Re: A common problem with SLAAC in "renumbering" scenarios

[Jan Zorz - Go6 <[e-mail]>]

On 31/01/2019 13:12, Mikael Abrahamsson wrote:
> On Thu, 31 Jan 2019, Sander Steffann wrote:
> 
>> A flash cell is at least capable of 1000 to 3000 erase/write cycles. 
>> Even if the prefix would change every single day that gives a lifetime 
>> of 3 to 9 years. And prefixes shouldn't change that often anyway. When 
>> looking at more realistic estimates line a change on average once a 
>> week you'l get to 20 years. Seems more than enough for low end extra 
>> cheap devices. I don't see this driving cost up, except for spending a 
>> few hours on properly engineering this.
> 
> There are places where they flap your WAN (PPPoE session for instance) 
> every day to renumber you. I have personally experienced this.
> 
> So it might be possible to do what you're saying but only writing 
> partial information of the prefix, so skip writing lifetimes, and just 
> keep the actual prefix. This is not what a typical DHCP server/client 
> does today, it re-writes the file every time the lease is renewed so it 
> knows about it. Some kind of compromise might be where a "hint" file is 
> written and the only time this is re-written is when the prefix is changed.

This is basically the idea. Write PD when first received, read when 
received again, compare, if not the same -> send RAs with lifetime 0 and 
write new prefix to that storage. Easy ;)

Cheers, Jan