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BESS WG                                                          Y. Wang
Internet-Draft                                                  Z. Zhang
Intended status: Standards Track                         ZTE Corporation
Expires: October 27, 2019                                 April 25, 2019


              ARP/ND Synching And IP Aliasing without IRB
            draft-wang-bess-evpn-arp-nd-synch-without-irb-00

Abstract

   This draft proposes an extension to [RFC7432] to do ARP synchronizing
   and IP aliasing for Layer 3 routes that is needed for pure L3 EVPN to
   build a complete IP ECMP.  The phrase "pure L3 EVPN" means that there
   is no MAC-VRF or IRB interface in the use case.

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
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   This Internet-Draft will expire on October 27, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  ARP/ND Synching and IP Aliasing . . . . . . . . . . . . . . .   3
     2.1.  Constructing MAC/IP Advertisement Route . . . . . . . . .   4
     2.2.  Constructing IP-EAD/EVI Route . . . . . . . . . . . . . .   5
     2.3.  Constructing EAD/ES Route . . . . . . . . . . . . . . . .   5
   3.  Fast Convergence for Routed Traffic . . . . . . . . . . . . .   5
   4.  Determining Reach-ability to Unicast IP Addresses . . . . . .   6
   5.  Forwarding Unicast Packets  . . . . . . . . . . . . . . . . .   6
   6.  Load Balancing of Unicast Packets . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [I-D.sajassi-bess-evpn-ip-aliasing] proposes an extension to
   [RFC7432] to do aliasing for Layer 3 routes that is needed for
   symmetric IRB to build a complete IP ECMP.  But typically there may
   be both IRB interfaces(to do EVPN IRB per-MAC-VRF basis) and VRF-
   interfaces in the same IP-VRF instance.  It is necessary to apply the
   EVPN control-plane to the VRF-interfaces in order to support both
   such situations and the pure L3 EVPN use case where no IRB interfaces
   will be found in the IP-VRF instances.

                                      +---------+
                   +-------------+    |         |
                   |             |    |         |
                  /|    PE1      |----|         |   +-------------+
                 / |             |    |  MPLS/  |   |             |
            LAG /  +-------------+    |  VxLAN/ |   |     PE3     |---H3
   H1---SW1=====                      |  NVGRE/ |   |             |
       /        \  +-------------+    |  SRv6   |---|             |
     H2          \ |             |    |         |   +-------------+
                  \|     PE2     |----|         |
                   |             |    |         |
                   +-------------+    |         |
                                      |         |
                                      |         |
                                      +---------+

         Figure 1: ARP/ND Synchronizing and IP Aliasing without IRB

   Consider a pair of multi-homed PEs PE1 and PE2.  Let there be two
   hosts H1 and H2 attached to them via a L2 switch SW1.  Consider



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   another PE PE3 and a host H3 attached to it.  The H1 and H2 represent
   subnet SN1 and the H3 represents subnet SN2.

   Note that it is different from [I-D.sajassi-bess-evpn-ip-aliasing] in
   the following aspects: There is no MAC-VRF or IRB interface on
   PE1/PE2/PE3.  And it is the IP-VRFs that are called as EVPN instance
   instead.  Such EVPN instance can be called pure L3 EVPN instance or
   L3 EVI for short.  The anycast gateway of H1/H2 is configured on a
   sub-interface on PE1/PE2.

   Note that the communication between H1 and H2 won't pass through any
   of the multi-homed PEs.  So it is not necessary for PE1/PE2 keeping a
   Broadcast domain and its IRB for SN1.

   Note that the SW1 multi-homing PE1 and PE2 via a LAG interface which
   maybe load-balance traffic to the PEs.

   This draft proposes an extension to do ARP/ND synchronizing and IP
   aliasing for Layer 3 routes that is needed for L3 EVI to build a
   complete IP ECMP.

1.1.  Terminology

   Most of the terminology used in this documents comes from [RFC7432]
   and [I-D.sajassi-bess-evpn-ip-aliasing] except for the following:

   VRF Interface: A interface that connects to a CE for an IP-VRF but is
   not an IRB interface.

   L3 EVI: An EVPN instance spanning the Provider Edge (PE) devices
   participating in that EVPN which contains VRF Interfaces and maybe
   contains IRB interfaces.

2.  ARP/ND Synching and IP Aliasing

   Host IP and MAC routes are learnt by PEs on the access side via a
   control plane protocol like ARP.  In case where a CE is multihomed to
   multiple PE nodes using a LAG and is running in All-Active Redundancy
   Mode, the Host IP will be learnt and advertised in the MAC/IP
   Advertisement only by the PE that receives the ARP packet.  The MAC/
   IP Advertisement with non-zero ESI will be received by both PE2 and
   PE3.

   As a result, after PE2 receives the MAC/IP Advertisement and imports
   it to the L3 EVI, PE2 installs an ARP entry to the VRF interface
   whose subnet matches the IP Address from the MAC/IP Advertisement.
   Such ARP entry is called remote synched ARP Entry in this document.




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   Note that the PEs follow [I-D.sajassi-bess-evpn-ip-aliasing] to
   achieve the ESI load balance except for the constructing of MAC/IP
   Advertisement Route and IP-EAD/EVI route.

   When PE3 load balance the traffic towards the multihomed Ethernet
   Segment, both PE1 and PE2 would have been prepared with corresponding
   ARP entry yet because of the ARP synching procedures.

