BESS WorkGroup Ali. Sajassi Internet-Draft Mankamana. Mishra Intended status: Standards Track Samir. Thoria Expires: 11 January 2024 Cisco Systems Jorge. Rabadan Nokia John. Drake Juniper Networks 10 July 2023 Per multicast flow Designated Forwarder Election for EVPN draft-ietf-bess-evpn-per-mcast-flow-df-election-09 Abstract [RFC7432] describes mechanism to elect designated forwarder (DF) at the granularity of (ESI, EVI) which is per VLAN (or per group of VLANs in case of VLAN bundle or VLAN-aware bundle service). However, the current level of granularity of per-VLAN is not adequate for some applications.[RFC8584] improves base line DF election by introducing HRW DF election. [RFC9251] introduces applicability of EVPN to Multicast flows, routes to sync them and a default DF election. This document is an extension to HRW base draft [RFC8584] and further enhances HRW algorithm for the Multicast flows to do DF election at the granularity of (ESI, VLAN, Mcast flow). 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 11 January 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. Sajassi, et al. Expires 11 January 2024 [Page 1] Internet-Draft Per multicast flow Designated Forwarder July 2023 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. The DF Election Extended Community . . . . . . . . . . . . . 4 4. HRW base per multicast flow EVPN DF election . . . . . . . . 5 4.1. DF election for IGMP (S,G) membership request . . . . . . 6 4.2. DF election for IGMP (*,G) membership request . . . . . . 6 4.3. Default DF election procedure . . . . . . . . . . . . . . 7 5. Procedure to use per multicast flow DF election algorithm . . 7 6. Triggers for DF re-election . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10 10. Normative References . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction EVPN based All-Active multi-homing is becoming the basic building block for providing redundancy in next generation data center deployments as well as service provider access/aggregation networks. [RFC7432] defines the role of a designated forwarder as the node in the redundancy group that is responsible to forward Broadcast, Unknown unicast, Multicast (BUM) traffic on that Ethernet Segment (CE device or network) in All-Active multi-homing. The default DF election mechanism allows selecting a DF at the granularity of (ES, VLAN) or (ES, VLAN bundle) for BUM traffic. While [RFC8584] improve on the default DF election procedure, some service provider residential applications require a finer granularity, where whole multicast flows are delivered on a single VLAN. Sajassi, et al. Expires 11 January 2024 [Page 2] Internet-Draft Per multicast flow Designated Forwarder July 2023 (Multicast sources) | | +---+ |CE4| +---+ | | +-----+-----+ +------------| PE-1 |------------+ | | | | | +-----------+ | | | | EVPN | | | | | | (DF) (NDF)| +-----------+ +-----------+ | |EVI-1| | | |EVI-1| | | PE-2 |------------------------| PE-3 | +-----------+ +-----------+ AC1 \ / AC2 \ / \ ESI-1 / \ / \ / +---------------+ | CE2 | +---------------+ | | (Multiple receivers) Figure 1: Multi-homing Network of EVPN for IPTV deployments Consider the above topology, which shows a typical residential deployment scenario, where multiple receivers are behind an all- active multihoming segments. All of the multicast traffic is provisioned on EVI-1. Assume PE-2 get elected as DF. According to [RFC7432], PE-2 will be responsible for forwarding multicast traffic to that Ethernet segment. Sajassi, et al. Expires 11 January 2024 [Page 3] Internet-Draft Per multicast flow Designated Forwarder July 2023 * Forcing sole data plane forwarding responsibility on PE-2 is a limitation in the current DF election mechanism. The topology at Figure 1 would always have only one of the PE to be elected as DF irrespective of which current DF election mechanism is in use defined in [RFC7432] or [RFC8584]. * The problem may also manifest itself in a different way. For example, AC1 happens to use 80% of its available bandwidth to forward unicast data. And now there is need to serve multicast receivers where it would require more than 20% of AC1 bandwidth. In this case, AC1 becomes oversubscribed and multicast traffic drop would be observed even though there is already another link (AC2) present in network which can be used more efficiently load balance the multicast traffic. In this document, we propose an extension to the HRW base draft to allow DF election at the granularity of (ESI, VLAN, Mcast flow) which would allow multicast flows to be better distributed among redundancy group PEs to share the load. 2. Terminology 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] . With respect to EVPN, this document follows the terminology that has been defined in [RFC7432] and [RFC4601] for multicast terminology. 