Lorenzo, I think we have to ensure that the specifications work for all kinds of devices. take a bath scale for example, that’s essentially disconnected until someone steps on it. there are going to be levels of deep sleep.
this particular case though sounds like a software bug, rather than an IETF RFC bug. cheers, Ole > On 12 Jun 2015, at 10:11 , Lorenzo Colitti <[email protected]> wrote: > > On Fri, Jun 12, 2015 at 4:54 PM, Ole Troan <[email protected]> wrote: > > That sounds like a bad idea. If devices send an RS every time the user > > turns the screen on, and the router responds with a multicast RA, any > > medium-size network or larger will have multicast RAs flying around every 3 > > seconds and killing everyone's battery. > > then it turns into a silly race… the network is forced to send RAs at very > high frequency, because hosts that wake up with expired routers, don’t RS… > > No, that's not what it turns into. > > The right way to do this is for the network to send periodic RAs at a > reasonable interval - say, 10 minutes - and for the hosts to wake up when RAs > arrive, process them, and go back to sleep. > > This is already how things work. Wifi chipsets already have to wake up every > few tens/hundred of milliseconds ms to listen for multicast packets. Hosts > already need to wake up when they receive unicast packets (well - on some > manufacturers, only unicast IPv4 packets :-)), because people want to receive > chat messages when the device is asleep. Hosts also need to reply when they > receive broadcast ARP - because otherwise the link routers can't to talk to > them, and they users can't receive chat messages. > > There is plenty of battery power even on a watch to wake the CPU up once > every 10 minutes - in fact, it's probably awake much more often than that > already > > The only thing required to make this work well is that if a network has > hundreds or thousands of nodes per subnet, then it must send solicited RAs > unicast. > > do we agree that a host that wakes up and has expired its last default router > should restart router discovery? > > That's not necessary. For things to work well a host needs to be able to > maintain connectivity even when asleep. So it needs to be able to receive > unicast packets, and it needs to process RAs (e.g., so it can know that it > has lost connectivity when it receives an RA with a default lifetime of 0). > If it is processing RAs, then its RA will not expire.
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