Re: rfc4941bis: Invalid addresses used by ongoing sessions

Fernando Gont <fgont@si6networks.com> Tue, 11 February 2020 05:16 UTC

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Subject: Re: rfc4941bis: Invalid addresses used by ongoing sessions
To: Mark Smith <markzzzsmith@gmail.com>, Gyan Mishra <hayabusagsm@gmail.com>
Cc: 6MAN <6man@ietf.org>
References: <c6ba9a00-cb44-2022-5009-34211966518c@si6networks.com> <CABNhwV0mb8dL_4Ef5UxAbcRbP18nH9Ztvx8XHJ0Z0GM-NaCwgw@mail.gmail.com> <CAO42Z2zB6gpKwZ=DfRVEbURNyKPJWAOqLqrFvW8T_uc59=9tiw@mail.gmail.com>
From: Fernando Gont <fgont@si6networks.com>
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Date: Tue, 11 Feb 2020 02:16:25 -0300
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On 10/2/20 23:25, Mark Smith wrote:
> 
> 
> On Tue, 11 Feb 2020, 13:13 Gyan Mishra, <hayabusagsm@gmail.com 
> <mailto:hayabusagsm@gmail.com>> wrote:
> 
> 
> 
> 
>     On Mon, Feb 10, 2020 at 11:12 AM Fernando Gont
>     <fgont@si6networks.com <mailto:fgont@si6networks.com>> wrote:
> 
>         Folks,
> 
>         As currently specified, temporary addresses are removed when
>         they become
>         invalid (i.e., the Valid Lifetime expires).
> 
>         Section 6 ("6.  Future Work") of the draft
>         (https://tools.ietf.org/id/draft-ietf-6man-rfc4941bis-06.txt) still
>         keeps the following text from RFC4941.
> 
>         6.  Future Work
> 
>             An implementation might want to keep track of which
>         addresses are
>             being used by upper layers so as to be able to remove a
>         deprecated
>             temporary address from internal data structures once no
>         upper layer
>             protocols are using it (but not before).  This is in contrast to
>             current approaches where addresses are removed from an
>         interface when
>             they become invalid [RFC4862], independent of whether or not
>         upper
>             layer protocols are still using them.  For TCP connections, such
>             information is available in control blocks.  For UDP-based
>             applications, it may be the case that only the applications have
>             knowledge about what addresses are actually in use. 
>         Consequently, an
>             implementation generally will need to use heuristics in
>         deciding when
>             an address is no longer in use.
> 
> 
>         I wonder if this text should be:
> 
>         1) moved more into the body of the document and made a "MAY"
>         (which for
>         TCP is very straightforward),
> 
>         2) Be left "as is", or,
> 
>         3) Removed from the document
> 
> 
>         The implications of #1 above is that it can't prevent long-lived
>         connections that employ temporary addresses from being torn
>         down, at the
>         expense of possibly increasing the number of concurrent IPv6
>         addresses.
> 
> 
>        Gyan> So for TCP apps it maybe easier to track via active TCB
>     blocks so those long lived connections could be tracked.  So those
>     long lived TCP connections would not be impacted and torn down. 
>     Other apps using UDP may not be as easily tracked and so maybe using
>     the deprecated address, however due to difficulty of tracking maybe
>     torn down as a side effect of option #1. 
> 
> 
> 
> Long lived connections using temporary addresses should not be a 
> consideration, because long lived connections should not be using 
> temporary addresses.
> 
> "Temporary" and "long lived" (persistent, stable) are opposites that can 
> never be resolved.

In that case, would you go for #2 above? And, what's your position 
regarding reducing the preferred and valid lifetimes?

Thanks!
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492