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TRILL Working Group                                      Donald Eastlake
INTERNET-DRAFT                                                Zhenbin Li
                                                          Shunwan Zhuang
                                                              Haibo Wang
                                                                  Huawei
Intended status: Proposed Standard
Expires: September 2, 2018                                 March 3, 2018


                   EVPN All Active Usage Enhancement
          <draft-eastlake-bess-enhance-evpn-all-active-00.txt>


Abstract

   A principal feature of EVPN is the ability to support multihoming
   from a customer equipment (CE) to multiple provider edge equipment
   (PE) active with all-active links. This draft specifies an
   improvement to load balancing such links.



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 BESS working group mailing list <bess@ietf.org>.

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D. Eastlake, et al                                              [Page 1]


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Table of Contents

      1. Introduction............................................3
      1.1 Terminology and Acronyms...............................3

      2. Improved Load Balancing.................................5
      2.1 Problem 1: Traffic Bypassing...........................5
      2.2 Problem 2: VID Encapsulation Confusion.................6

      3. VLAN-Redirect-Extended Community Attribute..............7

      4. Operation...............................................8
      4.1 Establishment..........................................8
      4.2 Handling Link Failure..................................8

      5. IANA Considerations.....................................9
      6. Security Considerations.................................9

      Normative References......................................10
      Informative References....................................10

      Acknowledgements..........................................10
      Authors' Addresses........................................11





























D. Eastlake, et al                                              [Page 2]


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1. Introduction

   A principal feature of EVPN is the ability to support multihoming
   from a customer equipment (CE) to multiple provider edge equipment
   (PE) with links used in an all-active redundancy mode. That mode is
   where a device is multihomed to a group of two or more PEs and where
   all PEs in such redundancy group can forward traffic to/from the
   multihomed device or network for a given VLAN [RFC7209]. This draft
   specifies an improvement in load balancing such PE to CE all-active
   multi-homing links.

   In the case where a CE is multihomed to multiple PE nodes, using a
   Link Aggregation Group (LAG) with All-Active redundancy, it is
   possible that only a single PE learns a set of the MAC addresses
   associated with traffic transmitted by the CE.  This leads to a
   situation where remote PE nodes receive MAC/IP Advertisement routes
   for these addresses from a single PE, even though multiple PEs are
   connected to the multihomed segment.

   To address this issue, EVPN (Ethernet VPN [RFC7432]) introduces the
   concept of "aliasing", which is the ability of a PE to signal that it
   has reachability to an EVPN instance (EVI) on a given Ethernet
   segment (ES) even when it has learned no MAC addresses from that
   EVI/ES.  The Ethernet A-D per EVI route is used for this purpose.  A
   remote PE that receives a MAC/IP Advertisement route with a non-
   reserved ESI SHOULD consider the advertised MAC address to be
   reachable via all PEs that have advertised reachability to that MAC
   address's EVI/ES via the combination of an Ethernet A-D per EVI route
   for that EVI/ES (and Ethernet tag, if applicable) AND Ethernet A-D
   per ES routes for that ES with the "Single-Active" bit in the flags
   of the ESI Label extended community set to 0.



1.1 Terminology and Acronyms

   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.

   This document uses the following acronyms and terms:

   A-D - Auto Discovery.

   All-Active Redundancy Mode - When a device is multihomed to a group
      of two or more PEs and when all PEs in such redundancy group can
      forward traffic to/from the multihomed device or network for a
      given VLAN.


D. Eastlake, et al                                              [Page 3]


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   CE - Customer Edge equipment.

   ES - Ethernet Segment.

   ESI - Ethernet Segment Identifier.

   EVI - EVPN Instance.

   EVPN - Ethernet VPN.

   FRR - Fast ReRoute.

   MAC - Media Access Control.

   PE - Provider Edge equipment.