3. The DF Election Extended Community [RFC8584] defines an extended community, which would be used for PEs in redundancy group to reach a consensus as to which DF election procedure is desired. A PE can notify other participating PEs in redundancy group about its willingness to support Per multicast flow base DF election capability by signaling a DF election extended community along with Ethernet-Segment Route (Type-4). The current proposal extends the existing extended community defined in [RFC8584]. This draft defines new a DF type. * DF type (1 octet) - Encodes the DF Election algorithm values (between 0 and 255) that the advertising PE desires to use for the ES. This document requests two new types in the DF type field: - Type 4: HRW base per (S,G) multicast flow DF election (explained in this document) Sajassi, et al. Expires 11 January 2024 [Page 4] Internet-Draft Per multicast flow Designated Forwarder July 2023 - Type 5: HRW base per (*,G) multicast flow DF election (explained in this document) * The [RFC8584] describes encoding of capabilities associated to the DF election algorithm using Bitmap field. When these capabilities bits are set along with the DF type-4 and type-5, they need to be interpreted in context of this new DF type-4 and type-5. For example, consider a scenario where all PEs in the same redundancy group (same ES) can support both AC-DF, DF type-4 and DF type-5 and receive such indications from the other PEs in the ES. In this scenario, if a VLAN is not active in a PE, then the DF election procedure on all PEs in the ES should factor that in and exclude that PE in the DF election per multicast flow. * A PE SHOULD attach the DF election Extended Community to ES route and Extended Community MUST be sent if the ES is locally configured for DF type Per Multicast flow DF election. Only one DF Election Extended community can be sent along with an ES route. * When a PE receives the ES Routes from all the other PEs for the ES, it checks if all of other PEs have advertised their desire to proceed by Per multicast flow DF election. If all peering PEs have done so, it performs DF election based on Per multicast flow procedure. But if: - There is at least one PE which advertised route-4 ( AD per ES Route) which does not indicate its capability to perform Per multicast flow DF election. OR - There is at least one PE signaling single active in the AD per ES route it MUST be considered as an indication to support of only Default DF election [RFC7432] and DF election procedure in [RFC7432] MUST be used. 4. HRW base per multicast flow EVPN DF election This document is an extension of [RFC8584], so this draft does not repeat the description of HRW algorithm itself. EVPN PE does the discovery of redundancy groups based on [RFC7432]. If redundancy group consists of N peering EVPN PE nodes, after the discovery all PEs build an unordered list of IP address of all the nodes in the redundancy group. The procedure defined in this draft does not require the list of PEs to be ordered. Address [i] denotes the IP address of the [i]th EVPN PE in redundancy group where (0 < i <= N ). Sajassi, et al. Expires 11 January 2024 [Page 5] Internet-Draft Per multicast flow Designated Forwarder July 2023 4.1. DF election for IGMP (S,G) membership request The DF is the PE who has maximum weight for (S, G, V, Es) where * S - Multicast Source * G - Multicast Group * V - VLAN ID. * Es - Ethernet Segment Identifier Address[i] is address of the ith PE. The PEs IP address length does not matter as only the lower-order 31 bits are modulo significant. 1. Weight * The weight of PE(i) to (S,G,VLAN ID, Es) is calculated by function, weight (S,G,V, Es, Address(i)), where (0 < i <= N), PE(i) is the PE at ordinal i. * Weight (S,G,V, Es, Address(i)) = (1103515245. ((1103515245.Address(i) + 12345) XOR D(S,G,V,ESI))+12345) (mod 2^31) * In case of tie, the PE whose IP address is numerically least is chosen. 2. Digest * D(S,G,V, Es) = CRC_32(S,G,V, Es) * Here D(S,G,V,Es) is the 31-bit digest (CRC_32 and discarding the MSB) of the Source IP, Group IP, Vlan ID and Es. The CRC MUST proceed as if the architecture is in network byte order (big-endian). 4.2. DF election for IGMP (*,G) membership request The DF is the PE who has maximum weight for (G, V, Es) where * G - Multicast Group * V - VLAN ID. * Es - Ethernet Segment Identifier Sajassi, et al. Expires 11 January 2024 [Page 6] Internet-Draft Per multicast flow Designated Forwarder July 2023 Address[i] is address of the ith PE. The PEs IP address length does not matter as only the lower-order 31 bits are modulo significant. 1. Weight * The weight of PE(i) to (G,VLAN ID, Es) is calculated by function, weight (G,V, Es, Address(i)), where (0 < i <= N), PE(i) is the PE at ordinal i. * Weight (G,V, Es, Address(i)) = (1103515245. ((1103515245.Address(i) + 12345) XOR D(G,V,ESI))+12345) (mod 2^31) * In case of tie, the PE whose IP address is numerically least is chosen. 2. Digest * D(G,V, Es) = CRC_32(G,V, Es) * Here D(G,V,Es) is the 31-bit digest (CRC_32 and discarding the MSB) of the Group IP, Vlan ID and Es. The CRC MUST proceed as if the architecture is in network byte order (big-endian). 4.3. Default DF election procedure Per multicast DF election procedure would be applicable only when host behind Attachment Circuit (of the Es) start sending IGMP membership requests. Membership requests are synced using procedure defined in [RFC9251], and each of the PE in redundancy group can use per flow DF election and create DF state per multicast flow. The HRW DF election "Type 1" procedure defined in [RFC8584] MUST be used for the Es DF election and SHOULD be performed on Es even before learning multicast membership request state. This default election procedure MUST be used at port level but will be overwritten by Per flow DF election as and when new membership request state are learnt. 