[Pce] Shepherd's Review of draft-ietf-pce-pcep-stateful-pce-gmpls-17
Dhruv Dhody <dd@dhruvdhody.com> Fri, 18 February 2022 18:52 UTC
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Subject: [Pce] Shepherd's Review of draft-ietf-pce-pcep-stateful-pce-gmpls-17
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Hi Authors, Thank you for your work on this document. I have finished my Shepherd review and have some concerns that I would like to see resolved before shipping this to the AD. In case the format of this email is off, see https://notes.ietf.org/draft-ietf-pce-pcep-stateful-pce-gmpls-17?view <https://notes.ietf.org/#Major>Major - RFC 8779 added the Routing Granularity (RG) flag in the RP object for Explicit Label Control (ELC). Since RP object is not used in stateful messages how is the RG indicated in the stateful PCEP messages? - How does one identify if the LSP is a GMPLS LSP? Is it based on the presence of any of the generalized object types? If yes - we should add text and perhaps make generalized end-point mandatory for all messages. Or should there be some other way to signal this? - Several issues with LSP exclusion subobject (Section 7.2.2) - What is the role of the Attribute field (which identifies interface, node, or SRLG) but in this instance, it is the LSP? Do you really need this field? - Symbolic Path Name is unique in the context of a PCC, but no PCC address is encoded in the sub-object. Is the use limited to an LSP originating from the same ingress and thus sharing the PCC? This is under-specified. - Error Handling - The error case in section 8.1 is not clear. How is it specific to GMPLS? If such error handling is needed it should be done outside the scope of this document. - Creating a new Error-Type (LSP state information missing) seems to be an overkill. Please reuse Error-Type=19 Invalid Operation for instance. - RFC 8779 does not mandate LABEL-REQUEST TLV whereas this document does. The reason needs to be stated clearly. - It should be clearly stated that all the error checks for GMPLS objects and TLVs for PCReq/PCRep in RFC 8779 are also applicable to PCRpt/PCUpd/PCInitiate messages. - Error handling is missing in case of stateful PCEP message for GMPLS LSP, without the capability advertisement by both PCEP peers. - Section 11 - Please expand this section by adding all subsections as per RFC 6123 (the usual practice for PCE WG documents). See RFC 8779 for guidance. - Section 12 - Please expand the security consideration with reference to RFC8253, RFC8281, RFC8779 etc. Also, do list security issues specific to the stateful control of GMPLS LSP. <https://notes.ietf.org/#Minor0>Minor - Abstract - I have concern over the use of the term “technology-agnostic” here. How about - OLD: The PCE communication Protocol (PCEP) has been extended to support stateful PCE functions where the PCE retains information about the paths already present in the network, but those extensions are technology-agnostic. NEW: The PCE communication Protocol (PCEP) has been extended to support stateful PCE functions where the Stateful PCE maintains information about paths and resource usage within a network, but these extensions do not cover all requirements for GMPLS networks. END - Introduction - Some suggested changes -- OLD: Such a PCE is usually referred as a stateless PCE. To request path computation services to a PCE, [RFC5440] defines the PCE communication Protocol (PCEP) for interaction between a Path Computation Client (PCC) and a PCE, or between two PCEs. PCEP as specified in [RFC5440] mainly focuses on MPLS networks and the PCEP extensions needed for GMPLS-controlled networks are provided in [RFC8779]. NEW: A PCE that only maintains TED is referred to as a stateless PCE. [RFC5440] describes the Path Computation Element Communication Protocol (PCEP) for interaction between a Path Computation Client (PCC) and a PCE, or between two PCEs, enabling computation of TE LSPs. PCEP is further extended to support GMPLS-controlled networks as per [RFC8779]. END -- OLD: In order for these applications to able to exploit the capability of stateful PCEs, extensions to PCEP are required. NEW: In order for these applications to be able to exploit the capability of stateful PCEs, extensions to PCEP for GMPLS are required. END -- OLD: [RFC8231] provides the