Re: [addr-select-dt] Proposed default policy table

"Tony Hain" <alh-ietf@tndh.net> Tue, 13 July 2010 18:28 UTC

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From: Tony Hain <alh-ietf@tndh.net>
To: 'Aleksi Suhonen' <Aleksi.Suhonen@tut.fi>, addr-select-dt@ietf.org
References: <0f4301cb1ec0$297b4650$7c71d2f0$@com> <4C3A5931.40709@tut.fi>
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Date: Tue, 13 Jul 2010 11:27:52 -0700
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Subject: Re: [addr-select-dt] Proposed default policy table
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I have no problem with leaving more space, I just didn't want to take people
too far from what existed... ;)

I don't believe we are actually deprecating 3ffe::, just operationally
removing it from use at this time. It was never defined with a specific
functionality in the stack, so it should not get downgraded unnecessarily.
Due to the explicit 2000::/3 not covering it, 3ffe:: will fall into
'default', so it does get a lower preference indirectly.

Tony


> -----Original Message-----
> From: addr-select-dt-bounces@ietf.org [mailto:addr-select-dt-
> bounces@ietf.org] On Behalf Of Aleksi Suhonen
> Sent: Sunday, July 11, 2010 4:52 PM
> To: addr-select-dt@ietf.org
> Subject: Re: [addr-select-dt] Proposed default policy table
> 
> Hi,
> 
> Tony wrote:
> > I suggest leaving 10, 40,&  80 in the precedence so people can move
> IPv4 or
> > ULA around without feeling the need to rewrite the other labels (they
> don't
> > have to, but an obvious hole to park it in reduces confusion).
> 
> The number of bits in the precedence value has not been defined, but I
> understand that most implementations use at least 32 bits anyway. I
> would like to see the default precedence values multiplied by 100 to
> leave more room for algorithmically generated entries and manual
> tinkering.
> 
> There are only 4 values available between fc00::/8 and fd00::/8 for
> example. Those could be easily consumed after a couple of corporate
> fusions.
> 
> I guess the idea has been that local administration can override all
> values to their liking. However, my understanding of the best practises
> for system and network administration is that the defaults are changed
> as little as possible. And the defaults should preferably "shine
> through" from under local modifications. This means that when the
> defaults are changed due to some software update, they might adversely
> interfere with the local changes.
> 
> I don't mind it if the default precedences are multiplied by even more
> than a hundred, I just feel it is important that there should be more
> space between the default values.
> 
> Tony Hain also wrote:
>  > Precedence  Label  Prefix
>  > ----------  -----  --------------------------------
>   ...
>  >          1      6  fec0::/16
> 
> Aren't we removing site local completely while we're at it? Or if it
> should be kept around, then why not add 3ffe::/16 too for the same
> reason?
> 
> --
> 	Aleksi Suhonen
> 	Department of Communications Engineering
> 	Tampere University of Technology
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