[Jingle] [Fwd: [Summit] Jingle topics (was: Re: introduction)]

Robert McQueen robert.mcqueen at collabora.co.uk
Wed Jul 23 19:53:08 CDT 2008

Peter Saint-Andre wrote:
> Robert McQueen wrote:
>> * getting rid of weird SIP hang-overs in jingle like profiles
> +1

Lets just do that. Redundant stuff is bad. We can determine the
transport and that RTP is beong used by inspecting the XML namespaces in
use, and determine whether SRTP is there by looking for the appropriate
element. This is a good reason to put the SRTP element in the RTP
description XEP itself, because otherwise a gateway could fail by not
understanding the <crypto xmlns="...srtp"> element, and turning the SRTP
offer into a plain RTP/AVP one.

>> * sensible fallbacks between jingle transports, content-replace is kinda
>> loss
> I think we also need to figure out renegotiation of an existing session
> (IMHO this is closely connected to what you are calling "sensible
> fallbacks").

I think we covered this, transport-replace seems OK, and we're going to
try and avoid other renegotiations if we can get away with it. :)

>> * TLS over jingle stuff
> By this do you mean (1) encryption of Jingle-negotiated media such as
> voice or video (e.g., via SRTP or DTLS) or (2) use of Jingle to
> negotiate an encrypted end to end XMPP session as in XEP-0247?

I meant TLS'd XMPP streams over Jingle. Seems pretty good, most of what
we need to do is just define some best practices for clients to generate
keys, and do some continuity checking at least.

>> * jingle descriptions for "arbitrary stream protocol" transportation,
>> like any DNS-SD service (rfb, chess, whatever)
> Looking forward to hearing what this is.

I think I should just write this, it's pretty trivial, and we really
want it for Telepathy Tubes. Just so you can invite your contacts to
connect to your local DAAP/VNC/HTTP/whatever service.

>> * other APIs which are useful for collaborative applications (shared
>> document models, but not weird bonghits like SXE)
> Please, tell us what you really think. :) Is this connected to the stuff
>   we talked about in Brussels for exchanging DOM object changes (or even
> random JSON data etc.)?

Yeah, we didn't talk at all about this. I think SXE is pretty crazy
because it seems like some huge explosion of the XML to make totally
minor changes. If you have a shared DOM, you can use existing standards
like xpath to name an existing node and say "insert a child node",
"delete this node", or "replace this node". I didn't look at SXE in a
lot of detail, but it seemed like an incredibly verbose way of achieving
not a lot more than this. I don't think it actually addresses the hard
stuff like how do you keep a consistent document model across multiple
clients, which is what actually makes collaborative applications hard to
develop, not the "how do I stuff bytes from A to B".

The background to this is that OLPC has fed back to us and said that
they don't think Telepathy Tubes are a particularly good API for writing
collaborative applications on. I don't disagree, we just had two
requirements in mind - one was allowing people to re-use existing wire
protocols when appropriate, but have Telepathy take care of NAT punching
or relating, which we invented stream tubes for, and the other was
exposing a multi-user primitive that we could implement on top of MUC or
multicast, which we invented D-Bus tubes for.

We were hoping to get some push back from OLPC activity authors about
what they'd rather see in the APIs, because we had very unclear
requirements when we started out, other than "enable collaborative
applications somehow", but we never really got that feedback. People who
try to write collaborative activities on OLPC in general fail to do it,
because they still have to know distributed computing and network stuff,
even for simple things like a game which has shared state and only one
player changing it at a time.

Lots of people (Inkscape, Abiword) have also got code which just speaks
XMPP directly with their own ad-hoc extensions, but this doesn't have
any prospects of interoperating, sends lots of data through IBB, doesn't
encourage code sharing (Telepathy's NAT traversal or Jingle
implementation isn't really available, nor UI elements, etc), and
wouldn't work in situations where Telepathy could do something different
(like our link-local backend's multicast MUCs).

I'd like to see something that will a) allow us to make life easier for
application developers, b) be implementable by us on both link-local and
server-based XMPP (and maybe even other protocols), and c) ideally be
interoperable with other clients.

This probably isn't the right forum to discuss this however, but feel
free to forward me around a bit more... :D

>> * stacking/layering/nesting jingle transports, so we can say "here's a
>> reliability layer, on top of an unreliable transport" or "here's a TLS
>> layer on top of this unsecure transport"
> Again, I'm looking forward to hearing your descriptions of these.

We kinda decided a generic stacking thing was a bad idea, but I did come
up with a way to run several reliable streams on top of one pseudo
TCP-on-ICE connection, which I'll come back to in my later post on
pseudo TCP.

>> I'm also interested in seeing if people have interest in Jingle
>> descriptions for including existing stream protocols, datagram
>> protocols, and D-Bus IPC, so that we can standardise/interoperate
>> Telepathy's Tubes (http://telepathy.freedesktop.org/wiki/Tubes,
>> http://people.collabora.co.uk/~robot101/telepathy-guadec-2008.pdf).
> OK.

This is the same as what I meant above. :D

> /psa


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