fundamental extensions needed for stateful PCE to support general functionality. NEW: [RFC8231] specifies a set of extensions to PCEP to enable stateful control of TE LSPs where they are configured on the PCC, and control over them could be delegated to the PCE. END -- OLD: Section 3 provides General context of Stateful PCE and PCEP for GMPLS are provided in Section 3, and PCE initiation requirement for GMPLS is provided in section 4. Protocol extensions are included in section 5, as a solution to address such requirements. NEW: Section 3 provides a general context of the usage of Stateful PCE and PCEP for GMPLS. The requirements including PCE-initiation for GMPLS LSPs is provided in Section 4. PCEP message extensions are specified in Section 6, as a solution to address such requirements. END -- - The document uses the term “remote-initiated” at various places (which does not align with RFC 8281), please use PCE-initiated. - Please consider adding a terminology section - Section 3 - Some suggested changes -- OLD: This section is built on the basis of Stateful PCE in [RFC8231] and PCEP for GMPLS in [RFC8779]. NEW: This section is built on the basis of Stateful PCE specified in [RFC8231] and PCEP extension for GMPLS specified in [RFC8779]. END -- OLD: For passive stateful PCEs, PCReq/PCRep messages are used to convey path computation instructions. GMPLS-technology specific Objects and TLVs are defined in [RFC8779], so this document just points at that work and only adds the stateful PCE aspects where applicable. NEW: For passive stateful PCEs, PCReq/PCRep messages are used to request for path computation. GMPLS-technology specific Objects and TLVs are defined in [RFC8779], this document builds on it and adds the stateful PCE aspects where applicable. END -- - Section 4 - The 2nd requirement does not state what is new here for GMPLS – could be removed? - The last requirement for protection - isn’t it already satisfied by RFC 8754. I also don’t see any extension in this document for this requirement either – can it be removed? - Section 5.1 - Suggested change -- OLD: Capability Advertisement has been specified in [RFC8231], and can be achieved by using the "STATEFUL-PCE-CAPABILITY" in the PCEP TLV Type Indicators. Another GMPLS-CAPABILITY TLV in the PCEP TLV Type Indicators has been defined in [RFC8779]. According to [RFC8779], IANA created a registry to manage the value of the GMPLS-CAPABILITY TLV's field. New bits, LSP-UPDATE-CAPABILITY (TBD1) and LSP- INSTANTIATION-CAPABILITY (TBD2), are introduced as flags to indicate the capability for LSP update and remote LSP initiation in GMPLS networks. NEW: Capability Advertisement has been specified in [RFC8231], and can be achieved by using the "STATEFUL-PCE-CAPABILITY TLV" in the Open message. Another GMPLS-CAPABILITY TLV has been defined in [RFC8779]. A subregistry to manage the Flag field of the GMPLS-CAPABILITY TLV is created by the IANA as requested by [RFC8779]. New bits, LSP-UPDATE-CAPABILITY (TBD1) and LSP-INSTANTIATION-CAPABILITY (TBD2), are introduced as flags to indicate the capability for LSP update and LSP initiation in GMPLS networks. END -- - Section 5.2 - Suggested change -- OLD: PCCs need to report the attributes of LSPs to the PCE to enable stateful operation of a GMPLS network. This process is known as LSP state synchronization. NEW: After the session between the PCC and a stateful PCE is initialized, the PCE must learn the state of a PCC's LSPs (including its attributes) before it can perform path computations or update LSP attributes in a PCC. This process is known as LSP state synchronization. END -- - Section 6 - Suggested change -- OLD: This section describes how the PCEP messages are extended by using Routing Backus-Naur Form (RBNF) [RFC5511] formats. Contents in this section are for informative purpose. NEW: This section uses the Routing Backus-Naur Form (RBNF) [RFC5511] to illustrate the PCEP messages. The RBNF in this section is reproduced for informative purposes. END -- - Section 6.1 - The use of RBNF from RFC 8231 misses the use of the END-POINTS object which is one of the requirements for GMPLS and using the RBNF from RFC 8623 would be quite confusing. If you must include RBNF it could be added as an example in the appendix, but I suggest removing it from here. You could instead add