PCE Working Group Q. Zhao Internet-Draft K. Zhao Intended status: Experimental Z. Li Expires: September 3, 2015 D. Dhody U. Palle Huawei Technologies B. Zhang Telus Ltd. March 2, 2015 PCEP Procedures and Protocol Extensions for Using PCE as a Central Controller (PCECC) of LSPs draft-zhao-pce-pcep-extension-for-pce-controller-01 Abstract In certain networks deployment scenarios, service providers would like to keep all the existing MPLS functionalities in both MPLS and GMPLS while removing the complexity of existing signaling protocols such as LDP and RSVP-TE. In [I-D.zhao-pce-central-controller-user-cases], we propose to use the PCE [RFC5440] as a central controller (PCECC) so that LSP can be calculated/ signaled/initiated and label forwarding entries are downloaded through a centralized PCE server to each network devices along the LSP path while leveraging the existing PCE technologies as much as possible. This draft specify the procedures and PCEP protocol extensions for using the PCE as the central controller and user cases where LSPs are calculated/setup/initiated and label forwarding entries are downloaded through extending the existing PCE architectures and PCEP. This document also discuss the role of PCECC in Segment Routing (SR). Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any Zhao, et al. Expires September 3, 2015 [Page 1] Internet-Draft PCECC March 2015 time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 3, 2015. Copyright Notice Copyright (c) 2015 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 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. PCECC Modes . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 6 5. Procedures for Using the PCE as the Central Controller (PCECC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 7 5.2. New LSP Functions . . . . . . . . . . . . . . . . . . . . 7 5.3. PCECC Capability Advertisement . . . . . . . . . . . . . 8 5.4. Label Range Reservation . . . . . . . . . . . . . . . . . 8 5.5. LSP Operations . . . . . . . . . . . . . . . . . . . . . 9 5.5.1. Basic PCECC Mode . . . . . . . . . . . . . . . . . . 9 5.5.1.1. PCECC LSP Setup . . . . . . . . . . . . . . . . . 9 5.5.1.2. Label Download . . . . . . . . . . . . . . . . . 11 5.5.1.3. Label Cleanup . . . . . . . . . . . . . . . . . . 11 5.5.1.4. PCE Initiated PCECC LSP . . . . . . . . . . . . . 12 5.5.1.5. PCECC LSP Update . . . . . . . . . . . . . . . . 13 5.5.1.6. PCECC LSP State Report . . . . . . . . . . . . . 14 5.5.2. PCECC Segment Routing (SR) . . . . . . . . . . . . . 15 5.5.2.1. PCECC SR-BE . . . . . . . . . . . . . . . . . . . 15 5.5.2.2. PCECC SR-TE . . . . . . . . . . . . . . . . . . . 16 6. PCEP messages . . . . . . . . . . . . . . . . . . . . . . . . 17 6.1. The PCLRResv message . . . . . . . . . . . . . . . . . . 17 6.2. The PCLabelUpd message . . . . . . . . . . . . . . . . . 18 7. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . . 19 Zhao, et al. Expires September 3, 2015 [Page 2] Internet-Draft PCECC March 2015 7.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 19 7.1.1. PCECC Capability TLV . . . . . . . . . . . . . . . . 20 7.2. LABEL-RANGE Object . . . . . . . . . . . . . . . . . . . 20 7.3. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . . 21 7.4. Label Object . . . . . . . . . . . . . . . . . . . . . . 21 7.4.1. NextHop TLV . . . . . . . . . . . . . . . . . . . . . 22 7.5. FEC Object . . . . . . . . . . . . . . . . . . . . . . . 24 8. Security Considerations . . . . . . . . . . . . . . . . . . . 25 9. Manageability Considerations . . . . . . . . . . . . . . . . 26 9.1. Control of Function and Policy . . . . . . . . . . . . . 26 9.2. Information and Data Models . . . . . . . . . . . . . . . 26 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 26 9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 26 9.5. Requirements On Other Protocols . . . . . . . . . . . . . 26 9.6. Impact On Network Operations . . . . . . . . . . . . . . 26 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 12.1. Normative References . . . . . . . . . . . . . . . . . . 26 12.2. Informative References . