Interworking of GMPLS Control and Centralized Controller System
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|Authors||Haomian Zheng , Xianlong Luo , Zheyu Fan , Yi Lin|
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CCAMP Working Group Haomian Zheng Internet Draft Xianlong Luo Category: Informational Zheyu Fan Yi Lin Huawei Technologies Expires: April 30, 2018 October 30, 2017 Interworking of GMPLS Control and Centralized Controller System draft-zheng-ccamp-gmpls-controller-inter-work-00 Abstract Generalized Multi-Protocol Label Switching (GMPLS) control allows each network element (NE) to perform resource discovery, routing and signaling in a distributed manner. On the other hand, with the development of software-defined transport networking technology, central controllers are introduced to transport networks to control a set of NEs. In transport networks, the GMPLS control has many mature mechanisms such as RSVP-TE, OSPF-TE, and LMP, so that GMPLS can be applied for the NE-level control in the centralized controller systems. This document describes how GMPLS control interworks with centralized controller systems (e.g. ACTN) in transport network. 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. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Zheng, et al. Expires April 2018 [Page 1] Internet-Draft GMPLS and Controller Interwork October 2017 This Internet-Draft will expire on April 30, 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. Conventions used in this document 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]. Table of Contents 1. Introduction ................................................ 3 2. Overview .................................................... 3 2.1. Overview of GMPLS Control Plane ........................... 3 2.2. Overview of Centralized Controller System ................. 4 2.3. GMPLS Control Interwork with Centralized Controller System 4 3. Link Management Protocol .................................... 5 4. Routing Options ............................................. 6 4.1. OSPF-TE ................................................ 6 4.2. ISIS-TE ................................................ 6 5. Path Computation ............................................ 6 5.1. Constraint-based Path Computing in GMPLS Control ....... 6 5.2. Path Computation Element (PCE) ......................... 7 6. Signaling Options ........................................... 7 6.1. RSVP-TE ................................................ 8 6.2. CR-LDP ................................................. 8 7. Recovery .................................................... 8 8. Network Management .......................................... 8 9. IANA Considerations ......................................... 8 Zheng Expires April 2018 [Page 2] Internet-Draft GMPLS and Controller Interwork October 2017 10. References ................................................. 9 10.1. Normative References .................................. 9 10.2. Informative References ............................... 11 11. Authors' Addresses ........................................ 11 1. Introduction Generalized Multi-Protocol Label Switching (GMPLS) [RFC3945] extends MPLS to support different classes of interfaces and switching capabilities such as Time-Division Multiplex Capable (TDM), Lambda Switch Capable (LSC), and Fiber-Switch Capable (FSC). Each network element (NE) running a control plane collects network information from other NEs and provisions services through signaling in a distributed manner. On the other hand, Software-Defined Networking (SDN) technologies have been introduced to control the transport network in a centralized manner. Central controllers, which can locate outside of the network, can collect network information from each node and provision services to corresponding nodes. One of the examples is the Abstraction and Control of Traffic Engineered Networks (ACTN) [I-D.ietf-teas-actn-framework], which defines a hierarchical architecture with PNC, MDSC and CNC as central controllers for different network abstraction levels. In such centralized controller systems, GMPLS can be applied for the NE-level control. Introducing GMPLS in centralized controller system can reuse the mature mechanisms defined for GMPLS and be practical for legacy transport networks. This document describes how GMPLS control interworks with centralized controller system in transport network. 2. Overview In this section, overviews of GMPLS control plane and centralized controller system are discussed as well as the cooperation between GMPLS control plane and centralized controller system. 