[alanpearce]

This can be enabled or disabled under the System Settings > Battery > Options > Wake for network access (Always / Power adapter / Never). Or possibly the phone registers it as connected for a while after it sends its last packet?

[mbreese]

IIRC, Macs also do tricky networking things to make it faster to come back online from sleep. I'd be curious if the computer is actually sending packets vs. just keeping the address configured and waiting.

(That may just be on iOS though...)