[tor-dev] Proposal 214: Allow 4-byte circuit IDs in a new link protocol

[Roger Dingledine]

On Tue, Nov 06, 2012 at 10:10:15PM -0500, Nick Mathewson wrote:
> > And if a very few do, maybe the solution is to
> > move to a new TLS connection for those rare cases, rather than impose
> > a 2-byte penalty on every cell in all cases.)
> 
> Maaaybe, but I sure can't think of a sane testable design for that.  Can
> you?  To do this sanely, we'd need to negotiate this before we exchange any
> actual data, and predict in advance that we'd want it. (We wouldn't want to
> do it on-the-fly for connections that happen to have large numbers of
> circuits: that way lies madness.)
> 
> Also, I think those "rare cases" are communications between the busiest Tor
> nodes.  I think those communications might represent a reasonably large
> fraction of total Tor bytes, such that having a fallback mode might not
> save us so much.

Ah. By "a new TLS connection", I didn't mean a new design or anything --
I meant simply a second TLS connection.

> And also, this only adds 1/256 additonal overhead before TLS happens.  Not
> huge IMO.  We could save far more than that by more intelligent TLS use, if
> we needed to.

I agree that it's an ok price to pay if we decide it's the best way to go.

--Roger