On 22 Feb 2018, at 06:20, Petr Špaček <petr.spa...@nic.cz> wrote:

> On 22.2.2018 11:38, Joe Abley wrote:
> 
>> A few people now have mentioned that they like zero padding. What is
>> it about zero padding or fixed-size labels that makes implementation
>> easier than specifying no zero padding?
> 
> It is important to note that this 'special label trigger' is not seen
> anywhere else in DNS, so this is first piece of code which has to match
> DNS labels in the 'hot path'.
> 
> I think it is a good and easy optimization to minimize use of
> regexes/string matching in the hot path, and simple condidion
> if (label_len == X || label_len == Y)
> before the heavy-weight pattern matching will reduce frequency of regex
> use significantly.

You could use the simple condition (X < label_len < Y) in the same way without 
zero-padding and I suspect get a similar benefit.

Really, so long as the format is standardised I don't think it matters much. 
It's not like we're going to see a significant number of experiments of this 
kind; more like a small flurry of Duane/Geoff action once every five years. [*]

But I think mandatory zero-padding is ugly, and it does make me a little bit 
sad. :-)


Joe

[*] perhaps try not to dwell too long on the phrase "Duane/Geoff action"

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