# Multi-period DASH in AWS Elemental MediaPackage
The ability to insert multiple periods in DASH manifests for both VOD and live is available in AWS Elemental MediaPackage.
A period is a chunk of content in the DASH manifest, defined by a start time and duration. By default, the entire manifest is contained in one period but MediaPackage can partition the DASH manifest into multiple periods to indicate boundaries between ads and the main content. For example, if you're using MediaPackage with a downstream ad service such as AWS Elemental MediaTailor, choose **Trigger new period on ads** on the MPEG-DASH endpoint in MediaPackage. This option tells MediaPackage that the DASH manifest is to be formatted with multiple periods.
+ For information about AWS Elemental MediaTailor, see the [https://docs.aws.amazon.com/mediatailor/latest/ug/](https://docs.aws.amazon.com/mediatailor/latest/ug/).
+ For information about DASH-ISO endpoints in MediaPackage, see [Creating a DASH endpoint](endpoints-dash.md).
+ For more information about how multi-period DASH works in MediaPackage, see the following *How it Works* section.
## How multi-period DASH works
To use the multi-period DASH feature, the input to MediaPackage must have SCTE-35 ad marker messages. These messages inform MediaPackage of where to create period boundaries. This is how MediaPackage processes those messages:
1. MediaPackage detects the SCTE-35 messages from the input source.
1. Using the attributes of the SCTE-35 messages, MediaPackage calculates where the boundaries are between the end of the main content and the ads. This calculation is (scte35 `ptsAdjustment` \$1 scte35 `ptsTime`) / (EventStream `timescale`).
**Example**
In the following example, the period starts at 44.075 seconds because (183003 \$1 3783780) / 90000 = 44.075:
```
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```
1. MediaPackage inserts the `EventStream`, `Event`, and `scte35` tags with additional information into the manifest and surrounds the ad period with a `Period` tag, as shown in the preceding example. MediaPackage groups all adaptation sets before the first ad period into a period, and any subsequent adaptation sets after the ad are grouped into a period, until the next SCTE-35 marker. Here is a complete manifest example with multiple periods. It uses `SpliceInsert` SCTE-35 ad markers:
**Example**
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