PCE Working Group Young Lee Dhruv Dhody Internet Draft Huawei Intended Status: Standard Expires: June 27, 2018 Daniele Ceccarelli Ericsson December 27, 2017 PCEP Extensions for Stitching LSPs in Hierarchical Stateful PCE Model draft-lee-pce-lsp-stitching-hpce-01.txt Abstract This document extends the Path Communication Element Communication Protocol (PCEP) to coordinate an end-to-end inter-domain tunnel setup over a multi-domain networks in the context of Hierarchical Stateful PCE environments. This document uses Stitching Label (SL) to stich per-domain LSPs. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt Lee & Dhody Expires June 27, 2018 [Page 1] Internet-Draft PCEP for multi-domain LSP stitching December 2017 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire June 27, 2018. Copyright Notice Copyright (c) 2017 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...................................................2 2. Network Settings and concepts..................................4 2.1. Stateful H-PCE Stitching Procedure........................6 2.2. Applicability to ACTN....................................10 3. Security Considerations.......................................10 4. IANA Considerations...........................................10 5. References....................................................11 5.1. Normative References.....................................11 5.2. Informative References...................................11 Appendix A. Contributor Addresses................................14 Author's Addresses...............................................14 1. Introduction In Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS), a Traffic Engineering Database (TED) is used in computing paths for connection oriented packet services and for circuits. The TED contains all relevant information that a Path Computation Element (PCE) needs to perform its computations. It is important that the TED should be complete and accurate anytime so that the PCE can perform path computations. In MPLS and GMPLS networks, Interior Gateway routing Protocols (IGPs) have been used to create and maintain a copy of the TED at Lee & Dhody Expires June 27 2018 [Page 2] Internet-Draft PCEP for multi-domain LSP stitching December 2017 each node. One of the benefits of the PCE architecture [RFC4655] is the use of computationally more sophisticated path computation algorithms and the realization that these may need enhanced processing power not necessarily available at each node participating in an IGP. [Stateful-PCE] describes a set of extensions to PCEP to provide stateful control. A stateful PCE has access to not only the information carried by the network's Interior Gateway Protocol (IGP), but also the set of active paths and their reserved resources for its computations. PCC can delegate the rights to modify the LSP parameters to an Active Stateful PCE. [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can be used for computing end-to-end paths for inter-domain MPLS Traffic Engineering (TE) and GMPLS Label Switched Paths (LSPs). Within the Hierarchical PCE (H-PCE) architecture [RFC6805], the Parent PCE (P-PCE) is used to compute a multi-domain path based on the domain connectivity information. A Child PCE (C-PCE) may be responsible for a single domain or multiple domains, it is used to compute the intra-domain path based on its domain topology information. [Stateful H-PCE] presents general considerations for stateful PCE(s) in hierarchical PCE architecture. In particular, the behavior changes and additions to the existing stateful PCE mechanisms (including PCE-initiated LSP setup and active PCE usage) in the context of networks using the H-PCE architecture. Section 3.3.1 of [Stateful H-PCE] describe the per domain stitched LSP mode, where the individual per domain LSP are stitched together. [PCE-CC] introduces the architecture for PCE as a central controller, and examines the