   Single-Active Redundancy Mode - When a device or a network is
      multihomed to a group of two or more PEs and when only a single PE
      in such a redundancy group can forward traffic to/from the
      multihomed device or network for a given VLAN.

   VPN - Virtual Private Network.






























D. Eastlake, et al                                              [Page 4]


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2. Improved Load Balancing

   Consider the example in Figure 1. CE1 is multihomed to PE1 and PE2.
   CE1 typically uses a hash algorithm to determine whether to send a
   particular traffic to PE1 or to PE2. Thus, if such taffic from CE1 is
   only sent to PE1, then PE1 will learn CE1's MAC address(es) and that
   PE2 will not.

   PE3 and PE4 can do aliasing [RFC7432] because PE1 and PE2 will be
   advertising the same ESI. Thus PE3 and PE4 will expect that a MAC
   address reachable from PE1 will also be reachable from PE2. This
   aliasing will cause PE3 and PE4 to load balance to CE1's MAC(s),
   sending some traffice to PE1 and some to PE2.

                                .........
              +----------+      .       .      +----------+
              | PE1 MAC  +------+       +------+ PE3      |
              | Learning |      .       .      |          |
              +----------+      .       .      +----------+
             /     ^            .       .            |     \
        +---+      |            . EVPN  .            |     +---+
        |CE1|      |            . MPLS  .            |     |CE2|
        +---+      |            .       .            |     +---+
             \     |            .       .            |    /
              +----------+      .       .      +----------+
              | PE2      |      .       .      | PE4      |
              |          +------+       +------+          |
              +----------+      .       .      +----------+
                                .........

                       Figure 1. Current Situtation

   There are two problems associated with this situation.  Section 3
   describes the mechanism to address these problems.



2.1 Problem 1: Traffic Bypassing

   Since PE2 has not learning CE1's MAC(s), the MAC lookup at PE2 will
   find that MAC address associated with PE1. PE2 will then tunnel the
   traffic to PE1.

   As an enchancement that solves this problem, PE1 can send MAC
   address(es) with VLAN and ESI information. PE2 will then receive the
   MAC address(es) and VLAN that PE1 associates with the ESI and can use
   this to update its forwarding tables. (See Figure 2.) As a result,
   when traffic addressed to a CE1 MAC arrives at PE2, it can send it on
   the appropriate local interface and VLAN. This avoids the unncessary
   extra hop through PE1 for such traffic arriving at PE2.


D. Eastlake, et al                                              [Page 5]


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                                .........
              +----------+      .       .      +----------+
              | PE1 MAC  +------+       +------+ PE3      |
              | Learning |      .       .      |          |
              +----------+      .       .      +----------+
             /     ^            .       .            |     \
        +---+      |            . EVPN  .            |     +---+
        |CE1|    Sy|nc          . MPLS  .            |     |CE2|
        +---+      |            .       .            |     +---+
             \     v            .       .            |    /
              +----------+      .       .      +----------+
              | PE2      |      .       .      | PE4      |
              |          +------+       +------+          |
              +----------+      .       .      +----------+
                                .........

                        Figure 2. With Enhancement



2.2 Problem 2: VID Encapsulation Confusion

    If CE1 is connected through a VLAN and has only one VLAN under the
   EVPN instance of PE2, the unicast traffic can be directly sent to the
   appropriate interface and encapsulated with the appropriate VID and
   forwarded to CE1.

   However, there may be multiple ways for CE1 to connect to PE1 and
   PE2, including Ethernet Tag, Ethernet Tag termination, and QinQ.  PE2
   cannot obtain the appropriate VLANs and cannot forward the unicast
   traffic to CE1 directly.





















D. Eastlake, et al                                              [Page 6]


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3. VLAN-Redirect-Extended Community Attribute

   This document defines a new BGP extended community attribute called
   the VLAN-Redirect-Extended Community attribute as shown in Figure 3.