5. Procedure to use per multicast flow DF election algorithm Sajassi, et al. Expires 11 January 2024 [Page 7] Internet-Draft Per multicast flow Designated Forwarder July 2023 Multicast Source | | | | +---------+ +--------------+ PE-4 +--------------+ | | | | | +---------+ | | | | EVPN CORE | | | | | | | +---------+ +---------+ +---------+ | PE-1 +--------+ PE-2 +---------+ PE-3 | | EVI-1 | | EVI-1 | | EVI-1 | +---------+ +---------+ +---------+ |__________________|___________________| AC-1 ESI-1 | AC-2 AC-3 +---------+ | CE-1 | | | +---------+ | | | | Multicast Receivers Figure-2 : Multihomed network Figure-2 shows multihomed network. Where EVPN PE-1, PE-2, PE-3 are multihomed to CE-1. Multiple multicast receivers are behind all active multihoming segment. 1. PEs connected to the same Ethernet segment can automatically discover each other through exchange of the Ethernet Segment Route. This draft does not change any of this procedure, it still uses the procedure defined in [RFC7432]. 2. Each of the PEs in redundancy group advertise Ethernet segment route with extended community indicating their ability to participate in per multicast flow DF election procedure. Since Per multicast flow would not be applicable unless PE learns about membership request from receiver, there is a need to have the default DF election among PEs in redundancy group for BUM Sajassi, et al. Expires 11 January 2024 [Page 8] Internet-Draft Per multicast flow Designated Forwarder July 2023 traffic. Until multicast membership state are learnt, we use the the DF election procedure in Section 4.3, namely HRW per (v,Es) as defined in [RFC8584] . 3. When a receiver starts sending membership requests for (s1,g1), where s1 is multicast source address and g1 is multicast group address, CE-1 could hash membership request (IGMP join) to any of the PEs in redundancy group. Let's consider it is hashed to PE- 2. [RFC9251] defines a procedure to sync IGMP join state among redundancy group of PEs. Now each of the PE would have information about membership request (s1,g1) and each of them run DF election procedure Section 4.1 to elect DF among participating PEs in redundancy group. Consider PE-2 gets elected as DF for multicast flow (s1,g1). 1. PE-1 forwarding state would be nDF for flow (s1,g1) and DF for rest other BUM traffic. 2. PE-2 forwarding state would be DF for flow (s1,g1) and nDF for rest other BUM traffic. 3. PE-3 forwarding state would be nDF for flow (s1,g1) and rest other BUM traffic. 4. As and when new multicast membership request comes, same procedure as above would continue. 5. If Section 3 has DF type 4, For membership request (S,G) it MUST use Section 4.1 to elect DF among participating PEs. And membership request (*,G) MUST use Section 4.2 to elect DF among participating PEs. 6. Triggers for DF re-election There are multiple triggers which can cause DF re-election. Some of the triggers could be 1. Local ES going down due to physical failure or configuration change triggers DF re-election at peering PE. 2. Detection of new PE through ES route. 3. AC going up / down 4. ESI change 5. Remote PE removed / Down Sajassi, et al. Expires 11 January 2024 [Page 9] Internet-Draft Per multicast flow Designated Forwarder July 2023 6. Local configuration change of DF election Type and peering PE consensus on new DF Type This document does not provide any new mechanism to handle DF re- election procedure. It uses the existing mechanism defined in [RFC7432]. Whenever either of the triggers occur, a DF re-election would be done. and all of the flows would be redistributed among existing PEs in redundancy group for ES. 7. Security Considerations The same Security Considerations described in [RFC7432] are valid for this document. 8. IANA Considerations Allocation of DF type in DF extended community for EVPN. 9. Acknowledgement Authors would like to acknowledge helpful comments and contributions of Luc Andre Burdet. 10. 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, . [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, DOI 10.17487/RFC4601, August 2006, . [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, . [RFC8584] Rabadan, J., Ed., Mohanty, S., Ed., Sajassi, A., Drake, J., Nagaraj, K., and S. Sathappan, "Framework for Ethernet VPN Designated Forwarder Election Extensibility", RFC 8584, DOI 10.17487/RFC8584, April 2019, . Sajassi, et al. Expires 11 January 2024 [Page 10] Internet-Draft Per multicast flow Designated Forwarder July 2023 [RFC9251] Sajassi, A., Thoria, S., Mishra, M., Patel, K., Drake, J., and W. Lin, "Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Proxies for Ethernet VPN (EVPN)", RFC 9251, DOI 10.17487/RFC9251, June 2022, . Authors' Addresses Ali Sajassi Cisco Systems 821 Alder Drive, MILPITAS, CALIFORNIA 95035 United States Email: sajassi@cisco.com Mankamana Mishra Cisco Systems 821 Alder Drive, MILPITAS, CALIFORNIA 95035 United States Email: mankamis@cisco.com Samir Thoria Cisco Systems 821 Alder Drive, MILPITAS, CALIFORNIA 95035 United States Email: sthoria@cisco.com Jorge Rabadan Nokia 777 E. Middlefield Road Mountain View, CA 94043 United States Email: jorge.rabadan@nokia.com John Drake Juniper Networks Email: jdrake@juniper.net Sajassi, et al. Expires 11 January 2024 [Page 11]