Centralized EVPN DF Election
draft-hao-bess-evpn-centralized-df-03

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INTERNET-DRAFT                                           Donald Eastlake
Intended status: Proposed Standard                            Weiguo Hao
                                                               Lili Wang
                                                               Yizhou Li
                                                          Shunwan Zhuang
                                                                  Huawei
Expires: April 13, 2019                                 October 14, 2018

                      Centralized EVPN DF Election
               draft-hao-bess-evpn-centralized-df-03.txt

Abstract

   This document proposes a centralized DF Designated Forwarder election
   mechanism to be used between an SDN (Software Defined Network)
   controller and each PE (Provider Edge) device in an EVPN network.
   Such a mechanism overcomes some issues with the current standalone DF
   election defined in RFC 7432. A new BGP capability and an additional
   DF Election Result Route Type are specified to support this
   centralized DF election mechanism.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the authors or the BESS working group mailing list: bess@ietf.org.

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D. Eastlake, et al                                              [Page 1]
INTERNET-DRAFT                              Centralized EVPN DF Election

Table of Contents

      1. Introduction............................................3
      2. Conventions used in this document.......................4

      3. Solution Overview.......................................5
      3.1 Centralized DF Election Capability.....................5

      4. DF Election Result Route Type...........................7
      4.1 DF Election Result Route Encoding......................7
      4.2 Centralized DF Election procedures.....................9

      5. Security Considerations................................10
      6. IANA Considerations....................................11

      Normative References......................................12
      Informative References....................................12

      Acknowledgments...........................................13
      Authors' Addresses........................................13

D. Eastlake, et al                                              [Page 2]
INTERNET-DRAFT                              Centralized EVPN DF Election

1. Introduction

   [RFC7432] defines a standardized Designated Forwarder (DF) election
   mechanism in EVPN networks to appoint one Provider Edge (PE) device
   as the DF from a candidate list of PEs for each VLAN (or VLAN bundle)
   connecting to a multi-homed Customer Edge (CE) device or access
   network. The DF PE is responsible for sending broadcast, multicast
   and unknown unicast traffic (BUM) to the multi-homed CE device or
   network and non-DF PEs must drop such traffic. This DF based
   mechanism is used to prevent duplicated packet injection into the
   multi-homed access network via multiple PEs.

   In [RFC7432] the DF is selected according to the VLAN modulus
   "service-carving" algorithm in order to perform load balancing for
   multi-destination traffic destined to a given segment. The algorithm
   can ensure each participating PE independently and unambiguously
   determines which one of the participating PEs is the DF; however, use
   of this algorithm has some drawbacks as follows [EVPN-HRW-DF]:

   1. Uneven load balancing in some VLAN configuration cases when the
      Ethernet tags have a non-uniform distribution, for instance when
      the Ethernet tags in use are all even or all odd.

   2. Unnecessary service disruption when PEs join or leave a redundancy
      group. In Figure 1 below, say v1, v2 and v3 are VLANs configured
      on ES2 with associated Ethernet tags of value 3, 4 and 5
      respectively.  So PE1, PE2 and PE3 are also the DFs for v1, v2 and
      v3 respectively.  Now when PE3 goes down, PE2 will become the DF
      for v1 and v3 while PE1 will become the DF for v2, so needless
      churn of v1 and v2 occurs causing unnecessary service disruption
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