2.1. Overview of GMPLS Control Plane GMPLS separates the control plane and the data plane to support time-division, wavelength, and spatial switching, which are significant in transport networks. For the NE level control in GMPLS, each node has its controller to perform service provisioning, Zheng Expires April 2018 [Page 3] Internet-Draft GMPLS and Controller Interwork October 2017 protection, and restoration. At the same time, the controller can negotiate available link resources with controllers in adjacent nodes, and it can also collect node and link resources in the network to construct the network topology and compute routing paths for serving service requests. Several protocols have been designed for GMPLS control [RFC3945] including link management [RFC4204], signaling [RFC3471], and routing [RFC4202] protocols. The controllers applying these protocols communicate with each other to exchange resource information and establish LSP. In this way, controllers in different nodes in the network have the same network topology and provision services by their local policies. 2.2. Overview of Centralized Controller System With the development of SDN technologies, centralized controller system has been introduced to transport networks such as ACTN. In centralized controller system, a controller is aware of the network topology and is responsible for provisioning incoming service requests. In ACTN, multiple abstraction levels are designed and controllers at different levels implement different functions. This kind of abstraction enables multi-vendor, multi-domain, and multi- technology control. For example in ACTN, an MDSC coordinates several PNCs controlling different domains. Each PNC reports its topology, which can be abstracted, to the MDSC, so that the MDSC learns the picture of multiple domains. When a multi-domain service arrives at the MDSC, the MDSC first computes an end-to-end routing path. Then the MDSC splits this path to multiple segment according to domain boundaries and allocate each segment to corresponding PNC for detailed path computation and LSP segment setup. After each PNC reporting the establishment of corresponding LSP segment, this multi-domain service is accommodated. 2.3. GMPLS Control Interwork with Centralized Controller System Centralized controller system as ACTN provides the architecture and communication between central controllers of different abstraction levels to coordinate multiple domains. Within each domain, GMPLS control can be applied to each NE. The bottom-level central controller like PNC can act as a NE to collect network information and initiate LSP. Following figure shows an example of GMPLS interworking with ACTN. Zheng Expires April 2018 [Page 4] Internet-Draft GMPLS and Controller Interwork October 2017 +----------+ | MDSC | +----------+ ^ ^ | | +---------+ +---------+ | RESTConf / YANG models | V V +---------+ +---------+ | PNC | | PNC | +---------+ +---------+ ^ ^ ^ ^ | | | | OSPF-TE| |PCEP OSPF-TE| |PCEP | | | | | V | V .-------------. Inter- .-------------. / \ domain / \ | LMP | link | LMP | | OSPF-TE ========== OSPF-TE | | RSVP-TE | | RSVP-TE | \ / \ / `------------` `------------` GMPLS domain GMPLS domain Figure 1: Example of GMPLS interworks with ACTN In Figure 1, each domain runs GMPLS control. The PNC listens LSAs flooded in the domain and learns the topology. For path computation in the domain with PNC implementing a PCE, NEs use PCEP to ask the PNC for a path and get replies. The MDSC communicates with PNCs using RESTConf or YANG models. As a PNC has learned its domain topology, it can report the topology to the MDSC. When a service arrives, the MDSC computes the path and coordinates PNCs to establish the corresponding LSP segment. 3. Link Management Protocol Link management protocol (LMP) [RFC4204] runs between a pair of nodes and is used to manage TE links. In addition to setup and maintain control channels, LMP can be used to verify the data link connectivity and correlate the link property. In this way, link Zheng Expires April 2018 [Page 5] Internet-Draft GMPLS and Controller Interwork October 2017 resources, which are fundamental resources in the network, are discovered by both ends of the link. 4. Routing Options In GMPLS control, link state information is flooded within the network as defined in [RFC4202]. Each node in the network can build the network topology according to the flooded link state information. Routing protocols such as OSPF-TE [RFC4203] and ISIS-TE [RFC5307] have been extended to support different interfaces in GMPLS. In centralized controller system, central controller can be placed at the GMPLS network and passively receive the information flooded in the network. In this way, the central controller can construct and update the network topology. 