Rapid DHCP: Or, how do Macs get on the network so fast?

This is a great example of Apple's detail-oriented focus on real-world user experience, and helps explain why people prefer Macs even if they can't always explain why. Lots of little things just work better. You (where "you" == myself and many others, even if not /you/ personally) are left overall with an experience of less frustration.

Well, in that case they might not be following the protocol. And in some cases break the connectivity for others...

Is this case the Mac user may get a better UX, but the user who's IP was just stolen has a worse one.

I'd like to see evidence that this happens enough to matter. Any time you use a Bloom filter you recognize that doing great in most cases is much better than doing OK in every case.

What does a bloom filter have to do with this? Generally when someone uses a probabilistic data structure, they ensure its used in a manner that becomes consistent (e.g., as a caching layer). If by not following the dhcp spec, macs are breaking other peoples' connectivity, there's no recovery save them disabling/reenabling the network for them manually.

First, they don't break the DHCP spec -- everything they do is completely within spec. Second, ARP resolution doesn't require any manual resolution. Third, show me that the OS X ARP system is breaking other peoples' connectivity.

The Bloom filter was an analogy. Optimize for the common case, not the rare case.

DHCP (rfc2131) doesn't really talk about IP exhaustion.

It's undefined behavior, and there's a bunch of people in here saying that server's have every right to violate DHCP leases, otherwise someone can take over a network by continually claiming all of a Class C by continually making DHCP requests.

That argument makes sense, but it goes very strongly against the grain of what I would think a DHCP lease meant, whcih is that it's a contract for a specific amount of time. If it is indeed a contract for a specific amount of time, the client has every right to claim what they're contractually obliged to. This was my initial assumption, and I believe it's Apple's rather valid assumption.

It's not a case of Apple not following the protocol. It's a case of the real world being more complex than the protocol.

Look at parts 3.1, 3.2, 4.4 and Fig. 5 of the DHCP protocol. They describe what a client must do on initialization. For example, section 3.2 describes what a client should do if they have a previously assigned addressed they would like to keep using. It seems to me the behavior here is very precisely defined.

Maybe a networking expert can correct me but it seems to me that those initial ARP requests before the DHCP request are not exactly in accordance with the protocol.