motivations and applicability for PCEP as a southbound interface. Section 2.1.3 describes the approach with hierarchical controllers. [BRPC-Stitch] describes how inter-domain labels over the inter- domain interfaces are determined in the multi-domain BRPC-based PCE environments. Further, the document introduces the concept of Stitching Label (SL) and Inter-domain Path Setup Type [PST]. This document also uses these concepts in the hierarchical Stateful PCE model. This document extends the Path Communication Element Communication Protocol (PCEP) to coordinate an end-to-end tunnel for a virtual network over multi-domain networks in the context of Hierarchical Stateful PCE environments. Lee & Dhody Expires June 27 2018 [Page 3] Internet-Draft PCEP for multi-domain LSP stitching December 2017 2. Network Settings and concepts This section describes network settings for this draft. Figure 1 shows the context of Hierarchical Stateful PCE architecture where multi-domain LSP stitching is required for an end-to-end tunnel associated with a VN member. +-----------+ + Parent + + PCE + +-----------+ . . . . . . . . . . . . Stateful +-----+ . +-----+ +-----+ C-PCE for + PCE + + PCE + + PCE + Domain A +-----+ Domain B +-----+ Domain C +-----+ . . . . . . . . . . . . . . . ___ ___ ___ ( ) ( ) ( ) ( o ) ( o ) ( o--o) ( / \ ) ( |\ ) ( | | ) EP1-------(o-o---o-o)==========(o-o-o-o-o)==========(o--o--o-o)--------EP2 |( \ / )| |( \ / )| |( | / )| |( o )| |( o )| |( o-o )| | (___) | | (___) | | (___) | | | | | | | |Domain |Inter-domain|Domain |Inter-domain|Domain | | A | A-B | B | B-C | C | |<----->|<---------->|<----->|<---------->|<------> E2E Tunnel <------------------------------------------------> Figure 1: Multi-domain LSP stitching for an end-to-end tunnel The draft provides PCE mechanisms to identify and isolate an end-to- end tunnel for a virtual network by concatenating a set of LSP/tunnel segments comprising an end-to-end tunnel. From Figure 1, there are a set of segments comprising an end-to-end tunnel: Per Lee & Dhody Expires June 27 2018 [Page 4] Internet-Draft PCEP for multi-domain LSP stitching December 2017 Domain LSP A, Inter-domain Link A-B, Per Domain LSP B, Inter-domain Link B-C, and Per Domain C. It is important to realize that this end-to-end tunnel for a virtual network should be identifiable from other tunnels in the networks so as to guarantee its performance objective associated with this particular tunnel. See Section 2.2 for ACTN applicability for detailed discussion on this aspect. As per [BRPC-Stitch], Stitching Label (SL) is defined as a dedicated label that is used to stitch two tunnels (RSVP-TE tunnels or Segment Routing paths). This label is exchanged between exit BN(i) and entry BN(i+1) via PCEP. In case of H-PCE, the SL is conveyed from entry BN(i+1) to the child PCE(i+1) to the parent PCE, and then to child PCE(i) to the entry BN(i). The exit BN(i) learns the SL via the per- domain LSp setup technique (RSVP-TE, SR, PCECC etc). [BRPC-Stitch] define new LSP setup types for BRPC mode, this document also uses the same LSP setup type for the Stateful H-PCE mode. o TBD1: Inter-Domain Traffic engineering end-to-end path is setup using H-PCE method. This new LSP-TYPE value MUST be set in a PCInitiate messages sends by a P-PCE (Parent PCE) to its C-PCE (child PCE) of transit and destination domains to initiate a new inter-domain LSP tunnel. In turn, the C-PCE MUST return a Stitching Label SL in the RRO of the PCRpt message to P-PCE. o TBD2: Inter-Domain Traffic engineering local path is setup using RSVP-TE. This new LSP-TYPE value MUST be set in the PCInitiate message sends by a C-PCE(i) requesting to a PCC of domain(i) to initiate a new local LSP tunnel(i) which is part of an inter-domain LSP tunnel. This LSP-TYPE value MUST be used by the C- PCE(i) only after receiving a PCInitiate message with an LSP-TYPE equal to TBD1 from a P-PCE. In turn, the PCC of domain(i) MUST