4.1. OSPF-TE OSPF-TE is introduced for TE networks in [RFC3630]. OSPF extensions have been defined in [RFC4203] to enable the capability of link state information for GMPLS network. Based on this work, OSPF protocol has been extended to support technology-specific routing. The routing protocol for OTN, WSON and optical flexi-grid network are defined in [RFC7138], [RFC7688] and [I-D.ietf-ccamp-flexible- grid-ospf-ext], respectively. 4.2. ISIS-TE ISIS-TE is introduced for TE networks in [RFC5305] and is extended to support GMPLS routing functions [RFC5307], and has been updated to [RFC7074] to support the latest GMPLS switching capability and Types fields. 5. Path Computation Once a controller learn the network topology, it can utilize the available resources to serve service requests by performing path computation. Path computation is one of the key objectives in various types of controllers. In the given architecture, it is possible for different components that have the capability to compute the path. 5.1. Constraint-based Path Computing in GMPLS Control In GMPLS control, a routing path is computed by the ingress node [RFC3473] and is based on the ingress node TED. Constraint-based Zheng Expires April 2018 [Page 6] Internet-Draft GMPLS and Controller Interwork October 2017 path computation is performed according to the local policy of the ingress node. 5.2. Path Computation Element (PCE) PCE has been introduced in [RFC4655] as a functional component that provides services to compute path in a network. In [RFC5440], the path computation is accomplished by using the Traffic Engineering Database (TED), which maintains the link resources in the network. The emergence of PCE efficiently improve the quality of network planning and offline computation, but there is a risk that the computed path may be infeasible if there is a diversity requirement, because stateless PCE has no knowledge about the former computed paths. To address this issue, stateful PCE has been proposed in [RFC8231]. Besides the TED, an additional LSP Database (LSP-DB) is introduced to archive each LSP computed by the PCE. In this way, PCE can easily figure out the relationship between the computing path and former computed paths. In this approach, PCE provides computed paths to PCC, and then PCC decides which path is deployed and when to be established. In PCE Initiation [I-D.ietf-pce-pce-initiated-lsp], PCE is allowed to trigger the PCC to setup, maintenance, and teardown of the PCE- initiated LSP under the stateful PCE model. This would allow a dynamic network that is centrally controlled and deployed. In centralized controller system, the PCE can be implement in a central controller, and the central controller performs path computation according to its local policies. On the other hand, the PCE can also be placed outside of the central controller. In this case, the central controller acts as a PCC to request path computation to the PCE through PCEP. 6. Signaling Options Signaling mechanism is used to setup LSPs in GMPLS control. Messages are sent hop by hop between the ingress node and the egress node of the LSP to allocate labels. Once the labels are allocated along the path, the LSP setup is accomplished. Signaling protocols such as RSVP-TE [RFC3473] and CR-LDP [RFC3472] have been extended to support different interfaces in GMPLS. In centralized controller system, the central controller can manage LSPs by using PCE-initiation [I-D.ietf-pce-pce-initiated-lsp] to Zheng Expires April 2018 [Page 7] Internet-Draft GMPLS and Controller Interwork October 2017 notify the corresponding ingress node. The ingress node will maintain the LSP through GMPLS signaling. 6.1. RSVP-TE RSVP-TE is introduced in [RFC3209] and extended to support GMPLS signaling in [RFC3473]. Several label formats are defined for a generalized label request, a generalized label, suggested label and label sets. Based on [RFC3473], RSVP-TE has been extended to support technology-specific signaling. The RSVP-TE extensions for OTN, WSON, optical flexi-grid network are defined in [RFC7139], [RFC7689], and [RFC7792], respectively. 6.2. CR-LDP In order to support the label formats and signaling mechanism defined in [RFC3471], CR-LDP is extended in [RFC3472]. Several label formats are defined and bidirectional LSPs are supported. 