Re: Reducing the battery impact of ND

Erik Nordmark <> Wed, 22 January 2014 22:12 UTC

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Date: Wed, 22 Jan 2014 14:12:10 -0800
From: Erik Nordmark <>
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To: Ole Troan <>, Erik Nordmark <>
Subject: Re: Reducing the battery impact of ND
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On 1/22/14 1:57 PM, Ole Troan wrote:

>> It may or may not be the right thing to do for the future, but I think that requires a bit more work then forcing some edits into a document which has almost completed the WG process. I think resilient-rs has significant benefits in its current form and scope.
> not trying to speak for Lorenzo, but I don't think he is proposing replacing periodic RAs with periodic RSs.


I think that is the effective result of what you two are cooking up.

> example: a host successfully does router discovery. RA lifetime is relatively short, e.g. 3 * router advertisement interval.
> host doesn't receive any of the multicast RAs (network drops them or whatever).

You are speculating about some particular failure or misfeature in the 
network that makes it (persistently? sometimes?) drop multicast RAs. It 
would be good to flesh out that particular failure mode to see
  - whether it is realistic, and
  - what impact it has elsewhere.

For instance, the failure could be that all ICMP packets to the host are 
dropped (due to some misconfigured security policy - we've seen those in 
IPv4). That would drop unicast RAs as well, and affect the old path MTU 
discovery protocol.

Or it could be that link-local multicast is misconfigured or broken, 
resulting in DNSSD and other protocols breaking.

Having every host on the planet send a RS every 30 seconds "just in 
case" doesn't sound helpful.


> what would be the best behaviour for the end-user?
> a) host sits quietly and waits for a periodic RA
> b) host restarts the initial router discovery
> cheers,
> Ole