Historical protocol elements and behaviours

Scope and introduction

This chapter documents historical protocol elements and historical behaviours.

Note: the conventions set out here are not yet followed throughout the Tor specifications.

Definition of "Historical"

A historical protocol element or behaviour is one which is neither generated/exhibited, nor recognised/consumed/handled, by any supported version of the Tor implementations.

It should not be necessary to consider historical information to understand the behaviour of the live Tor network. It may be necessary to consider it for some special purposes: for example, as part of developing tools for processing historical data (eg, old consensuses); or, tools which use probing to try to determine the underlying version of possibly mendacious remote software.

If any supported Tor implementation generates or handles a behavior, it should be described in the main body, not relegated to Historical status. Such a behaviour must be understood to understand the existing live network, and its implementations, even though it may be obsolete or deprecated.

Representation of historical material

Where practical, we move historical material out of the mainline text.

We then document the historical elements here. The structure of this chapter approximately mirrors (as a subset) the structure of the main, current, parts of the spec. Each historical protocol element is placed in its appropriate context.

When that isn't convenient, historical material remains in the main text. In this case we mark it non-normative, and introduce it with a "Historical" subheading.