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 1. Introduction In certain network deployment scenarios, service providers would like to have the ability to dynamically adapt to a wide range of customer's requests for the sake of flexible network service delivery, Software Defined Networks(SDN) has provides additional flexibility in how the network is operated compared to the traditional network. The existing networking ecosystem has become awfully complex and highly demanding in terms of robustness, performance, scalability, flexibility, agility, etc. By migrating to the SDN enabled network from the existing network, service providers and network operators must have a solution which they can evolve easily from the existing network into the SDN enabled network while keeping the network services remain scalable, guarantee robustness and availability etc. Taking the smooth transition between traditional network and the new SDN enabled network into account, especially from a cost impact assessment perspective, using the existing PCE components from the current network to function as the central controller of the SDN network is one choice, which not only achieves the goal of having a centralized controller, but also leverages the existing PCE network components. Zhao, et al. Expires September 3, 2015 [Page 3] Internet-Draft PCECC March 2015 The Path Computation Element communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to perform route computations in response to Path Computation Clients (PCCs) requests. PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model [I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to enable active control of MPLS-TE and GMPLS tunnels. [I-D.ietf-pce-pce-initiated-lsp] describes the setup and teardown of PCE-initiated LSPs under the active stateful PCE model, without the need for local configuration on the PCC, thus allowing for a dynamic MPLS network that is centrally controlled and deployed. [I-D.ietf-pce-remote-initiated-gmpls-lsp] complements [I-D.ietf-pce-pce-initiated-lsp] by addressing the requirements for remote-initiated GMPLS LSPs. Segment Routing (SR) technology leverages the source routing and tunneling paradigms. A source node can choose a path without relying on hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is specified as a set of "segments" advertised by link-state routing protocols (IS-IS or OSPF). [I-D.ietf-spring-segment-routing] provides an introduction to SR technology. The corresponding IS-IS and OSPF extensions are specified in [I-D.ietf-isis-segment-routing-extensions] and [I-D.ietf-ospf-segment-routing-extensions], respectively. A Segment Routed path (SR path) can be derived from an IGP Shortest Path Tree (SPT). Segment Routed Traffic Engineering paths (SR-TE paths) may not follow IGP SPT. Such paths may be chosen by a suitable network planning tool and provisioned on the source node of the SR-TE path. It is possible to use a stateful PCE for computing one or more SR-TE paths taking into account various constraints and objective functions. Once a path is chosen, the stateful PCE can instantiate an SR-TE path on a PCC using PCEP extensions specified in [I-D.ietf-pce-pce-initiated-lsp] using the SR specific PCEP extensions described in [I-D.ietf-pce-segment-routing]. PCECC may further use PCEP protocol for SR label distribution instead of IGP extensions with some benefits. Current MPLS label has local meaning. That is, MPLS label is always allocated by the downstream node to the upstream node. Then the MPLS label is only identified by the neighboring upstream node and downstream node. The label allocation is done locally and signaled through the LDP/RSVP-TE/BGP protocol. To ease the label allocation and signaling mechanism, PCE can be conveniently used as a central Zhao, et al. Expires September 3, 2015 [Page 4] Internet-Draft PCECC March 2015 controller with Label download capability. Further PCE can also be used to manage the label range and SRGB etc. The PCECC solution introduced in [I-D.zhao-pce-central-controller-user-cases] allow for a dynamic MPLS network that is eventually controlled and deployed without the deployment of RSVP-TE protocol or extended IGP protocol with node/ adjacency segment identifiers signaling capability while providing all the key MPLS functionalities needed by the service providers. This draft specify the procedures and PCEP protocol extensions for using the PCE as the central controller and user cases where LSPs are calculated/setup/initiated/downloaded through extending the existing PCE architectures and PCEP. 