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Re: [Ntp] draft-ietf-ntp-roughtime-05: tag change makes implementation more complex

Watson Ladd <watsonbladd@gmail.com> Tue, 21 September 2021 03:43 UTC

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From: Watson Ladd <watsonbladd@gmail.com>
Date: Mon, 20 Sep 2021 20:43:25 -0700
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To: JP Sugarbroad <taralx@gmail.com>
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Subject: Re: [Ntp] draft-ietf-ntp-roughtime-05: tag change makes implementation more complex
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On Mon, Sep 20, 2021 at 8:32 PM JP Sugarbroad <taralx@gmail.com> wrote:
>
> Isn't the requirement to have tags in order?

Addition is commutative. And if PAD was at the end before, it wouldn't
be if we made a tag that was three letters long and started with three
letters after PAD. An implementation that assumed that would likely be
a problem.

Could you perhaps say more about why this is a barrier to your
implementation? It's easy enough for my coauthor and I to change them
back, but we'd like to know why.
>
> On Mon, Sep 20, 2021, 19:56 Watson Ladd <watsonbladd@gmail.com> wrote:
>>
>> On Sun, Sep 19, 2021 at 12:22 PM JP Sugarbroad <taralx@gmail.com> wrote:
>> >
>> > In the pre-ietf draft, short tags were padded with FF, putting them at the end of the tag sequence. Now they're padded with 00, which puts them at the start. So packets start with PAD rather than ending with it, noticeably complicating packet construction.
>>
>> Dear JP,
>>
>> I don't think this complicates packet construction much. If you know
>> the length of all elements ahead of time, and then compute the PAD,
>> nothing changes. If you are accumulating elements and putting PAD at
>> the end after knowing the length, it's a little bit of buffer
>> manipulation.
>>
>> Sincerely,
>> Watson Ladd
>>
>> >
>> > --
>> > JP Sugarbroad <taralx@gmail.com>
>> > "Please let me know if there's any further trouble I can give you."
>> >     -- Unknown
>> > _______________________________________________
>> > ntp mailing list
>> > ntp@ietf.org
>> > https://www.ietf.org/mailman/listinfo/ntp
>>
>>
>>
>> --
>> Astra mortemque praestare gradatim



-- 
Astra mortemque praestare gradatim

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