PeSIT E protocol
PeSIT (Protocole d'Échange pour un Système Interbancaire de Télécompensation) is the file-transfer protocol used by French banks and on the SIT network. PeSIT Wizard implements PeSIT E — the TLS- capable version — and is validated for interoperability against IBM Sterling Connect:Express 1.5.
What the node implements
| Feature | Notes |
|---|---|
| CRC (PI 1) | Fletcher checksum negotiated in CONNECT / ACONNECT, verified on every entity. |
| Compression (PI 21) | Horizontal / vertical / mixed, negotiated in ORF / ACK(ORF). |
| Multi-article DTF | Up to 255 articles per DTF, entities filled up to the negotiated size (PI 25). |
| Segmentation | DTFDA / DTFMA / DTFFA carry one article that spans several entities. |
| Synchronisation points | With a window (PI 7 byte 3); asynchronous acknowledgement. |
| Restart / resynchronisation | Persistent per-transfer checkpoints (sync number ↔ byte offset ↔ article count), correct PI 13 / 15 / 18 on both sides. |
| Record formats | Binary undefined / fixed / variable, text variable / fixed. |
| EBCDIC (PI 16) | CP037 translation of article bytes on the wire. |
| Diagnostics | The full Annex D catalogue with Connect:Express-compatible texts, plus PI 29 complements. |
| TLS | With or without a transport-length header (TCPIP_HEADER), mTLS, PEM material. |
| Pre-connection | The 24-byte EBCDIC hors-SIT message, for Connect:Express partners of type T / O. |
| Clean cancellation | F.CANCEL (IDT) then CRF / DESELECT / RELEASE. |
Record formats
An article is one logical record. On the wire:
- Binary undefined (
BU) — the file is cut into articles of the record length; the last may be shorter. The default for arbitrary files. - Binary fixed (
BF) — every article is exactly the record length. - Text variable (
TV) — one article per line; the line feed is stripped on send and appended on receive. - Text fixed (
TF) — likeTV, padded with spaces to the record length.
Interoperability
The Connect:Express interoperability suite (in the source repository, run in Docker) exercises transfers both ways — small and multi-megabyte, with synchronisation points and concurrency — plus TLS both ways, F.CANCEL mid-transfer, restart and replay. All suites are green against Connect:Express 1.5.
For the full parameter catalogue and the state tables, see the source documentation.