I am a frequent user and tester of synchronous Internet applications -- iChat, Skype, various SIP phones such as Eyebeam, and a variety of desktop videoconferencing solutions. I have had very mixed performance with these lately.
Last night I wondered if I had any new 'podcast' videos (since I had subscribed to a del.ici.o.us feed of funny videos, following this hint). And then it struck me: by leaving iTunes running while trying to do a videoconference, I was opening the possibility of another network and CPU-intensive operation occurring while I was trying to talk to someone. Some of those videos are hundreds of megabytes -- hardly what you want downloading while you are in a videoconference with your boss!
This possibility hadn't previously occurred to me, but once I started thinking about it, I started to think of all the other apps that do periodic checks and possibly download significant amounts of stuff: Safari with its RSS feeds, NetNewsWire and its RSS feeds, even Mail and the periodic checks that it does.
The simple solution, of course, is to quit these apps when attempting a voice or video connection. A longer term solution would be for these apps to 'notice' what else is happening on the network interface and alert the user somehow. In fact, given this trend, it might make sense for Apple to build this in as a framework that is available to all application developers and include some sort of priority setting ("ask all other apps to stop doing periodic network checks while I am in iChat"...) which would be simpler and less intrusive than having to quit the application.
There is precedent for this. iChat already sends a message to iTunes to stop playing the current song. As Apple moves to integrate more communication services on the computer, they are going to have work out a way for them all to get along. Currently third party applications, like Skype, don't take advantage of even simple things like pausing iTunes, but hopefully they will do that AND pause network-instensive (and CPU intensive) activity, at least as an option.
If this isn't a system function, perhaps it is an opportunity for a third party app: something that you could 'register' your various network intensive and CPU intensive applications with and then when you started using one, it would offer to (or automatically) pause the others.
In the meantime, I will be manually quitting apps when I have an important conference call. I hope this hint helps others in this situation -- especially those of us without a lot of bandwidth/CPU to spare.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051022080913981