Why are iOS updates so big every time changing e. g. from 4.3.2 to 4.3.3 iPhone 3G

Each update is the full iOS operating system.

Typically, when you update a desktop (Windows or Mac) OS, you just get the changes (patch or delta update). Apple chose to provide all iOS updates as the full OS, rather than just the changes.

I suppose that's because Apple felt it was a safer, more robust, easier-to-manage process. Users simply download and install one file, and whatever version of the system you're on, you know it's complete and correct.

Prior to the advent of the iPhone. mobile device software updates were very chancy, and required a level of understanding and technical competence. You'd get multiple versions of the same update, depending where in the world you were and what features you wanted; you'd get separate updates for the basic OS and for the radio; the installation processes was multi-step and had severe bricking risks. So the Apple process was, at the time, a breath of fresh air. It was easy to understand, didn't need any technical knowledge, and was consistent.

However, for some time, there would only be 2 or so iOS updates a year - one for the new version, usually in June/July, and one bug-fix/feature-add; the iOS files were smaller (around 200MB originally); and there were less variations in version for different devices (which probably affects file size).

Now we get more frequent updates (3 in the last couple of months), and the files are 600MB+. iOS 4 is more complex than previous versions, hence the increased file size; and its complexity may well be creating room for more bugs (hence the more frequent updates).

There is a suggestion that iOS5 will include the ability to update over the air (i.e direct to the phone, rather than via iTunes). That presupposes that the updates will be as patches/deltas, since 600MB (more, probably, since each iOS version is bigger than the last) is an unreasonable over-the-air download, both for users and carriers.

If that happens (only speculation thus far - nothing official from Apple), that will help those of us who have less-than-perfect broadband (in my case, I get  reasonably solid 2MB connection, but I have to update 3 different devices, so I get the pleasure of 1.8GB of download).

If the over-the-air method comes to pass, I suspect we might get an option - take just the changes over the air, or take the full file via iTunes.

Hope all that makes sense

Each update is the full iOS operating system.

Typically, when you update a desktop (Windows or Mac) OS, you just get the changes (patch or delta update). Apple chose to provide all iOS updates as the full OS, rather than just the changes.

I suppose that's because Apple felt it was a safer, more robust, easier-to-manage process. Users simply download and install one file, and whatever version of the system you're on, you know it's complete and correct.

Prior to the advent of the iPhone. mobile device software updates were very chancy, and required a level of understanding and technical competence. You'd get multiple versions of the same update, depending where in the world you were and what features you wanted; you'd get separate updates for the basic OS and for the radio; the installation processes was multi-step and had severe bricking risks. So the Apple process was, at the time, a breath of fresh air. It was easy to understand, didn't need any technical knowledge, and was consistent.

However, for some time, there would only be 2 or so iOS updates a year - one for the new version, usually in June/July, and one bug-fix/feature-add; the iOS files were smaller (around 200MB originally); and there were less variations in version for different devices (which probably affects file size).

Now we get more frequent updates (3 in the last couple of months), and the files are 600MB+. iOS 4 is more complex than previous versions, hence the increased file size; and its complexity may well be creating room for more bugs (hence the more frequent updates).

There is a suggestion that iOS5 will include the ability to update over the air (i.e direct to the phone, rather than via iTunes). That presupposes that the updates will be as patches/deltas, since 600MB (more, probably, since each iOS version is bigger than the last) is an unreasonable over-the-air download, both for users and carriers.

If that happens (only speculation thus far - nothing official from Apple), that will help those of us who have less-than-perfect broadband (in my case, I get  reasonably solid 2MB connection, but I have to update 3 different devices, so I get the pleasure of 1.8GB of download).

If the over-the-air method comes to pass, I suspect we might get an option - take just the changes over the air, or take the full file via iTunes.

Hope all that makes sense

Nice summary.

What's interesting is the moral (if not legal) point of who is liable for the cost of these massive downloads.

A security update is, it could be argued, the patching of a software/firmware product that isn't "fit for purpose". The "fix" is necessary for the proper and continued secure functioning of the device. Sure, some security patches fix unforseen issues that have literally come out the blue and taken everyone by surprise. Sure – but I've worked in IT long enough to know that some security issues are also caused by other factors such as staff incompetence, limited project budgets and short timeframes.

Now, it's one thing to put up with a small(ish) security patch that the user can opt to download separately from the rest of the update bundle; it's quite another to endure a massive update package simply because the security upgrade (and/or App security updates, if applicable) cannot be installed seperately. The first of these is, of course, possible under OSX; but it's not under iOS.

Here's a real-world example: iOS 1.5.1 has just been released and the iPhone and iPad update packages together total about 1500Mb. Tough luck for anyone who owns both products. Now, each contains security improvements that cannot be downloaded on their own, but consider the following facts:

Australia's main teleco is Telstra and their cheapest ADSL plan is 5GB a month (then slowed to an unusable snail pace for data over this limit). This plan costs AUD$30 (per month).

Fortunately I'm not on this plan, but many of Australians will be or will be on similar. And going by the above example they'd each be paying around AUD $9.00 to receive Apple security updates, inseperably bundled into the whole download. More, if they have additional Apple products. And aside from the cost, they'd be losing over 25% of their download quota.

Be interesting to hear more on this subject. What do you think?

Nice summary.

What's interesting is the moral (if not legal) point of who is liable for the cost of these massive downloads.

A security update is, it could be argued, the patching of a software/firmware product that isn't "fit for purpose". The "fix" is necessary for the proper and continued secure functioning of the device. Sure, some security patches fix unforseen issues that have literally come out the blue and taken everyone by surprise. Sure – but I've worked in IT long enough to know that some security issues are also caused by other factors such as staff incompetence, limited project budgets and short timeframes.

Now, it's one thing to put up with a small(ish) security patch that the user can opt to download separately from the rest of the update bundle; it's quite another to endure a massive update package simply because the security upgrade (and/or App security updates, if applicable) cannot be installed seperately. The first of these is, of course, possible under OSX; but it's not under iOS.

Here's a real-world example: iOS 1.5.1 has just been released and the iPhone and iPad update packages together total about 1500Mb. Tough luck for anyone who owns both products. Now, each contains security improvements that cannot be downloaded on their own, but consider the following facts:

Australia's main teleco is Telstra and their cheapest ADSL plan is 5GB a month (then slowed to an unusable snail pace for data over this limit). This plan costs AUD$30 (per month).

Fortunately I'm not on this plan, but many of Australians will be or will be on similar. And going by the above example they'd each be paying around AUD $9.00 to receive Apple security updates, inseperably bundled into the whole download. More, if they have additional Apple products. And aside from the cost, they'd be losing over 25% of their download quota.

Be interesting to hear more on this subject. What do you think?

If people update OTA directly on the iOS device it's only approx 50Mb instead of the full iOS system, this is including the security updates. This means getting the exact same features, but for less the size, since the update done OTA is pretty much just a patch.