On 2013-09-23, at 09:41, Glen Kent <glen.k...@gmail.com> wrote:

> BTW Linux distributions are available to download via bittorrent, so we
> dont really need Akamai/Limelight here. Is there a reason why Apple has not
> adopted bit-torrent for distribution? Are there legal/commercial
> implications using bit-torrent?

There are upstream congestion issues frequently associated with bittorrent. If 
you compare

(a) five thousand students on a campus wifi network trying to download a 1GB 
image from a nearby Akamai cache, and

(b) five thousand students on a campus wifi network seeding a 1GB image to 
people all over the world

it's not obvious that more pain results from (a) than (b).

Even given the ability of Apple to control the behaviour of the bittorrent 
agent (which presumably would be built into iOS) the impact of such a strategy 
on an event of this size seems very hard to predict, given a narrow time base 
and an unknowable number of local network constraints.

It doesn't seem impossible to try and optimise the fan-out by giving network 
operators hooks to influence peer selection based on local topology. But it 
also doesn't sound like an easy general problem to solve (or a problem that 
anybody necessarily wants to spend money on if the relief is only going to be 
felt once per year on major iOS updates).

(Remember as well that the scale here is very different. With iOS, Apple is the 
major Unix vendor on the planet by some margin. No other single Linux or other 
Unix/Unix-like distribution comes close, and I am guessing no single operating 
system triggers the update enthusiasm observed with iOS.)


Joe


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