# SMPP ESME trunk settings reference This reference describes the fields available when creating or editing an SMPP ESME trunk, and the connection details shown in the trunk's credentials window. The settings are grouped by the sections of the trunk form in the DIDWW User Panel. For configuration steps, see [Create an SMPP ESME trunk](how-to-guides/create-smpp-esme-trunk.html) or [Manage SMPP ESME trunks](how-to-guides/manage-smpp-esme-trunk.html). This page covers trunk settings only. For protocol details, see the [SMPP specification](../technical-data/smpp-specification.html#service-incoming-sms). ## General settings The **General** section identifies the trunk, sets its DIDWW SMPP server location, and restricts the IP addresses that can connect. | Field | Availability | Description | | --- | --- | --- | | Friendly name | Required | Unique name used to identify the trunk. For example, `My SMPP ESME SMS Trunk`. | | System type | Optional | Value that categorizes the type of ESME that binds to the DIDWW SMSC. For example, `VMS` (voice mail system) or `OTA` (over-the-air activation system). Your application sends this value as the `system_type` bind parameter. | | Server location | Required | DIDWW SMPP server location of the trunk: **US, NY** or **NL, AMS**. The location determines the host that your application binds to. Your firewall must allow your application to open connections to the IP address of the location. See [Server locations and IP addresses](../technical-data/smpp-specification.html#smpp-endpoints). | | Allowed IP addresses | Optional | IP addresses from which connections are allowed, in the format `(IPv4|IPv6)[/mask]`. For example, `203.0.113.10/32`. Entries in any other format are marked as invalid. If the field is empty, all IP addresses are allowed. | ## Source address settings The **Source Address Settings** section controls which DID numbers can be used as the sender ID for outbound SMS. | Field | Availability | Description | | --- | --- | --- | | Allow any DID(s) for SMS OUT | Optional | Controls how sender IDs are assigned. When the toggle is on, all DIDs with Outbound P2P SMS enabled in your account can be used as the sender ID. When the toggle is off, only the numbers in **Allowed source addresses** can be used. Default: on. | | Available source addresses | Optional | DIDs that you can add to **Allowed source addresses** when **Allow any DID(s) for SMS OUT** is off. The list shows only DIDs that support outbound P2P SMS, with their **Country**, **Number**, and **Description**. Filters: **Source address**, **Description**, **Country**, and **Region**. | | Allowed source addresses | Optional | DIDs that can be used as the sender ID when **Allow any DID(s) for SMS OUT** is off. Only the numbers in this list are available as sender IDs. | ## Trunk group settings The optional **Trunk Group Configuration** section assigns the trunk to an existing [SMS trunk group](../trunk-groups/sms-trunk-groups.html). | Field | Availability | Description | | --- | --- | --- | | Assign to trunk group | Optional | Existing SMS trunk group to which the trunk is assigned. | | Priority | Optional | Priority of the trunk within the selected trunk group. It determines the order in which trunks are used. The system attempts to contact the target SMS trunk with the highest-numbered priority first. Trunks with the same priority are tried in a random order. Range: `0` to `32767`. Default: `1`. | ## Credentials and connection information DIDWW generates the trunk credentials when the trunk is created. The credentials window shows them together with the connection details and a summary of the trunk's access settings. To open it, see [View SMPP ESME trunk credentials](how-to-guides/view-smpp-esme-trunk-credentials.html). | Field | Description | | --- | --- | | Host | Host that your application binds to. It matches the trunk's **Server location**: `us.sms-out.didww.com` for **US, NY** or `eu.sms-out.didww.com` for **NL, AMS**. | | Port | Port for SMPP over plain TCP: `2775`. For SMPP over TLS, use port `2776` with the same credentials, and set the TLS server name (SNI) and hostname verification to `sms-out.didww.com`. See [SMPP over TLS](../technical-data/smpp-specification.html#smpp-tls). | | System ID | Identifies your ESME in the bind request. Used as the `system_id` bind parameter. | | Password | Used with the System ID for authentication. Used as the `password` bind parameter. The password is hidden until you click the eye icon. To replace the credentials, see [Regenerate SMPP ESME trunk credentials](how-to-guides/regenerate-smpp-esme-trunk-credentials.html). | | System Type | Value of the trunk's **System type** field. Used as the `system_type` bind parameter. | | Allowed IPs | IP addresses configured in **Allowed IP addresses**. Empty when all IP addresses are allowed. | | Allowed Source Addresses | Source addresses that the trunk allows, as configured in **Source Address Settings**. Shows **Any** when **Allow any DID(s) for SMS OUT** is on. | For all bind parameters, see [Bind parameters for SMPP ESME trunks](../technical-data/smpp-specification.html#smpp-bind-parameters). ## Related resources - [Create an SMPP ESME trunk](how-to-guides/create-smpp-esme-trunk.html) - Create a trunk and configure the settings described on this page. - [Manage SMPP ESME trunks](how-to-guides/manage-smpp-esme-trunk.html) - Edit or delete an existing trunk. - [Bind an SMPP ESME trunk](how-to-guides/bind-smpp-esme-trunk.html) - Connect your application with the trunk credentials. - [SMPP ESME trunk](smpp-esme-trunk.html) - Understand how your application connects to DIDWW and exchanges messages. - [Assign an SMS trunk](../../../phone-numbers/my-numbers/how-to-guides/assign-sms-trunk.html#assigning-sms-trunk) - Assign the trunk to one or more DID numbers to receive inbound SMS. - [SMPP specification](../technical-data/smpp-specification.html#service-incoming-sms) - Review protocol details, including encoding, concatenation, and all available DIDWW endpoints.