nerd question about push, sms. ??

Not sure of all of the differences but the primary one is that the text message can go over the cell "phone" network (like a phone call) whereas some of the other features go over the data network. This is why they all claim they need to charge more for the text messaging feature.

I think some of the push logic works by sending a special text message to the phone which tells the email application to fetch new email over the data network. Some of the other push logic requires the email applicatoin to keep a tcpip connection alive (over the data network) so that it can be notified when new mail arrives. The idea of both is to get new information (email and other stuff) to the phone as soon as it happens. This is opposed to the mail client just wakeing up every 15 min or so and doing a fetch to see if any mail has arrived.

The new Push Notification is really to allow other applications to be able to wake up on an event without having to stay alive using up resources.

 

As I understand it, the Apple Push Notification Service works in a similar way to MS Exchange Push.

With Exchange, your PDA keeps a TCP connection to the HTTP WebService open for as long as possible - re-opening it when the TCP session times out. When the server gets new data for your account, it sends a 'reply' through this TCP connection, which is then put back 'to sleep' waiting for the next data, or timeout.

With APNS, an Apple-provided background task on the iPhone / iPod Touch will maintain an open, long-lived TCP connection to an Apple-hosted server. Via the Push API, Apps will be able to have the Apple-hosted server act as a form of proxy for you when the App is closed. When a new message, or other data, is available via push, the APNS will send data through the open TCP connection to the iPhone / iPod, triggering the appropriate response (badge, sound or alert).

One side effect of this is that maintaining the open TCP connection will require that the device has a network connection all the time, WiFi, 3G or EDGE. This is likely to lead to reduced battery lifetime.

That's how I understand it should work anyhow - Apple could have come up with something different / better...

 

I think that's the general idea. This means that the client doesn't have to check regulary for new events on the server (pull) but the server tells the client when there is something new (push).
http://en.wikipedia.org/wiki/Push_technology
http://en.wikipedia.org/wiki/Apple_Push_Notification_Service

 

No - SMS works differently.

At startup, your phone contacts the network, and is assigned a number called the TMSI (the Temporary Mobile Station Identifier) - partly related to your SIM number and your phone's IMEI (International Mobile Equipment Identifier). The network maintains a record of your current TMSI, along with which cell your phone is currently associated with. Your phone also keeps a copy of the current TMSI stored on the SIM card.

When a Text message is sent to you, the network looks up your TMSI and forwards the message to the cell you are connected to, which then broadcasts the message, targeted to your TMSI.

Both can be considered 'push', but SMS does not require a 'live' connection with the messaging center - only that your phone is on, and registered with the network.