[Idr] Benjamin Kaduk's No Objection on draft-ietf-idr-bgp-ls-segment-routing-msd-17: (with COMMENT)
Benjamin Kaduk via Datatracker <noreply@ietf.org> Mon, 04 May 2020 21:53 UTC
Return-Path: <noreply@ietf.org>
X-Original-To: idr@ietf.org
Delivered-To: idr@ietfa.amsl.com
Received: from ietfa.amsl.com (localhost [IPv6:::1]) by ietfa.amsl.com (Postfix) with ESMTP id 2E60A3A10D1; Mon, 4 May 2020 14:53:01 -0700 (PDT)
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
From: Benjamin Kaduk via Datatracker <noreply@ietf.org>
To: The IESG <iesg@ietf.org>
Cc: draft-ietf-idr-bgp-ls-segment-routing-msd@ietf.org, idr-chairs@ietf.org, idr@ietf.org, Susan Hares <shares@ndzh.com>, aretana.ietf@gmail.com, shares@ndzh.com
X-Test-IDTracker: no
X-IETF-IDTracker: 6.129.0
Auto-Submitted: auto-generated
Precedence: bulk
Reply-To: Benjamin Kaduk <kaduk@mit.edu>
Message-ID: <158862918074.23288.8494237048042781894@ietfa.amsl.com>
Date: Mon, 04 May 2020 14:53:01 -0700
Archived-At: <https://mailarchive.ietf.org/arch/msg/idr/MleY5P9JwkQneaqagtusMV6ap0A>
Subject: [Idr] Benjamin Kaduk's No Objection on draft-ietf-idr-bgp-ls-segment-routing-msd-17: (with COMMENT)
X-BeenThere: idr@ietf.org
X-Mailman-Version: 2.1.29
List-Id: Inter-Domain Routing <idr.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/idr>, <mailto:idr-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/idr/>
List-Post: <mailto:idr@ietf.org>
List-Help: <mailto:idr-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/idr>, <mailto:idr-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 04 May 2020 21:53:01 -0000
Benjamin Kaduk has entered the following ballot position for draft-ietf-idr-bgp-ls-segment-routing-msd-17: No Objection When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-ls-segment-routing-msd/ ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- Not a whole lot of interesting comments on this one; it seems like a pretty straightforward codepoint allocation with relevant (security and other) considerations covered in other documents. I do appreciate the discussion in the security considerations section; it looks good. This document talks about the MSD as being the depth of a stack that a given node can "impose". Is there a similar consideration (or protocol element) for what a given node can read/process? (I think I remember such a document going by, but don't have enough keywords to search for it efficiently.) Is there a specific error-handling behavior to use when a Node MSD TLV is received with a value larger than the value of a Link MSD TLV associated with that node (for the same MSD-type)? Is that one of the things "left to the consumer of the BGP-LS information" by Sectoin 7? Section 1 In the future, it is expected that new MSD-Types will be defined to signal additional capabilities, e.g., ELs, SIDs that can be imposed through recirculation, or SIDs associated with another data plane such as IPv6. MSD advertisements may be useful even if SR itself is not enabled. For example, in a non-SR MPLS network, MSD defines the maximum label depth. It's slightly interesting that we still call it "MSD" even though there are potential uses in a broader scope. Perhaps just a historical legacy and we need to remain consistent with the name in common use... Though, perhaps the terminology section in this document does not need to be quite so constrained by the past. Section 3 identified by the corresponding Router-ID. Node MSD is the smallest MSD supported by the node on the set of interfaces configured for use. MSD values may be learned via a hardware API or may be It is a shame that the semantics are already locked in (as was noted by a previous review that I can't find right now?) and the efficient encoding of "large per-node value with smaller per-link values for exceptions" is not admissible. Section 5 MSD-type is not supported. The correct interpretation MUST be specified when an MSD-type is defined in [RFC8491]. Is this "is defined in the registry defined in [RFC8491]" or "is defined according to the procedures in [RFC8491]" or something else? The current text doesn't scan properly, as it implies that a future new MSD-type will be defined in RFC 8491, an immutable document. Section 7 Specifically, the malformed attribute tests for syntactic checks in the Fault Management section of [RFC7752] now encompass the new BGP- LS Attribute TLVs defined in this document. [...] Interestingly, the referenced section of 7752 does not seem to explicitly say that other invariant properties of TLV lengths (e.g., that they must be a multiple of 2 as for the ones defined by this document) should be checked. [RFC7752]. The MSD information introduced in BGP-LS by this specification, may be used by BGP-LS consumer applications like a SR path computation engine (PCE) to learn the SR SID stack handling https://www.rfc-editor.org/materials/abbrev.expansion.txt lists "PCE" as having a well-known expansion to "Path Computation Element" (not "engine") that can be used directly in abbreviated form without any expansion given. Section 8 issues when propagating the TLVs into BGP-LS. The advertisement of the node and link attribute information defined in this document presents no additional risk beyond that associated with the existing node and link attribute information already supported in [RFC7752]. I'd suggest hedging to "no significant additional risk", though I do not have an example of additional marginal risk at hand.
- [Idr] Benjamin Kaduk's No Objection on draft-ietf… Benjamin Kaduk via Datatracker
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Jeff Tantsura
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Ketan Talaulikar (ketant)
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Acee Lindem (acee)
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Benjamin Kaduk
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Alvaro Retana
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Benjamin Kaduk
- Re: [Idr] Benjamin Kaduk's No Objection on draft-… Jeff Tantsura