Internet Engineering Task Force N. Kumar Internet-Draft IJ. Wijnands Intended status: Informational M. Mishra Expires: May 7, 2020 Cisco November 4, 2019 Flex Algorithm for BIER draft-nainar-bier-flex-algo-00 Abstract Bit Index Explicit Replication (BIER) is an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to run explicit tree-building protocol or to maintain multicast-related, per-flow state. IGP protocols are extended to carry BFR-Id and other encapsulation informations that are used by traditional path computing algorithm using link metric for a loop-free best path selection. This document defines a constrained based path selection using IGP flexible Algorithm for BIER. 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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when and only when, they appear in all capitals, as shown here. 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 https://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." This Internet-Draft will expire on May 7, 2020. Kumar, et al. Expires May 7, 2020 [Page 1] Internet-Draft BIER Flex Algorithm November 2019 Copyright Notice Copyright (c) 2019 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 1.1. Acronyms and Terminology . . . . . . . . . . . . . . . . 3 1.1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . 3 1.1.2. Terminology . . . . . . . . . . . . . . . . . . . . . 3 2. Flexible Algorithm . . . . . . . . . . . . . . . . . . . . . 3 3. Constraint Forwarding Identifier . . . . . . . . . . . . . . 4 3.1. BFR ID Mapping for Flexible Algorithm . . . . . . . . . . 4 3.2. BIER-MPLS Label Mapping for Flexiblem Algorithm . . . . . 5 4. IGP Extensions Flexible Algorithm . . . . . . . . . . . . . . 6 4.1. ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction [RFC8279] defines Bit Index Explicit Replication (BIER), an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to run explicit tree-building protocol or to maintain multicast-related, per-flow state. [RFC8401] and [RFC8444] defines the IGP protocols extensions to carry BFR-Id and other encapsulation informations that are used by traditional path computing algorithm using link metric for a loop- free best path selection. Kumar, et al. Expires May 7, 2020 [Page 2] Internet-Draft BIER Flex Algorithm November 2019 The ability to compute constrained path using attributes beyond the basic link metric and steering the multicast traffic over such constrained path brings a lot of benefits such as efficient load distribution, path dis-jointness and resiliency. Bandwidth-aware, delay-sensitive or multi-planar are some of the examples for such constrained path selection. The path computation and traffic steering over flexible algorithm based constrained path requires advertising a set of Path constraints associated to each link and a unique dataplane based identifier to differentiate the data packets that needs to be steered over such computed constrained paths. This document specifies the IGP protocol extensions and the mechanism to implement IGP Flexible Algorithm for BIER network. 1.1. Acronyms and Terminology 1.1.1. Acronyms TBD 1.1.2. Terminology This document uses the terminologies defined in [RFC8279], [RFC8296], and so the readers are expected to be familiar with the same. 2. Flexible Algorithm Different types of contraints may be used to compute a path over the BIER network. Link performance and multi-plane are some of the common examples for such constraints. An example multiplane BIER network is shown in below figure 1. Kumar, et al. Expires May 7, 2020 [Page 3] Internet-Draft BIER Flex Algorithm November 2019 +---(gBFR1)--------------(gBFR2) / + + / | \ | \ / | \ | \ (BFIR) | (gBFR3)------------~(gBFR4)------+ \ | + | + \ \ | | | | \ \ + | | | \ +----(rBFR1)--------------(rBFR2) | (BFER) + | + | / \ | \ | / \ | \ | / + + / (rBFR3)---------------(rBFR4)---+ Figure 1. MultiPlane BIER Network The above BIER network is enabled with "green" and "red" planes by assigning a contiguous set of BFRs to each plane. For example, gBFR1, gBFR2, gBFR3 and gBFR4 belongs to "green" plane while rBFR1, rBFR2, rBFR3 and rBFR$ belong sto "red" plane. BFIR and BFER are enabled with both the planes. Any BFR must have a mechanism to identify the set of constraints associated to each algorithm so that a loop free path can be computed. Any BFR must have a mechanism to map the data packet to the associated constrained path for loop free constrained forwarding. 