[Pce] Benjamin Kaduk's Discuss on draft-ietf-pce-stateful-hpce-13: (with DISCUSS and COMMENT)
Benjamin Kaduk via Datatracker <noreply@ietf.org> Wed, 18 September 2019 22:09 UTC
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Date: Wed, 18 Sep 2019 15:09:50 -0700
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Subject: [Pce] Benjamin Kaduk's Discuss on draft-ietf-pce-stateful-hpce-13: (with DISCUSS and COMMENT)
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Benjamin Kaduk has entered the following ballot position for draft-ietf-pce-stateful-hpce-13: Discuss 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-pce-stateful-hpce/ ---------------------------------------------------------------------- DISCUSS: ---------------------------------------------------------------------- I think this should be pretty easy to resolve, though I'm not sure what the right way to do so it. Section 3 says: [I-D.ietf-pce-hierarchy-extensions] defines the H-PCE Capability TLV that is used in the Open message to advertise the H-PCE capability. [RFC8231] defines the Stateful PCE Capability TLV used in the Open message to indicate stateful support. The presence of both TLVs in an Open message indicates the support for stateful H-PCE operations as described in this document. There is no normative reference relationship (in either direction) between draft-ietf-pce-hierarchy-extension and this document; I think that the use of the capability TLV to imply both sets of functionality implies some sort of normative relationship; we wouldn't want version skew between documents to induce breaking changes. In particular, an implementation that already supports RFC 8231 and is implementing the hierarchy extensions would need to know to look at this document *and implement it*, or would unknowingly be noncompliant with this document and fail to interoperate with a peer that is compliant with this document. ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- Abstract This information may then be considered when computing new traffic engineered LSPs, and for associated and dependent LSPs, received from Path Computation Clients (PCCs). [...] nit: I'm not sure how to parse this sentence. The best thing I can come up with is that "when computing new traffic engineered LSPs" and "for associated [...]" are two separate cases, which each could independently consider the information in question. The first one makes sense, but for the second I'm left trying to parse "this information may then be considered for associated and dependent LSPs, received from PCCs", and it's not really clear what considering the PCE is going to do if it just sits there with information from the LSP-DB and information from PCCs (and not doing anything with the information). The Hierarchical Path Computation Element (H-PCE) architecture, provides an architecture to allow the optimum sequence of [...] nit: no comma here. Also, three paragraphs may be pushing the bounds of an abstract in RFC style. Section 1.1 path based on the domain connectivity information. A Child PCE (C-PCE) may be responsible for a single domain or multiple domains, it is used to compute the intra-domain path based on its domain topology information. nit: comma splice This document presents general considerations for stateful PCEs, and not Stateless PCEs, in the hierarchical PCE architecture. In particular, the behavior changes and additions to the existing stateful PCE mechanisms (including PCE-initiated LSP setup and active PCE usage) in the context of networks using the H-PCE architecture. nit: should "active PCE usage" read "active stateful PCE usage"? Section 1.2 The inter-domain LSP could be set up using the end-to-end signaling as described in [RFC6805]. Additionally a per-domain stitched LSP Should I be reading this "could be set up using" as "this document describes how to set [the LSP] up using"? Section 1.2.2 Different signaling methods for inter-domain RSVP-TE signaling are identified in [RFC4726]. Contiguous LSPs are achieved using the nit: are the two "signaling"s redundant? In case of a stateful P-PCE, the stateful P-PCE has to be aware of the inter-domain LSPs for it to consider them during path computation. For example, a domain diverse path from another LSP. nit: this last sentence is a sentence fragment. In this document, for the Contiguous LSP, the above interactions are only between the ingress domain C-PCE and the P-PCE. The use of stateful operations for an inter-domain LSP between the transit/egress domain C-PCEs towards the P-PCE is out of scope of this document. nit: I suggest rewording to avoid the ambiguity of "towards" as applying to the inter-domain LSP vs. the use of stateful operations. Section 3 in the topology). The P-PCE has no information about the content of the child domains. Each child