]> Update to the IANA Path Communication Element Protocol (PCEP) Numbers Registration Procedures and the Allowance of Experimental Error Codes Huawei
India dhruv.ietf@gmail.com
Old Dog Consulting
adrian@olddog.co.uk
RTG pce This document updates the registration procedure within the IANA "Path Computation Element Protocol (PCEP) Numbers" registry group. This specification changes some of the registries with Standards Action to IETF Review as defined in RFC 8126 and thus updates RFCs 8231, 8233, 8281, 8623, 8664, 8685, 8697, 8733, 8745, 8779, 8780, 8800, 8934, 9050, 9059, 9168, 9357, 9504, 9603, and 9604. Designating "experimental use" sub-ranges within codepoint registries is often beneficial for protocol experimentation in controlled environments. Although the registries for PCEP messages, objects, and TLV types have sub-ranges assigned for Experimental Use, the registry for PCEP Error-Types and Error-values currently does not. This document updates RFC 5440 by designating a specific range of PCEP Error-Types for Experimental Use.
Introduction The IANA "Path Computation Element Protocol (PCEP) Numbers" registry group was populated by several RFCs produced by the Path Computation Element (PCE) Working Group. Most of the registries include IETF Review as the registration procedure. There are a few registries that use Standards Action. Thus, the values in those registries can be assigned only through the Standards Track or Best Current Practice RFCs in the IETF Stream. This memo changes the policy from Standards Action to IETF Review to allow any type of RFC under the IETF Stream to make the allocation request. Further, in , IANA assigns values to the PCEP parameters. The allocation policy for each of these parameters specified in is IETF Review . In consideration of the benefits of conducting experiments with PCEP and the utility of experimental codepoints , codepoint ranges for PCEP messages, objects, and TLV types for Experimental Use are designated in . However, protocol experiments may also need to return protocol error messages indicating experiment-specific error cases. It will often be that previously assigned error codes (in the "PCEP-ERROR Object Error Types and Values" registry) can be used to indicate the error cases within an experiment, but there may also be instances where new, experimental error codes are needed. In order to run experiments, it is important that the codepoint values used in the experiments do not collide with existing codepoints or any future allocations. This document updates by changing the allocation policy for the registry of PCEP Error-Types to mark some of the codepoints as assigned for Experimental Use. As stated in , experiments using these codepoints are not intended to be used in general deployments, and due care must be taken to ensure that two experiments using the same codepoints are not run in the same environment.
Standards Action PCEP Registries Affected The following table lists the registries under the "Path Computation Element Protocol (PCEP) Numbers" registry group whose registration policies have been changed from Standards Action to IETF Review. The affected registries list this document as an additional reference. Where this change has been applied to a specific range of values within the particular registry, that range is given in the Remarks column. PCEP Registries Affected
Registry RFC Remarks
BU Object Type Field
LSP Object Flag Field
STATEFUL-PCE-CAPABILITY TLV Flag Field
LSP-ERROR-CODE TLV Error Code Field
SRP Object Flag Field
SR-ERO Flag Field
PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators
SR Capability Flag Field
WA Object Flag Field
Wavelength Restriction TLV Action Values
Wavelength Allocation TLV Flag Field
S2LS Object Flag Field
H-PCE-CAPABILITY TLV Flag Field
H-PCE-FLAG TLV Flag Field
ASSOCIATION Flag Field
ASSOCIATION Type Field
AUTO-BANDWIDTH-CAPABILITY TLV Flag Field
Path Protection Association Group TLV Flag Field
Generalized Endpoint Types 0-244
GMPLS-CAPABILITY TLV Flag Field
DISJOINTNESS-CONFIGURATION TLV Flag Field
SCHED-PD-LSP-ATTRIBUTE TLV Opt Field
Schedule TLVs Flag Field
FLOWSPEC Object Flag Field
Bidirectional LSP Association Group TLV Flag Field
PCECC-CAPABILITY sub-TLV
CCI Object Flag Field for MPLS Label
TE-PATH-BINDING TLV BT Field
TE-PATH-BINDING TLV Flag Field
LSP-EXTENDED-FLAG TLV Flag Field
LSP Exclusion Subobject Flag Field
SRv6-ERO Flag Field
SRv6 Capability Flag Field
Future registries in the "Path Computation Element Protocol (PCEP) Numbers" registry group should prefer to use IETF Review over Standards Action.