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Terminology The following terminology is used in this document. IGP: Interior Gateway Protocol. Either of the two routing protocols, Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS). PCC: Path Computation Client: any client application requesting a path computation to be performed by a Path Computation Element. PCE: Path Computation Element. An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints. TE: Traffic Engineering. 3. PCECC Modes The following PCECC modes are supported - o Basic PCECC. o PCECC SR. * PCECC SR-BE (Best Effort). Zhao, et al. Expires September 3, 2015 [Page 5] Internet-Draft PCECC March 2015 * PCECC SR-TE (Traffic Engineered). In basic PCECC mode, the forwarding is similar to RSVP-TE signalled LSP without the RSVP-TE signaling. The PCECC allocates and download the label entries along the LSP. The rest of processing is similar to the existing stateful PCE mechanism. In case of SR, there are two modes for SR-BE and SR-TE. For SR-BE, the forwarding is similar to LDP LSP without LDP signaling or IGP-SR extension. The SR Node label are allocated and distributed in the domain centrally by the PCE via PCEP. Each node (PCC) rely on local IGP for the nexthop calculation. For SR-TE, the forwarding uses label stack similar to IGP based SR-TE without IGP-SR extension. The SR node and adj labels are allocated and distributed in the domain centrally by the PCE via PCEP by PCECC. Rest of the processing is similar to existing stateful PCE with SR mechanism. 4. PCEP Requirements Following key requirements associated PCECC should be considered when designing the PCECC based solution: 1. PCEP speaker supporting this draft MUST have the capability to advertise its PCECC capability to its peers. 2. Path Computation Client (PCC) supporting this draft MUST have a capability to communicate local label range or global label range or both to PCE. 3. Path Computation Element (PCE) supporting this draft SHOULD have the capability to negotiate a global label range for a group of clients and communicate the final global label range to PCC. 4. PCEP speaker not supporting this draft MUST be able to reject PCECC related message with a reason code that indicates no support for PCECC. 5. PCEP SHOULD provide a means to identify PCECC based LSP in the PCEP messages. 6. PCEP SHOULD provide a means to update (or cleanup) the label- download or label-map entry to the PCC. 5. Procedures for Using the PCE as the Central Controller (PCECC) Zhao, et al. Expires September 3, 2015 [Page 6] Internet-Draft PCECC March 2015 5.1. Stateful PCE Model Active stateful PCE is described in [I-D.ietf-pce-stateful-pce]. PCE as a central controller (PCECC) reuses existing Active stateful PCE mechanism as much as possible to control the LSP. 5.2. New LSP Functions This document defines the following new PCEP messages and extends the existing messages to support PCECC: (PCLRResv): a PCEP message sent by a PCC to a PCE to ask for the label range reservation or a PCE to a PCC to send the reserved label range. The PCLRResv message described in Section 6.1. (PCLabelUpd): a PCEP message sent by a PCE to a PCC to download or cleanup the Label entry. The PCLabelUpd message described in Section 6.2. (PCRpt): a PCEP message described in [I-D.ietf-pce-stateful-pce]. PCRpt message MAYBE used to send PCECC LSP Reports. (PCInitiate): a PCEP message described in [I-D.ietf-pce-pce-initiated-lsp]. PCInitiate message is used to setup PCE-Initiated LSP based on PCECC mechanism. (PCUpd): a PCEP message described in [I-D.ietf-pce-stateful-pce]. PCUpd message is used to send PCECC LSP Update. The new LSP functions defined in this document are mapped onto the messages as shown in the following table. +----------------------------------------+--------------------------+ | Function | Message | +----------------------------------------+--------------------------+ | PCECC Capability advertisement | Open | | Label Range Reservation | PCLRResv | | Label entry Update | PCLabelUpd | | Label entry Cleanup | PCLabelUpd | | PCECC Initiated LSP | PCInitiate | | PCECC LSP Update | PCUpd | | PCECC LSP State Report | PCRpt | | PCECC LSP Delegation | PCRpt | +----------------------------------------+--------------------------+ Zhao, et al. Expires September 3, 2015 [Page 7] Internet-Draft PCECC March 2015 5.3. PCECC Capability Advertisement During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) advertise their support of PCECC extensions. A PCEP Speaker includes the "PCECC Capability" TLV, described in Section 7.1.1 of this document, in the OPEN Object to advertise its support for PCECC extensions. The presence of the PCECC Capability TLV in PCC's OPEN Object indicates that the PCC is willing to function as a PCECC client. The presence of the PCECC Capability TLV in PCE's OPEN message indicates that the PCE is interested in function as a PCECC server. The PCEP protocol extensions for PCECC MUST NOT be used if one or both PCEP Speakers have not included the PCECC Capability TLV in their respective OPEN message. If the PCEP Speakers support the extensions of this draft but did not advertise this capability then a PCErr message with Error-Type=19(Invalid Operation) and Error- Value=[TBD] (Attempted LSP setup/download/label-range reservation if PCECC capability was not advertised) will be generated and the PCEP session will be terminated. L flag and G flag defined in PCECC Capability TLV specifies the local and global label range reservation capability. A PCC or a PCE MUST include both PCECC-CAPABILITY TLV and STATEFUL- PCE-CAPABILITY TLV in OPEN Object to support the extensions defined in this document. If PCECC-CAPABILITY TLV is advertised and STATEFUL-PCE-CAPABILITY TLV is not advertised in OPEN Object, it SHOULD send a PCErr message with Error-Type=19 (Invalid Operation) and Error-value=[TBD](stateful pce capability was not advertised) and terminate the session. 5.4. Label Range Reservation After PCEP initial state synchronization, the label range is reserved. If L flag is advertised in OPEN Object by PCEP speakers, a PCC reserves a local label range and is communicated using PCLRResv message to a PCE. The PCE maintains the local label range of each node and further during LSP setup, a label is assigned to each node from the corresponding local label range reserved. If G flag is advertised in OPEN Object by PCEP speakers,a PCC reserves a global label range and is advertised in PCLRResv message to a PCE. The PCE MAY negotiate and reserves the global label range Zhao, et al. Expires September 3, 2015 [Page 8] Internet-Draft PCECC March 2015 and also sends the negotiated global label range in PCLRResv message to the PCC. Please refer [I-D.li-mpls-global-label-framework] for MPLS global label allocation. A PCC MUST send PCLRResv message immediately after the initial LSP synchronization completion. A PCE SHOULD not send PCLabelUpd message to a PCC before PCLRResv message received. If the PCC received PCLabelUpd message and not initiated label range reservation, it SHOULD send a PCErr message with Error-type=[TBD] (label range not reserved) and Error-value=[TBD]. The label range reservation sequence is shown below. +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |--- PCLRResv, label type=1 --->|local label range reserved | (100-500) |global label range negotiated | label type=2 | | (600-1000) | | | |<--- PCLRResv, label type=2 ---|global label range reserved | (700-1000) | | | [Editor's Note: This section of the document would be updated with more details about Label Block Negotiation, Reservation, Adjustment etc in a future revision of the document.] 5.5. LSP Operations The PCEP messages pertaining to PCECC MUST include PATH-SETUP-TYPE TLV [I-D.sivabalan-pce-lsp-setup-type] in the SRP object to clearly identify the PCECC LSP is intended. 