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| author | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
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| committer | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
| commit | 4bfd864f10b68b71482b35c818559068ef8d5797 (patch) | |
| tree | e3989f47a7994642eb325063d46e8f08ffa681dc /doc/rfc/rfc9050.txt | |
| parent | ea76e11061bda059ae9f9ad130a9895cc85607db (diff) | |
doc: Add RFC documents
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diff --git a/doc/rfc/rfc9050.txt b/doc/rfc/rfc9050.txt new file mode 100644 index 0000000..27c3f1b --- /dev/null +++ b/doc/rfc/rfc9050.txt @@ -0,0 +1,1707 @@ + + + + +Internet Engineering Task Force (IETF) Z. Li +Request for Comments: 9050 S. Peng +Category: Standards Track Huawei Technologies +ISSN: 2070-1721 M. Negi + RtBrick Inc + Q. Zhao + Etheric Networks + C. Zhou + HPE + July 2021 + + + Path Computation Element Communication Protocol (PCEP) Procedures and + Extensions for Using the PCE as a Central Controller (PCECC) of LSPs + +Abstract + + The Path Computation Element (PCE) is a core component of Software- + Defined Networking (SDN) systems. + + A PCE as a Central Controller (PCECC) can simplify the processing of + a distributed control plane by blending it with elements of SDN and + without necessarily completely replacing it. Thus, the Label + Switched Path (LSP) can be calculated/set up/initiated and the label- + forwarding entries can also be downloaded through a centralized PCE + server to each network device along the path while leveraging the + existing PCE technologies as much as possible. + + This document specifies the procedures and Path Computation Element + Communication Protocol (PCEP) extensions for using the PCE as the + central controller for provisioning labels along the path of the + static LSP. + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + https://www.rfc-editor.org/info/rfc9050. + +Copyright Notice + + Copyright (c) 2021 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (https://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + +Table of Contents + + 1. Introduction + 2. Terminology + 2.1. Requirements Language + 3. Basic PCECC Mode + 4. PCEP Requirements + 5. Procedures for Using the PCE as a Central Controller (PCECC) + 5.1. Stateful PCE Model + 5.2. New LSP Functions + 5.3. New PCEP Object + 5.4. PCECC Capability Advertisement + 5.5. LSP Operations + 5.5.1. PCE-Initiated PCECC LSP + 5.5.2. PCC-Initiated PCECC LSP + 5.5.3. Central Controller Instructions + 5.5.3.1. Label Download CCI + 5.5.3.2. Label Cleanup CCI + 5.5.4. PCECC LSP Update + 5.5.5. Re-delegation and Cleanup + 5.5.6. Synchronization of Central Controller Instructions + 5.5.7. PCECC LSP State Report + 5.5.8. PCC-Based Allocations + 6. PCEP Messages + 6.1. The PCInitiate Message + 6.2. The PCRpt Message + 7. PCEP Objects + 7.1. OPEN Object + 7.1.1. PCECC Capability Sub-TLV + 7.2. PATH-SETUP-TYPE TLV + 7.3. CCI Object + 7.3.1. Address TLVs + 8. Security Considerations + 8.1. Malicious PCE + 8.2. Malicious PCC + 9. Manageability Considerations + 9.1. Control of Function and Policy + 9.2. Information and Data Models + 9.3. Liveness Detection and Monitoring + 9.4. Verify Correct Operations + 9.5. Requirements on Other Protocols + 9.6. Impact on Network Operations + 10. IANA Considerations + 10.1. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators + 10.2. PCECC-CAPABILITY Sub-TLV's Flag Field + 10.3. PCEP Path Setup Type Registry + 10.4. PCEP Object + 10.5. CCI Object Flag Field + 10.6. PCEP-Error Object + 11. References + 11.1. Normative References + 11.2. Informative References + Acknowledgments + Contributors + Authors' Addresses + +1. Introduction + + The Path Computation Element (PCE) [RFC4655] was developed to offload + the path computation function from routers in an MPLS traffic- + engineered (TE) network. It can compute optimal paths for traffic + across a network and can also update the paths to reflect changes in + the network or traffic demands. Since then, the role and function of + the PCE have grown to cover a number of other uses (such as GMPLS + [RFC7025]) and to allow delegated control [RFC8231] and PCE-initiated + use of network resources [RFC8281]. + + According to [RFC7399], Software-Defined Networking (SDN) refers to a + separation between the control elements and the forwarding components + so that software running in a centralized system, called a + controller, can act to program the devices in the network to behave + in specific ways. A required element in an SDN architecture is a + component that plans how the network resources will be used and how + the devices will be programmed. It is possible to view this + component as performing specific computations to place traffic flows + within the network given knowledge of the availability of network + resources, how other forwarding devices are programmed, and the way + that other flows are routed. This is the function and purpose of a + PCE, and the way that a PCE integrates into a wider network control + system (including an SDN system) is presented in [RFC7491]. + + In early PCE implementations, where the PCE was used to derive paths + for MPLS Label Switched Paths (LSPs), paths were requested by network + elements (known as Path Computation Clients (PCCs)), and the results + of the path computations were supplied to network elements using the + Path Computation Element Communication Protocol (PCEP) [RFC5440]. + This protocol was later extended to allow a PCE to send unsolicited + requests to the network for LSP establishment [RFC8281]. + + The PCE was developed to derive paths for MPLS LSPs, which are + supplied to the head end of the LSP using the PCEP. But SDN has a + broader applicability than signaled MPLS and GMPLS TE networks, and + the PCE may be used to determine paths in a range of use cases. PCEP + has been proposed as a control protocol for use in these environments + to allow the PCE to be fully enabled as a central controller. + + [RFC8283] introduces the architecture for the PCE as a central + controller as an extension to the architecture described in [RFC4655] + and assumes the continued use of PCEP as the protocol used between + the PCE and PCC. [RFC8283] further examines the motivations and + applicability for PCEP as a Southbound Interface (SBI) and introduces + the implications for the protocol. [PCECC] describes the use cases + for the PCECC architecture. + + A PCECC can simplify the processing of a distributed control plane by + blending it with elements of SDN and without necessarily completely + replacing it. Thus, the LSP can be calculated/set up/initiated and + the label-forwarding entries can also be downloaded through a + centralized PCE server to each network device along the path while + leveraging the existing PCE technologies as much as possible. + + This document specifies the procedures and PCEP extensions for using + the PCE as the central controller for static LSPs, where LSPs can be + provisioned as explicit label instructions at each hop on the end-to- + end path. Each router along the path must be told what label- + forwarding instructions to program and what resources to reserve. + The PCE-based controller keeps a view of the network and determines + the paths of the end-to-end LSPs, and the controller uses PCEP to + communicate with each router along the path of the end-to-end LSP. + + While this document is focused on the procedures for the static LSPs + (referred to as the basic PCECC mode in Section 3), the mechanisms + and protocol encodings are specified in such a way that extensions + for other use cases are easy to achieve. For example, the extensions + for the PCECC for Segment Routing (SR) are specified in [PCECC-SR] + and [PCECC-SRv6]. + +2. Terminology + + The terminology used in this document is the same as that described + in the [RFC8283]. + +2.1. Requirements Language + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and + "OPTIONAL" in this document are to be interpreted as described in + BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all + capitals, as shown here. + +3. Basic PCECC Mode + + In this mode, LSPs are provisioned as explicit