Experimental Error-Types Per this document, IANA has designated four PCEP Error-Type codepoints (252-255) for Experimental Use. IANA maintains the "PCEP-ERROR Object Error Types and Values" registry under the "Path Computation Element Protocol (PCEP) Numbers" registry group. IANA has changed the assignment policy for the "PCEP-ERROR Object Error Types and Values" registry as follows: PCEP-ERROR Object Error Types and Values Registry Assignment Policy
Range Registration Procedures Note
0-251 IETF Review The IETF Review procedure applies to all Error-values (0-255) for Error-Types in this range.
252-255 Experimental Use The Experimental Use policy applies to all Error-values (0-255) for Error-Types in this range.
Furthermore, IANA has added the following entry to the registry: PCEP-ERROR Object Error Types and Values Registry
Error-Type Meaning Error-value Reference
252-255 Reserved for Experimental Use 0-255: Reserved for Experimental Use RFC 9756
Advice on Experimentation An experiment that wishes to return experimental error codes should use one of the experimental Error-Type values as defined in this document. The experiment should agree on, between all participating parties, which Error-Type to use and which Error-values to use within that Error-Type. The experiment will describe what the meanings of those Error-Type/Error-value pairs are. Those Error-Types and Error-values should not be recorded in any public (especially any IETF) documentation. Textual or symbolic names for the Error-Types and Error-values may be used to help keep the documentation clear. If multiple experiments are taking place at the same time using the same implementations, care must be taken to keep the sets of Error-Types/Error-values distinct. Note that there is no scope for experimental Error-values within existing non-experimental Error-Types. This reduces the complexity of the registry and implementations. Experiments should place all experimental Error-values under the chosen experimental Error-Types. If, at some future time, the experiment is declared a success and moved to IETF work targeting publication on the Standards Track, each pair of Error-Types/Error-values will need to be assigned by IANA from the registry. In some cases, this will involve assigning a new Error-Type with its subtended Error-values. In other cases, use may be made of an existing Error-Type with new subtended Error-values being assigned. The resulting change to code in an implementation is as simple as changing the numeric values of the Error-Types and Error-values.
Handling of Unknown Experimentation A PCEP implementation that receives an experimental Error-Type in a PCEP message and does not recognize the Error-Type (i.e., is not part of the experiment) will treat the error as it would treat any other unknown Error-Type (such as from a new protocol extension). An implementation that is notified of a PCEP error will normally close the PCEP session (see ). In general, PCEP implementations are not required to take specific action based on Error-Types but may log the errors for diagnostic purposes. An implementation that is part of an experiment may receive an experimental Error-Type but not recognize the Error-value. This could happen because of any of the following reasons:
  • a faulty implementation
  • two implementations not being synchronized with respect to which Error-values to use in the experiment
  • more than one experiment being run at the same time
As with unknown Error-Types, an implementation receiving an unknown Error-value is not expected to do more than log the received error and may close the PCEP session.
IANA Considerations This memo is entirely about updating the IANA "Path Computation Element Protocol (PCEP) Numbers" registry group.
Security Considerations This memo does not change the security considerations for any of the updated RFCs. Refer to and for further details of the specific security measures applicable to PCEP. asserts that the existence of experimental codepoints introduces no new security considerations. However, implementations accepting experimental error codepoints need to consider how they parse and process them in case they come, accidentally, from another experiment. Further, an implementation accepting experimental codepoints needs to consider the security aspects of the experimental extensions. provides various design considerations for protocol extensions (including those designated as experimental).
References Normative References Informative References
Rationale for Updating All Registries with Standards Action This specification updates all the mentioned registries with the Standards Action policy. The PCE WG considered keeping Standards Action for some registries, such as flag fields with limited bits where the space is tight, but decided against it. The Working Group Last Call and IETF Last Call processes should be enough to handle the case of frivolous experiments taking over the few codepoints. The working group could also create a new protocol field and registry for future use as done in the past (see ).
Consideration of RFC 8356 It is worth noting that deliberately chose to make experimental codepoints available only in the PCEP messages, objects, and TLV type registries. gives a brief explanation of why that decision was taken, stating that:
The justification for this decision is that, if an experiment finds that it wants to use a new codepoint in another PCEP sub-registry, it can implement the same function using a new experimental object or TLV instead.
While it is true that an experimental implementation could assign an experimental PCEP object and designate it the "experimental errors object", using it to carry arbitrary contents including experimental error codes, such an approach would cause unnecessary divergence in the code. The allowance of experimental Error-Types is a better approach that will more easily enable the migration of successful experiments onto the Standards Track.
Acknowledgements Thanks to for the initial discussion behind this document. Thanks to , , , , , and for the review comments. Thanks to for the OPSDIR review. Thanks to for the GENART review. Thanks to for the ArtArt review. Thanks to for the SECDIR review.
Contributors Huawei Technologies
zhenghaomian@huawei.com