Re: [dnsext] I-D Action: draft-ietf-dnsext-dnssec-algo-signal-04.txt

On Mar 9, 2012, at 4:07 AM, Miek Gieben wrote:

> I read a comment in the draft that this option list can get very long, which
> indeed is true. 
> 
> How about the following scheme:
> 
> A resolver indicates the highest algorithm number it understands and thus *also*
> all *previous* algorithms. This way the whole option can be shortened to 4
> bytes:
> 
> 0: OPTION-CODE
> 1: DAU byte value
> 2: DHU byte value
> 3: N3U byte value
> 
> And maybe this option can be renamed to Crypto Understood.
> 

That was the layout of the previous versions, but without the NSEC3 hash understood (only added it this version).  The problem was that it violated the basic format for EDNS options (Code, Length, Data).  It could be:

0: OPTION-CODE
1: DATA LENGTH
2: DAU byte length
3: DHU byte length
4: N3U byte length

One reason we made it three unique options was so clients could mix and match if they wanted.  Especially since there is only one NSEC3 hash algorithm code assigned for now.

Scott

> A drawback is that a number of current specified features aren't available
> with this scheme.
> 
> Regards,
>    Miek Gieben
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