CustomField2. - You must use the CustomFieldX names in API requests and responses, but you may want to define constants for them in your code that represent the values that you are storing in each one. - Any user interface in your application should also have user-friendly labels for the custom fields. - If your company uses the [M2M Management Center](https://m2mdeveloper.verizon.com/managementcenterhelp.html), the administrator can define labels for the custom fields that match how you are using them in your application. - You can set custom field values when you [activate devices](/docs/standard-apis/connectivity-management/api-endpoints/device-management/list-devices-information/listdevicesinformation), and you can change them with the [PUT /devices/actions/customFields](/docs/standard-apis/connectivity-management/api-endpoints/device-management/update-devices-custom-fields/updatedevicescustomfields) request. - You can use custom fields in many API requests to only apply the request to devices that have a specified value.