> Tychron Atlas API & Provisioning Reference — chapter 32 of 35 as Markdown. Web version: https://docs.tychron.com/api-reference/smpp/
> Source: https://docs.tychron.com/api-reference/ · Updated 2026-08-12 · Generated from the Atlas OpenAPI spec (https://api.atlas.tychron.online/api/v1/openapi is the live contract; this file is a dated snapshot of it).
> Source revision: atlas_api_reference_2026-08-12.md · sha256 482ebd3b014af053 · sanitize gate v1 clean · reconciled with OpenAPI 2026.8.25-p01 (spec sha256 cc049ef38c71cd6e) on 2026-09-05 · content last modified 2026-09-09 · newer definition under review since 2026-09-09 (not yet reconciled)
> Scope: the Atlas platform API only. The SMS, MMS, CNAM, LRN and MCL services are separate APIs with their own specifications: https://docs.tychron.com/openapi/
> Machine index: https://docs.tychron.com/llms.txt

# SMPP

## Supported TLVs

| Name                 | Hex      | Type    | Description                                 |
| -------------------- | -------- | ------- | ------------------------------------------- |
| `sar_msg_ref_num`    | `0x020C` | Integer | SAR Reference Number                        |
| `sar_total_segments` | `0x020E` | Integer | SAR Total Segments                          |
| `sar_segment_seqnum` | `0x020F` | Integer | SAR Segment Sequence Number                 |
| `custom_message_id`  | `0x3040` | String  | Contains the `id` (ULID) of the SMS segment |

### SAR

Segmentation and Reassembly

If one is familiar with UDH based concatenation, then SAR shouldn't be a foreign concept, it is essentially the same structure:

* `sar_msg_ref_num` - Used to identify which "complete" message this segment refers to, combined with the destination and source addresses to make the unique key
* `sar_total_segments` - The total number of segemnts in the complete message
* `sar_segment_seqnum` - Which segment of the message it is

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Previous chapter: https://docs.tychron.com/api-reference/events.md  
Next chapter: https://docs.tychron.com/api-reference/schemas.md  
Complete reference in one file: https://docs.tychron.com/llms-full.txt