5.5.1. Basic PCECC Mode 5.5.1.1. PCECC LSP Setup Inorder to setup a LSP based on PCECC mechanism, a PCC MUST delegate the LSP by sending a PCRpt message with Path Setup Type set for basic PCECC (see Section 7.3) and D (Delegate) flag (see [I-D.ietf-pce-stateful-pce]) set in the LSP object. Zhao, et al. Expires September 3, 2015 [Page 9] Internet-Draft PCECC March 2015 The LSP-ID in LSP-IDENTIFIER TLV (which usually corresponds to the RSVP-TE LSP-ID) for PCECC LSP MUST always be generated by the PCE. In the first PCRpt message of PCECC LSP, LSP ID of LSP-IDENTIFIER TLV is set to zero. When a PCE received PCRpt message with P and D flags set, it generates LSP ID; calculates the path and assign labels along the path; and setup the path by sending PCLabelUpd message to each node along the path of the LSP. The PCE SHOULD send the PCUpd message with the same PLSP-ID to the Ingress PCC in response to the delegate PCRpt message. The PCECC LSPs MUST be delegated to a PCE at all times. LSP deletion operation for PCECC LSP is same as defined in [I-D.ietf-pce-stateful-pce]. If the PCE received PCRpt message for LSP deletion then it does Label cleanup operation as described in Section 5.5.1.3 for the corresponding LSP. The Basic PCECC LSP setup sequence is as shown below. +-------+ +-------+ |PCC | | PCE | |Ingress| +-------+ +------| | | | PCC +-------+ | | Transit| | | +------| | |--- PCRpt,PLSP-ID=1, P=1, D=1 --->| PCECC LSP |PCC +--------+ | (LSP ID=0) |(LSPID=1) |Egress | | | | +--------+ | | | | | | | |<------ PCLabelUpd,PLSP-ID=1 ------------------ | Label | | | (LSP ID=1) | download | | | | | |<----- PCLabelUpd,PLSP-ID=1 ----------- | Label | | | (LSP ID=1) | download | | | | | | |<--- PCLabelUpd,PLSP-ID=1 ------- | Label | | | (LSP ID=1) | download | | | | | | |<-- PCUpd,PLSP-ID=1, P=1, D=1 ---- | PCECC LSP | | | (LSP ID=1) | Update | | | | Zhao, et al. Expires September 3, 2015 [Page 10] Internet-Draft PCECC March 2015 The PCECC LSP are considered to be 'up' by default. The Ingress MAY further choose to deploy a data plane check mechanism and report the status back to the PCE via PCRpt message. 5.5.1.2. Label Download Inorder to setup an LSP based on PCECC, the PCE sends a PCLabelUpd message to each node of the LSP to download the Label entry as described in Section 5.5.1.1. The LSP object in PCLabelUpd MUST include the LSP-IDENTIFIER TLV. If a node (PCC) received a PCLabelUpd message but failed to download the Label entry, it MUST send a PCErr message with Error-type=[TBD] (label download failed) and Error-value=[TBD]. 5.5.1.3. Label Cleanup Inorder to delete an LSP based on PCECC, the PCE sends a PCLabelUpd message to each node along the path of the LSP to cleanup the Label entry. If the PCC received a PCLabelUpd message but does not recognize the label, the PCC MUST generate a PCErr message with Error-Type 19(Invalid operation) and Error-Value=3, "Unknown Label". The R flag in SRP object defined in [I-D.ietf-pce-pce-initiated-lsp] specifies the deletion of Label Entry in the PCLabelUpd message. Zhao, et al. Expires September 3, 2015 [Page 11] Internet-Draft PCECC March 2015 +-------+ +-------+ |PCC | | PCE | |Ingress| +-------+ +------| | | | PCC +-------+ | | Transit| | | +------| | |--- PCRpt,PLSP-ID=1,P=1,D=1,R=1--->| PCECC LSP |PCC +--------+ | (LSP ID=1) | remove |Egress | | | | +--------+ | | | | | | | |<------ PCLabelUpd, PLSP-ID=1 ------------------ | Label | | | (LSP ID=1, R=1) | cleanup | | | | | |<----- PCLabelUpd, PLSP-ID=1 ----------- | Label | | | (LSP ID=1, R=1) | cleanup | | | | | | |<--- PCLabelUpd, PLSP-ID=1 ------- | Label | | | (LSP ID=1, R=1) | cleanup | | | | 5.5.1.4. PCE Initiated PCECC LSP The LSP Instantiation operation is same as defined in [I-D.ietf-pce-pce-initiated-lsp]. Inorder to setup a PCE Initiated LSP based on PCECC mechanism, a PCE sends PCInitiate message with Path Setup Type set for basic PCECC (see Section 7.3) to the Ingress PCC. The Ingress PCC MUST also set D (Delegate) flag (see [I-D.ietf-pce-stateful-pce]) and C (Create) flag (see [I-D.ietf-pce-pce-initiated-lsp]) in LSP object of PCRpt message. The PCC responds with first PCRpt message with the status as "GOING- UP" and assigned PLSP-ID. The rest of the PCECC LSP setup operations are same as those described in Section 5.5.1.1. The LSP deletion operation for PCE Initiated PCECC LSP is same as defined in [I-D.ietf-pce-pce-initiated-lsp]. The