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Date:   Mon, 13 Apr 2020 03:04:29 -0300
From:   Fernando Gont <fgont@...networks.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH net-next] Implement draft-ietf-6man-rfc4941bis

On 13/4/20 02:22, Stephen Hemminger wrote:
> On Wed, 8 Apr 2020 07:44:58 -0300
> Fernando Gont <fgont@...networks.com> wrote:
> 
>> Implement the upcoming rev of RFC4941 (IPv6 temporary addresses):
>> https://tools.ietf.org/html/draft-ietf-6man-rfc4941bis-09
>>
[...]
>>   
>>   temp_valid_lft - INTEGER
>>   	valid lifetime (in seconds) for temporary addresses.
>> -	Default: 604800 (7 days)
>> +	Default: 172800 (2 days)
> 
> You can't change defaults for existing users without a really good
> argument.

The number of extra addresses you get when the Valid Lifetime is 7 days 
tends to exacerbate the stress caused on network elements/devices. There 
are references in the I-D.

Additionally, the motivation of temporary addresses is indeed privacy 
and reduced exposure. With a default VL of 7 days, and address that 
becomes revealed is reachable for one whole week. That's not very 
"temporary" as the name would imply.

The only use case for a VL of 7 days could be some application that is 
expecting to have long lived connections. But if you want to have a long 
lived connections, you probably shouldn't be using a temporary address.

And even more in the era of mobile devices, I'd argue that general 
applications should be prepared and robust to address changes (nodes 
swaps wifi <-> 4G, etc.)

This is, of the top of my head, the reason why we decided to modify the 
default valid lifetime in the upcoming revision of the standard.

Thoughts?

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@...networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492




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