Re: [Idr] WGLC for draft-ietf-idr-rfc5575bis-04

Job Snijders <job@ntt.net> Mon, 16 October 2017 16:30 UTC

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Date: Mon, 16 Oct 2017 18:30:46 +0200
From: Job Snijders <job@ntt.net>
To: Christoph Loibl <c@tix.at>
Cc: draft-ietf-idr-rfc5575bis@ietf.org, idr@ietf.org
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Subject: Re: [Idr] WGLC for draft-ietf-idr-rfc5575bis-04
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On Mon, Oct 16, 2017 at 01:00:26PM +0000, Christoph Loibl wrote:
> > I'm sorry, but I still don't understand. 9.0.0.0/8 and 10.5.0.0/24 don't
> > overlap, shouldn't they both be installed as ACLs? Maybe I don't
> > understand when this algorithm is used?
> 
> Both are actually installed (but the order is determined). This
> algorithm is used for sorting the ACL terms. 

Ah! I see now, thank you for your patience and clarification. For some
reason I derailed into the LPM routing mindset. OK, back to the original
issue. 

OLD: For IP prefix values (IP destination and source prefix) precedence
     is given to the lowest IP value of the common prefix length; if the
     common prefix is equal, then the most specific prefix has
     precedence

PERHAPS:
    For IP prefix values (destination or source) the common high-order
    bits are compared. The number of common bits to compare is the
    lowest prefix-length of the two prefixes. If the high-order bits are
    equal, the prefix with the longer prefix-length has higher
    precedence. If the common high-order bits are different, the prefix
    with the lowest numeric value takes higher precedence.

> >>>   Another question, and I realise this is a big ask: Is it
> >>>   possible to replace the pseudocode with an actual code example?
> >>>   Pseudo languages tend to not follow any specific set of rules
> >>>   and therefor oftentimes
> >> 
> >> IF the group thinks we shall use this - please carefully analyse
> >> the behaviour. I am sure I have hidden some bugs in there and I am
> >> sure it is possible to beautify what I came up with (I am not the
> >> programmer).
> > 
> > I think this is a very good direction and I hope the WG sees this as
> > path forward too.
> > 
> > In the I-D I'd leave out the unittest part for the sake of brevity.
> > I'd also specify what version of python this code was tested
> > against. And of course you can include a link to that github
> > repository in the I-D.  For other drafts we've taken a similar
> > approach.
> 
> Can you point me to some I-Ds that use a similar approach - maybe one
> can learn from that.

You can put the relevant python code inside CDATA block to preserve
formatting.

    <figure>
    <artwork><![CDATA[
    
    my python code ..

    ]]></artwork>
    </figure>

And in the paragraph introducing the code reference the full codebase as
following:

    The full python implementation of 'flowspec-cmp' is available at
    <eref target="https://github.com/stoffi92/flowspec-cmp">https://github.com/stoffi92/flowspec-cmp</eref>;.

Be sure to add something liberal like a BSD-2 Clause LICENSE file to the
repository.

Kind regards,

Job