[jdev] discovery services

Julian Missig julian at jabber.org
Wed Mar 23 16:07:02 CST 2005

On 23 Mar 2005, at 16:47, Justin Karneges wrote:

> On Wednesday 23 March 2005 01:13 pm, Julian Missig wrote:
>> Yes, except that the iChat way of doing this makes a *lot* of sense.
>> I don't know how you're expecting to to distribute presence using  
>> DNS-
>> SD, but with iChat, the "service" it's advertising *is* the presence.
>> So this is sort of by definition single-user.
> Ahhh, I see now.  So does it actually advertise a Jabber <presence>  
> stanza
> over DNS-SD?  Or is it some alternative format?  And how is this  
> process "by
> definition single-user"?  It seems like if you can include one  
> presence chunk
> in the advertisement, you could include two (at the risk of  
> violating iChat's
> existing protocol), but again I know very little about DNS-SD.
> I still feel it would be more Jabber-like to obtain the presence  
> over the
> Jabber connection, but I can see how doing it over DNS-SD might be  
> more
> optimized for the situation.

What "Jabber connection" are you talking about?

I don't mean to be presumptuous or rude, but I really don't think  
you've thought through DNS-SD and how peer-to-peer Jabber would work  
with it nearly enough...

There's a local subnet. It has 50 users on it. How are you expecting  
that those 50 users will get one another's presence? DNS-SD means  
that we can treat the "service" as a presence packet (because really,  
it is advertising the availability of a service) and advertise our  
presence as a DNS-SD service. There's no need to open up 50 TCP  
connections and send <presence/> packets to all 50. It's all handled  
by Multicast DNS for us. There's no "Jabber connection" taking place  
until one user wants to send a message to another--then we're opening  
a TCP socket and sending a <message>.

I don't see why you need the 'from' attribute because you already  
know who the TCP socket connection is from and you already have their  
information from the DNS-SD service packet.


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