return a Stitching Label SL in the RRO of the PCRpt message. o TBD3: Inter-Domain Traffic engineering local path is setup using Segment Routing (SR). This new LSP-TYPE value MUST be set in the PCInitiate message sends by a C-PCE(i) requesting to a PCC of domain(i) to initiate a new Segment Routing path which is part of an inter-domain Segment Routing path. This LSP-TYPE value MUST be used by the C-PCE(i) only after receiving a PCInitiate message with Lee & Dhody Expires June 27 2018 [Page 5] Internet-Draft PCEP for multi-domain LSP stitching December 2017 an LSP-TYPE equal to TBD1 from a P-PCE. In turn, the PCC MUST return a Stitching Label SL in the RRO of the PCRpt message. [Editor's Note - This draft authors plan to discuss with authors of [BRPC-Stitch] to simplify this, as any new path setup type like PCECC would require another path-setup type to be defined here.] Thus, these LSP-TYPE value MUST be set in PCEP messages sends by a Parent PCE to child PCE as well as between child PCE and the PCCs when SL is used. 2.1. Stateful H-PCE Stitching Procedure Taking the sample hierarchical domain topology example from [RFC6805] as the reference topology for the entirety of this document. ----------------------------------------------------------------- | Domain 5 | | ----- | | |PCE 5| | | ----- | | | | ---------------- ---------------- ---------------- | | | Domain 1 | | Domain 2 | | Domain 3 | | | | | | | | | | | | ----- | | ----- | | ----- | | | | |PCE 1| | | |PCE 2| | | |PCE 3| | | | | ----- | | ----- | | ----- | | | | | | | | | | | | ----| |---- ----| |---- | | | | |BN11+---+BN21| |BN23+---+BN31| | | | | - ----| |---- ----| |---- - | | | | |S| | | | | |D| | | | | - ----| |---- ----| |---- - | | | | |BN12+---+BN22| |BN24+---+BN32| | | | | ----| |---- ----| |---- | | | | | | | | | | | | ---- | | | | ---- | | | | |BN13| | | | | |BN33| | | | -----------+---- ---------------- ----+----------- | | \ / | | \ ---------------- / | | \ | | / | | \ |---- ----| / | | ----+BN41| |BN42+---- | Lee & Dhody Expires June 27 2018 [Page 6] Internet-Draft PCEP for multi-domain LSP stitching December 2017 | |---- ----| | | | | | | | ----- | | | | |PCE 4| | | | | ----- | | | | | | | | Domain 4 | | | ---------------- | | | ----------------------------------------------------------------- Section 3.3.1 of [Stateful H-PCE] describes the per-domain stitched LSP mode and list all the steps needed. To support SL based stitching, the steps are modified as follows - Using the reference architecture described in Figure above: (1) The P-PCE (PCE5) is requested to initiate a LSP. Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine the end to end path, which are broken into per-domain LSPs say - o S-BN41 o BN41-BN33 o BN33-D For LSP (BN33-D) (2) The P-PCE (PCE5) sends the initiate request to the child PCE (PCE3) via PCInitiate message for LSP (BN33-D) with ERO=(BN33..D) and LSP-TYPE=TBD1. (3) The PCE3 further propagates the initiate message to BN33 with the ERO and LSP-TYPE=TBD2/TBD3 based on setup type. (4) BN33 initiates the setup of the LSP as per the path and reports to the PCE3 the LSP status ("GOING-UP"). Lee & Dhody Expires June 27 2018 [Page 7] Internet-Draft PCEP for multi-domain LSP stitching December 2017 (5) The PCE3 further reports the status of the LSP to the P-PCE (PCE5). (6) The node BN33 notifies the LSP state to PCE3 when the state is "UP" it also carry the stitching label (SL33) in RRO as (SL33,BN33..D). (7) The PCE3 further reports the status of the LSP to the P-PCE (PCE5) as well as carry the stitching label (SL33) in RRO as (SL33,BN33..D). For LSP (BN41-BN33) (8) The P-PCE (PCE5) sends the initiate request to the child PCE (PCE4) via PCInitiate message for LSP (BN41-BN33) with ERO=(BN41..BN42,SL33,BN33) and LSP-TYPE=TBD1. (9) The PCE4 further propagates the initiate message to BN41 with the ERO and LSP-TYPE=TBD2/TBD3 based on setup type. In case of RSVP_TE, the node BN41 encode the stitching