   It is important to explain that typically there may be both IRB
   interface and VRF interface in an IP-VRF instance, which is called as
   the "VRF interface in EVPN IRB" use-case in this document.  But each
   IRB/VRF interface is independent to each other in EVPN control plane.
   So the use-case here is constrained to a pure L3 EVPN schema, Because
   it is enough to describe all the control-plane updates for both the
   pure L3 EVPN use-case and the "VRF interface in EVPN IRB" use-case.

   In current EVPN control-plane for "VRF interface in EVPN IRB" use-
   case, the VRF interface is considered as "external link" and it just
   inter-operates with the EVPN control-plane.  But in this document it
   is assumed to be better if the EVPN control-plane directly applied to
   the VRF interface.

2.1.  Constructing MAC/IP Advertisement Route

   This draft introduces a new usage/construction of MAC/IP
   Advertisement route to enable Aliasing for IP addresses in pure L3
   EVPN use-cases.  The usage/construction of this route remains similar
   to that described in RFC 7432 with a few notable exceptions as below.

   * The Route-Distinguisher should be set to the corresponding L3VPN
   context.

   * The Ethernet Tag should be set to 0.

   * The MAC/IP Advertisement SHOULD carry one or more IP VRF Route-
   Target (RT) attributes.

   * The ESI SHOULD be set to the ESI of the VRF interface from which
   the ARP entry is learned.

   Note that the ESI is not used to install remote synched ARP entries
   to corresponding VRF interfaces on PE1/PE2.  It is only used to load
   balance traffic on PE3.

   * The MPLS Label1 should be set to implicit-null.  Note that no MAC-
   VRF can be found here.





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   * The MPLS Label2 should be set to the local label of the IP-VRF in
   MPLS or VXLAN EVPN.  But it should be set to implicit-null in SRv6
   EVPN.

   Note that the label may be VNI label or MPLS label.

   Note that in SRv6 EVPN an L3 Service SID MAY also be advertised along
   with the route following [I-D.dawra-bess-srv6-services].

   * The RMAC Extended Community attribute SHOULD be carried in VXLAN
   EVPN.

2.2.  Constructing IP-EAD/EVI Route

   Note that the MAC/IP Advertisement is used for two reasons.  It is
   used between PE1 and PE2 to synch the ARP entries to each other.  It
   is used between PE1/PE2 and PE3 to achieve the load balance to ES
   adjacent PEs.

   The usage/construction of this route remains similar to that
   described in [I-D.sajassi-bess-evpn-ip-aliasing] with a few notable
   exceptions as below.

   * The MPLS Label should be set to the local label of the IP-VRF in
   MPLS EVPN or VXLAN EVPN.  But it should be set to implicit-null in
   SRv6 EVPN.

   Note that in SRv6 EVPN an L3 Service SID MAY also be advertised along
   with the route following [I-D.dawra-bess-srv6-services].

2.3.  Constructing EAD/ES Route

   The usage/construction of this route remains similar to that
   described in section 3.1.1. of [I-D.sajassi-bess-evpn-ip-aliasing]
   with a few notable exceptions as explained as below.

   There may be no MAC-VRF RTs in the EAD/ES Route.

3.  Fast Convergence for Routed Traffic

   The procedures for Fast Convergence do not change from
   [I-D.sajassi-bess-evpn-ip-aliasing] except for a few notable
   exceptions as explained as below.

   The local ARP entries and remote synced ARP entries is installed/
   learned on a VRF interface rather than an IRB interface.

   There is no MAC entry.



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4.  Determining Reach-ability to Unicast IP Addresses

   The procedures for local/remote host learning and MAC/IP
   Advertisement route constructing are described above.  The procedures
   for Route Resolution do not change from
   [I-D.sajassi-bess-evpn-ip-aliasing].

5.  Forwarding Unicast Packets

   It is the same as [I-D.sajassi-bess-evpn-ip-aliasing].

6.  Load Balancing of Unicast Packets

   It is the same as [I-D.sajassi-bess-evpn-ip-aliasing].

7.  Security Considerations

   This document does not introduce any new security considerations
   other than already discussed in [RFC7432] and [RFC8365].

8.  IANA Considerations

   There is no IANA consideration.

9.  Normative References

   [I-D.dawra-bess-srv6-services]
              Dawra, G., Filsfils, C., Dukes, D., Brissette, P.,
              Sethuram, S., Camarillo, P., Leddy, J.,
              daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d.,
              Steinberg, D., Raszuk, R., Decraene, B., Matsushima, S.,
              and S. Zhuang, "SRv6 BGP based Overlay services", draft-
              dawra-bess-srv6-services-00 (work in progress), March
              2019.

   [I-D.sajassi-bess-evpn-ip-aliasing]
              Sajassi, A., Badoni, G., Warade, P., and S. Pasupula, "L3
              Aliasing and Mass Withdrawal Support for EVPN", draft-
              sajassi-bess-evpn-ip-aliasing-00 (work in progress), July
              2017.

   [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>.






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   [RFC8365]  Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
              Uttaro, J., and W. Henderickx, "A Network Virtualization
              Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
              DOI 10.17487/RFC8365, March 2018,
              <https://www.rfc-editor.org/info/rfc8365>.

Authors' Addresses

   Yubao(Bob) Wang
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing
   China

   Email: yubao.wang2008@hotmail.com


   Zheng(Sandy) Zhang
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing
   China

   Email: zzhang_ietf@hotmail.com



























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