Re: [Idr] IETF LC for IDR-ish document <draft-ietf-grow-bgp-reject-05.txt> (Default EBGP Route Propagation Behavior Without Policies) to Proposed Standard

Brian Dickson <brian.peter.dickson@gmail.com> Fri, 05 May 2017 22:07 UTC

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From: Brian Dickson <brian.peter.dickson@gmail.com>
Date: Fri, 5 May 2017 15:07:25 -0700
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To: Enke Chen <enkechen@cisco.com>
Cc: Robert Raszuk <robert@raszuk.net>, idr wg <idr@ietf.org>
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Subject: Re: [Idr] IETF LC for IDR-ish document <draft-ietf-grow-bgp-reject-05.txt> (Default EBGP Route Propagation Behavior Without Policies) to Proposed Standard
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Top-reply, to make it easy to read the summary responses. I speak only for
myself, of course.

1) CE - either existing CE stuff can handle this during upgrades (qv
discussion about upgrade vs out-of-the-box), and/or suitable warnings.
Use of "permit all" policy achieves the desired effect on CE, and satisfies
the requirements of this standard.

2) ORF - there is no guarantee that ORF is configured or present, and
cannot be checked prior to bringing up BGP. Thus, "No." Just, no, ORF is
not adequate for this.

3) Yes, permit all would be sufficient. All that is needed is an *explicit*
policy, regardless of what it is.

This all can be expressed by the difference between two mathematical
comparisons:
X>=0
X>0

If X is the place-holder for "policy", and "0" means no policy is
configured, all that is required is ANY value of X which is not 0.

There is no minimum positive value for "X", in other words - just as long
as it is not 0.

There is no requirement that the same rules be used by any given
implementation. There is no interoperability requirement, as these are all
local (implementations and policies configured).

The "X>0" must be a forcing function, so BCP is not sufficient.

That is the intent and purpose of "-reject".

Respectfully,

Brian

On Fri, May 5, 2017 at 2:38 PM, Enke Chen <enkechen@cisco.com>; wrote:

