I would like to design webapps (eg. games) that have low latency. I presume that the header of ajax would add latency. What I really would like is a protocol where the connection is never broken, and both client and server can push data to each other immediately. (and thus comet isn't really a choice, since there is communication only one side). Better would be to send data as binary and compress it.
Edit: I want an alternative to java/flash/silverlight because my platform is ipad/iphone, which DOES NOT support java/flash/silverlight
Please do not recommend any thing that is/needs java/flash/silverlight, thank you
Depending on your timeline and ability to impose user requirements, you could use WebSockets. See link text for info about browser support.