[tahoe-dev] new project

[cardsw at critical.com]

On Mon, Aug 13, 2012 at 11:03 AM, Miles Fidelman
<mfidelman at meetinghouse.net> wrote:
> ...
> "smart documents that talk to each other via a peer-to-peer protocol."
> - start by writing and sending an HTML email to a group of people...
> - on receipt, the copies establish a peer-to-peer connection - updates to
> one copy propagate to every other copy... thinking about using
> tahoe-lafs files as a distributed publish-subscribe mechanism...

Nathan <nejucomo at gmail.com> responded:
> ...
> Of course a Tahoe-LAFS-centric approach could be to use capabilities
> as both a document storage system *and* a peer-to-peer message channel
> for this kind of application...

We have been working on a pub-sub distributed virtual blackboard using
Tahoe-LAFS and the NACK Oriented Reliable Multicast (NORM) transport
protocol.

IP multicast groups can also be protected/accessed using capabilities, see
the DIstributed PoLicy enfOrceMent Architecture (DIPLOMA) research papers
(not us).

An urgent short message that does not require archival is sent using NORM.

Anything else is uploaded to a Tahoe grid, then its readcap is sent via
NORM.

Each message is a new immutable file.

We intend to support mutable files not with the current native Tahoe
approach, but rather by versioning and delta coding, so each new version is
a new immutable file, containing either a snapshot of the entirety of the
file, or else just meta-data, a readcap to the previous version and a
description of the transformation required to turn it into the current
version (think git, darcs, duplicity, rsync, Delta-V/WebDAV, conditional
Kolmogorov complexity, etc.). This part is still in a conceptual design not
yet coding stage.

As the local replica of the file might reside in one Tahoe grid, and the
global version graph (with metadata and transformation descriptions) might
reside in another, we need to deal with nodes connecting to multiple grids.

Although we have not yet dealt with the versioning, we have kludged
together the basic Tahoe/NORM mechanism, and used it to coordinate
frequency assignments in a cognitive radio network in our lab.

Obviously some benefits of multicast are efficient scalability and support
for push traffic (which improves not only efficient scalability but also
latency).


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