label instructions at + each hop on the end-to-end path. Each router along the path must be + told what label-forwarding instructions to program and what resources + to reserve. The controller uses PCEP to communicate with each router + along the path of the end-to-end LSP. + + [RFC8283] examines the motivations and applicability for the PCECC + and use of PCEP as an SBI. Section 3.1.2 of [RFC8283] highlights the + use of the PCECC for label allocation along the static LSPs, and it + simplifies the processing of a distributed control plane by blending + it with elements of SDN and without necessarily completely replacing + it. This allows the operator to introduce the advantages of SDN + (such as programmability) into the network. Further, Section 3.3 of + [PCECC] describes some of the scenarios where the PCECC technique + could be useful. Section 4 of [RFC8283] also describes the + implications on the protocol when used as an SDN SBI. The operator + needs to evaluate the advantages offered by the PCECC against the + operational and scalability needs of the PCECC. + + As per Section 3.1.2 of [RFC8283], the PCE-based controller will take + responsibility for managing some part of the MPLS label space for + each of the routers that it controls and may take wider + responsibility for partitioning the label space for each router and + allocating different parts for different uses. The PCC MUST NOT make + allocations from the label space set aside for the PCE to avoid + overlap and collisions of label allocations. It is RECOMMENDED that + the PCE makes allocations (from the label space set aside for the + PCE) for all nodes along the path. For the purpose of this document, + it is assumed that the exclusive label range to be used by a PCE is + known and set on both PCEP peers. A future extension could add the + capability to advertise this range via a possible PCEP extension as + well (see [PCE-ID]). The rest of the processing is similar to the + existing stateful PCE mechanism. + + This document also allows a case where the label space is maintained + by the PCC and the labels are allocated by it. In this case, the PCE + should request the allocation from the PCC, as described in + Section 5.5.8. + +4. PCEP Requirements + + The following key requirements should be considered when designing + the PCECC-based solution: + + 1. A PCEP speaker supporting this document needs to have the + capability to advertise its PCECC capability to its peers. + + 2. A PCEP speaker needs means to identify PCECC-based LSPs in the + PCEP messages. + + 3. PCEP procedures need to allow for PCC-based label allocations. + + 4. PCEP procedures need to provide a means to update (or clean up) + label entries downloaded to the PCC. + + 5. PCEP procedures need to provide a means to synchronize the labels + between the PCE and the PCC via PCEP messages. + +5. Procedures for Using the PCE as a Central Controller (PCECC) + +5.1. Stateful PCE Model + + Active stateful PCE is described in [RFC8231]. A PCE as a Central + Controller (PCECC) reuses the existing active stateful PCE mechanism + as much as possible to control LSPs. + +5.2. New LSP Functions + + Several new functions are required in PCEP to support the PCECC. + This document extends the existing messages to support the new + functions required by the PCECC: + + PCInitiate: A PCEP message described in [RFC8281]. A PCInitiate + message is used to set up a PCE-initiated LSP based on a PCECC + mechanism. It is also extended for Central Controller + Instructions (CCI) (download or clean up the label-forwarding + instructions in the context of this document) on all nodes along + the path, as described in Section 6.1. + + PCRpt: A PCEP message described in [RFC8231]. A PCRpt message is + used to send the PCECC LSP Reports. It is also extended to report + the set of CCI (label-forwarding instructions in the context of + this document) received from the PCE, as described in Section 6.2. + Section 5.5.6 describes the use of a PCRpt message during + synchronization. + + PCUpd: A PCEP message described in [RFC8231]. A PCUpd message is + used to send the PCECC LSP Updates. + + The new functions defined in this document are mapped onto the PCEP + messages, as shown in Table 1. + + +================================+============+ + | Function | Message | + +================================+============+ + | PCECC Capability advertisement | Open | + +--------------------------------+------------+ + | Label entry Add | PCInitiate | + +--------------------------------+------------+ + | Label entry Clean up | PCInitiate | + +--------------------------------+------------+ + | PCECC-Initiated LSP | PCInitiate | + +--------------------------------+------------+ + | PCECC LSP Update | PCUpd | + +--------------------------------+------------+ + | PCECC LSP State Report | PCRpt | + +--------------------------------+------------+ + | PCECC LSP Delegation | PCRpt | + +--------------------------------+------------+ + | PCECC Label Report | PCRpt | + +--------------------------------+------------+ + + Table 1: Functions Mapped to the PCEP Messages + +5.3. New PCEP Object + + This document defines a new PCEP object called CCI (Section 7.3) to + specify the Central Controller Instructions. In the scope of this + document, this is limited to label-forwarding instructions. Future + documents can create new CCI object-types for other types of Central + Controller Instructions. The CC-ID is the unique identifier for the + CCI in PCEP. The PCEP messages are extended in this document to + handle the PCECC operations. + +5.4. PCECC Capability Advertisement + + During the PCEP initialization phase, PCEP speakers (PCE or PCC) + advertise their support of and willingness to use PCEP extensions for + the PCECC using these elements in the OPEN message: + + * a new Path Setup Type (PST) (Section 7.2) in the PATH-SETUP-TYPE- + CAPABILITY TLV to indicate support for PCEP extensions for the + PCECC - 2 (Traffic engineering path is set up using PCECC mode) + + * a new PCECC-CAPABILITY sub-TLV (Section 7.1.1) with the L bit set + to '1' inside the PATH-SETUP-TYPE-CAPABILITY TLV to indicate a + willingness to use PCEP extensions for the PCECC-based Central + Controller Instructions for label download + + * the STATEFUL-PCE-CAPABILITY TLV [RFC8231] (with the I flag set + [RFC8281]) + + The new PST is to be listed in the PATH-SETUP-TYPE-CAPABILITY TLV by + all PCEP speakers that support the PCEP extensions for the PCECC in + this document. + + The new PCECC-CAPABILITY sub-TLV is included in the PATH-SETUP-TYPE- + CAPABILITY TLV in the OPEN object to indicate a willingness to use + the PCEP extensions for the PCECC during the established PCEP + session. Using the L bit in this TLV, the PCE shows the intention to + function as a PCECC server, and the PCC shows a willingness to act as + a PCECC client for label download instructions (see Section 7.1.1). + + If the PCECC-CAPABILITY sub-TLV is advertised and the STATEFUL-PCE- + CAPABILITY TLV is not advertised, or is advertised without the I flag + set, in the OPEN object, the receiver MUST: + + * send a PCErr message with Error-Type=19 (Invalid Operation) and + Error-value=17 (Stateful PCE capability was not advertised) and + + * terminate the session. + + If a PCEP speaker receives the PATH-SETUP-TYPE-CAPABILITY TLV with + the PCECC PST but without the PCECC-CAPABILITY sub-TLV, it MUST: + + * send a PCErr message with Error-Type=10 (Reception of an invalid + object) and Error-value=33 (Missing PCECC Capability sub-TLV) and + + * terminate the PCEP session. + + The PCECC-CAPABILITY sub-TLV MUST NOT be used without the + corresponding PST being listed in the PATH-SETUP-TYPE-CAPABILITY TLV. + If it is present without the corresponding PST listed in the PATH- + SETUP-TYPE-CAPABILITY TLV, it MUST be ignored. + + If one or both speakers (PCE and PCC) have not indicated support and + willingness to use the PCEP extensions for the PCECC, the PCEP + extensions for the PCECC MUST NOT be used. If a PCECC operation is + attempted when both speakers have not agreed in the OPEN messages, + the receiver of the message MUST: + + * send a PCErr message with Error-Type=19 (Invalid Operation) and + Error-value=16 (Attempted PCECC operations when PCECC capability + was not advertised) and + + * terminate the PCEP session. + + A legacy PCEP speaker (that does not recognize the PCECC Capability + sub-TLV) will ignore the sub-TLV in accordance with [RFC8408] and + [RFC5440]. As per [RFC8408], the legacy PCEP speaker, on receipt of + an unsupported PST in a Request Parameter (RP) / Stateful PCE Request + Parameter (SRP) object, will: + + * send a PCErr message with Error-Type=21 (Invalid traffic + engineering path setup type) and Error-value=1 (Unsupported path + setup type) and + + * terminate the PCEP session. + +5.5. LSP Operations + + The PCEP messages pertaining to a PCECC MUST include the PATH-SETUP- + TYPE TLV [RFC8408] in the SRP object [RFC8231] with the PST set to + '2' to clearly identify that the PCECC LSP is intended. + +5.5.1. PCE-Initiated PCECC LSP + + The LSP instantiation operation is defined in [RFC8281]. In order to + set up a PCE-initiated LSP based on the PCECC mechanism, a PCE sends + a PCInitiate message with the PST set to '2' for the PCECC (see + Section 7.2) to the ingress PCC. + + The label-forwarding instructions (see Section 5.5.3) from the PCECC + are sent after the initial PCInitiate and PCRpt message exchange with + the ingress PCC, as per [RFC8281] (see Figure 1). This is done so + that the PCEP-specific identifier for the LSP (PLSP-ID) and other LSP + identifiers can be obtained from the ingress and can be included in + the label-forwarding instruction in the next set of PCInitiate + messages along the path, as described below. + + An LSP-IDENTIFIERS TLV [RFC8231] MUST be included for the PCECC LSPs; + it uniquely identifies the LSP in the network. Note that the fields + in the LSP-IDENTIFIERS TLV are described for the RSVP-signaled LSPs + but are applicable to the PCECC LSP as well. The LSP object is + included in the CCI (label download Section 7.3) to identify the + PCECC LSP for this instruction. The PLSP-ID is the original + identifier used by the ingress PCC, so a transit/egress Label + Switching Router (LSR) could have multiple Central Controller + Instructions that have the same PLSP-ID. The PLSP-ID in combination + with the source (in the LSP-IDENTIFIERS TLV) MUST be unique. The + PLSP-ID is included for maintainability reasons to ease debugging. + As per [RFC8281], the LSP object could also include the SPEAKER- + ENTITY-ID TLV to identify the PCE that initiated these instructions. + Also, the CC-ID is unique in each PCEP session, as described in + Section 7.3. + + On receipt of a PCInitiate message for the PCECC LSP, the PCC + responds with a PCRpt message with the status set to 'Going-up' and + carrying the assigned PLSP-ID (see Figure 1). The ingress PCC also + sets the D (Delegate) flag (see [RFC8231]) and C (Create) flag (see + [RFC8281]) in the LSP object. When the PCE receives this PCRpt + message with the PLSP-ID, it assigns labels along the path and sets + up the path by sending a PCInitiate message to each node along the + path of the LSP, as per the PCECC technique. The CC-ID uniquely + identifies the Central Controller Instructions within a PCEP session. + Each node along the path (PCC) responds with a PCRpt message to + acknowledge the CCI with the PCRpt messages including the CCI and LSP + objects. + + The ingress node would receive one CCI object with the O bit (out- + label) set. The transit node(s) would receive two CCI objects with + the in-label CCI without the O bit set and the out-label CCI with the + O bit set. The egress node would receive one CCI object without the + O bit set (see Figure 1). A node can determine its role based on the + setting of the O bit in the CCI object(s) and the LSP-IDENTIFIERS TLV + in the LSP object. + + The LSP deletion operation for the PCE-initiated PCECC LSP is the + same as defined in [RFC8281]. The PCE should further perform the + label entry cleanup operation, as described in Section 5.5.3.2, for + the corresponding LSP. + + +-------+ +-------+ + |PCC | | PCE | + |ingress| +-------+ + +------| | | + | PCC +-------+ | + | transit| | | + +------| | |<--PCInitiate,PLSP-ID=0,PST=2---------| PCECC LSP + |PCC +--------+ | | Initiate + |egress | | |----PCRpt,PLSP-ID=2,D=1,C=1---------->| PCECC LSP + +--------+ | | (GOING-UP) | + | | | | + |<-------PCInitiate,CC-ID=X,PLSP-ID=2----------------| Label + | | | | download + |--------PCRpt,CC-ID=X,PLSP-ID=2-------------------->| CCI + | | | | + | |<------PCInitiate,CC-ID=Y1,Y2,PLSP-ID=2-----| Label + | | | | download + | |-------PCRpt,CC-ID=Y1,Y2,PLSP-ID=2--------->| CCI + | | | | + | | |<----PCInitiate,CC-ID=Z,PLSP-ID=2-----| Label + | | | | download + | | |-----PCRpt,CC-ID=Z,PLSP-ID=2--------->| CCI + | | | | + | | |<---PCUpd,PLSP-ID=2,PST=2,D=1---------| PCECC LSP + | | | (UP) | Update + | | |----PCRpt,PLSP-ID=2,D=1,C=1---------->| + | | | (UP) | + + Figure 1: PCE-Initiated PCECC LSP + + Once the label operations are completed, the PCE MUST send a PCUpd + message to the ingress PCC. As per [RFC8231], the PCUpd message is + with the D flag set. + + The PCECC LSPs are considered to be 'up' by default (on receipt of a + PCUpd message from the PCE). The ingress could further choose to + deploy a data-plane check mechanism and report the status back to the + PCE via a PCRpt message to make sure that the correct label + instructions are made along the path of the PCECC LSP (and it is + ready to carry traffic). The exact mechanism is out of scope of this + document. + + In the case where the label allocations are made by the PCC itself + (see Section 5.5.8), the PCE could request an allocation to be made + by the PCC; then, the PCC would send a PCRpt message with the + allocated label encoded in the CC-ID object (as shown in Figure 2) in + the configuration sequence from the egress towards the ingress along + the path. + + +-------+ +-------+ + |PCC | | PCE | + |ingress| +-------+ + +------| | | + | PCC +-------+ | + | transit| | | + +------| | |<--PCInitiate,PLSP-ID=0,PST=2,--------| PCECC LSP + |PCC +--------+ | | Initiate + |egress | | |----PCRpt,PLSP-ID=2,D=1,C=1---------->| PCECC LSP + +--------+ | | (GOING-UP) | + | | | | + |<-------PCInitiate,CC-ID=X,PLSP-ID=2----------------| Label + | | | C=1,O=0 | download + |--------PCRpt,CC-ID=X,PLSP-ID=2-------------------->| CCI + | | | Label=L1 | + | |<------PCInitiate,PLSP-ID=2,----------------| Labels + | | | CC-ID=Y1,C=1,O=0 | download + | | | CC-ID=Y2,C=0,O=1,L1 | CCI + | |-------PCRpt,PLSP-ID=2--------------------->| + | | | CC-ID=Y1,O=0,Label=L2 | + | | | CC-ID=Y2,O=1 | + | | |<----PCInitiate,CC-ID=Z,PLSP-ID=2-----| Label + | | | C=0,O=1,L2 | download + | | |-----PCRpt,CC-ID=Z,PLSP-ID=2--------->| CCI + | | | | + | | |<---PCUpd,PLSP-ID=2,PST=2,D=1---------| PCECC LSP + | | | (UP) | Update + + Figure 2: PCE-Initiated PCECC LSP (PCC Allocation) + + In this example, it should be noted that the request is made to the + egress node with the C bit set in the CCI object to indicate that the + label allocation needs to be done by the egress, and the egress + responds with the allocated label to the PCE. The PCE further + informs the transit PCC without setting the C bit to '1' in the CCI + object for the out-label, but the C bit is set to '1' for the in- + label, so the transit node makes the label allocation (for the in- + label) and reports to the PCE. Similarly, the C bit is unset towards + the ingress to complete all the label allocations for the PCECC LSP. + +5.5.2. PCC-Initiated PCECC LSP + + In order to set up an LSP based on the PCECC mechanism where the LSP + is configured at the PCC, a PCC MUST delegate the LSP by sending a + PCRpt message with the PST set for the PCECC (see Section 7.2) and D + (Delegate) flag (see [RFC8231]) set in the LSP object (see Figure 3). + + When a PCE receives the initial PCRpt message with the D flag and PST + set to '2', it SHOULD calculate the path and assign labels along the + path in addition to setting up the path by sending a PCInitiate + message to each node along the path of the LSP, as per the PCECC + technique (see Figure 3). The CC-ID uniquely identifies the CCI + within a PCEP session. Each PCC further responds with the PCRpt + messages, including the CCI and LSP