Re: [OSPF] Alvaro's DISCUSS on OSPF Admin Tags

Hi Alia, Shraddha,

From: Alia Atlas <akatlas@gmail.com<mailto:akatlas@gmail.com>>
Date: Sunday, November 8, 2015 at 1:59 AM
To: Acee Lindem <acee@cisco.com<mailto:acee@cisco.com>>
Cc: Shraddha Hegde <shraddha@juniper.net<mailto:shraddha@juniper.net>>, OSPF WG List <ospf@ietf.org<mailto:ospf@ietf.org>>, OSPF ADs <ospf-ads@tools.ietf.org<mailto:ospf-ads@tools.ietf.org>>
Subject: Re: [OSPF] Alvaro's DISCUSS on OSPF Admin Tags

Hi Acee,

Thanks very much for reading through and pulling out the relevant questions.
I'd like to see this conversation resolve quickly.

On Sat, Nov 7, 2015 at 9:58 AM, Acee Lindem (acee) <acee@cisco.com<mailto:acee@cisco.com>> wrote:
Hi Shraddha,

I’ve read through this discussion and I’m wondering why we just can’t
remove this normative text with respect to the interpretation of OSPF Node
Admin tags?

   1. Since the tags are advertised by a single node, why is do they have
to be unordered? It seems there should be a reason for this even if this
semantic is retained.

I can understand this restriction in terms of implementation complexity &
assumptions.  A router that receives the tag list might want to store them in
numerical order or such for easier searching.  If the tag order matters, there
can be rather different requirements in terms of how the listener uses the
information.

Perhaps the answer is that we don’t see a use case for maintaining tag order given that they may come from multiple sources it adds a lot of complexity to try and maintain order. Note that the order independence is also in RFC 5130 (IS-IS prefix admin tags) - see section 4.

   2. Why can’t they be advertised in multiple flooding scopes? There
could be one set of tags applicable at the area scope and another
applicable at the AS wide scope.

I agree that I don't see implementation complexity logic driving this.  Perhaps
it allows for storing tags per device in a flat structure instead of requiring that
they are stored per area?

I wouldn’t think so.

Regardless, this feels like it has more impact on operational complexity of
having to define the same meaning for different tags for different areas.

This restriction of a single flooding scope wouldn’t preclude this.

Thanks,
Acee

Regards,
Alia

In essence, since the tags are purely opaque, it seems you could simply
remove the last 2-3 paragraphs of section 3.2.1 and the last paragraph of
section 3.2.2 as these seem to be rather arbitrary restrictions.

Thanks,
Acee

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