Seven per hour doesn't seem like very many. Does this mean I would have to wait and average of 4.25 (worst case 8.5) minutes before my phone can connect to a new network? That doesn't seem very user friendly. Or can my phone request the information from its end when I want to connect?
Router configurations suck (power out of mobile devices, that is)
Unknown and unseen to most users, your smartphone is “talking” in its sleep, and that can sap your battery. The problem? Routing advertisements, one of the fundamental operating principles of the Internet, can demand enough communications to have a noticeable impact on battery life. Router advertisements are multicasts that …
COMMENTS
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Tuesday 16th February 2016 07:26 GMT Eugene Crosser
> Does this mean I would have to wait and average of 4.25 (worst case 8.5) minutes before my phone can connect to a new network?
No.
When a device connects to a network, it may, and usually do, send "router solicitation" multicast packet, to which the router(s) respond with "router advertisement" instantly. "Gratuitous" RAs are there to ensure that things are eventually corrected if the process did not work first time.
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Tuesday 16th February 2016 10:19 GMT Warm Braw
There is scope in the RFC for the router to send the advertisement either to the device that sent to the solicitation, or to the "all-nodes" group. In the latter case, you risk waking up other sleeping devices to process an RA they didn't ask for, but this seems to be the likely default implementation. This is probably a case where sending the RA directly to the soliciting device would be a better choice.
Oh for the days of "default gateway"...
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Tuesday 16th February 2016 09:53 GMT TRT
So...
the packet is obviously pre-processed in some way by the receiver chip and the fact it's a multicast packet which requires further processing is sufficient then for the receiver to wake the processor... which is fine for battery powered mobiles, but what about mains powered WiFi devices that aren't so bothered about power budgets? Do we then get into the realm of segregated multicasts, such that devices on battery listen on one 'multicast sub-net' and those on mains listen to another? Or is it easier just to redesign the mobile with either a smarter wifi chip that can process the RA itself, or one that just ignores multicasts altogether?
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