label SL33 as part of the ERO to make sure the node BN42 uses the label SL33 towards node BN33. In case of SR, the label SL33 is part of the label stack pushed at node BN41. (10) BN41 initiates the setup of the LSP as per the path and reports to the PCE4 the LSP status ("GOING-UP"). (11) The PCE4 further reports the status of the LSP to the P-PCE (PCE5). (l2) The node BN41 notifies the LSP state to PCE4 when the state is "UP" it also carry the stitching label (SL41) in RRO as (SL41,BN41..BN33). Lee & Dhody Expires June 27 2018 [Page 8] Internet-Draft PCEP for multi-domain LSP stitching December 2017 (13) The PCE4 further reports the status of the LSP to the P-PCE (PCE5) as well as carry the stitching label (SL41) in RRO as (SL41,BN41..BN33). For LSP (S-BN41) (14) The P-PCE (PCE5) sends the initiate request to the child PCE (PCE1) via PCInitiate message for LSP (S-BN41) with ERO=(S..BN13,SL41,BN41). (15) The PCE1 further propagates the initiate message to node S with the ERO. In case of RSVP_TE, the node S encode the stitching label SL41 as part of the ERO to make sure the node BN13 uses the label SL41 towards node BN41. In case of SR, the label SL41 is part of the label stack pushed at node S. (16) S initiates the setup of the LSP as per the path and reports to the PCE1 the LSP status ("GOING-UP"). (17) The PCE1 further reports the status of the LSP to the P-PCE (PCE5). (18) The node S notifies the LSP state to PCE1 when the state is"UP". (19) The PCE1 further reports the status of the LSP to the P-PCE (PCE5). In this way, per-domain LSP are stitched together using the stitching label (SL). The per-domain LSP MUST be setup from the destination domain towards the source domain one after the other. Lee & Dhody Expires June 27 2018 [Page 9] Internet-Draft PCEP for multi-domain LSP stitching December 2017 Once the per-domain LSP is setup, the entry BN chooses a free label for the Stitching Label SL and add a new entry in its MPLS LFIB with this SL label. The SL from the destination domain is propagated to adjacent transit domain, towards the source domain at each step. This happens through the entry BN to C-PCE to the P-PCE and vice- versa. In case of RSVP-TE, the entry BN further propagates the SL label to the exit BN via RSVP-TE. In case of SR, the SL label is pushed as part of the SR label stack. 2.2. Applicability to ACTN [ACTN] describes framework for Abstraction and Control of TE Networks (ACTN), where each Physical Network Controller (PNC) is equivalent to C-PCE and P-PCE is the Multi-Domain Service Coordinator (MDSC). The Per domain stitched LSP as per the Hierarchical PCE architecture described in Section 3.3.1 and Section 4.1 of [Stateful H-PCE] is well suited for ACTN. The stitching label (SL) mechanism as described in this document is well suited for ACTN when per domain LSP needs to be stitched to form an E2E tunnel or a VN Member. It is to be noted that certain VNs require isolation from other clients. The stitching label mechanism described in this document can be applicable to the VN isolation use-case by uniquely identifying the concatenated stitching labels across multi-domain only to a certain VN member or an E2E tunnel. 3. Security Considerations Procedures and protocol extensions defined in this document do not effect the overall PCEP security model. See [RFC5440], [I-D.ietf- pce-pceps]. It is suggested that any mechanism used for securing the transmission of other PCEP message be applied here as well. As a general precaution, it is RECOMMENDED that these PCEP extensions only be activated on authenticated and encrypted sessions belonging to the same administrative authority. 