text like this - The format of the PCRpt message is specified in [RFC8231] and extended in [RFC8623] to include the END-POINTS object. Some RBNF constructs usage for GMPLS is described as follows: - Suggested change -- OLD: GENERALIZED-BANDWIDTH object has been defined in [RFC8779] to address the limitation of the BANDWIDTH object, with supporting the following: NEW: [RFC8779] extended the BANDWIDTH object encoding to allow the object to express the generalized bandwidth to allow: END -- - Plus you should add text about END-POINTS, LSPA, IRO, XRO, and SWITCH-LAYER objects in this list to be consistent with section 5.2 - Section 6.2 - same change as 6.1 and this statement is incorrect - “The SRP object is OPTIONAL”. - Section 6.3 - if you decide to move the RBNF for others then it would make sense to do it for PCInitiate as well. - The END-POINTS object type text is applicable for all messages and not just PCInitiate. Maybe repeat it for PCRpt and PCUpd as well. - Query: Is END-POINTS mandatory only for PCInitiate? Why? I am wondering if the rules for END-POINTS are only applicable for PCInitiate, if not we need to move to a commonplace! (Section 7.1 does not limit to PCInitiate ) - Section 7.2.1 - Update the text for S and I flag to make sure it applies to GMPLS LSP only. - Suggested change when XRO itself is OPTIONAL (also update similar text in 8.2) - -- OLD: This sub-object is OPTIONAL in the exclude route object (XRO) and can be present multiple times. When a stateful PCE receives a PCReq message carrying this sub-object, it MUST search for the identified LSP in its LSP-DB and then exclude from the new path computation all resources used by the identified LSP. NEW: This sub-object MAY be present multiple times in the exclude route object (XRO) to exclude resources from multiple LSPs. When a stateful PCE receives a PCEP message carrying this sub-object, it MUST search for the identified LSP in its LSP-DB and then exclude from the new path computation all resources used by the identified LSP. END -- - Section 8.2 - Error is limited to PCReq, I suggest changing that to PCReq/PCRpt or just PCEP message. Also, update the error string to match with the general style - https://www.iana.org/assignments/pcep/pcep.xhtml#pcep-error-object - Section 10 - Please update the text in the IANA consideration to say that you are requesting the allocation and not that IANA has already made the allocation. - Section 10.2 - Please update -- OLD: IANA maintains the "PCEP Parameters" registry containing a subregistry called "PCEP Objects". This registry has a subregistry for the XRO (Exclude Route Object) listing the sub-objects that can be carried in the XRO. IANA is requested to assign a further sub- object that can be carried in the XRO as follows: NEW: IANA maintains the various XRO Subobjects types within the "XRO Subobjects" subregistry of the PCEP Numbers registry. IANA is requested to allocate a codepoint for another XRO subobject as follows: END -- - Section 10.3 - You need to also add New values are to be assigned by Standards Action [RFC8126]. Each bit should be tracked with the following qualities: o Bit number (counting from bit 0 as the most significant bit) o Capability description o Defining RFC <https://notes.ietf.org/#Nits>Nits - The title - s/Path Computation Element (PCE) Protocol/Path Computation Element Communication Protocol (PCEP)/ ; PCE is well known as per https://www.rfc-editor.org/materials/abbrev.expansion.txt - Expand on first use or expand in the terminology section - WSON - OTN - SONET - SDH - PCUpd - PCRpt - PCReq - PCRep - PCInitiate - TDM - L2SC - OTN-TDM - LSC - TSpec - WDM - LSPA - IRO - XRO - ERO - MEF - Add suitable references when mentioning - active stateful PCE and passive stateful PCE - delegation - explicit label control - bidirectional co-routed LSP - s/GMPLS CAPABILITY TLV/GMPLS-CAPABILITY TLV/ - Section 5.2 - s/The END-POINTS object is carried/The END-POINTS object can be carried/ - s/GENERALIZED-BANDWIDTH/Generalized bandwidth/ - s/“label request” TLV/LABEL-REQUEST TLV/ - s/unnumbered endpoint TLV/UNNUMBERED-ENDPOINT TLV/ Thanks, Dhruv
- [Pce] Shepherd's Review of draft-ietf-pce-pcep-st… Dhruv Dhody
- [Pce] 答复: Shepherd's Review of draft-ietf-pce-pce… Zhenghaomian
- Re: [Pce] Shepherd's Review of draft-ietf-pce-pce… Dhruv Dhody