Re: [v6ops] Stability and Resilience (was Re: A common...)

[Fernando Gont <[e-mail]>]

On 22/2/19 14:43, Timothy Winters wrote:
> 
> 
> On Fri, Feb 22, 2019 at 12:30 PM Tim Chown <[e-mail]
> <mailto:[e-mail]>> wrote:
> 
>     Hi,
> 
>>     On 22 Feb 2019, at 17:04, Owen DeLong <[e-mail]
>>     <mailto:[e-mail]>> wrote:
>>>
[....]
>>
>>     If the prefix is written to nv men, wouldn’t it also be possible
>>     for implementers to send rapid deprecation RAs for any prefix not
>>     renewed?
>>
>>     In other words, after reboot, try to reacquire same prefix. If
>>     that doesn’t work, when you advertise the new prefix, you could
>>     also include the old prefix with a very short preferred and valid
>>     lifetime (e.g. 1 second) in the first RA, which should be sent to
>>     the all nodes on link multicast?
>>
>>     It doesn’t eliminate the problem, but 1 second additional duration
>>     would be barley noticeable amid the minute or so it takes most
>>     home gateways to reboot. 
> 
>     That's similar in spirit to RAmond, which we used to use when seeing
>     rogue RAs on our campus network.  It would auto-deprecate any
>     prefixes that shouldn't be there. (http://ramond.sourceforge.net/)

IIRC, ramond debrecates the default router, not the advertised prefixes....


> 
>     The snag is that I suspect most OSes would ignore a valid timer of 1
>     second, given the 7200 second (2 hour) minimum defined in RFC 4862
>     (unless the RA is authenticated, somehow).  The preferred timer can
>     be zero.  When RAmond was written, if we used a valid timer less
>     than 7200 seconds it seemed that the deprecating RAs were ignored. 
>     That was 10+ years ago though.  Perhaps Tim Winters has data on
>     whether that rule is implemented today in practice; I'd assume the
>     tests he runs might include that.  
> 
> So we test that IPv6 implementations set the address to two hours if the
> address was higher then gets a low value (such as 1).   Currently there
> is no way to make it less then two hours if a Rogue RA gets out and
> gives out a longer address lifetime.

Yep. As per RFC4862.

-- 
Fernando Gont
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