4. IANA Considerations This document requests IANA actions to allocate code points for the protocol elements defined in this document. Lee & Dhody Expires June 27 2018 [Page 10] Internet-Draft PCEP for multi-domain LSP stitching December 2017 5. References 5.1. Normative References [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [RFC4674] Le Roux, J., Ed., "Requirements for Path Computation Element (PCE) Discovery", RFC 4674, October 2006. [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, January 2008. [RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, January 2008. [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The OSPF Opaque LSA Option", RFC 5250, July 2008. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008. [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. 5.2. Informative References [JMS] Java Message Service, Version 1.1, April 2002, Sun Microsystems. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. Lee & Dhody Expires June 27 2018 [Page 11] Internet-Draft PCEP for multi-domain LSP stitching December 2017 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [BGP-LS] Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.Ray, "North-Bound Distribution of Link-State and TE information using BGP", draft-ietf-idr-ls-distribution, work in progress. [S-PCE-GMPLS] X. Zhang, et. al, "Path Computation Element (PCE) Protocol Extensions for Stateful PCE Usage in GMPLS- controlled Networks", draft-ietf-pce-pcep-stateful-pce- gmpls, work in progress. [RFC7399] A. Farrel and D. king, "Unanswered Questions in the Path Computation Element Architecture", RFC 7399, October 2015. [RFC7449] Y. Lee, G. Bernstein, "Path Computation Element Communication Protocol (PCEP) Requirements for Wavelength Switched Optical Network (WSON) Routing and Wavelength Assignment", RFC 7449, February 2015. [RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)", RFC 4456, April 2006. [RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and PCE Control of Wavelength Switched Optical Networks", RFC 6163, [G.680] ITU-T Recommendation G.680, Physical transfer functions of optical network elements, July 2007. [ACTN-Frame] D.Ceccarelli, and Y. Lee (Editors), "Framework for Abstraction and Control of TE Networks", draft-ietf-teas- actn-framework, work in progress. [RFC6805] A. Farrel and D. King, "The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS", RFC 6805, November 2012. [PCEP-LS-Arch] Y. Lee, D. Dhody and D. Ceccarelli, "Architecture and Requirement for Distribution of Link-State and TE Information via PCEP", draft-leedhody-teas-pcep-ls, work in progress. Lee & Dhody Expires June 27 2018 [Page 12] Internet-Draft PCEP for multi-domain LSP stitching December 2017 [PCEP-LS] D. Dhody, Y. Lee and D. Ceccarelli "PCEP Extension for Distribution of Link-State and TE Information.", work in progress, September 21, 2015[Stateful-PCE] Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP Extensions for Stateful PCE", draft-ietf-pce-stateful-pce, work in progress. [PCE-Initiated] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model", draft-ietf-pce-pce-initiated-lsp, work in progress. [Stateful H-PCE] D. Dhody, Y. Lee and D. Ceccarelli, "Hierarchical Stateful Path Computation Element (PCE)", draft-ietf-pce- stateful-hpce, work-in-progress. [FlexOSPF] X. Zhang, H. Zheng, R. Casellas, O. Gonzalez de Dios, D. Ceccarelli, "GMPLS OSPF Extensions in support of Flexi- grid DWDM networks", draft-ietf-ccamp-flexible-grid-ospf- ext-05, work in progress. [PST] Sivabalan, S., Medved, J., Minei, I., Crabbe, E., Varga, R., Tantsura, J., and J. Hardwick, "Conveying path setup type in PCEP messages", draft-ietf-pce-lsp-setup-type-03 work in progress. Lee & Dhody Expires June 27 2018 [Page 13] Internet-Draft PCEP for multi-domain LSP stitching December 2017 Appendix A. Contributor Addresses Author's Addresses Young Lee Huawei Technologies 5340 Legacy Drive, Building 3 Plano, TX 75023, USA Email: leeyoung@huawei.com Dhruv Dhody Huawei Technologies Divyashree Techno Park, Whitefield Bangalore, Karnataka 560066 India Email: dhruv.ietf@gmail.com Daniele Ceccarelli Ericsson Torshamnsgatan,48 Stockholm Sweden Email: daniele.ceccarelli@ericsson.com Lee & Dhody Expires June 27 2018 [Page 14]