default-iids: Clarifying the use of stable addresses

[Fernando Gont <[e-mail]>]

Folks,

In the hopes of making this document more clear regarding whether this
document is requiring the use of stable addresses, how about adding the
following text:

"SLAAC has traditionally resulted in stable addresses, since the IID
 has been generated by embedding a stable layer-2 numeric identifier
 (e.g., a MAC address). [RFC4941] implies, throughout the
 specification, that temporary addresses are generated and employed
 along with temporary addresses.

 We note that depending on the specific device type and/or operating
 environment, a host may or may not want to configure and/or use a
 stable address, but may e.g., exclusively use temporary addresses.

 This document does not require that stable addresses be actively
 employed or even generated, but simply provides a recommendation
 regarding how stable addresses should be generated when a node decides
 to do so.

 Similarly, this document is orthogonal to other privacy improvements
 such as MAC address randomization. This document aims to mitigate known
 security and privacy implications of stable IPv6 addresses in a
 hardware/protocol-independent manner, without any assumptions on the
 security/privacy properties of the underlying layers.
"

If you have suggestions for improvement, please do let me know, and send
proposed tweaks.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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