PBB-EVPN ISID-based CMAC-Flush
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|Authors||Jorge Rabadan , Senthil Sathappan , Kiran Nagaraj , Masahiro Miyake , Taku Matsuda|
|RFC stream||Internet Engineering Task Force (IETF)|
RTGDIR Early review (of -04) Has Nits
|Additional resources||Mailing list discussion|
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|IESG||IESG state||I-D Exists|
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BESS Workgroup J. Rabadan, Ed. Internet-Draft S. Sathappan Intended status: Standards Track K. Nagaraj Expires: May 3, 2021 Nokia M. Miyake T. Matsuda Softbank October 30, 2020 PBB-EVPN ISID-based CMAC-Flush draft-ietf-bess-pbb-evpn-isid-cmacflush-01 Abstract Provider Backbone Bridging (PBB) can be combined with Ethernet VPN (EVPN) to deploy Ethernet Local Area Network (ELAN) services in large Multi-Protocol Label Switching (MPLS) networks (PBB-EVPN). Single- Active Multi-homing and per-ISID Load-Balancing can be provided to access devices and aggregation networks. In order to speed up the network convergence in case of failures on Single-Active Multi-Homed Ethernet Segments, PBB-EVPN defines a flush mechanism for Customer MACs (CMAC-flush) that works for different Ethernet Segment Backbone MAC (BMAC) address allocation models. This document complements those CMAC-flush procedures for cases in which no PBB-EVPN Ethernet Segments are defined (the attachment circuit is associated to a zero Ethernet Segment Identifier) and a Service Instance Identifier based (ISID-based) CMAC-flush granularity is required. 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 3, 2021. Rabadan, et al. Expires May 3, 2021 [Page 1] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 Copyright Notice Copyright (c) 2020 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. Terminology and Conventions . . . . . . . . . . . . . . . 4 2. Solution requirements . . . . . . . . . . . . . . . . . . . . 5 3. EVPN BGP Encoding for ISID-based CMAC-flush . . . . . . . . . 6 4. Solution description . . . . . . . . . . . . . . . . . . . . 7 4.1. ISID-based CMAC-Flush activation procedures . . . . . . . 8 4.2. CMAC-Flush generation . . . . . . . . . . . . . . . . . . 8 4.3. CMAC-flush process upon receiving a CMAC-flush notification . . . . . . . . . . . . . . . . . . . . . . 9 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 10 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 10.1. Normative References . . . . . . . . . . . . . . . . . . 10 10.2. Informative References . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction [RFC7623] defines how Provider Backbone Bridging (PBB) can be combined with Ethernet VPN (EVPN) to deploy ELAN services in very large MPLS networks. [RFC7623] also describes how Single-Active Multi-homing and per-ISID Load-Balancing can be provided to access devices and aggregation networks. When Access Ethernet/MPLS Networks exists, [I-D.ietf-bess-evpn-virtual-eth-segment] describes how virtual Ethernet Segments can be associated to a group of Ethernet Virtual Circuits (EVCs) or even Pseudowires (PWs). In order to speed up the network convergence in case of failures on Single-Active Multi-Homed Ethernet Segments, [RFC7623] defines a CMAC-flush Rabadan, et al. Expires May 3, 2021 [Page 2] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 mechanism that works for different Ethernet Segment BMAC address allocation models. In some cases, the administrative entities that manage the access devices or aggregation networks don't demand Multi-Homing Ethernet Segments (ES) from the PBB-EVPN provider, but simply multiple single- homed ES. If that is the case, the PBB-EVPN network is no longer aware of the redundancy offered by the access administrative entity. Figure 1 shows an example where the PBB-EVPN network provides four different Attachment Circuits (ACs) for ISID1, with those ACs not being part of any ES or vES (therefore they are referred to as null vES). <--PBB-EVPN Network---> ISID1 vES +-----+ +-----+ +----+ null| PE1 +---------+ PE3 |vES null |CE1 +--------+ BM1 | | BM3 | +---------+ +-+--+ act| | | |===== | | G.8032 +-+---+ +---+-+ | \act | ISID1 | Access | | | \ +-+--+ | Ring | IP/MPLS | | ==|CE3 | | | | | / +-+--+ |stb vES +-+---+ +---+-+ | /stb | +-+--+ null| PE2 | | PE4 +----- | |CE2 +--------+ BM2 | | BM4 | +---------+ +----+ act| +---------+ |vES null ISID1 +-----+ +-----+ <-MPLS Ag-> Network Figure 1: PBB-EVPN and non-ES based redundancy In the example in Figure 1, CE1 and CE2 provide redundant connectivity for ISID1 through the use of G.8032 Ethernet Ring Protection Switching. CE3 provides redundant active-standby PW connectivity for ISID1. In the two cases the ACs are connected to null ES, hence the PEs will keep their ACs active and the CEs