PCE should further perform Label entry cleanup operation as described in Section 5.5.1.3 for the corresponding LSP. The PCE Initiated PCECC LSP setup sequence is shown below. Zhao, et al. Expires September 3, 2015 [Page 12] Internet-Draft PCECC March 2015 +-------+ +-------+ |PCC | | PCE | |Ingress| +-------+ +------| | | | PCC +-------+ | | Transit| | | +------| | |<---PCInitiate,PLSP-ID=0,P=1,D=1---| PCECC LSP |PCC +--------+ | | Initiate |Egress | | |--- PCRpt,PLSP-ID=2,P=1,D=1,C=1--->| PCECC LSP +--------+ | | (LSP ID=0,GOING-UP) |(LSPID=2 | | | | assigned) |<------ PCLabelUpd, PLSP-ID=2 ------------------ | Label | | | (LSP ID=2) | download | | | | | |<----- PCLabelUpd, PLSP-ID=2 ----------- | Label | | | (LSP ID=2) | download | | | | | | |<--- PCLabelUpd, PLSP-ID=2 ------- | Label | | | (LSP ID=2) | download | | | | | | |<-- PCUpd, PLSP-ID=2, P=1, D=1---- | PCECC LSP | | | (LSP ID=2) | Update | | | | 5.5.1.5. PCECC LSP Update Incase of a modification of PCECC LSP with a new path, a PCE sends a PCUpd message to the Ingress PCC. When a PCC received a PCUpd message for an existing LSP, a PCC MUST follow the make-before-break procedure. On successful traffic switch over to the new LSP, PCC sends a PCRpt message to the PCE for the deletion of old LSP. Further the PCE does cleanup operation for the old LSP described in Section 5.5.1.3. The PCECC LSP Update and make-before-break sequence is shown below. Zhao, et al. Expires September 3, 2015 [Page 13] Internet-Draft PCECC March 2015 +-------+ +-------+ |PCC | | PCE | |Ingress| +-------+ +------| | | | PCC +-------+ | | Transit| | | +------| | | | |PCC +--------+ | | |Egress | | | | +--------+ | | | | | | | Modify LSP |<------ PCLabelUpd, PLSP-ID=1 ------------------ | (LSPID=3 | | | (LSP ID=3) | assigned) | | | | | |<----- PCLabelUpd, PLSP-ID=1 ----------- | Label | | | (LSP ID=3) | download | | | | | | |<--- PCLabelUpd, PLSP-ID=1 ------- | Label | | | (LSP ID=3) | download | | | | | | |<-- PCUpd, PLSP-ID=1, P=1, D=1---- | PCECC | | | (LSP ID=3) | LSP Update | | | | | | |--- PCRpt,PLSP-ID=1,P=1,D=1,R=1--->| Delete | | | (LSP ID=1) | old LSP | | | | |<------ PCLabelUpd, PLSP-ID=1 ------------------ | Label | | | (LSP ID=1, R=1) | cleanup | | | | | |<----- PCLabelUpd, PLSP-ID=1 ----------- | Label | | | (LSP ID=1, R=1) | cleanup | | | | | | |<--- PCLabelUpd, PLSP-ID=1 ------- | Label | | | (LSP ID=1, R=1) | cleanup The modified PCECC LSP are considered to be 'up' by default. The Ingress MAY further choose to deploy a data plane check mechanism and report the status back to the PCE via PCRpt message. 5.5.1.6. PCECC LSP State Report As mentioned before, an Ingress PCC MAY choose to apply any OAM mechanism to check the status of LSP in the Data plane and MAY further send its status in PCRpt message to the PCE. Zhao, et al. Expires September 3, 2015 [Page 14] Internet-Draft PCECC March 2015 5.5.2. PCECC Segment Routing (SR) Segment Routing (SR) as described in [I-D.ietf-spring-segment-routing] depends on "segments" that are advertised by Interior Gateway Protocols (IGPs). The SR-node allocate and advertise the SID (node, adj etc) and flood via the IGP. This document proposes a new mechanism where PCE allocate the SID (label) centrally and uses PCEP to advertise the SID. In some deployments PCE (and PCEP) are better suited than IGP because of centralized nature of PCE and direct TCP based PCEP session to the node. 5.5.2.1. PCECC SR-BE Each node (PCC) is allocated a node-SID (label) by the PCECC. The PCECC sends PCLabelUpd to update the label map of each node to all the nodes in the domain. Each node (PCC) uses the local information to determines the next-hop and download the label forwarding instructions accordingly. The PCLabelUpd message in this case MUST not have LSP object but uses new FEC object. +-------+ +-------+ |PCC | | PCE | |3.3.3.3| +-------+ +------| | | | PCC +-------+ | | 2.2.2.2| | | +------| | | | |PCC +--------+ | | |1.1.1.1 | | | | +--------+ | | | | | | | |<------ PCLabelUpd, FEC=1.1.1.1----------------- | Label Map | | | Label=X | update |Find | | | |Nexthop|<----- PCLabelUpd, FEC=1.1.1.1---------- | Label Map |locally| | Label=X | update | | | | | | |<--- PCLabelUpd, FEC=1.1.1.1------ | Label Map | | | Label=X | update | | | | The forwarding behavior and the end result is similar to IGP based "Node-SID" in SR. Thus, from anywhere in the domain, it enforces the ECMP-aware shortest- path forwarding of the packet towards the related node. Zhao, et al. Expires September 3, 2015 [Page 15] Internet-Draft PCECC March 2015 PCE rely on the Node label cleanup using the same PCLabelUpd message. 