7. Recovery The GMPLS recovery functions are described in [RFC4426]. Two models, span protection and end-to-end protection and restoration, are discussed with different protection schemes and message exchange requirements. Related RSVP-TE extensions to support end-to-end recovery is described in [RFC4872]. The extensions in [RFC4872] include protection, restoration, preemption, and rerouting mechanisms for an end-to-end LSP. Besides end-to-end recovery, a GMPLS segment recovery mechanism is defined in [RFC4873]. By introducing secondary record route objects, LSP segment can be switched to another path like fast rereoute [RFC4090]. 8. Network Management TBD. 9. Security Considerations TBD. 10. IANA Considerations This document requires no IANA actions. Zheng Expires April 2018 [Page 8] Internet-Draft GMPLS and Controller Interwork October 2017 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC3472] Ashwood-Smith, P., Ed. and L. Berger, Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Constraint-based Routed Label Distribution Protocol (CR- LDP) Extensions", RFC 3472, January 2003. [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Architecture", RFC 3945, October 2004. [RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005. [RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005. [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC4204] Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204, October 2005. Zheng Expires April 2018 [Page 9] Internet-Draft GMPLS and Controller Interwork October 2017 [RFC4426] Lang, J., Ed., Rajagopalan, B., Ed., and D. Papadimitriou, Ed., "Generalized Multi-Protocol Label witching (GMPLS) Recovery Functional Specification", RFC 4426, March 2006. [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [RFC4872] Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou, Ed., "RSVP-TE Extensions in Support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS) Recovery", RFC 4872, May 2007. [RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel, "GMPLS Segment Recovery", RFC 4873, May 2007. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008. [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, October 2008. [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. [RFC7074] Berger, L. and J. Meuric, "Revised Definition of the GMPLS Switching Capability and Type Fields", RFC 7074, November 2013. [RFC7138] Ceccarelli, D., Ed., Zhang, F., Belotti, S., Rao, R., and J. Drake, "Traffic Engineering Extensions to OSPF for GMPLS Control of Evolving G.709 Optical Transport Networks", RFC 7138, March 2014. [RFC7139] Zhang, F., Ed., Zhang, G., Belotti, S., Ceccarelli, D., and K. Pithewan, "GMPLS Signaling Extensions for Control of Evolving G.709 Optical Transport Networks", RFC 7139, March 2014. [RFC7688] Lee, Y., Ed. and G. Bernstein, Ed., "GMPLS OSPF Enhancement for Signal and Network Element Compatibility for Wavelength Switched Optical Networks", RFC 7688, November 2015. Zheng Expires April 2018 [Page 10] Internet-Draft GMPLS and Controller Interwork October 2017 [RFC7689] Bernstein, G., Ed., Xu, S., Lee, Y., Ed., Martinelli, G., and H. Harai, "Signaling Extensions for Wavelength Switched Optical Networks", RFC 7689, November 2015. [RFC7792] Zhang, F., Zhang, X., Farrel, A., Gonzalez de Dios, O., and D. Ceccarelli, "RSVP-TE Signaling Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks", RFC 7792, March 2016. [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path Computation Element Communication Protocol (PCEP) Extensions for Stateful PCE", RFC 8231, September 2017. [I-D.ietf-ccamp-flexible-grid-ospf-ext] Zhang, X., Zheng, H., Casellas, R., Dios, O., and D. Ceccarelli, "GMPLS OSPF-TE Extensions in support of Flexi-grid DWDM networks", draft- ietf-ccamp-flexible-grid-ospf-ext-09 (work in progress), February 2017. [I-D.ietf-pce-pce-initiated-lsp] 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-11 (work in progress), October 2017. [I-D.ietf-teas-actn-framework] Ceccarelli, D. and Y. Lee, "Framework for Abstraction and Control of Traffic Engineered Networks", draft-ietf-teas-actn-framework-11 (work in progress), October 2017. 11.2. Informative References 12. Authors' Addresses Haomian Zheng Huawei Technologies F3 R&D Center, Huawei Industrial Base, Bantian, Longgang District, Shenzhen 518129 P.R.China Email: firstname.lastname@example.org Xianlong Luo Huawei Technologies Zheng Expires April 2018 [Page 11] Internet-Draft GMPLS and Controller Interwork October 2017 F3 R&D Center, Huawei Industrial Base, Bantian, Longgang District, Shenzhen 518129 P.R.China Email: email@example.com Zheyu Fan Huawei Technologies F3 R&D Center, Huawei Industrial Base, Bantian, Longgang District, Shenzhen 518129 P.R.China Email: firstname.lastname@example.org Yi Lin Huawei Technologies F3 R&D Center, Huawei Industrial Base, Bantian, Longgang District, Shenzhen 518129 P.R.China Email: email@example.com Zheng Expires April 2018 [Page 12]