# SMS trunk group reference

This reference describes the fields available when creating or editing an SMS
trunk group, the SMS trunk types that can be members of a group, and the
priority rules that set the order in which member trunks are attempted.

For configuration steps, see [Create an SMS trunk group](how-to-guides/create-sms-trunk-group.html), [Set priorities in
an SMS trunk
group](how-to-guides/set-sms-trunk-group-priorities.html), or [Manage SMS
trunk groups](how-to-guides/manage-sms-trunk-groups.html). For the actions on the
**SMS Trunks** page, see [SMS trunks reference](../sms-trunks-reference.html).

## General settings

The **Create SMS Trunk Group** and **Edit SMS Trunk Group** forms contain the
following fields.

| Field | Availability | Description |
| --- | --- | --- |
| Friendly name | Required | Unique name used to identify the trunk group in the **SMS Trunks** list. For example, `My SMS Trunk Group`. A name that another group already uses is rejected with the message "has already been taken". |
| SMS trunks | Optional | Member trunks of the group. A group can be saved without member trunks, and trunks can be added later by editing the group. To provide failover, select at least two. The list shows only trunks of the [supported types](#sms-trunk-group-reference-member-types) that are not already part of another trunk group. Click **Remove All** to clear the selection. |

## SMS trunk types

The following SMS trunk types can be members of a trunk group.

| Trunk type | Group membership |
| --- | --- |
| SMS to Email | Supported |
| HTTP IN | Supported |
| SMPP ESME | Supported |
| SMPP SMSC | Supported |

SMS trunk groups provide failover for inbound SMS. To receive messages through
a group, assign it to one or more DID numbers that support inbound SMS, in the
same way as a single SMS trunk. See [Assign an SMS
trunk](../../../phone-numbers/my-numbers/how-to-guides/assign-sms-trunk.html#assigning-sms-trunk).

## Priority settings

Each member trunk has a **Priority** field. It appears in the **Priority**
column when the trunk group is expanded in the **SMS Trunks** list.

| Rule | Description |
| --- | --- |
| Priority values | From `0` to `32767`. A trunk that is added to a group gets Priority `1`. |
| Priority order | A higher value represents a higher priority. The trunk with the highest number in the **Priority** field is attempted first. |
| Failover | If a delivery attempt fails, DIDWW tries the next member trunk in priority order. For example, with priorities `2`, `1`, and `0`, DIDWW attempts `2` first, then `1`, followed by `0`. |
| Equal priorities | Member trunks with the same Priority are attempted in random order. |

## Related resources

- [Create an SMS trunk group](how-to-guides/create-sms-trunk-group.html) -
  Create a group and select its member trunks.
- [Set priorities in an SMS trunk group](how-to-guides/set-sms-trunk-group-priorities.html) - Set the order in which
  member trunks are attempted.
- [Manage SMS trunk groups](how-to-guides/manage-sms-trunk-groups.html) -
  Update the name or modify the members of a trunk group, or delete it.
- [SMS trunk groups](sms-trunk-groups.html) - Understand how trunk groups
  provide failover for inbound SMS.
- [Assign an SMS trunk](../../../phone-numbers/my-numbers/how-to-guides/assign-sms-trunk.html#assigning-sms-trunk) - Assign the trunk group to
  DID numbers to receive inbound messages.
- [SMS trunks reference](../sms-trunks-reference.html) - Look up the filters,
  columns, and actions on the SMS Trunks page.