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Versions: 00 01                                                         
BESS Working Group                                               H. Wang
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                             D. Eastlake
Expires: January 13, 2022                         Futurewei Technologies
                                                                  T. Zhu
                                                     Huawei Technologies
                                                           July 12, 2021


                    EVPN ELAN FRR Loop Prevent label
                   draft-wang-bess-evpn-frr-label-01

Abstract

   This document describes how to use Fast Re-Route (FRR) labels avoid
   traffic loop in CE failures when deploying FRR protection in EVPN
   scenarios.

Requirements Language

   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 RFC 2119 [RFC2119].

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 January 13, 2022.

Copyright Notice

   Copyright (c) 2021 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



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   (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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  FRR Label Extended Community  . . . . . . . . . . . . . . . .   3
   3.  The Control Plane Process . . . . . . . . . . . . . . . . . .   4
   4.  The Data Plane Process  . . . . . . . . . . . . . . . . . . .   4
   5.  Other considerations  . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   In the EVPN active-active scenario, to solve the failure of a CE
   access channel to one PE, we can deploy Fast Re-Route (FRR)
   protection mode to achieve fast convergence.  All active PEs can be
   deployed with FRR.  When a link failure occurs on the CE connection
   to the PE, traffic can be rapidly FRR to another PE to improve the
   switching performance.  However, if the CE device fails, both the two
   PEs sense that their CE link is faulty at the same time.  They will
   each perform fast switching according to the FRR.  Then the traffic
   will loop between the dual PEs.

   If one PE detects a failure and withdraw the ES-AD route, the other
   PE, after receiving the withdrawal of the ES-AD route, deletes the
   FRR path to the PE, and the loop is eliminated.  The time until the
   loop is eliminated may be short, but during this time, the loop will
   cause traffic congestion between the dual-homing PEs.













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                  +-----+
                  | CE2 |
                  +-----+
                     |
                  +-----+
                  | EVI1|
                  | PE3 |
                  +-----+
                  /      \
                 /        \
                /          \
               /            \
              /              \
         +-----+             +-----+
         | PE1 |             | PE2 |
         | EVI1|-------------| EVI1|
         +-----+             +-----+
               \             /
                \           /
                ESI1      ESI1
                  \ Trunk /
                  +\-----/+
                  | \   / |
                  +---+---+
                      |
                   +-----+
                   | CE1 |
                   +-----+
        Figure 1: Basic networking of the EVPN all-active scenario

2.  FRR Label Extended Community

   The FRR Label Extended Community is a new transitive Extended
   Community having a Type field value of 0x06 and the Sub-Type TBD.  It
   may be advertised along with MAC/IP Advertisement routes and Ethernet
   A-D per EVI routes.

   The FRR Label Extended Community is encoded as an 8-octet value, as
   follows:

        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=TBD  | Flags(1 octet)|  Reserved=0   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Reserved=0   |          FRR Label                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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3.  The Control Plane Process

   If we enable the FRR LABEL function for an instance, then when the PE
   advertises the MAC-IP route or Ethernet A-D per EVI route of the
   instance, it also carries an FRR Label Extended Community attribute.

   When another PE on the dual-homed side receives the MAC-IP route or
   the EVI-AD route, and uses the Label in the FRR Label Extended
   Community attribute as the label for the Edge FRR path.  The single-
   homing-side PE receives the MAC-IP route or Ethernet A-D per EVI
   route advertised by the PE will ignores the FRR Label Extended
   Community attribute.

   Because the FRR Label Extended Community attribute is an optional
   transitve attribute, if there are RR devices or ASBR devices in the
   network, the attributes can be transparently transmitted and
   processed by the final PE device.

   Taking Figure 1 as an example, the EVI1 of PE2 enables the FRR LABEL
   function, and PE2 applies for a new label.  PE2 advertises the MAC-IP
   route and the Ethernet A-D per EVI route carries the label through
   the FRR Label Extended Community attribute.  Because CE1 is dual-
   homed to PE1 and PE2, PE1 learns the MAC address of CE1 from the data
   plane.  Therefore, when PE1 receives the MAC-IP route or Ethernet A-D
   per EVI route from PE2, it can generate the MAC address learned from
   CE1 to form an edge FRR entry and the label filled in the FRR entry
   is the FRR label.

   For PE3, even if CE1 is dual-homed to PE1 and PE2 in single-active
   mode, PE3 form FRR does not use the FRR label.

   The feature is available for EVPN ELAN service , EVPN VPWS and EVPN
   L3VPN service.

4.  The Data Plane Process

   The PE receives the traffic from the network side and finds the
   corresponding bridge-domain according to the Label.  If the Label is
   a normal EVI label, the MAC address is normally queried.  If the
   local outbound interface of the MAC fails, the FRR of the MAC is
   further protected.  If the Label is an FRR label, the MAC address
   continues to be queried normally.  If the local outbound interface of
   the MAC fails, the FRR of the MAC is no longer protected.

   Taking Figure 1 as an example.  CE2 send traffic to CE1, traffic
   arrived PE3 will encapsulate PE2 's EVI label and send to PE1.
   Traffic arrived at PE1 and use the EVI label to lookup MAC table, but
   find the out-interface is failed.  PE1 will do MAC FRR for that and



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   encapsulate the FRR label, which is advertised by PE2.  Traffic
   arrived at PE2 and use the FRR label to lookup MAC table.  The
   traffic will send to CE1 according to the MAC infomation.  When the
   MAC's out-interface is failed, the traffic will dropped to avoid
   traffic loop.

5.  Other considerations

   The solution of this document is not only applicable to the EVPN
   scenario.  The traditional L3VPN can also use this solution to
   achieve rapid loop breaking.

6.  IANA Considerations

   IANA is requested to assign a new type of FRR label extended
   community with value TBD.

7.  Security Considerations

   TBD

8.  Acknowledgements

9.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

Authors' Addresses

   Haibo Wang
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road
   Beijing  100095
   China

   Email: rainsword.wang@huawei.com












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   Donald E. Eastlake
   Futurewei Technologies
   2386 Panoramic Circle
   Apopka  FL 32703
   USA

   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com


   Tong Zhu
   Huawei Technologies
   101 software Avenue, Yuhua District
   Nanjing  210012
   China

   Email: zhu.tong@huawei.com


































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