will be responsible for the per-ISID load balancing while avoiding loops. For instance, CE2 will block its link to CE1 and CE3 will block its forwarding path to PE4. In this situation, a failure in one of the redundant ACs will make the CEs to start using their redundant paths, however those failures will not trigger any CMAC-flush procedures in the PEs that implement [RFC7623]. For example, if the active PW from CE3 fails, PE3 will not issue any CMAC-flush message and therefore the remote PEs will continue pointing at PE3's BMAC to reach CE3's CMACs, until the CMACs age out in the ISID1 forwarding tables. Rabadan, et al. Expires May 3, 2021 [Page 3] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 [RFC7623] provides a CMAC-flush solution based on a shared BMAC update along with the MAC Mobility extended community where the sequence number is incremented. However, the procedure is only used along with Ethernet Segments. Even if that procedure could be used for null Ethernet Segments, as in the example of Figure 1, the [RFC7623] CMAC-flush procedure would result in unnecessary flushing of unaffected ISIDs on the remote PEs, and subsequent flooding of unknown unicast traffic in the network. This document describes an extension of the [RFC7623] CMAC-flush procedures, so that in the above failure example, PE3 can trigger a CMAC-flush notification that makes PE1, PE2 and PE4 flush all the CMACs associated to PE3's BMAC and (only) ISID1. This new CMAC-flush procedure explained in this document will be referred to as "PBB-EVPN ISID-based CMAC-flush" and can be used in PBB-EVPN networks with null or non-null (virtual) Ethernet Segments. 1.1. Terminology and Conventions 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 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. EVPN: Ethernet Virtual Private Networks, as in [RFC7432]. EVI: EVPN Instance. MAC-VRF: A Virtual Routing and Forwarding table for MAC addresses. PBB-EVPN: Provider-Backbone-Bridging and EVPN, as in [RFC7623]. PE: Provider Edge router. CE: Customer Edge router. CMAC: Customer MAC address. BMAC or BM: Backbone MAC address. ISID: Service Instance Identifier. B-Component: Backbone Component, as in [RFC7623]. I-Component: Service Instance Component, as in [RFC7623]. PW: Pseudowire. Rabadan, et al. Expires May 3, 2021 [Page 4] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 AC: Attachment Circuit. ES and ESI: Ethernet Segment and Ethernet Segment Identifier. Act: Active state, used with ACs or PWs that are operationally active. Stb: Standby state, used with ACs or PWs that are in a state where they cannot transmit traffic. G.8032: Ethernet Ring Protection. RD: Route Distinguisher. RT: Route Target. BMAC/ISID route: an EVPN MAC/IP Advertisement route that uses a BMAC in the MAC address field and an ISID in the Ethernet Tag field, and it is used to notify remote PEs about the required CMAC-flush procedure for the CMACs associated with the advertised BMAC and ISID. BMAC/0 route: an EVPN MAC/IP Advertisement route that uses a BMAC in the MAC address field and a zero Ethernet Tag ID. Familiarity with the terminology in [RFC7623] is expected. 2. Solution requirements The following requirements are followed by the CMAC-flush solution described in this document: a. The solution solves black-hole scenarios in case of failures on null ES ACs (Attachment Circuits not associated to ES, that is, ESI=0) when the access device/network is responsible for the redundancy. b. This extension works with Single-Active non-null ES and virtual ES, irrespective of the PE BMAC address assignment (dedicated per-ES BMAC or shared BMAC, as in [RFC7623]). c. In case of failure on the egress PE, the solution provides a CMAC-flush notification at BMAC and ISID granularity level. d. The solution provides a reliable CMAC-flush notification in PBB- EVPN networks that use Route-Reflectors (RRs), without causing "double flushing" or no flushing for certain ISIDs due to the notification messages being aggregated at the RR. Rabadan, et al. Expires May 3, 2021 [Page 5] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 e. The solution coexists in [RFC7623] networks where there are PEs that do not support this specification. f. The solution SHOULD be enabled/disabled by an administrative option on a per-PE and per-ISID basis. 3. EVPN BGP Encoding for ISID-based CMAC-flush The solution does not use any new BGP attributes but reuses the MAC Mobility extended community as an indication of CMAC-flush (as in [RFC7623]) and encodes the ISID in the Ethernet Tag field of the EVPN MAC/IP advertisement route. As a reference, Figure 2 shows the MAC Mobility extended community and the EVPN MAC/IP advertisement route that are used specified in [RFC7432] and used in this document as a CMAC-flush notification message. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=0x06 | Sub-Type=0x03 | Flags | Reserved=0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---------------------------------------+ | RD | +---------------------------------------+ | ESI = 0 | +---------------------------------------+ | Ethernet Tag ID = ISID | +---------------------------------------+ | MAC Address Length = 48 | +---------------------------------------+ | BMAC Address | +---------------------------------------+ | IP Address Length = 0 | +---------------------------------------+ | MPLS Label1 | +---------------------------------------+ Figure 2: CMAC-Flush notification encoding: BMAC/ISID route Where: o The route's RD and RT are the ones corresponding to its EVI. Alternatively to the EVI's RT, the route MAY be tagged with an RT auto-derived from the Ethernet Tag (ISID) instead. [RFC7623] describes how the EVPN MAC/IP Advertisement routes can be Rabadan, et al. Expires May 3, 2021 [Page 6] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 advertised along with the EVI RT or an RT that is derived from the ISID. o The Ethernet Tag encodes the ISID for which the PE that receives the route must flush the CMACs upon reception of the route. o The MAC address field encodes the BMAC Address for which the PE that receives the route must flush the CMACs upon reception of the route. o The MAC Mobility extended community is used as in [RFC7623], where a delta in the sequence number between two updates for the same BMAC/ISID will be interpreted as a CMAC-flush notification for the corresponding BMAC and ISID. All the other fields are set and used as defined in [RFC7623]. This document will refer to this route as the BMAC/ISID route, as opposed to the [RFC7623] BMAC/0 route (BMAC route sent with Ethernet Tag ID = 0). Note that this BMAC/ISID route will be accepted and reflected by any [RFC7432] RR, since no new attributes or values are used. A PE receiving the route will process the received BMAC/ISID update only in case of supporting the procedures described in this document. 4. Solution description Figure 1 will be used in the description of the solution. CE1, CE2 and CE3 are connected to ACs associated to ISID1, where no (Multi- Homed) Ethernet Segments have been enabled, and the ACs and PWs are in active or standby state as per Figure 1. Enabling or disabling ISID-based CMAC-flush SHOULD be an administrative choice on the system that MAY be configured per ISID (I-Component). When enabled on a PE: a. The PE will be able to generate BMAC/ISID routes as CMAC-Flush notifications for the remote PEs. b. he PE will be able to process BMAC/ISID routes received from remote PEs. When ISID-based CMAC-flush is disabled, the PE will follow the [RFC7623] procedures for CMAC-flush. This CMAC-flush specification is described in three sets of procedures: Rabadan, et al. Expires May 3, 2021 [Page 7] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 o ISID-based CMAC-flush activation o CMAC-flush notification generation upon AC failures o CMAC-flush process upon receiving a CMAC-flush notification 4.1. ISID-based CMAC-Flush activation procedures The following behavior MUST be followed by the PBB-EVPN PEs following this specification. Figure 1 is used as a reference. o As in [RFC7623], each PE advertises a shared BMAC in a BMAC/0 route (with BM1, BM2, BM3 and BM4 in the MAC address field, respectively). This is the BMAC that each PE will use as BMAC SA (Source Address) when encapsulating the frames received on any local single-homed AC. Each PE will import the received BMAC/0 routes from the remote PEs and will install the BMACs in its B-component MAC-VRF. For instance, PE1 will advertise BM1/0 and will install BM2, BM3 and BM4 in its MAC-VRF. o Assuming ISID-based CMAC-flush is activated for ISID 1, the PEs will advertise the shared BMAC with ISID 1 encoded in the Ethernet Tag. That is, PE1 will advertise BM1/1 and will receive BM2/1, BM3/1 and BM4/1. The receiving PEs MUST use these BMAC/ISID routes only for CMAC-flush procedures and they MUST NOT be used them to add/withdraw any BMAC entry in the MAC-VRFs. As per [RFC7623], only BMAC/0 routes can be used to add/withdraw BMACs in the MAC-VRFs. o The above procedure MAY also be used for dedicated BMACs (BMACs allocated per Ethernet Segment). 