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Subject: Re: [kmip] Diagram showing difference between 32-bit and 64-bit binaryalignment proposals

A 32-bit alignment constraint means that TTL (Tag/Type/Length) can be 8 or 12 bytes, and Value a multiple of 4 bytes.
A 64-bit alignment constraint means that TTL is 8 bytes (or even a multiple thereof), and Value a multiple of 8 bytes.

Hence, the decisions on the TTL and Value do not seem to be completely independent.

I'd suggest that:

1) we decide first which alignment to follow first: 32-bit or 64-bit, and
2) we decide next the size of the TTL, in accordance with the alignment, as explained above.


Matthew.Ball@Sun.COM wrote on 05/06/2009 11:29:47 PM:

> Hi Scott,

> I was trying to reduce permutations, but maybe it makes sense to
> have the following breakdown of independent decisions tomorrow:

> Shall the Tag/Type/Length fields occupy 8 bytes (as described in the
> 64-bit proposal) or 12 bytes (as described in the 32-bit proposal)?

> Shall the Value field be aligned to 4 byte or 8 byte boundaries?
> I suspect the preference may be to use 8 bytes for the Tag/Type/
> Length fields, and align the Value field to 4 byte boundaries --
> essentially a hybrid of the 32-bit and 64-bit proposals.  Do folks agree?

> Thanks!

> -Matt
> Scott Kipp wrote:

> Matt, 
> Thanks for putting this together.  It is clearer when you have
> diagrams like this.  It seems like we ought to reserve bits/octets
> if we aren't going to use them in a field.  It's kind of odd that
> the 32-bit proposal header takes up 3 words and the 64 bit proposal
> header takes up 2 words.  The TTLV format should be a different
> discussion than the bit alignment.  I prefer the TTLV format of the
> 64 bit alignment proposal, but either will do. 

> One thing your diagram doesn't show is that padding in the 32-bit
> proposal is either 1 to 3 bytes while the padding in the 64 bit
> proposal is 1 to 7 bytes to get the alignment.  Your examples in the
> other proposals clearly show this. 

> Thanks for clearing this up,
> Scott 
> From: Matthew.Ball@Sun.COM [
> Sent: Wednesday, May 06, 2009 3:41 PM
> To: kmip@lists.oasis-open.org
> Subject: [kmip] Diagram showing difference between 32-bit and 64-bit
> binary alignment proposals

> Hi Folks,

> I've put together a diagram that shows the difference between the
> 32-bit and 64-bit proposals in graphic detail.  For these types of
> comparisons, words don't quite express the idea as well as pictures do.

> As the poll showed, the group is about halfway split between 32-bit
> and 64-bit, and I'm hoping that this diagram will show that the 64-
> bit proposal works just as well for 32-bit applications.   :)

> With any luck we'll reach a conclusion via e-mail and will be able
> to have a quick vote in tomorrow's meeting to pick one of these
> proposals.  I do prefer the 64-bit option as more useful, but would
> be happy to approve the 32-bit version if that's the group's favorite.

> Let me know if you have any comments or questions!

> Cheers,

> -Matt
> [attachment "matthew_ball.vcf" deleted by Robert Haas/Zurich/IBM]

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