OSPF Working Group X. XuInternet-Draft Alibaba IncIntended status: Standards Track S. KiniExpires: April 27, 2020 P. Psenak C. Filsfils S. Litkowski Cisco Systems, Inc. M. Bocci Nokia October 25, 2019Signaling Entropy Label Capability and Entropy Readable Label-stackDepth Using OSPFdraft-ietf-ospf-mpls-elc-12Abstract Multiprotocol Label Switching (MPLS) has defined a mechanism to load- balance traffic flows using Entropy Labels (EL). An ingress Label Switching Router (LSR) cannot insert ELs for packets going into a given tunnel unless an egress LSR has indicated via signaling that it has the capability to process ELs, referred to as Entropy Label Capability (ELC), on that tunnel. In addition, it would be useful for ingress LSRs to know each LSR's capability of reading the maximum label stack depth and performing EL-based load-balancing, referred to as Entropy Readable Label Depth (ERLD). This document defines a mechanism to signal these two capabilities using OSPF and OSPFv3. These mechanism is particularly useful in the environment where Segment Routing (SR) is used, where label advertisements are done via protocols like OSPF and OSPFv3.Status of This Memo This Internet-Draft is submitted in full conformance with the provisions ofBCP 78 andBCP 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 athttps://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 time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."Xu, et al. Expires April 27, 2020 [Page 1]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 This Internet-Draft will expire on April 27, 2020.Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject toBCP 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 Contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . .22. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .33. Advertising ELC Using OSPF . . . . . . . . . . . . . . . . .33.1. Advertising ELC Using OSPFv2 . . . . . . . . . . . . . .43.2. Advertising ELC Using OSPFv3 . . . . . . . . . . . . . .44. Advertising ERLD Using OSPF . . . . . . . . . . . . . . . . .45. Signaling ELC and ERLD in BGP-LS . . . . . . . . . . . . . .46. Acknowledgements . . . . . . . . . . . . . . . . . . . . . .57. IANA Considerations . . . . . . . . . . . . . . . . . . . . .58. Security Considerations . . . . . . . . . . . . . . . . . . .59. Contributors . . . . . . . . . . . . . . . . . . . . . . . .510. References . . . . . . . . . . . . . . . . . . . . . . . . .610.1. Normative References . . . . . . . . . . . . . . . . . .610.2. Informative References . . . . . . . . . . . . . . . . .8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .81. Introduction [RFC6790] describes a method to load-balance Multiprotocol Label Switching (MPLS) traffic flows using Entropy Labels (EL). It also introduces the concept of Entropy Label Capability (ELC) and defines the signaling of this capability via MPLS signaling protocols. Recently, mechanisms have been defined to signal labels via link- state Interior Gateway Protocols (IGP) such as OSPF [I-D.ietf-ospf-segment-routing-extensions]. In such scenarios, the signaling mechanisms defined in [RFC6790] are inadequate. This draft defines a mechanism to signal the ELC using OSPF. This mechanism is useful when the label advertisement is also done via OSPF.Xu, et al. Expires April 27, 2020 [Page 2]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 In addition, in the cases where stacked LSPs are used for whatever reasons (e.g., SR-MPLS [I-D.ietf-spring-segment-routing-mpls]), it would be useful for ingress LSRs to know each intermediate LSR's capability of reading the maximum label stack depth and performing EL-based load-balancing. This capability, referred to as Entropy Readable Label Depth (ERLD) as defined in [I-D.ietf-mpls-spring-entropy-label] may be used by ingress LSRs to determine the position of the EL label in the stack, and whether it's necessary to insert multiple ELs at different positions in the label stack.2. Terminology This document makes use of the terms defined in [RFC6790], [RFC7770] and [I-D.ietf-mpls-spring-entropy-label]. 