> Hi, Folks:
>
> I still believe that the draft is BCP material. In addition, I would like
> see several
> points (raised by Robert R and others) addressed in the draft:
>
> 1) Inbound filter on the CE:
>
>    Requiring inbound filtering makes sense for the providers, and I
> believe that
>    is the common practice.  But it is not needed and has little to do with
> route
>    leaking on the CE side.  Currently for the customers that receive full
> routes
>    or partial routes from their providers, there is no need for inbound
> filters
>    (and no rational way to generate such a filter in many cases) and they
> are not
>    used in many cases.
>
>    The draft should document these facts about the inbound filter.
>
> 2) ORF:
>
>    Certainly it would be just as effective as "outbound filtering" if a
> customer
>    registers its prefixes with IRR and then relies on receiving the ORF
> (from its
>    provider) generated from the IRR.
>
>    This should be noted in the draft.
>
> 3) Policy definition
>
>    Again as pointed out many times, would "permit all" considered as an
> acceptable
>    policy?  Such policy does nothing or very little to help route leaking
> reduction.
>
>    This should also be noted in the draft.
>
> Regards,  -- Enke
>
> On 5/5/17 2:34 AM, Robert Raszuk wrote:
> > Hi John,
> >
> > If someone make a point of the discussion and stops arguing about it ib
> next 100 emails does
> > not mean that the rough consensus was reached on his or her comment.
> >
> > Honestly to me I do not see that rough consensus to adopt this change as
> standard track
> > document has been reached on IDRWG mailing list.
> >
> > Moreover document does not define what policy is. Is accepting ORF a
> policy or not ?
> > No clarity will lead to very inconsistent implementations.
> >
> > Cheers,
> > R.
> >
> > PS I uderstand that forcing inbound policy is to push folks to apply
> BCP38. But this at best is applicable only at the ISP inbound side ....
> >
> > On May 5, 2017 12:41 AM, "John G. Scudder" <jgs@juniper.net <mailto:
> jgs@juniper.net>>; wrote:
> >
> >     Hi All,
> >
> >     Below is my summary of this mail thread, FYI.
> >
> >     As I understand it the next steps will be for the GROW AD (Warren)
> in consultation with the GROW chairs (Pete and Chris) to decide.
> >
> >     Thanks to all for your participation.
> >
> >     --John
> >
> >     The thread "[Idr] IETF LC for IDR-ish document
> <draft-ietf-grow-bgp-reject-05.txt> (Default EBGP Route Propagation
> Behavior Without Policies) to Proposed Standard" started on April 19 and by
> May 1 had accumulated well over a hundred messages from 27 or so
> contributors.
> >
> >     The thread defies a simple declaration of "there was consensus".
> However, and somewhat to my surprise, after reading back through the
> history and trying to give special attention to issues opened but
> subsequently rebutted, I think we do have consensus supporting advancement.
> >
> >     There was quite a bit of discussion about the intended status of the
> document -- Standards Track vs. Informational vs. BCP, Updates 4271 or not.
> In the end, I think the best we can really say is that there was no
> consensus to choose something other than what the doc currently says. I've
> counted those who had document status objections under "con".
> >
> >     If it were up to me to call consensus (which it is not) I would say
> there is rough consensus to advance the document on the Standards Track,
> updating 4271. I might consider offering a few extra days of LC for
> editorial comments *only*, with discussion of the document status and
> general outline and features of the solution being placed explicitly out of
> scope. This is because there were, interspersed among the many other
> comments, a few editorial ones, and I just don't have the energy to figure
> out if they were all taken in (although I think the authors have been
> fairly diligent about this). It's also because the most recent versions of
> the document have some fairly significant changes compared to -05.
> >
> >     Several issues were raised and discussed as part of the thread,
> including (but not limited to, I'm under no illusions that I've captured or
> even fairly represented every single point):
> >
> >     1. A number of people, largely from router vendors, expressed
> concern that changing defaults is difficult. These ranged from saying it
> was impossible, to merely difficult and not worth it. In response to this,
> others (including but not limited to other vendor folk) provided examples
> for how a default could be changed without invoking a flag day. Greg
> Hankins, in particular, provided a detailed explanation of his company's
> process. The proponents of "it's hard to change defaults" didn't follow up
> to the various rebuttals, so on the balance I would have to say they're "in
> the rough". It's a bit dicey to make this call since failure to follow up
> can also reflect simple fatigue, but in this case the conversation doesn't
> just tail off, it ends with concrete arguments on the "this can be done"
> side.
> >
> >     2. Related, there is the position that "yes of course anything can
> be done in software but the cost/benefit ratio isn't right". This is
> clearly a matter of personal taste so can't be dismissed (or supported)
> solely on the basis of logic.
> >
> >     3. Should the behavior be per-AFI/SAFI instead of global? Perhaps to
> apply only to Internet routing and not other applications?
> >     Pro: the motivation section of the document calls out the Internet
> use case
> >     Con: there's no clear, unambiguous way to actually specify this
> (AFI/SAFI 1/1 can be used in a VPN context, e.g.). different defaults for
> different AFI/SAFI is confusing for the user and the extra complexity not
> required.
> >
> >     4. How about "default no-propagate" rather than "default
> no-advertise"?
> >     Pro: Keeps CE configurations more compact, less surprising behavior.
> >     Con: Behavior is actually more surprising (since harder to explain,
> less consistent). Doesn't cover all plausible use cases.
> >
> >     5. These defaults will hurt some deployments that want to rely on
> the old defaults. Examples, data centers, CEs.
> >     Pro: as stated.
> >     Con: it seems unlikely anyone is actually relying on default
> behavior in their data center, since defaults vary between vendors, can any
> examples be brought forward? None offered, instead a couple DC operators
> stated support for the draft as written. For CEs, discussion around upgrade
> strategies without breaking existing deployments, see #1.
> >
> >     6. This should not update 4271, not be Standards Track, it should be
> a BCP, should be Informational, etc.
> >     Pro: It's not protocol, but just defaults, doesn't affect state
> machine, wire encoding.
> >     Con: Plenty of Standards Track documents specify defaults when
> considered important to operation of protocol, and even more ephemeral
> things such as textual encodings.
> >     Pro: It should be a BCP and/or shouldn't update 4271 because it's
> bad to make existing implementations nonconformant.
> >     Con: Formally, it doesn't work that way. Also, the point is to ask
> implementations to change.
> >
> >     7. There are various other proposals to mitigate route leaks and
> provide BGP security features.
> >     Pro: implied, "we've already got one"
> >     Con: some of these are still in flight, not even WG docs. None
> address exactly the same issues. Some don't even overlap.
> >
> >     8. Why not just do perfect filtering at the service provider border?
> It's an education problem!
> >     Pro: perfect filtering prevents harm from route leaks.
> >     Con: decades of experience indicate strategies that require
> perfection are not successful.
> >
> >     Taking a rough head count, here's here I understand people's
> positions to have ended up:
> >
> >     Commented, no discernible position on advancing the doc -- 2
> >
> >     chris morrow
> >     alvaro retana
> >
> >     Pro -- 16
> >
> >     john scudder
> >     randy bush
> >     brian dickson
> >     joe provo
> >     warren kumari
> >     jared mauch
> >     job snijders
> >     gert doering
> >     mik abrahamson
> >     jeff haas -- support, though would prefer BCP
> >     greg hankins
> >     nick hilliard
> >     jay borkenhagen
> >     ian dickinson
> >     martijn schmidt
> >     keyur patel
> >
> >     Con -- On procedural grounds (should be a BCP, or should be
> Informational) -- 3
> >
> >     eric rosen -- would be OK as Informational, opposes other statuses
> >     tony przygienda -- it should be a BCP
> >     enke chen -- fine if it's a BCP. changing defaults is infeasible
> ("in the rough")
> >
> >     Con -- In the rough -- 2
> >
> >     acee lindem -- contrary to auto-discovery (rebutted, in the rough),
> should have a 'backwards compatibility' section
> >     jeff tantsura -- changing defaults "can not be changed". -- in the
> rough
> >
> >     Con -- Other objections, in most cases not explicitly stated as
> opposing advancement but that's my reading of their mood -- 4
> >
> >     robert raszuk -- not explicitly, but has raised numerous "but what
> about...", all or most replied to
> >     alex azimov -- 'it'll just result in empty policy' and 'route leaks
> are rare anyway', both later rebutted and not replied (so, "in the rough")
> >     tom petch -- not explicitly, but generally skeptical tone to
> comments. specifically requested an analysis of what harms the proposal
> might cause. (not done or replied to AFAIK)
> >     bruno decraene -- would rather improve route-leak draft, numerous
> other points and suggestions, mostly replied to, too much to summarize
> >     _______________________________________________
> >     Idr mailing list
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> >
> >
> >
> >
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