Re: [yang-doctors] Yangdoctors last call review of draft-ietf-ospf-yang-09

Ladislav Lhotka <lhotka@nic.cz> Tue, 09 January 2018 07:51 UTC

Return-Path: <lhotka@nic.cz>
X-Original-To: yang-doctors@ietfa.amsl.com
Delivered-To: yang-doctors@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 2703E126C0F; Mon, 8 Jan 2018 23:51:42 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -7.009
X-Spam-Level:
X-Spam-Status: No, score=-7.009 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, T_RP_MATCHES_RCVD=-0.01, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=nic.cz
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kA0u_-GV1Y8b; Mon, 8 Jan 2018 23:51:39 -0800 (PST)
Received: from mail.nic.cz (mail.nic.cz [IPv6:2001:1488:800:400::400]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id B2F0A126B7F; Mon, 8 Jan 2018 23:51:39 -0800 (PST)
Received: from birdie (cst-prg-29-195.cust.vodafone.cz [46.135.29.195]) by mail.nic.cz (Postfix) with ESMTPSA id CFDA563A36; Tue, 9 Jan 2018 08:51:36 +0100 (CET)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=nic.cz; s=default; t=1515484297; bh=gyFFYFbfilhKcWADNPrRmC52Ybx9yxsj71hhSfcvPPs=; h=From:To:Date; b=QeHshiUTt+PAxuH8ooibzfOiEPcowO2BppHW3gQ+wB1nGfuxdSd147fvz8reZlCxe 7WDwoOs/1ahXAOdoE5Of+CtLv64yM1pjAqO28/pQ+XuayvO83LOn6UchQcwoVzvgfn LPq8p1/ZcDQOf8YIVQB3gxOz3atjugsKdHkWzumM=
Message-ID: <1515484295.18448.9.camel@nic.cz>
From: Ladislav Lhotka <lhotka@nic.cz>
To: "Acee Lindem (acee)" <acee@cisco.com>, "yang-doctors@ietf.org" <yang-doctors@ietf.org>
Cc: "draft-ietf-ospf-yang.all@ietf.org" <draft-ietf-ospf-yang.all@ietf.org>, "ietf@ietf.org" <ietf@ietf.org>, "ospf@ietf.org" <ospf@ietf.org>
Date: Tue, 09 Jan 2018 08:51:35 +0100
In-Reply-To: <D6792F3D.E8CD1%acee@cisco.com>
References: <151255960762.30655.17225294251460480729@ietfa.amsl.com> <D6792F3D.E8CD1%acee@cisco.com>
Organization: CZ.NIC
Content-Type: text/plain; charset="UTF-8"
X-Mailer: Evolution 3.26.3
Mime-Version: 1.0
Content-Transfer-Encoding: 8bit
X-Virus-Scanned: clamav-milter 0.99.2 at mail
X-Virus-Status: Clean
Archived-At: <https://mailarchive.ietf.org/arch/msg/yang-doctors/HKJolr7uBKEx9NqNZ63ePi3iMx8>
Subject: Re: [yang-doctors] Yangdoctors last call review of draft-ietf-ospf-yang-09
X-BeenThere: yang-doctors@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: Email list of the yang-doctors directorate <yang-doctors.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/yang-doctors>, <mailto:yang-doctors-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/yang-doctors/>
List-Post: <mailto:yang-doctors@ietf.org>
List-Help: <mailto:yang-doctors-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/yang-doctors>, <mailto:yang-doctors-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 09 Jan 2018 07:51:42 -0000

Hi Acee,

please see inline.

On Mon, 2018-01-08 at 19:28 +0000, Acee Lindem (acee) wrote:
> Hi Lada,
> 
> Apologies for the delay. We somewhat got hung up on 4 and 6. See inline.
> 
> On 12/6/17, 6:26 AM, "Ladislav Lhotka" <lhotka@nic.cz> wrote:
> 
> > Reviewer: Ladislav Lhotka
> > Review result: Ready with Issues

...

> > 
> > 3. Maybe the draft could mention that implementations should supply a
> >   default routing domain as a system-controlled resource.
> 
> Isn’t this more of an RFC8022BIS statement? I guess we could state this as
> an assumption.

Probably, but it is not a YANG issue, so I'd leave it to you routing folks to
decide.

>  
> 
> > 4. In "when" expressions, the module uses literal strings for
> >   identities. This is known to be problematic, the XPath functions
> >   derived-from() or derived-from-or-self() should be used instead.
> 
> Why is this problematic? Is it because the types can be extended?

That's one reason: derived identities should often also satisfy the constraint.

But the more serious problem is that things like

    when "../../../../../../../rt:type = 'ospf:ospfv3'"

rely on plain string comparison that depends od the actual prefix used for the
"rt:type" value. For one, according to RFC 7951 the JSON encoding of this value
would be "ietf-ospf:ospfv3" so the above expression is always false. 

> > 
> > 6. The types of LSA headers are modelled as integers. While OSPF gurus
> >   probably know these numbers by heart, it is not very
> >   reader-frienly. So at least some references to documents defining
> >   these numbers should be provided, but my suggestion is to consider
> >   implementing them with identities. It seems it might also be useful
> >   to define some "abstract" identities for these types. For example,
> >   if "opaque-lsa" is defined, then the definition of container
> >   "opaque" could simply use
> > 
> >     when "derived-from(../../header/type, 'ospf:opaque-lsa')";
> > 
> >   instead of
> > 
> >      when "../../header/type = 9 or "
> >              + "../../header/type = 10 or "
> >              + "../../header/type = 11";
> 
> I guess I don’t see the identities as always being better. We will
> consider this one.

In what situations could the numbers be better?

...

Thanks, Lada

-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67