The Ceridwen Self Issue Client uses 3M SIP version 2 (Standard Interchange Protocol, developed by 3M for library self issue) to communicate with a suitable 3M SIP enabled library system. 3M SIP is an industry standard protocol for patron checkout of library materials.

The Ceridwen 3M SIP Circulation Library for Java is an Open Source (GPL v3) implementation of the 3M SIP version 2 protocol (SIP2). It includes both client and server implementations and support both telnet and socket based communications.