Re: [tcpm] I-D Action:draft-ietf-tcpm-tcp-auth-opt-01.txt

[Joe Touch <[e-mail]>]

Adam Langley wrote:
> On Wed, Jul 16, 2008 at 3:38 PM, Joe Touch <[e-mail]> wrote:
>> Both of these seem strange. They end up making the end of the option align,
>> but disturb the front of the option. Why don't they pad at the end?
> 
> So here's my hypothesis (and it's only a guess really):
> 
> It's good to write in 32-bit words for speed reasons. Also, some
> architectures make writing non-aligned 32-bit words hard. Now,
> consider the SACK and timestamp options, you want to write a 32-bit
> header followed by a payload (2 32-bit words for timestamp and 2*n
> words for SACK). So you want the payload to be 32-bit aligned for both
> writing and reading. 

That makes sense, but putting the pad at the beginning of every option 
vs. at the end of that option makes no sense AFIACT.

(putting the pad for each option is inefficient, esp. since options 
aren't all that big a space and need to be byte-parsed anyway).

Joe

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