[standards-jig] Fw: Potential problem in the future

Robert Norris rob at cataclysm.cx
Tue Jan 21 04:13:02 UTC 2003

> I am sure this has become apparent to some of you already but it just
> dawned on me so I thought I would share it.  Jabberd currently on a
> linux box, suffers from a 1024 session limit per port.  This could
> cause some serious problems in the future when jabber really takes hold
> on the market.  Not so much in client limitations but in s2s
> limitations.

The easiest way around this that I'm aware of is to have multiple s2s
"components" (in quotes because its not always implemented as a seperate
component). This could be done in a limited fashion right now using 1.4
- one s2s (the catch-all service) will be used for outgoing connections,
but you can setup as many as you wanted, all listening on different IP
addresses (or ports) and running in their own processes, listening for
incoming connections.

These ports can be balanced in all the normal ways (layer 4 switching,
DNS round-robin, or even some clever stuff using SRV weights).

To be able to use more than one s2s for outgoing connections requires
some support from the router, but this could be worked around by writing
a proxy connects to a router as a single s2s service (and the catch-all
service), and then accepts connections from multiple s2s components,
each in their own process. Nick Perez is working on something very
similar to this at the moment (if I understood him correctly ;) ).

For services that can't afford large numbers of s2s components (because
they don't have the hardware, or the spare IPs, or special switching
equipment, or control over their DNS, or any combination of these ;) )
it would be possible to write a s2s component that drops connections
after they've been idle for a certain amount of time, or perhaps once it
has, say, 1000 open connections (so it staus under the 1024 limit). s2s
connections don't have to remain open, its just more efficient to keep
them open. It's entirely possible to open a connection, do dialback,
send a single packet and then close the connection. Everything will work
fine, it'll just be a bit slower.

And you can always increase the number of available file descriptors per
process, if your operating system supports it.

Now I've got some fun ideas :)


Robert Norris                                       GPG: 1024D/FC18E6C2
Email+Jabber: rob at cataclysm.cx                Web: http://cataclysm.cx/
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