How to configure the SMPP Validity Period field

What is the Validity Period Field?

The Validity Period in SMPP (Short Message Peer-to-Peer Protocol) is a null-terminated string field in PDUs like submit_sm that defines how long an SMSC will attempt to deliver a message before discarding it. This field is critical for:

  • Preventing indefinite retries for undeliverable messages
  • Managing SMSC storage resources
  • Handling time-sensitive content (e.g., OTPs, promotions)

Field Format and Structure

The validity period uses the same absolute time format as the scheduled delivery time (SMPP v3.4 specification): 

YYMMDDhhmmssnnp

Where components match the scheduled delivery time format. Common relative format shortcuts are also supported:

Format Example Description
Absolute 231215235959000+ Dec 15, 2023 23:59:59 UTC+0
Relative 000003000000000R 3 days from submission time
Special Values:
- NULL: Use SMSC default validity (typically 24-72 hours)
- 00: SMSC default validity (legacy systems)

Key Validity Period Formats

1. Absolute Time Format

YYMMDDhhmmssnnp // Full format
231215143000000+  // Dec 15, 2023 14:30:00 UTC+0

2. Relative Time Format

00000X000000000R // X = Days (00-99)
000003000000000R  // 3 days validity

Use Cases

1. OTP Expiration (Short Validity)

validity_period: "000000010000000R" // 1 hour validity

2. Promotional Campaign (Extended Validity)

validity_period: "000007000000000R" // 7 days validity

3. Midnight Expiry (Absolute Time)

validity_period: "231215235959000+" // Expires Dec 15, 2023 23:59:59 UTC+0

Example SMPP PDUs

Example 1: 24-Hour Validity (Relative Format)

0000001D  // Command Length (29 bytes)
00000004  // Command ID (SubmitSM)
00000001  // Sequence Number
...
00        // Priority Flag
00        // Schedule Delivery Time
303030303234303030303030305200  // "00002400000000R" (24 hours)
00        // Registered Delivery
...

Example 2: Absolute Expiry Time

0000002A  // Command Length (42 bytes)
00000004  // Command ID (SubmitSM)
00000002  // Sequence Number
...
00        // Schedule Delivery Time
3233313231323332353935393030302B00  // "231212235959000+" (Dec 12, 2023 23:59:59 UTC+0)
...

Interactions with Other Fields

  • scheduled_delivery_time: Validity period countdown starts from scheduled time if set
  • priority_flag: High-priority messages may override validity period settings on some SMSCs
  • registered_delivery: Delivery receipts are sent even after validity period expiration

Common Pitfalls

  • Using relative format without the 'R' suffix
  • Setting validity periods longer than SMSC limits (e.g., 30 days max)
  • Mismatching time zones between scheduled time and validity period
  • Assuming all SMSCs support relative format (verify with provider)
SMSC Behavior Note:
Many SMSCs convert relative periods to absolute timestamps upon message receipt. The countdown continues even if the SMSC restarts.

Validity Period vs SMSC Defaults

Validity Period Value SMSC Behavior
NULL or 00 Uses SMSC default (varies by provider)
Explicit value Honors value (within SMSC limits)
Past timestamp Message discarded immediately

Conclusion

The Validity Period field is essential for controlling message lifecycle in SMPP. While absolute timestamps provide precision, relative formats offer simplicity for common use cases. Always coordinate validity settings with SMSC policies and test edge cases (e.g., daylight saving transitions). For detailed implementations, refer to SMPP v3.4 Section 5.2.18 and GSM 03.40 documentation.

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