[Juser] 'lightweighting' Jabber chat for sllloooooow links...& UDP?!

Peter Saint-Andre stpeter at jabber.org
Thu May 18 10:42:23 CDT 2006


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This list is for end users of Jabber clients. You probably meant to post
it to the developers list (which I'm cc'ing):

http://mail.jabber.org/mailman/listinfo/jdev

Lines, David wrote:
> hi. i am looking to set up Jabber chat over a HF radio link at a speed of
> 4.8kbps and with high latency (ping ~ 7secs)!! i would love any assistance
> in where i can start to tweak for this situation. while the data rate will
> not be high for text chat, the high latency means i need to reduce any
> handshaking as much as possible. with a sniffer i notice there is a large
> amount of handshaking taking place even after the connection is established.
> i havent yet looked into detail what these packets are doing but i guess i'm
> in for a crash course in xmpp/xml/impp?! 

What do you mean by "handshaking"?

You don't need a packet sniffer to see the XMPP traffic, just run the
right kind of client in debug mode and watch the XML fly by.

> My initial high level thoughts are to 'turn off' negotiation for voice and
> video. 

That's a client thing, not a server thing.

> I notice 'Keep_Alives' is a client option that could be turned off. i
> know there are proprietry lightweight LAN chat apps but I want to keep to
> open source standards, ie Jabber. 

See below.

> Is there provision for 'pipe-lining'
> multiple xmpp commands (ie similar to what is proposed for SMTP with
> Pipelining (RFC-2197) - basically sending several commands at once and
> waiting for the respective ACKs to return in 1 packet).

You can send multiple XMPP stanzas at once -- it's asynchronous.

> Also can Jabber be set for a UDP connection instead of TCP? The standard
> (RFC-3920) implies TCP but doesn't explicitly rule out UDP, but this forum
> reply does!

There is no UDP binding for XMPP, but there is an HTTP binding:

http://www.jabber.org/jeps/jep-0124.html

It's possible that we might define a UDP binding at some point, but it's
not a high priority for me.

> I see Jingle is looking at RTP over UDP. 

Jingle is transport-agnostic. Another transport for Jingle is IAX2
(Asterisk), and more transports may be on the way.

> I'm new to all of this but I see
> there are <transport> commands. I'm currently evaluating Wildfire-2.6.2 and
> they aren't any configuration options for UDP. IANA reserves xmpp port 5222
> for TCP and UDP. Could this be possible with access to the client and/or
> server source codes?

You could hack the source code from your server of choice to support a
UDP binding, but we'd prefer to define the protocol first (or concurrently).

> And one more qu... can Jabber talk client to client, or client to client
> after the server goes down. Initial testing shows that once the server is
> gone so does any client to client chat (basically it is relayed through the
> server)

Yes, it can: http://www.jabber.org/jeps/jep-0174.html

Peter

- --
Peter Saint-Andre
Jabber Software Foundation
http://www.jabber.org/people/stpeter.shtml

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