5.5.2.2. PCECC SR-TE A Segment Routed Best Effort path (SR-BE path) can be derived from an IGP Shortest Path Tree (SPT) as explained above. On the other hand, SR-TE paths may not follow IGP SPT. Such paths may be chosen by a PCE and provisioned on the source node of the SR-TE path. [I-D.ietf-pce-segment-routing] extends PCEP to allow a stateful PCE to compute and initiate SR-TE paths, as well as a PCC to request a path subject to certain constraint(s) and optimization criteria in SR networks. For SR-TE, apart from node-SID, Adj-SID is used where each adjacency is allocated an Adj-SID (label) by the PCECC. The PCECC sends PCLabelUpd to update the label map of each Adj to the corresponding nodes in the domain. Each node (PCC) download the label forwarding instructions accordingly. Similar to SR-BE, the PCLabelUpd message in this case MUST not have LSP object but uses new FEC object. +-------+ +-------+ |PCC | | PCE | |3.3.3.3| +-------+ +------| | | | PCC +-------+ | | 2.2.2.2| | | +------| | | | |PCC +--------+ | | |1.1.1.1 | | | | +--------+ | | | | | | | |<------ PCLabelUpd, FEC=10.1.1.1 / ------------- | Label Map | | | 10.1.1.2 | update | | | Label=A | | | | | | |<----- PCLabelUpd, FEC=10.1.1.2--------- | Label Map | | | 10.1.1.1 | update | | | Label=B | | | | | The forwarding behavior and the end result is similar to IGP based "Adj-SID" in SR. Zhao, et al. Expires September 3, 2015 [Page 16] Internet-Draft PCECC March 2015 The Path Setup Type MUST be set for PCECC SR-TE (see Section 7.3). The rest of the PCEP procedures and mechanism are similar to [I-D.ietf-pce-segment-routing]. PCE rely on the Adj label cleanup using the same PCLabelUpd message. 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 that specify the set of objects that the message can carry. An implementation MUST form the PCEP messages using the object ordering specified in this document. 6.1. The PCLRResv message A Label Range Reservation message (also referred to as PCLRResv message) is a PCEP message sent by a PCC to a PCE for the reservation of label range or by PCE to PCC to send reserved label range for the network. The Message-Type field of the PCEP common header for the PCLRResv message is set to [TBD]. The format of a PCLRResv message is as follows: PCLRResv Message>::= Where: ::= Where ::=[] There are two mandatory objects that MUST be included within each in the PCLRResv message: the SRP Object and LABEL-RANGE object. SRP object is defined in [I-D.ietf-pce-stateful-pce] and this document extends the use of SRP object in PCLRResv message. If the SRP object is missing, the receiving PCE MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=10 (SRP object missing). Zhao, et al. Expires September 3, 2015 [Page 17] Internet-Draft PCECC March 2015 PCC generates the value of SRP-ID-number in SRP object of PCLRResv message send to a PCE. The PCE MUST include the same SRP-ID-number in SRP object of PCLRResv message sent to the PCC in response to PCLRResv message. LABEL-RANGE object is defined in Section 7.2. If the LABEL-RANGE object is missing, the receiving PCE MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=[TBD] (Label object missing). [Editor's Note: This section of the document would be updated with more details about Label Block Negotiation, Reservation, Adjustment etc in a future revision of the document.] 6.2. The PCLabelUpd message The Label Update Message (also referred to as PCLabelUpd) is a PCEP message sent by a PCE to a PCC to download label or update the label map. The same message is also used to cleanup the Label entry. The Message-Type field of the PCEP common header for the PCLabelUpd message is set to [TBD]. The format of the PCLabelUpd message is as follows: ::= Where: ::= [] ::= (|) Where: ::= ::=