4.2. CMAC-Flush generation If, for instance, there is a failure on PE1's AC, PE1 will generate an update including BM1/1 along with the MAC Mobility extended community where the Sequence Number has been incremented. The reception of the BM1/1 with a delta in the sequence number will trigger the CMAC-flush procedures on the receiving PEs. o An AC going operationally down MUST generate a BMAC/ISID with a higher Sequence Number. If the AC going down makes the entire local ISID go operationally down, the PE will withdraw the BMAC/ ISID route for the ISID. o An AC going operationally up SHOULD NOT generate any BMAC/ISID update, unless it activates its corresponding ISID, in which case the PE will advertise the BMAC/ISID route. Rabadan, et al. Expires May 3, 2021 [Page 8] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 o An AC receiving a G.8032 flush notification or a flush message in any other protocol from the access network MAY propagate it to the remote PEs by generating a BMAC/ISID route update with higher Sequence Number. 4.3. CMAC-flush process upon receiving a CMAC-flush notification A PE receiving a CMAC-flush notification will follow these procedures: o A received BMAC/ISID route (with non-zero ISID) MUST NOT add/ remove any BMAC to/from the MAC-VRF. o An update of a previously received BMAC/ISID route with a delta Sequence Number, MUST flush all the CMACs associated to that ISID and BMAC. CMACs associated to the same ISID but different BMAC MUST NOT be flushed. o A received BMAC/ISID withdraw (with non-zero ISID) MUST flush all the CMACs associated to that BMAC and ISID. Note that the CMAC-flush procedures described in [RFC7623] for BMAC/0 routes are still valid and a PE receiving [RFC7623] CMAC-flush notification messages MUST observe the behavior specified in [RFC7623]. 5. Conclusions The ISID-based CMAC-flush solution described in this document has the following benefits: a. The solution solves black-hole scenarios in case of failures on null ES ACs, since the CMAC-flush procedures are independent of the Ethernet Segment definition. b. This extension can also be used with Single-Active non-null ES and virtual ES, irrespective of the PE BMAC address assignment (dedicated per-ES BMAC or shared BMAC). c. It provides a CMAC-flush notification at BMAC and ISID granularity level, therefore flushing a minimum number of CMACs and reducing the amount of unknown unicast flooding in the network. d. It provides a reliable CMAC-flush notification in PBB-EVPN networks that use RRs. RRs will propagate the CMAC-flush notifications for all the affected ISIDs and irrespective of the order in which the notifications make it to the RR. Rabadan, et al. Expires May 3, 2021 [Page 9] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 e. The solution can coexist in a network with systems supporting or not supporting this specification. 6. Security Considerations Security considerations described in [RFC7623] apply to this document. In addition, this document suggests additional procedures, that can be activated on a per ISID basis, and generate additional EVPN MAC/IP Advertisement routes in the network. The format of these additional EVPN MAC/IP Advertisement routes is backwards compatible with [RFC7623] procedures and should not create any issues on receiving PEs not following this specification, however, the additional routes may consume extra memory and processing resources on the receiving PEs. Because of that, it is RECOMMENDED to activate this feature only when necessary (when multi-homed networks or devices are attached to the PBB-EVPN PEs), and not by default in any PBB-EVPN PE. 7. IANA Considerations 8. Acknowledgments The authors want to thank Vinod Prabhu, Sriram Venkateswaran, Laxmi Padakanti, Ranganathan Boovaraghavan for their review and contributions. 9. Contributors 10. References 10.1. Normative References [RFC7623] Sajassi, A., Ed., Salam, S., Bitar, N., Isaac, A., and W. Henderickx, "Provider Backbone Bridging Combined with Ethernet VPN (PBB-EVPN)", RFC 7623, DOI 10.17487/RFC7623, September 2015, <https://www.rfc-editor.org/info/rfc7623>. [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, <https://www.rfc-editor.org/info/rfc7432>. [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>. Rabadan, et al. Expires May 3, 2021 [Page 10] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. 10.2. Informative References [I-D.ietf-bess-evpn-virtual-eth-segment] Sajassi, A., Brissette, P., Schell, R., Drake, J., and J. Rabadan, "EVPN Virtual Ethernet Segment", draft-ietf-bess- evpn-virtual-eth-segment-06 (work in progress), March 2020. Authors' Addresses Jorge Rabadan (editor) Nokia 777 Middlefield Road Mountain View, CA 94043 USA Email: firstname.lastname@example.org Senthil Sathappan Nokia 701 E. Middlefield Road Mountain View, CA 94043 USA Email: email@example.com Kiran Nagaraj Nokia 701 E. Middlefield Road Mountain View, CA 94043 USA Email: firstname.lastname@example.org M. Miyake Softbank Email: email@example.com Rabadan, et al. Expires May 3, 2021 [Page 11] Internet-Draft PBB-EVPN ISID-based CMAC-flush October 2020 T. Matsuda Softbank Email: firstname.lastname@example.org Rabadan, et al. Expires May 3, 2021 [Page 12]