The 3.0 version of TIER protocol has been Project TIER website since October 5, 2016. View the 3.0 specifications here.
Version 2.0 of the Protocol was posted on the Project TIER website from December 21, 2015 through October 5, 2016.
Unlike later versions, all of which are software-neutral, version 2.0 was written in several flavors, each of which is available below in pdf format.
Version 2.1 was never posted on-line, but was circulated in draft form from the fall of 2015 through the summer of 2016. Version 2.1 consisted of two parts, Specifications and Process, which were presented in two separate documents. Both of these documents are available below in .pdf format.
The first version of the TIER Protocol was not given a version number, but we now refer to it as version 1.0. It was posted on the Project TIER website on October 7, 2013, and was available there until it was replaced by Version 2.0 on December 21, 2015.
The text of version 1.0 is available below in .pdf format.