SLNP

SLNP (Simple Library Network Protocol) is a protocol developed in Germany for national ILL. Simple text based messages are used for communication between libraries for resource sharing. Each German region uses a central ILL server (ZFL) that manages the resource sharing communication. ZFL handles the patron resource sharing request, patron authentication, availability check, creating the borrowing and lending requests and routing the replies between the lender and the borrower.

As the SLNP communication contains patron personal information, the traffic must be secured to comply with privacy requirements. SLNP communicates over a TCP/IP connection. To secure SLNP communication with Alma, ZFL uses an open source SSL encryption wrapper called Stunnel, which is a lightweight component installed locally on standard operating systems. This component creates a secure “tunnel” communication over a specific port and also serves as a means to uniquely identify each institution.

The resource sharing workflow starts with the patron search of a title in the library portal. If the item is not available in the library the patron can fill in an ILL form which is sent to the central ILL server (ZFL). ZFL server checks the patron authentication with the borrowing library before continuing the resource sharing workflow.

After the patron authentication, ZFL sends availability check one by one to each of the libraries owning the requested material. The libraries reply whether the material is available or not for sharing. At the same time ZFL send a message  to the borrowing library which results with the creation of a borrowing request.

When one of the lending libraries can supply the requested material it sends a shipping message to ZFL while shipping the item to the borrowing library. ZFL server updates the borrowing library with the actual material supplier. As now the material supplier is known the partner is changed from NCIP to the SLNP that represents the lending library. The requested material arrives in the borrowing library and the patron receives it.

When the patron returns the borrowed material the borrowing library sends it to the lending library. At the same time it sends a notification to ZFL server.