TRAILING-WINDOW

Trailing window. The tolerance window for accepting a late-arriving EDI message.

Definition

The trailing window is the duration during which an EDI system continues to accept a message whose source timestamp is old — typically because it has been retransmitted after several failures, or held temporarily at a transit hub. It is the upstream counterpart of the look-back window: the latter handles duplicates on the inbound side, the former handles age tolerance on the producing side. Typical values: 24-72h for real-time flows, up to 7 days for batches.

Origin

The concept is inherent to the asynchronous nature of EDI flows: AS2 and AS4 guarantee best-effort delivery, never delivery time. RFC 4130 explicitly mentions Late MDN cases that may arrive hours after the original message. PEPPOL recommends a 72h trailing window in its BIS, and OASIS defines in ebMS3 a Message Retention Period concept that is very close.

Example in context

An accounting system receives on 15 May 2026 at 09:00 an invoice issued by a supplier on 12 May 2026 at 17:30, retransmitted after two intermediate failures. The 7-day trailing window being open, the system accepts the invoice, timestamps it both on source (12 May) and reception (15 May) sides, and starts the accounting sequence. If the same invoice arrived on 25 May 2026 (beyond 7 days), it would be rejected with a request to retransmit with a new timestamp and new MessageId.

Related terms

• Look-back window — symmetric window for duplicate detection.
• Audit trail — journal that traces source vs reception timestamps.
• Idempotency — property securing the processing of late retransmissions.