objects. + + Once the CCI (label operations) are completed, the PCE MUST send the + PCUpd message to the ingress PCC. As per [RFC8231], this PCUpd + message should include the path information calculated by the PCE. + + Note that the PCECC LSPs MUST be delegated to a PCE at all times. + + The LSP deletion operation for the PCECC LSPs is the same as defined + in [RFC8231]. If the PCE receives a PCRpt message for LSP deletion, + then it does label the cleanup operation, as described in + Section 5.5.3.2, for the corresponding LSP. + + The basic PCECC LSP setup sequence is as shown in Figure 3. + + +-------+ +-------+ + |PCC | | PCE | + |ingress| +-------+ + +------| | | + | PCC +-------+ | + | transit| | | + +------| | |---PCRpt,PLSP-ID=1,PST=2,D=1-------->| PCECC LSP + |PCC +--------+ | | + |egress | | | | + +--------+ | | | + | | | | + |<-------PCInitiate,CC-ID=X,PLSP-ID=1---------------| Label + | | | L1,O=0 | download + |--------PCRpt,CC-ID=X,PLSP-ID=1------------------->| CCI + | | | | + | |<------PCInitiate,PLSP-ID=1,---------------| Labels + | | | CC-ID=Y1,O=0,L2 | download + | | | CC-ID=Y2,O=1,L1 | CCI + | |-------PCRpt,CC-ID=Y1,Y2,PLSP-ID=1-------->| + | | | | + | | |<----PCInitiate,CC-ID=Z,PLSP-ID=1----| Label + | | | L2,O=1 | download + | | |-----PCRpt,CC-ID=Z,PLSP-ID=1-------->| CCI + | | | | + | | |<---PCUpd,PLSP-ID=1,PST=2,D=1--------| PCECC LSP + | | | | Update + | | | | + + Figure 3: PCC-Initiated PCECC LSP + + In the case where the label allocations are made by the PCC itself + (see Section 5.5.8), the PCE could request an allocation to be made + by the PCC; then, the PCC would send a PCRpt message with the + allocated label encoded in the CC-ID object, as shown in Figure 4. + + +-------+ +-------+ + |PCC | | PCE | + |ingress| +-------+ + +------| | | + | PCC +-------+ | + | transit| | | + +------| | |---PCRpt,PLSP-ID=1,PST=2,D=1-------->| PCECC LSP + |PCC +--------+ | | + |egress | | | | + +--------+ | | | + | | | | + |<-------PCInitiate,CC-ID=X,PLSP-ID=1---------------| Label + | | | C=1 | download + |--------PCRpt,CC-ID=X,PLSP-ID=1------------------->| CCI + | | | Label=L1 | + | |<------PCInitiate,PLSP-ID=1,---------------| Labels + | | | CC-ID=Y1,C=1 | download + | | | CC-ID=Y2,C=0,L1 | CCI + | |-------PCRpt,PLSP-ID=1-------------------->| + | | | CC-ID=Y1,Label=L2 | + | | | CC-ID=Y2 | + | | |<----PCInitiate,CC-ID=Z,PLSP-ID=1----| Label + | | | C=0,L2 | download + | | |-----PCRpt,CC-ID=Z,PLSP-ID=1-------->| CCI + | | | | + | | |<---PCUpd,PLSP-ID=1,PST=2,D=1--------| PCECC LSP + | | | | Update + | | | | + + Figure 4: PCC-Initiated PCECC LSP (PCC Allocation) + + | Note: + | + | The O bit is set as before (and thus not included). + + In the case where the label allocations are made by the PCC itself + (see Section 5.5.8), the procedure remains the same, with just an + additional constraint on the configuration sequence. + + The rest of the PCC-initiated PCECC LSP setup operations are the same + as those described in Section 5.5.1. + +5.5.3. Central Controller Instructions + + The new CCI for the label operations in PCEP are done via the + PCInitiate message (Section 6.1) by defining a new PCEP object for + CCI operations. The local label range of each PCC is assumed to be + known by both the PCC and the PCE. + +5.5.3.1. Label Download CCI + + In order to set up an LSP based on the PCECC, the PCE sends a + PCInitiate message to each node along the path to download the label + instructions, as described in Sections 5.5.1 and 5.5.2. + + The CCI object MUST be included, along with the LSP object in the + PCInitiate message. The LSP-IDENTIFIERS TLV MUST be included in the + LSP object. The SPEAKER-ENTITY-ID TLV SHOULD be included in the LSP + object. + + If a node (PCC) receives a PCInitiate message that includes a label + to download (as part of CCI) that is out of the range set aside for + the PCE, it MUST send a PCErr message with Error-Type=31 (PCECC + failure) and Error-value=1 (Label out of range) and MUST include the + SRP object to specify the error is for the corresponding label update + via a PCInitiate message. If a PCC receives a PCInitiate message but + fails to download the label entry, it MUST send a PCErr message with + Error-Type=31 (PCECC failure) and Error-value=2 (Instruction failed) + and MUST include the SRP object to specify the error is for the + corresponding label update via a PCInitiate message. + + A new PCEP object for CCI is defined in Section 7.3. + +5.5.3.2. Label Cleanup CCI + + In order to delete an LSP based on the PCECC, the PCE sends Central + Controller Instructions via a PCInitiate message to each node along + the path of the LSP to clean up the label-forwarding instruction. + + If the PCC receives a PCInitiate message but does not recognize the + label in the CCI, the PCC MUST generate a PCErr message with Error- + Type=19 (Invalid operation) and Error-value=18 (Unknown Label) and + MUST include the SRP object to specify the error is for the + corresponding label cleanup (via a PCInitiate message). + + The R flag in the SRP object defined in [RFC8281] specifies the + deletion of the label entry in the PCInitiate message. + + +-------+ +-------+ + |PCC | | PCE | + |ingress| +-------+ + +------| | | + | PCC +-------+ | + | transit| | | + +------| | | | + |PCC +--------+ | | + |egress | | | | + +--------+ | | | + | | | | + |<-------PCInitiate,CC-ID=X,PLSP-ID=2----------------| Label + | | | R=1 | cleanup + |--------PCRpt,CC-ID=X,PLSP-ID=2-------------------->| CCI + | | | R=1 | + | |<------PCInitiate,CC-ID=Y1,Y2,PLSP-ID=2-----| Label + | | | R=1 | cleanup + | |-------PCRpt,CC-ID=Y1,Y2,PLSP-ID=2--------->| CCI + | | | R=1 | + | | |<----PCInitiate,CC-ID=Z,PLSP-ID=2-----| Label + | | | R=1 | cleanup + | | |-----PCRpt,CC-ID=Z,PLSP-ID=2--------->| CCI + | | | R=1 | + | | |<--PCInitiate,PLSP-ID=2,PST=2,R=1-----| PCECC LSP + | | | | remove + + Figure 5: Label Cleanup + + As per [RFC8281], following the removal of the label-forwarding + instruction, the PCC MUST send a PCRpt message. The SRP object in + the PCRpt message MUST include the SRP-ID-number from the PCInitiate + message that triggered the removal. The R flag in the SRP object + MUST be set. + + In the case where the label allocation is made by the PCC itself (see + Section 5.5.8), the removal procedure remains the same, adding the + sequence constraint. + +5.5.4. PCECC LSP Update + + The update is done as per the make-before-break procedures, i.e., the + PCECC first updates new label instructions based on the updated path + and then informs the ingress to switch traffic before cleaning up the + former instructions. New CC-IDs are used to identify the updated + instructions; the identifiers in the LSP object uniquely identify the + existing LSP. Once new instructions are downloaded, the PCE further + updates the new path at the ingress, which triggers the traffic + switch on the updated path. The ingress PCC acknowledges with a + PCRpt message, on receipt of the PCRpt message, the PCE does the + cleanup operation for the former LSP, as described in + Section 5.5.3.2. + + +-------+ +-------+ + |PCC | | PCE | + |ingress| +-------+ + +------| | | + | PCC +-------+ | + | transit| | | + +------| | | | + |PCC +--------+ | | + |egress | | | | + +--------+ | | | + | | | | New Path + |<------ PCInitiate,CC-ID=XX,PLSP-ID=1 -------------| for LSP + | | | | trigger + |--------PCRpt,CC-ID=XX,PLSP-ID=1------------------>| new CCI + | | | | + | |<------PCInitiate,CC-ID=YY1,YY2,PLSP-ID=1--| Label + | | | | download + | |-------PCRpt,CC-ID=YY1,YY2,PLSP-ID=1------>| CCI + | | | | + | | |<----PCInitiate,CC-ID=ZZ,PLSP-ID=1---| Label + | | | | download + | | |-----PCRpt,CC-ID=ZZ,PLSP-ID=1------->| CCI + | | | | + | | |<---PCUpd,PLSP-ID=1,PST=2,D=1--------| PCECC + | | | SRP=S | LSP Update + | | | | + | | |---PCRpt,PLSP-ID=1,PST=2,D=1-------->| Trigger + | | | (SRP=S) | Delete + | | | | former CCI + | | | | + |<-------PCInitiate,CC-ID=X,PLSP-ID=1---------------| Label + | | | R=1 | cleanup + |--------PCRpt,CC-ID=X,PLSP-ID=1------------------->| CCI + | | | R=1 | + | |<------PCInitiate,CC-ID=Y1,Y2,PLSP-ID=1----| Label + | | | R=1 | cleanup + | |-------PCRpt,CC-ID=Y1,Y2,PLSP-ID=1-------->| CCI + | | | R=1 | + | | |<----PCInitiate,CC-ID=Z,PLSP-ID=1----| Label + | | | R=1 | cleanup + | | |-----PCRpt,CC-ID=Z,PLSP-ID=1-------->| CCI + | | | R=1 | + + Figure 6: PCECC LSP Update + + The modified PCECC LSPs are considered to be 'up' by default. The + ingress could further choose to deploy a data-plane check mechanism + and report the status back to the PCE via a PCRpt message. The exact + mechanism is out of scope of this document. + + In the case where the label allocations are made by the PCC itself + (see Section 5.5.8), the procedure remains the same. + +5.5.5. Re-delegation and Cleanup + + As described in [RFC8281], a new PCE can gain control over an + orphaned LSP. In the case of a PCECC LSP, the new PCE MUST also gain + control over the CCI in the same way by sending a PCInitiate message + that includes the SRP, LSP, and CCI objects and carries the CC-ID and + PLSP-ID identifying the instructions that it wants to take control + of. + + Further, as described in [RFC8281], the State Timeout Interval timer + ensures that a PCE crash does not result in automatic and immediate + disruption for the services using PCE-initiated LSPs. Similarly the + Central Controller Instructions are not removed immediately upon PCE + failure. Instead, they are cleaned up on the expiration of this + timer. This allows for network cleanup without manual intervention. + The PCC MUST support the removal of CCI as one of the behaviors + applied on expiration of the State Timeout Interval timer. + + In the case of the PCC-initiated PCECC LSP, the control over the + orphaned LSP at the ingress PCC is taken over by the mechanism + specified in [RFC8741] to request delegation. The control over the + CCI is described above using [RFC8281]. + +5.5.6. Synchronization of Central Controller Instructions + + The purpose of CCI synchronization (labels in the context of this + document) is to make sure that the PCE's view of CCI (labels) matches + with the PCC's label allocation. This synchronization is performed + as part of the LSP State Synchronization, as described in [RFC8231] + and [RFC8232]. + + As per LSP State Synchronization [RFC8231], a PCC reports the state + of its LSPs to the PCE using PCRpt messages and, as per [RFC8281], + the PCE would initiate any missing LSPs and/or remove any LSPs that + are not wanted. The same PCEP messages and procedures are also used + for the CCI synchronization. The PCRpt message includes the CCI and + the LSP object to report the label-forwarding instructions. The PCE + would further remove any unwanted instructions or initiate any + missing instructions. + +5.5.7. PCECC LSP State Report + + As mentioned before, an ingress PCC MAY choose to apply any + Operations, Administration, and Maintenance (OAM) mechanism to check + the status of the LSP in the data plane and MAY further send its + status in a PCRpt message to the PCE. + +5.5.8. PCC-Based Allocations + + The PCE can request the PCC to allocate the label using the + PCInitiate message. The C flag in the CCI object is set to '1' to + indicate that the allocation needs to be made by the PCC. The PCC + MUST try to allocate the label and MUST report to the PCE via a PCRpt + or PCErr message. + + If the value of the label is 0 and the C flag is set to '1', it + indicates that the PCE is requesting the allocation to be made by the + PCC. If the label is 'n' and the C flag is set to '1' in the CCI + object, it indicates that the PCE requests a specific value 'n' for + the label. If the allocation is successful, the PCC MUST report via + the PCRpt message with the CCI object. If the value of the label in + the CCI object is invalid, it MUST send a PCErr message with Error- + Type=31 (PCECC failure) and Error-value=3 (Invalid CCI). If it is + valid but the PCC is unable to allocate it, it MUST send a PCErr + message with Error-Type=31 (PCECC failure) and Error-value=4 (Unable + to allocate the specified CCI). + + If the PCC wishes to withdraw or modify the previously assigned + label, it MUST send a PCRpt message without any label or with the + label containing the new value, respectively, in the CCI object. The + PCE would further trigger the label cleanup of the older label, as + per Section 5.5.3.2. + +6. PCEP Messages + + As defined in [RFC5440], a PCEP message consists of a common header + followed by a variable-length body made of a set of objects that can + be either mandatory or optional. An object is said to be mandatory + in a PCEP message when the object must be included for the message to + be considered valid. For each PCEP message type, a set of rules is + defined, which specifies the set of objects that the message can + carry. An implementation MUST form the PCEP messages using the + object ordering specified in this document. + + The LSP-IDENTIFIERS TLV MUST be included in the LSP object for the + PCECC LSP. + + The message formats in this document are specified using Routing + Backus-Naur Form (RBNF) encoding, as specified in [RFC5511]. + +6.1. The PCInitiate Message + + The PCInitiate message [RFC8281] can be used to download or remove + the labels; this document extends the message, as shown below. + + <PCInitiate Message> ::= <Common Header> + <PCE-initiated-lsp-list> + + Where: + + * <Common Header> is defined in [RFC5440]. + + <PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request> + [<PCE-initiated-lsp-list>] + + <PCE-initiated-lsp-request> ::= + (<PCE-initiated-lsp-instantiation>| + <PCE-initiated-lsp-deletion>| + <PCE-initiated-lsp-central-control>) + + <PCE-initiated-lsp-central-control> ::= <SRP> + <LSP> + <cci-list> + + <cci-list> ::= <CCI> + [<cci-list>] + + Where: + + * <PCE-initiated-lsp-instantiation> and <PCE-initiated-lsp-deletion> + are as per [RFC8281]. + + * The LSP and SRP object is defined in [RFC8231]. + + When a PCInitiate message is used for the CCI (labels), the SRP, LSP, + and CCI objects MUST be present. The SRP object is defined in + [RFC8231]; if the SRP object is missing, the receiving PCC MUST send + a PCErr message with Error-Type=6 (Mandatory Object missing) and + Error-value=10 (SRP object missing). The LSP object is defined in + [RFC8231], and if the LSP object is missing, the receiving PCC MUST + send a PCErr message with Error-Type=6 (Mandatory Object missing) and + Error-value=8 (LSP object missing). The CCI object is defined in + Section 7.3, and if the CCI object is missing, the receiving PCC MUST + send a PCErr message with Error-Type=6 (Mandatory Object missing) and + Error-value=17 (CCI object missing). More than one CCI object MAY be + included in the PCInitiate message for a transit LSR. + + To clean up entries, the R (remove) bit MUST be set in the SRP object + to be encoded along with the LSP and CCI objects. + + The CCI object received at the ingress node MUST have the O bit (out- + label) set. The CCI object received at the egress MUST have the O + bit unset. If this is not the case, the PCC MUST send a PCErr + message with Error-Type=31 (PCECC failure) and Error-value=3 (Invalid + CCI). Other instances of the CCI object, if present, MUST be + ignored. + + For the point-to-point (P2P) LSP setup via the PCECC technique, at + the transit LSR, two CCI objects are expected for incoming and + outgoing labels associated with the LSP object. If any other CCI + object is included in the PCInitiate message, it MUST be ignored. If + the transit LSR did not receive two CCI objects, with one of them + having the O bit set and another with the O bit unset, it MUST send a + PCErr message with Error-Type=31 (PCECC failure) and Error-value=3 + (Invalid CCI). + + Note that, on receipt of the PCInitiate message with CCI object, the + ingress, egress, or transit role of the PCC is identified via the + ingress and egress IP address encoded in the LSP-IDENTIFIERS TLV. + +6.2. The PCRpt Message + + The PCRpt message can be used to report the labels that were + allocated by the PCE to be used during the State Synchronization + phase or as an acknowledgment to a PCInitiate message. + + <PCRpt Message> ::= <Common Header> + <state-report-list> + + Where: + + <state-report-list> ::= <state-report>[<state-report-list>] + + <state-report> ::= (<lsp-state-report>| + <central-control-report>) + + <lsp-state-report> ::= [<SRP>] + <LSP> + <path> + + <central-control-report> ::= [<SRP>] + <LSP> + <cci-list> + + <cci-list> ::= <CCI> + [<cci-list>] + + Where: + + * <path> is as per [RFC8231], and the LSP and SRP objects are also + defined in [RFC8231]. + + When a PCRpt message is used to report the CCI (labels), the LSP and + CCI objects MUST be present. The LSP object is defined in [RFC8231], + and if the LSP object is missing, the receiving PCE MUST send a PCErr + message with Error-Type=6 (Mandatory Object missing) and Error- + value=8 (LSP object missing). The CCI object is defined in + Section 7.3, and if the CCI object is missing, the receiving PCE MUST + send a PCErr message with Error-Type=6 (Mandatory Object missing) and + Error-value=17 (CCI object missing). Two CCI objects can be included + in the PCRpt message for a transit LSR. + +7. PCEP Objects + + The PCEP objects defined in this document are compliant with the PCEP + object format defined in [RFC5440]. + +7.1. OPEN Object + + This document defines a new PST (2) to be included in the PATH-SETUP- + TYPE-CAPABILITY TLV in the OPEN object. Further, a new sub-TLV for + the PCECC capability exchange is also defined. + +7.1.1. PCECC Capability Sub-TLV + + The PCECC-CAPABILITY sub-TLV is an optional TLV for use in the OPEN + object in the PATH-SETUP-TYPE-CAPABILITY TLV when the Path Setup Type + list includes the PCECC Path Setup Type 2. A PCECC-CAPABILITY sub- + TLV MUST be ignored if the PST list does not contain PST=2. + + Its format is shown in Figure 7. + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Type=1 | Length=4 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Flags |L| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 7: PCECC Capability Sub-TLV + + The type of the TLV is 1, and it has a fixed length of 4 octets. + + The value comprises a single field: Flags (32 bits). Currently, the + following flag bit is defined: + + L bit (Label): If set to '1' by a PCEP speaker, the L flag indicates + that the PCEP speaker will support and is willing to handle the + PCEC-based Central Controller Instructions for label download. + The bit MUST be set to '1' by both a PCC and a PCE for the PCECC + label download/report on a PCEP session. + + Unassigned bits MUST be set to '0' on transmission and MUST be + ignored on receipt. + +7.2. PATH-SETUP-TYPE TLV + + The PATH-SETUP-TYPE TLV is defined in [RFC8408]; this document + defines a new PST value: + + PST=2: Path is set up via the PCECC mode. + + On a PCRpt/PCUpd/PCInitiate message, the PST=2 in the PATH-SETUP-TYPE + TLV in the SRP object MUST be included for an LSP set up via the + PCECC-based mechanism. + +7.3. CCI Object + + The CCI object is used by the PCE to specify the forwarding + instructions (label information in the context of this document) to + the PCC and MAY be carried within a PCInitiate or PCRpt message for + label download/report. + + CCI Object-Class is 44. + + CCI Object-Type is 1 for the MPLS label. + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | CC-ID | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Reserved1 | Flags |C|O| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Label | Reserved2 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + // Optional TLV // + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 8: CCI Object + + The fields in the CCI object are as follows: + + CC-ID: A PCEP-specific identifier for the CCI information. A PCE + creates a CC-ID for each instruction; the value is unique within + the scope of the PCE and is constant for the lifetime of a PCEP + session. The values 0 and 0xFFFFFFFF are reserved and MUST NOT be + used. Note that [SECURITY-ID] gives advice on assigning transient + numeric identifiers, such as the CC-ID, so as to minimize security + risks. + + Reserved1 (16 bit): Set to 'zero' while sending; ignored on receipt. + + Flags (16 bit): A field used to carry any additional information + pertaining to the CCI. Currently, the following flag bits are + defined: + + * O bit (out-label) : If the bit is set to '1', it specifies the + label is the out-label, and it is mandatory to encode the next- + hop information (via Address TLVs (Section 7.3.1) in the CCI + object). If the bit is not set, it specifies the label is the + in-label, and it is optional to encode the local interface + information (via Address TLVs in the CCI object). + + * C Bit (PCC allocation): If the bit is set to '1', it indicates + that the label allocation needs to be done by the PCC for the + Central Controller Instruction. A PCE sets this bit to request + the PCC to make an allocation from its label space. A PCC + would set this bit to indicate that it has allocated the label + and report it to the PCE. + + * All unassigned bits MUST be set to 'zero' at transmission and + ignored at receipt. + + Label (20-bit): The label information. + + Reserved2 (12 bit): Set to 'zero' while sending; ignored on receive. + +7.3.1. Address TLVs + + [RFC8779] defines the IPV4-ADDRESS, IPV6-ADDRESS, and UNNUMBERED- + ENDPOINT TLVs for the use of Generalized Endpoint. The same TLVs can + also be used in the CCI object to associate the next-hop information + in the case of an outgoing label and local interface information in + the case of an incoming label. The next-hop information encoded in + these TLVs needs to be a directly connected IP address/interface + information. If the PCC is not able to resolve the next-hop + information, it MUST reject the CCI and respond with a PCErr message + with Error-Type=31 (PCECC failure) and Error-value=5 (Invalid next- + hop information). + +8. Security Considerations + + As per [RFC8283], the security considerations for a PCE-based + controller are a little different from those for any other PCE + system. That is, the operation relies heavily on the use and + security of PCEP, so consideration should be given to the security + features discussed in [RFC5440] and the additional mechanisms + described in [RFC8253]. It further lists the vulnerability of a + central controller architecture, such as a central point of failure, + denial of service, and a focus for interception and modification of + messages sent to individual Network Elements (NEs). + + In the PCECC operations, the PCEP sessions are also required to the + internal routers, thus increasing the resources required for the + session management at the PCE. + + The PCECC extension builds on the existing PCEP messages; thus, the + security considerations described in [RFC5440], [RFC8231], and + [RFC8281] continue to apply. [RFC8253] specifies the support of + Transport Layer Security (TLS) in PCEP, as it provides support for + peer authentication, message encryption, and integrity. It further + provides mechanisms for associating peer identities with different + levels of access and/or authoritativeness via an attribute in X.509 + certificates or a local policy with a specific accept-list of X.509 + certificates. This can be used to check the authority for the PCECC + operations. Additional considerations are discussed in following + sections. + +8.1. Malicious PCE + + In this extension, the PCE has complete control over the PCC to + download/remove the labels and can cause the LSPs to behave + inappropriately and cause a major impact to the network. As a + general precaution, it is RECOMMENDED that this PCEP extension be + activated on mutually authenticated and encrypted sessions across + PCEs and PCCs belonging to the same administrative authority, using + TLS [RFC8253], as per the recommendations and best current practices + in BCP 195 [RFC7525]. + + Further, an attacker may flood the PCC with the PCECC-related + messages at a rate that exceeds either the PCC's ability to process + them or the network's ability to send them, by either spoofing + messages or compromising the PCE itself. [RFC8281] provides a + mechanism to protect the PCC by imposing a limit. The same can be + used for the PCECC operations as well. + + As specified in Section 5.5.3.1, a PCC needs to check if the label in + the CCI object is in the range set aside for the PCE; otherwise, it + MUST send a PCErr message with Error-Type=31 (PCECC failure) and + Error-value=1 (Label out of range). + +8.2. Malicious PCC + + The