Version 2.0 of the protocol was published in 2006 and added support for flexible, more user-friendly notifications, and for the automated processing of payments for late fees.
SIP2 was widely adopted by library automation vendors, including ODILO, Lyngsoe Systems, Nexbib, Bibliotheca, Nedap, Checkpoint, Envisionware, FE Technologies, Meescan, Redia and open source integrated library system software such as Koha and Evergreen.
SIP is a simple protocol in which requests to perform operations are sent over a connection, and responses are sent in return.
[5] The protocol specifies messages to check books in and out, to manage fee payments, to request holds and renewals, and to carry out the other basic circulation operations of a library.
Two common methods are to use either stunnel[7] or SSH[8] to add a layer of encryption and/or an extra level of authentication.