```
Filename: 102-drop-opt.txt
Title: Dropping "opt" from the directory format
Author: Nick Mathewson
Created: Jan 2007
Status: Closed
Implemented-In: 0.2.0.x

Overview:

  This document proposes a change in the format used to transmit router and
  directory information.

  This proposal has been accepted, implemented, and merged into dir-spec.txt.

Proposal:

  The "opt" keyword in Tor's directory formats was originally intended to
  mean, "it is okay to ignore this entry if you don't understand it"; the
  default behavior has been "discard a routerdesc if it contains entries you
  don't recognize."

  But so far, every new flag we have added has been marked 'opt'.  It would
  probably make sense to change the default behavior to "ignore unrecognized
  fields", and add the statement that clients SHOULD ignore fields they don't
  recognize.  As a meta-principle, we should say that clients and servers
  MUST NOT have to understand new fields in order to use directory documents
  correctly.

  Of course, this will make it impossible to say, "The format has changed a
  lot; discard this quietly if you don't understand it." We could do that by
  adding a version field.

Status:

     * We stopped requiring it as of 0.1.2.5-alpha.  We'll stop generating it
       once earlier formats are obsolete.


```