back to article 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 …

  1. Old Handle

    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?

    1. 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?


      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.

      1. Warm Braw Silver badge

        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"...

  2. Kevin McMurtrie Silver badge

    DTIM and Beacon intervals

    WiFi already has a system for delayed processing of unicast (beacon TIM) and multicast (DTIM) data so that devices may sleep. A better request would be to device makers (Apple) to address bugs that require people to set extremely short intervals.

    1. jason 7

      Re: DTIM and Beacon intervals

      I've adjusted my wi-fi at home to be a little more relaxed on those than constantly screaming "Marco!...Polo!"

  3. TRT Silver badge


    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?

    1. Black Road Dude

      Re: So...

      or as many mobiles are now being designed with a main cpu(s) and a low power background process cpu is this whole thing irrelevant?

  4. Mike Shepherd

    They knew

    They knew what they were getting into when they bought their IPv6 tickets. I say "Let 'em crash!"

  5. Adrian 4 Silver badge

    "will be approximately 0.014 mAh”

    So that would be 14µAh, then ?

    1. Anonymous Coward
      Anonymous Coward

      Yes, and 14000nAh

    2. Dig

      "will be approximately 0.014 mAh”

      So that would be 14µAh, then ?

      Yes but that's per advertisement. If the router or routers are advertising once every ten seconds then that would equate to 5mahr or 100% more than the sleep current.

  6. HKmk23

    Your would do more good....

    Deleting Facebook! from your mobile device...

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