3. Constraint Forwarding Identifier This section explains different mechanism for identifying the constraints forwarding in the BIER encapsulated data packet. 3.1. BFR ID Mapping for Flexible Algorithm For each Flexible Algorithm, a domain wide unique BFR-ID will be assigned with BFR-Prefix for each participating BFER within the BIER domain. Kumar, et al. Expires May 7, 2020 [Page 4] Internet-Draft BIER Flex Algorithm November 2019 +---(gBFR1)--------------(gBFR2) / + + / | \ | \ / | \ | \ (BFIR) | (gBFR3)------------~(gBFR4)------+ \ | + | + \ \ | | | | \ \ + | | | \ +----(rBFR1)--------------(rBFR2) | (BFER) (0001 = red) + | + | / (0010 = green) \ | \ | / \ | \ | / + + / (rBFR3)---------------(rBFR4)---+ Figure 2. BFR-ID Mapping Each BFER is assigned with domain wide unique BFR-ID for each Flexible Algorithm. In Figure 2, BFER assigns 0001 for "red" plane while using 0010 for "green" plane. Any BFR participating in one plane may not have the BFR-ID associated with other planes. BFIR pushes the relevant BFR-ID to enforce the forwarding over any specific contraint path which can be influenced by a local policy. 3.2. BIER-MPLS Label Mapping for Flexiblem Algorithm For each Flexible Algorithm, a locally unique BIER-MPLS label is assigned by each participating BFR within the BIER domain. In this option, each BFER is assigned with just one BFR-ID as mentioned in [RFC8279]. +---(gBFR1)--------------(gBFR2) / + + / | \ | \ / | \ | \ (BFIR) | (gBFR3)------------~(gBFR4)------+ \ | + | + \ \ | | | | \ \ + | | | \ (BFR-ID = 0001) +----(rBFR1)--------------(rBFR2) | (BFER) (L1 = red) + | + | / (L2 = green) \ | \ | / \ | \ | / + + / (rBFR3)---------------(rBFR4)---+ Figure 3. BIER-MPLS Label Mapping Kumar, et al. Expires May 7, 2020 [Page 5] Internet-Draft BIER Flex Algorithm November 2019 Each BFR is assigned with locally unique BIER-MPLS for each Flexible Algorithm. The BIER-MPLS label along with the relevant constraints are advertised to other BFR using extensions defined in section x. In Figure 3, BFER is assigned with BFR-ID of 1 and advertise BIER- MPLS label L1 for "red" plane and L2 for "green" plane. BFIR pushes the relevant BIER-MPLS advertised by the nexthop. Any BFR participating in both the plane will have the forwarding instruction for both the planes populated in different BIFT. The incoming BIER-MPLS label is used to identify the plane and the BIFT to perform the lookup and forwarding. Additional details about non-MPLS BIER encapsulation will be included in later revisions. 4. IGP Extensions Flexible Algorithm This section defines the IGP protocol extensions for BIER Flexible Algorithm. 4.1. ISIS 4.2. OSPF 5. Security Considerations To be Updated. 6. IANA Considerations TBD. 7. Acknowledgements To be Updated. 8. References 8.1. 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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Kumar, et al. Expires May 7, 2020 [Page 6] Internet-Draft BIER Flex Algorithm November 2019 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, November 2017, . [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non- MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 2018, . [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. Zhang, "Bit Index Explicit Replication (BIER) Support via IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, . [RFC8444] Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A., Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 Extensions for Bit Index Explicit Replication (BIER)", RFC 8444, DOI 10.17487/RFC8444, November 2018, . [RFC8459] Dolson, D., Homma, S., Lopez, D., and M. Boucadair, "Hierarchical Service Function Chaining (hSFC)", RFC 8459, DOI 10.17487/RFC8459, September 2018, . 8.2. Informative References [I-D.ietf-lsr-flex-algo] Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- algo-04 (work in progress), September 2019. Authors' Addresses Nagendra Kumar Cisco Systems, Inc. Email: naikumar@cisco.com Ijsbrand Wijnands Cisco Systems, Inc. Email: iwijnand@cisco.com Kumar, et al. Expires May 7, 2020 [Page 7] Internet-Draft BIER Flex Algorithm November 2019 Mankamana Mishra Cisco Systems, Inc. Email: mankamis@cisco.com Kumar, et al. Expires May 7, 2020 [Page 8]