PCECC mechanism described in this document requires the PCE to + keep labels (CCI) that it downloads and relies on the PCC responding + (with either an acknowledgment or an error message) to request for + LSP instantiation. This is an additional attack surface by placing a + requirement for the PCE to keep a CCI/label replica for each PCC. It + is RECOMMENDED that PCE implementations provide a limit on resources + (in this case the CCI) a single PCC can occupy. [RFC8231] provides a + notification mechanism when such threshold is reached. + +9. Manageability Considerations + +9.1. Control of Function and Policy + + A PCE or PCC implementation SHOULD allow the PCECC capability to be + enabled/disabled as part of the global configuration. Section 6.1 of + [RFC8664] list various controlling factors regarding the Path Setup + Type. They are also applicable to the PCECC Path Setup Types. + Further, Section 6.2 of [RFC8664] describes the migration steps when + the Path Setup Type of an existing LSP is changed. + +9.2. Information and Data Models + + [RFC7420] describes the PCEP MIB; this MIB can be extended to get the + PCECC capability status. + + The PCEP YANG module [PCEP-YANG] could be extended to enable/disable + the PCECC capability. + +9.3. Liveness Detection and Monitoring + + Mechanisms defined in this document do not imply any new liveness + detection and monitoring requirements in addition to those already + listed in [RFC5440]. + +9.4. Verify Correct Operations + + The operator needs the following information to verify that PCEP is + operating correctly with respect to the PCECC Path Setup Type. + + * An implementation SHOULD allow the operator to view whether the + PCEP speaker sent the PCECC PST capability to its peer. + + * An implementation SHOULD allow the operator to view whether the + peer sent the PCECC PST capability. + + * An implementation SHOULD allow the operator to view whether the + PCECC PST is enabled on a PCEP session. + + * If one PCEP speaker advertises the PCECC PST capability, but the + other does not, then the implementation SHOULD create a log to + inform the operator of the capability mismatch. + + * If a PCEP speaker rejects a CCI, then it SHOULD create a log to + inform the operator, giving the reason for the decision (local + policy, label issues, etc.). + +9.5. Requirements on Other Protocols + + PCEP extensions defined in this document do not put new requirements + on other protocols. + +9.6. Impact on Network Operations + + PCEP extensions defined in this document do not put new requirements + on network operations. + +10. IANA Considerations + +10.1. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators + + [RFC8408] detailed the creation of the "PATH-SETUP-TYPE-CAPABILITY + Sub-TLV Type Indicators" subregistry. Further, IANA has allocated + the following codepoint: + + +=======+==================+===========+ + | Value | Meaning | Reference | + +=======+==================+===========+ + | 1 | PCECC-CAPABILITY | RFC 9050 | + +-------+------------------+-----------+ + + Table 2: PATH-SETUP-TYPE-CAPABILITY + Sub-TLV Type Indicators Subregistry + Addition + +10.2. PCECC-CAPABILITY Sub-TLV's Flag Field + + This document defines the PCECC-CAPABILITY sub-TLV; IANA has created + a new subregistry to manage the value of the PCECC-CAPABILITY sub- + TLV's 32-bit Flag field. New values are to be assigned by Standards + Action [RFC8126]. Each bit should be tracked with the following + qualities: + + * bit number (counting from bit 0 as the most significant bit) + + * capability description + + * defining RFC + + Currently, there is one allocation in this registry. + + +======+============+===========+ + | Bit | Name | Reference | + +======+============+===========+ + | 0-30 | Unassigned | RFC 9050 | + +------+------------+-----------+ + | 31 | Label | RFC 9050 | + +------+------------+-----------+ + + Table 3: Initial Contents of + the PCECC-CAPABILITY Sub-TLV + Subregistry + +10.3. PCEP Path Setup Type Registry + + [RFC8408] created a subregistry within the "Path Computation Element + Protocol (PCEP) Numbers" registry called "PCEP Path Setup Types". + IANA has allocated a new codepoint within this registry, as follows: + + +=======+============================+===========+ + | Value | Description | Reference | + +=======+============================+===========+ + | 2 | Traffic engineering path | RFC 9050 | + | | is set up using PCECC mode | | + +-------+----------------------------+-----------+ + + Table 4: Path Setup Type Registry Codepoint + Addition + +10.4. PCEP Object + + IANA has allocated new codepoints in the "PCEP Objects" subregistry + for the CCI object as follows: + + +==============+=============+=====================+===========+ + | Object-Class | Name | Object-Type | Reference | + | Value | | | | + +==============+=============+=====================+===========+ + | 44 | CCI Object- | 0: Reserved | RFC 9050 | + | | Type | 1: MPLS Label | | + | | | 2-15: Unassigned | | + +--------------+-------------+---------------------+-----------+ + + Table 5: PCEP Objects Subregistry Additions + +10.5. CCI Object Flag Field + + IANA has created a new subregistry to manage the Flag field of the + CCI object called "CCI Object Flag Field for MPLS Label". New values + are to be assigned by Standards Action [RFC8126]. Each bit should be + tracked with the following qualities: + + * bit number (counting from bit 0 as the most significant bit) + + * capability description + + * defining RFC + + Two bits are defined for the CCI Object flag field in this document + as follows: + + +======+======================================+===========+ + | Bit | Description | Reference | + +======+======================================+===========+ + | 0-13 | Unassigned | | + +------+--------------------------------------+-----------+ + | 14 | C Bit - PCC allocation | RFC 9050 | + +------+--------------------------------------+-----------+ + | 15 | O Bit - Specifies label is out-label | RFC 9050 | + +------+--------------------------------------+-----------+ + + Table 6: CCI Object Flag Field for MPLS Label Initial + Contents + +10.6. PCEP-Error Object + + IANA has allocated new error types and error values within the "PCEP- + ERROR Object Error Types and Values" subregistry of the "Path + Computation Element Protocol (PCEP) Numbers" registry for the + following errors: + + +============+===========+=======================+===========+ + | Error-Type | Meaning | Error-value | Reference | + +============+===========+=======================+===========+ + | 6 | Mandatory | 17: CCI object | RFC 9050 | + | | Object | missing | | + | | missing | | | + +------------+-----------+-----------------------+-----------+ + | 10 | Reception | 33: Missing PCECC | RFC 9050 | + | | of an | Capability sub-TLV | | + | | invalid | | | + | | object | | | + +------------+-----------+-----------------------+-----------+ + | 19 | Invalid | 16: Attempted PCECC | RFC 9050 | + | | Operation | operations when PCECC | | + | | | capability was not | | + | | | advertised | | + | | | | | + | | | 17: Stateful PCE | | + | | | capability was not | | + | | | advertised | | + | | | | | + | | | 18: Unknown Label | | + +------------+-----------+-----------------------+-----------+ + | 31 | PCECC | 1: Label out of range | RFC 9050 | + | | failure | | | + | | | 2: Instruction failed | | + | | | | | + | | | 3: Invalid CCI | | + | | | | | + | | | 4: Unable to allocate | | + | | | the specified CCI | | + | | | | | + | | | 5: Invalid next-hop | | + | | | information | | + +------------+-----------+-----------------------+-----------+ + + Table 7: PCEP-ERROR Object Error Types and Values Additions + +11. References + +11.