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 [BCP14] [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.3. Advertising ELC Using OSPF Even though ELC is a property of the node, in some cases it is advantageous to associate and advertise the ELC with the prefix. In multi-area networks, routers may not know the identity of the prefix originator in a remote area, or may not know the capabilities of such originator. Similarly, in a multi domain network, the identity of the prefix originator and its capabilities may not be known to the ingress LSR. If a router has multiple line cards, the router MUST NOT announce ELC unless all of its line-cards are capable of processing ELs. If the router supports ELs on all of its line cards, it SHOULD advertise the ELC with every local host prefix it advertises in OSPF. When an OSPF Area Border Router (ABR) advertises the prefix to the connected area based on the intra-area or inter-area prefix that is reachable in some other area, it MUST preserve the ELC signalling for such prefix. When an OSPF Autonomous System Boundary Router (ASBR) redistributes the prefix from another instance of the OSPF or from some other protocol, it SHOULD preserve the ELC signaling for the prefix. The exact mechanism used to exchange ELC between protocol instances onXu, et al. Expires April 27, 2020 [Page 3]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 the ASBR is outside of the scope of this document and is implementation specific.3.1. Advertising ELC Using OSPFv2 [RFC7684] defines the OSPFv2 Extended Prefix TLV to advertise additional attributes associated with a prefix. The OSPFv2 Extended Prefix TLV includes a one octet Flags field. A new flag in the Flags field is used to signal the ELC for the prefix: 0x20 - E-Flag (ELC Flag): Set by the advertising router to indicate that the prefix originator is capable of processing ELs.3.2. Advertising ELC Using OSPFv3 [RFC5340] defines the OSPFv3 PrefixOptions that are advertised along with the prefix. A new bit in the OSPFV3 PrefixOptions is used to signal the ELC for the prefix: 0x04 - E-Flag (ELC Flag): Set by the advertising router to indicate that the prefix originator is capable of processing ELs.4. Advertising ERLD Using OSPF A new MSD (Maximum SID Depth) type of the Node MSD sub-TLV [RFC8476], called ERLD is defined to advertise the ERLD of a given router. The scope of the advertisement depends on the application. Assignment of a MSD-Type for ERLD is defined in [I-D.ietf-isis-mpls-elc]. If a router has multiple line-cards with different capabilities for reading the maximum label stack depth, the router MUST advertise the smallest one. When the ERLD MSD-Type is received in the OSPFv2 or OSPFv3 Link MSD Sub-TLV, it MUST be ignored.5. Signaling ELC and ERLD in BGP-LS The OSPF extensions defined in this document can be advertised via BGP-LS [RFC7752] using existing BGP-LS TLVs. The ELC Flag included in the OSPFv2 Extended Prefix TLV and the OSPFv3 PrefixOptions, as defined inSection 3, is advertised using the Prefix Attribute Flags TLV (TLV 1170) of the BGP-LS IPv4/IPv6 Prefix NLRI Attribute as defined in section 2.3.2 of [I-D.ietf-idr-bgp-ls-segment-routing-ext].Xu, et al. Expires April 27, 2020 [Page 4]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 The ERLD MSD-type introduced for OSPF inSection 4 is advertised using the Node MSD TLV (TLV 266) of the BGP-LS Node NLRI Attribute as defined in section 3 of [I-D.ietf-idr-bgp-ls-segment-routing-msd].6. Acknowledgements The authors would like to thank Yimin Shen, George Swallow, Acee Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura , Bruno Decraene and Carlos Pignataro for their valuable comments.7. IANA Considerations This document requests IANA to allocate one flag from the OSPFv2 Extended Prefix TLV Flags registry: 0x20 - E-Flag (ELC Flag) This document requests IANA to allocate one flag from the OSPFv3 Prefix Options registry: 0x04 - E-Flag (ELC Flag)8. Security Considerations The security considerations as described in [RFC7770] and [I-D.ietf-mpls-spring-entropy-label] are applicable to this document. Incorrectly setting the E flag (ELC capable) (during origination, inter-area advertisement or redistribution) may lead to black-holing of the traffic on the egress node. Incorrectly setting of the ERLD value may lead to poor load-balancing of the traffic.9. Contributors The following people contributed