domain has at least one PCE capable of nit: we could potentially reword this in light of the remarks made about ACTN previously. computing paths across the domain. These PCEs are known as C-PCEs and have a direct relationship with the P-PCE. The P-PCE builds the It might be good to forward-reference where we talk about this relationship in more detail. (And, er, have more detail about the relationship than we currently do.) and have a direct relationship with the P-PCE. The P-PCE builds the domain topology map either via direct configuration (allowing network policy to also be applied) or from learned information received from each C-PCE. Policy cannot be applied to information learned at runtime? LSP State Report (EC-EP): a child stateful PCE sends an LSP state report to a Parent Stateful PCE whenever the state of a LSP changes. With respect to "whenever the state of a LSP changes", is there a possibility of a state-change that is visible to the C-PCE but does not affect anything that the P-PCE knows about? Is the state report still expected to be generated in such cases? object to identify the Ingress (PCC). The PLSP-ID used in the forwarded PCRpt by the C-PCE to P-PCE is same as the original one used by the PCC. I couldn't quickly find an authoritative definition of what the PLSP-ID is; I see some discussion in RFC 8231 for the LSP Object, but am not sure if there is prior usage. Section 3.1 paths. Each C-PCE computes a set of candidate path segments across its domain and sends the results to the P-PCE. The P-PCE uses this information to select path segments and concatenate them to derive the optimal end-to-end inter-domain path. The end-to-end path is then sent to the C-PCE that received the initial path request, and this C-PCE passes the path on to the PCC that issued the original request. This is basically the same language as in RFC 6805, so I don't really expect changing it to be the right thing to do, but I'm confused about how the P-PCE is getting "candidate" segments from the C-PCEs but only has to tell the head-end which path got picked. Are the other C-PCEs supposed to find out which of the candidates got used somehow? Section 3.2 a PCUpd message. For LSP delegated to the P-PCE via the child PCE, the P-PCE can use the same PCUpd message to request change to the C- PCE (the Ingress domain PCE), the PCE further propagates the update request to the PCC. nit: comma splice Section 4 I expect this to not be the case, but just to check: is there a possibility for differing levels of authorization for different PCCs, e.g., where PCC A is allowed to request LSPs within the domain and to any other domain, but PCC B is not allowed to request LSPs to/through a subset of domain peers, and PCC C is only allowed to request LSPs within the local domain? As Roman mentions, we don't have a picture of what "full security" means for child/parent communications. Thus it is RECOMMENDED to secure the PCEP session (between the P-PCE and the C-PCE) using either Transport Layer Security (TLS) [RFC8253] per the recommendations and best current practices in [RFC7525] or TCP Authentication Option (TCP-AO) [RFC5925]. It's not entirely clear to me that we need to call out TCP-AO here. Partially since, as Stephen noted in the secdir review, it doesn't seem to be implemented/deployed much, but also since RFC 8231 does call out that it recommends TLS for confidentiality protection, which TCP-AO does not provide. There don't seem to be specific threats enumerated there that the confidentiality protects against, so I am not making a strong recommendation to remove TCP-AO from this text, but I'd like to better understand why it was added. In case of TLS, due care needs to be taken while exposing the parameters of the X.509 certificate, such as subjectAltName:otherName which is set to Speaker Entity Identifier [RFC8232] as per [RFC8253], to ensure uniqueness and avoid any mismatch. I'm not entirely sure which "mismatch" we would be concerned about. And just to check: there aren't expected to be any privacy-like considerations for exposing the speaker entity identifier to a peer in a different domain, right? Section 5.7 I'm not sure how appropriate it is to fully delegate (e.g.) propagation of errors to draft-ietf-pce-enhanced-errors (which is not even a normative reference!) -- it seems important to describe some expectation of the error handling either in this document or in a normative reference thereof. Section 9.2 I think RFCs 5925, 7525, and 8253 should be normative, and RFC 7525 can be cited as BCP 195.
- [Pce] Benjamin Kaduk's Discuss on draft-ietf-pce-… Benjamin Kaduk via Datatracker
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Dhruv Dhody
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Dhruv Dhody
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk