[tor-dev] [DRAFT] Proposal: All Routers are Directory Servers

[Matthew Finkel]

On Thu, Jul 31, 2014 at 02:29:13PM +0300, George Kadianakis wrote:
> Matthew Finkel <matthew.finkel at gmail.com> writes:
> 
> > Hi All,
> >
> > Below is a draft proposal for making all relays also be directory
> > servers (by default). It's almost ready for a number, but it can use
> > some feedback beforehand (give or take a few days).
> >
> > Tonight I also found that Nick actually created a similar proposal
> > a few moons ago (Proposal 185: Directory caches without DirPort). This
> > new proposal may benefit from superseding that one, but I recommend they
> > remain distinct proposals, for now.
> >
> > In general I'm not tied to any of the proposed names, so suggestions
> > are welcome.
> >
> > Thanks!
> >
> 
> Thanks for the proposal!
> Some clarifying questions below:
> 

Thanks for the comments!

> >
> > =======================================================================
> >
> >
> > Filename: directory-servers-for-all.txt
> > Title: All routers are directory servers
> > Author: Matthew Finkel
> > Created: 29-Jul-2014
> > Status: Draft
> > Target: 0.2.6.x
> >
> > Overview:
> >
> >     (In practice we refer to the servers that mirror directory documents
> > as directory servers, directory mirrors, and directory caches. Sometimes
> > we also shorten directory to dir. This proposal attempts to consistently
> > use directory server to refer to this functionality. We also typically
> > use the term router and relay interchangably. This proposal uses (onion)
> > router.)
> >
> 
> Starting with a parenthesis might be considered a bit dry.
> I would maybe move this to a "terminology" section or something. 
> 

Probably better to get rid of it. Anyone reading this proposal probably
already knows these things.

> >
> > <snip>
> >     
> >     Currently directory servers are defined as such if they advertise
> > having an open directory port. We can no longer assume this is true. To
> > this end, we will introduce a new server descriptor line.
> >
> > 	"tunnelled-dir-server"
> >
> 
> I guess that's a '"tunneled-dir-server" NL' following the format of dir-spec.txt.
> 

Ah, yes indeed, good catch.

> >     The presence of this line indicates that the router accepts
> > tunnelled directory requests. For a router that implements this
> > proposal, this line MUST be added to its descriptor if it does not
> > advertise a directory port, and MAY be added if it also advertises an
> > open directory port. In addition to this, routers will now download and
> > cache all descriptors and documents listed in the consensus, regardless
> > of whether they are deemed useful or usable, exactly like the current
> > directory servers. All routers will also accept directory requests when
> > they are tunnelled over a connection established with a BEGIN_DIR cell,
> > the same way these connections are already accepted by bridges and
> > directory servers with an open DirPort.
> >
> 
> So, IIUC, from now on, just having an ORPort in your torrc means that
> you will be replying to BEGIN_DIR queries and advertising tunneled-dir-server.
> 
> This makes sense to me.
> 

Correct.

> >     Directory Authorities will now assign the V2Dir flag to a server if
> > it supports a version of the directory protocol which is useful to
> > clients and it has at least an open directory port or it has an open OR
> > port and advertises "tunnelled-dir-server" in its server descriptor.
> >
> >     Clients choose a directory by using the current criteria with the
> > additional qualification that a server only needs the V2Dir status flag
> > instead of requiring an open DirPort. When the client chooses which
> > directory server it will query, it checks if the server has an open
> > directory port and uses begindir if it does not. This will minimize the
> > increased number of clients that prefer begindir over direct connections
> > and thus also minimizes the additional overhead on the network from
> > clients establishing OR connections for directory requests.
> >
> 
> Does BEGIN_DIR actually impose additional overhead to the network?
> 
> It was my *impression* that BEGIN_DIR happens over a direct connection
> (a "one-hop circuit"). Is that false?

Nope, that's true. This was a mistake, I just reread the code, I
think I misunderstood part of it. There is still a little added
overhead due to the circuit that is created, compared to a direct HTTP
request, but maybe this isn't something we should worry about and we
should deprecate clients using the DirPort in newer versions?