to the content of this document and should be considered as co-authors:Xu, et al. Expires April 27, 2020 [Page 5]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 Gunter Van de Velde (editor) Nokia Antwerp BE Email: gunter.van_de_velde@nokia.com Wim Henderickx Nokia Belgium Email: wim.henderickx@nokia.com Keyur Patel Arrcus USA Email: keyur@arrcus.com10. References10.1. Normative References [BCP14] , <https://tools.ietf.org/html/bcp14>. [I-D.ietf-idr-bgp-ls-segment-routing-ext] Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., and M. Chen, "BGP Link-State extensions for Segment Routing",draft-ietf-idr-bgp-ls-segment-routing-ext-16 (work in progress), June 2019. [I-D.ietf-idr-bgp-ls-segment-routing-msd] Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G., and N. Triantafillis, "Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link-State",draft-ietf-idr-bgp-ls-segment-routing-msd-09 (work in progress), October 2019. [I-D.ietf-isis-mpls-elc] Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S., and M. Bocci, "Signaling Entropy Label Capability and Entropy Readable Label Depth Using IS-IS",draft-ietf-isis-mpls-elc-10 (work in progress), October 2019.Xu, et al. Expires April 27, 2020 [Page 6]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 [I-D.ietf-mpls-spring-entropy-label] Kini, S., Kompella, K., Sivabalan, S., Litkowski, S., Shakir, R., and J. Tantsura, "Entropy label for SPRING tunnels",draft-ietf-mpls-spring-entropy-label-12 (work in progress), July 2018. [I-D.ietf-spring-segment-routing-mpls] Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing with MPLS data plane",draft-ietf-spring-segment-routing-mpls-22 (work in progress), May 2019. [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>. [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6",RFC 5340, DOI 10.17487/RFC5340, July 2008, <https://www.rfc-editor.org/info/rfc5340>. [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and L. Yong, "The Use of Entropy Labels in MPLS Forwarding",RFC 6790, DOI 10.17487/RFC6790, November 2012, <https://www.rfc-editor.org/info/rfc6790>. [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement",RFC 7684, DOI 10.17487/RFC7684, November 2015, <https://www.rfc-editor.org/info/rfc7684>. [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP",RFC 7752, DOI 10.17487/RFC7752, March 2016, <https://www.rfc-editor.org/info/rfc7752>. [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities",RFC 7770, DOI 10.17487/RFC7770, February 2016, <https://www.rfc-editor.org/info/rfc7770>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.Xu, et al. Expires April 27, 2020 [Page 7]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 [RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, "Signaling Maximum SID Depth (MSD) Using OSPF",RFC 8476, DOI 10.17487/RFC8476, December 2018, <https://www.rfc-editor.org/info/rfc8476>.10.2. Informative References [I-D.ietf-ospf-segment-routing-extensions] Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Extensions for Segment Routing",draft-ietf-ospf-segment-routing-extensions-27 (work in progress), December 2018.Authors' Addresses Xiaohu Xu Alibaba Inc Email: xiaohu.xxh@alibaba-inc.com Sriganesh Kini Email: sriganeshkini@gmail.com Peter Psenak Cisco Systems, Inc. Eurovea Centre, Central 3 Pribinova Street 10 Bratislava 81109 Slovakia Email: ppsenak@cisco.com Clarence Filsfils Cisco Systems, Inc. Brussels Belgium Email: cfilsfil@cisco.comXu, et al. Expires April 27, 2020 [Page 8]
Internet-Draft Signaling ELC and ERLD using OSPF October 2019 Stephane Litkowski Cisco Systems, Inc. La Rigourdiere Cesson Sevigne France Email: slitkows@cisco.com Matthew Bocci Nokia Shoppenhangers Road Maidenhead, Berks UK Email: matthew.bocci@nokia.comXu, et al. Expires April 27, 2020 [Page 9]Datatracker
draft-ietf-ospf-mpls-elc-12
This is an older version of an Internet-Draft that was ultimately published asRFC 9089.
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| Authors | Xiaohu Xu,Sriganesh Kini,Peter Psenak,Clarence Filsfils,Stephane Litkowski,Matthew Bocci | ||
| Replaces | draft-xu-ospf-mpls-elc draft-ietf-idr-bgp-ls-segment-routing-rld | ||
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| Additional resources | Mailing list discussion |