Proposal: Optimistic Data for Tor: Server Side

Nick Mathewson nickm at
Tue Aug 3 18:27:35 UTC 2010

On Mon, Aug 2, 2010 at 10:31 AM, Ian Goldberg <iang at> wrote:
> (My first Tor proposal; hopefully it's in a sensible form...)
> Here's the server side of the proposal I promised in my rump session
> talk at PETS.  The server side seems harmless, and getting it deployed
> to a bunch of nodes before the client side gets out there seems like a
> good idea in any event.
> The client side yields both the performance improvements, as well as
> potential client fingerprinting issues.  That side will have to be
> carefully considered.
> Discuss.  ;-)

Thanks, Ian!  I've added it as proposal 174.

The proposal looks good to me.  I'll try to answer some of the points
that it was confused on:

> What do version numbers for hypothetical future protocol-compatible implementations look like, though?

They look like Tor version numbers, for whatever Tor version merges
the patch that implements this, and later.

> It is not clear exactly what an "unrecognized" stream is

An "unrecognized" stream is one for which we haven't yet received a
BEGIN cell.  We'll also need to modify the spec to say that older
versions of Tor didn't handle RELAY_DATA cells the same way that newer
ones did.

We should consider the patch independently from the proposal.  The
proposal itself looks fine.  Generally, we try discussing patches on
the tracker at  We're in a loose feature-freeze
right now in a hurried attempt to release an 0.2.2.x rc, but a later
version of the patch in this proposal has a good shot IMO for 0.2.3.x.
 Do you want to make the tracker entry for the patch, or should I? :)

Nick Mathewson

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