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

Thu May 18 17:51:49 CDT 2006

One level of indirection may solve many of your problems.

You probably want to run this client with some server side assist using a proxy server. The proxy server will sit on the higher bandwidth/remote end of your slow speed connection and mediate the communication with the XMPP server.

Given the constraints on the bandwidth and latency, you may also be better served by a simpler wire protocol between your device and the proxy instead of the more verbose XMPP protocol. Your proxy will still use XMPP over TCP to talk to the XMPP server but you could implement more of a 'state transfer approach' between your client and the proxy with the proxy doing most of the heavy lifting and data set reduction.

On the datarate issue - Many moons ago we developed an IM client for Mobitex ( the original blackberry network) that used a paging protocol. As I recall, more than messaging, what caused the most traffic was presence updates from every one on the contact list- which a server side proxy can help manage by filtering.   

Peter Saint-Andre <stpeter at jabber.org> wrote: -----BEGIN PGP SIGNED MESSAGE-----
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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  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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