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + <https://www.rfc-editor.org/info/rfc2119>. + + [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation + Element (PCE) Communication Protocol (PCEP)", RFC 5440, + DOI 10.17487/RFC5440, March 2009, + <https://www.rfc-editor.org/info/rfc5440>. + + [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax + Used to Form Encoding Rules in Various Routing Protocol + Specifications", RFC 5511, DOI 10.17487/RFC5511, April + 2009, <https://www.rfc-editor.org/info/rfc5511>. + + [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, + "Recommendations for Secure Use of Transport Layer + Security (TLS) and Datagram Transport Layer Security + (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May + 2015, <https://www.rfc-editor.org/info/rfc7525>. + + [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for + Writing an IANA Considerations Section in RFCs", BCP 26, + RFC 8126, DOI 10.17487/RFC8126, June 2017, + <https://www.rfc-editor.org/info/rfc8126>. + + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, <https://www.rfc-editor.org/info/rfc8174>. + + [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path + Computation Element Communication Protocol (PCEP) + Extensions for Stateful PCE", RFC 8231, + DOI 10.17487/RFC8231, September 2017, + <https://www.rfc-editor.org/info/rfc8231>. + + [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, + "PCEPS: Usage of TLS to Provide a Secure Transport for the + Path Computation Element Communication Protocol (PCEP)", + RFC 8253, DOI 10.17487/RFC8253, October 2017, + <https://www.rfc-editor.org/info/rfc8253>. + + [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path + Computation Element Communication Protocol (PCEP) + Extensions for PCE-Initiated LSP Setup in a Stateful PCE + Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, + <https://www.rfc-editor.org/info/rfc8281>. + + [RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. + Hardwick, "Conveying Path Setup Type in PCE Communication + Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, + July 2018, <https://www.rfc-editor.org/info/rfc8408>. + + [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., + and J. Hardwick, "Path Computation Element Communication + Protocol (PCEP) Extensions for Segment Routing", RFC 8664, + DOI 10.17487/RFC8664, December 2019, + <https://www.rfc-editor.org/info/rfc8664>. + + [RFC8779] Margaria, C., Ed., Gonzalez de Dios, O., Ed., and F. + Zhang, Ed., "Path Computation Element Communication + Protocol (PCEP) Extensions for GMPLS", RFC 8779, + DOI 10.17487/RFC8779, July 2020, + <https://www.rfc-editor.org/info/rfc8779>. + +11.2. Informative References + + [RFC4655] Farrel, A., Vasseur, JP., and J. Ash, "A Path Computation + Element (PCE)-Based Architecture", RFC 4655, + DOI 10.17487/RFC4655, August 2006, + <https://www.rfc-editor.org/info/rfc4655>. + + [RFC7025] Otani, T., Ogaki, K., Caviglia, D., Zhang, F., and C. + Margaria, "Requirements for GMPLS Applications of PCE", + RFC 7025, DOI 10.17487/RFC7025, September 2013, + <https://www.rfc-editor.org/info/rfc7025>. + + [RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path + Computation Element Architecture", RFC 7399, + DOI 10.17487/RFC7399, October 2014, + <https://www.rfc-editor.org/info/rfc7399>. + + [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J. + Hardwick, "Path Computation Element Communication Protocol + (PCEP) Management Information Base (MIB) Module", + RFC 7420, DOI 10.17487/RFC7420, December 2014, + <https://www.rfc-editor.org/info/rfc7420>. + + [RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for + Application-Based Network Operations", RFC 7491, + DOI 10.17487/RFC7491, March 2015, + <https://www.rfc-editor.org/info/rfc7491>. + + [RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., + and D. Dhody, "Optimizations of Label Switched Path State + Synchronization Procedures for a Stateful PCE", RFC 8232, + DOI 10.17487/RFC8232, September 2017, + <https://www.rfc-editor.org/info/rfc8232>. + + [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An + Architecture for Use of PCE and the PCE Communication + Protocol (PCEP) in a Network with Central Control", + RFC 8283, DOI 10.17487/RFC8283, December 2017, + <https://www.rfc-editor.org/info/rfc8283>. + + [RFC8741] Raghuram, A., Goddard, A., Karthik, J., Sivabalan, S., and + M. Negi, "Ability for a Stateful Path Computation Element + (PCE) to Request and Obtain Control of a Label Switched + Path (LSP)", RFC 8741, DOI 10.17487/RFC8741, March 2020, + <https://www.rfc-editor.org/info/rfc8741>. + + [PCECC] Li, Z. (., Dhody, D., Zhao, Q., Ke, K., Khasanov, B., + Fang, L., Zhou, C., Zhang, B., Rachitskiy, A., and A. + Gulida, "The Use Cases for Path Computation Element (PCE) + as a Central Controller (PCECC).", Work in Progress, + Internet-Draft, draft-ietf-teas-pcecc-use-cases-07, 8 + March 2021, <https://datatracker.ietf.org/doc/html/draft- + ietf-teas-pcecc-use-cases-07>. + + [PCEP-YANG] + Dhody, D., Ed., Hardwick, J., Beeram, V., and J. Tantsura, + "A YANG Data Model for Path Computation Element + Communications Protocol (PCEP)", Work in Progress, + Internet-Draft, draft-ietf-pce-pcep-yang-16, 22 February + 2021, <https://datatracker.ietf.org/doc/html/draft-ietf- + pce-pcep-yang-16>. + + [PCECC-SR] Li, Z., Peng, S., Negi, M. S., Zhao, Q., and C. Zhou, + "PCEP Procedures and Protocol Extensions for Using PCE as + a Central Controller (PCECC) for Segment Routing (SR) MPLS + Segment Identifier (SID) Allocation and Distribution.", + Work in Progress, Internet-Draft, draft-ietf-pce-pcep- + extension-pce-controller-sr-02, 25 March 2021, + <https://datatracker.ietf.org/doc/html/draft-ietf-pce- + pcep-extension-pce-controller-sr-02>. + + [PCECC-SRv6] + Li, Z., Peng, S., Geng, X., and M. S. Negi, "PCEP + Procedures and Protocol Extensions for Using PCE as a + Central Controller (PCECC) for SRv6", Work in Progress, + Internet-Draft, draft-dhody-pce-pcep-extension-pce- + controller-srv6-06, 21 February 2021, + <https://datatracker.ietf.org/doc/html/draft-dhody-pce- + pcep-extension-pce-controller-srv6-06>. + + [PCE-ID] Li, C., Chen, M., Wang, A., Cheng, W., and C. Zhou, "PCE + Controlled ID Space", Work in Progress, Internet-Draft, + draft-li-pce-controlled-id-space-08, 22 February 2021, + <https://datatracker.ietf.org/doc/html/draft-li-pce- + controlled-id-space-08>. + + [SECURITY-ID] + Gont, F. and I. Arce, "Security Considerations for + Transient Numeric Identifiers Employed in Network + Protocols", Work in Progress, Internet-Draft, draft-gont- + numeric-ids-sec-considerations-06, 5 December 2020, + <https://datatracker.ietf.org/doc/html/draft-gont-numeric- + ids-sec-considerations-06>. + +Acknowledgments + + We would like to thank Robert Tao, Changjing Yan, Tieying Huang, + Avantika, and Aijun Wang for their useful comments and suggestions. + + Thanks to Julien Meuric for shepherding this document and providing + valuable comments. Thanks to Deborah Brungard for being the + responsible AD. + + Thanks to Victoria Pritchard for a very detailed RTGDIR review. + Thanks to Yaron Sheffer for the SECDIR review. Thanks to Gyan Mishra + for the Gen-ART review. + + Thanks to Alvaro Retana, Murray Kucherawy, Benjamin Kaduk, Roman + Danyliw, Robert Wilton, Éric Vyncke, and Erik Kline for the IESG + review. + +Contributors + + Dhruv Dhody + Huawei Technologies + Divyashree Techno Park, Whitefield + Bangalore 560066 + Karnataka + India + + Email: dhruv.ietf@gmail.com + + + Satish Karunanithi + Huawei Technologies + Divyashree Techno Park, Whitefield + Bangalore 560066 + Karnataka + India + + Email: satishk@huawei.com + + + Adrian Farrel + Old Dog Consulting + United Kingdom + + Email: adrian@olddog.co.uk + + + Xuesong Geng + Huawei Technologies + China + + Email: gengxuesong@huawei.com + + + Udayasree Palle + + Email: udayasreereddy@gmail.com + + + Katherine Zhao + Futurewei Technologies + + Email: katherine.zhao@futurewei.com + + + Boris Zhang + Telus Ltd. + Toronto + Canada + + Email: boris.zhang@telus.com + + + Alex Tokar + Cisco Systems + Slovakia + + Email: atokar@cisco.com + + +Authors' Addresses + + Zhenbin Li + Huawei Technologies + Huawei Bld., No.156 Beiqing Rd. + Beijing + 100095 + China + + Email: lizhenbin@huawei.com + + + Shuping Peng + Huawei Technologies + Huawei Bld., No.156 Beiqing Rd. + Beijing + 100095 + China + + Email: pengshuping@huawei.com + + + Mahendra Singh Negi + RtBrick Inc + N-17L, 18th Cross Rd, HSR Layout + Bangalore 560102 + Karnataka + India + + Email: mahend.ietf@gmail.com + + + Quintin Zhao + Etheric Networks + 1009 S Claremont St. + San Mateo, CA 94402 + United States of America + + Email: qzhao@ethericnetworks.com + + + Chao Zhou + HPE + + Email: chaozhou_us@yahoo.com |