      0                   1                   2                   3
      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       0x06    | Sub-Type=TBA  |    Flags      |   Reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            S-VLAN             |            C-VLAN             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 3. VLAN-Redirect-Extended Community Attribute

   Where:

      0x06: EVPN Extended Community Type field.

      Sub-Type: Sub-Type field indicating that the extended community
         attribute is a VLAN-Redirect-Extended Community attribute, and
         the value is TBA by the IANA.

      Flags: 8 bits of identification information. Bit 0 set to 0
         indicates that the action is redirected to the VLANs in this
         community

      Reserved: Not used. MUST be sent as zero and ignored on receipt.

      S-VLAN: Outer VLAN information, can not be 0, 0 is illegal value

      C-VLAN: Inner VLAN information. When 0, it means there is no C-
         VLA.



















D. Eastlake, et al                                              [Page 7]


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4. Operation

   Operation with the solution specified in Section 3 and the topology
   shown in Figure 2 is described below.



4.1 Establishment

   1. PE1 learns MAC addresses from CE1, advertises them to PE2, carries
      the ESI value as ES1 and the next hop as PE1, and carries the
      VLAN- Redirect-Extended Community attributes.

   2. PE2 receives the MAC route advertised by PE1 and finds the
      interface that connects to CE1 locally according to the ESI value.
      At the same time, PE2 fill the VLAN information according to the
      VLAN-Redirect-Extended Community attributes

   3. At the same time, PE2 generates a fast reroute (FRR) entry
      according to the next hop information (PE1) of the MAC route, that
      is, a MAC address entry on PE2, where the primary path points to
      the CE1 link and the standby path points to PE1

   4. PE2 also sends the MAC as a local MAC route to PE1

   5. PE1 receives the MAC route advertised by PE2 and generates the FRR
      entry with the MAC route learned by CE1, that is, the MAC address
      entry on PE1, with the primary path pointing to the CE1 link and
      the secondary path pointing to PE2



4.2 Handling Link Failure

   1. When the link between PE1 and CE1 fails, PE1 withdraws the MAC
      address that advertised to PE2

   2. PE2 receives the MAC withdrawal from PE1, does not delete the MAC
      immediately, but starts an aging timer, and does not withdraw the
      MAC address that PE2 advertised to PE1.

   3. When the aging timer expires, and PE2 cannot receive the traffic
      from CE1, then PE2 withdraws the MAC address that advertised to
      PE1 and deletes the MAC entry.








D. Eastlake, et al                                              [Page 8]


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5. IANA Considerations

   IANA is requested to assign a new EVPN Extended Community SubType as
   follows:

      Sub-Type Value   Name                             Reference
      --------------  --------------------------------  ----------
           TBA        VLAN-Redirect Extended Community  [this doc]



6. Security Considerations

   TBD

   For general EVPN Security Considerations, see [RFC7432].




































D. Eastlake, et al                                              [Page 9]


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

   [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>.

   [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>.



Informative References

   [RFC7209] - Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
         Henderickx, W., and A. Isaac, "Requirements for Ethernet VPN
         (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014,
         <https://www.rfc-editor.org/info/rfc7209>.



Acknowledgements

   The authors of this document would like to thank the following for
   their comments and review of this document:

      TBD




















D. Eastlake, et al                                             [Page 10]


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Authors' Addresses

      Donald E. Eastlake, 3rd
      Huawei Technologies
      155 Beaver Street
      Milford, MA 01757 USA

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


      Zhenbin Li
      Huawei Technologies
      Huawei Bldg., No. 156 Beiqing Road
      Beijing 100095
      China

      Email: lizhenbin@huawei.com


      Shunwan Zhang
      Huawei Technologies
      Huawei Bldg., No. 156 Beiqing Road
      Beijing 100095
      China

      Email: zhuangshunwan@huawei.com


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

      Email: rainsword.wang@huawei.com
















D. Eastlake, et al                                             [Page 11]


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D. Eastlake, et al                                             [Page 12]


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