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Versions: 00 draft-keyupate-bess-evpn-virtual-hub

L2VPNs                                                          K. Patel
Internet-Draft                                                A. Sajassi
Intended status: Standards Track                           Cisco Systems
Expires: January 3, 2016                                        J. Drake
                                                  Juniper Networks, Inc.
                                                           W. Henderickx
                                                          Alcatel-Lucent
                                                            July 2, 2015


                   Virtual Hub-and-Spoke in BGP EVPNs
                   draft-keyupate-evpn-virtual-hub-00

Abstract

   Ethernet Virtual Private Network (EVPN) solution is becoming
   pervasive for Network Virtualization Overlay (NVO) services in data
   center (DC) applications and as the next generation virtual private
   LAN services in service provider (SP) applications.

   The use of host IP default route and host unknown MAC route within a
   DC is well understood in order to ensure that leaf nodes within a DC
   only learn and store host MAC and IP addresses for that DC.  All
   other host MAC and IP addresses from remote DCs are learned and
   stored in DC GW nodes thus alleviating leaf nodes from learning host
   MAC and IP addresses from the remote DCs.

   This draft further optimizes the MAC and IP address learning at the
   leaf nodes such that a leaf node within a DC only needs to learn and
   store MAC and IP addresses associated with the sites directly
   connected to it.  A leaf node does not need to learn and store MAC
   and IP addresses from any other leaf nodes thus reducing the number
   of learned MACs and IP addresses per EVI substantially.

   The modifications provided by this draft updates and extends RFC7024
   for BGP EVPN Address Family.

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 http://datatracker.ietf.org/drafts/current/.





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   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 3, 2016.

Copyright Notice

   Copyright (c) 2015 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
   (http://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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Routing Information Exchange for EVPN routes  . . . . . . . .   4
   5.  EVPN unknown MAC Route  . . . . . . . . . . . . . . . . . . .   5
     5.1.  Originating EVPN Unknown MAC Route by a V-Hub . . . . . .   5
     5.2.  Processing VPN-MAC EVPN unknown Route by a V-SPOKE  . . .   5
     5.3.  Aliasing  . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.4.  Split-Horizon And Mass Withdraw . . . . . . . . . . . . .   6
   6.  Forwarding Considerations . . . . . . . . . . . . . . . . . .   7
     6.1.  IP-only Forwarding  . . . . . . . . . . . . . . . . . . .   7
     6.2.  MAC-only Forwarding - Bridging  . . . . . . . . . . . . .   7
     6.3.  MAC and IP Forwarding - IRB . . . . . . . . . . . . . . .   7
   7.  Handling of the Broadcast and Multicast traffic . . . . . . .   8
   8.  ARP/ND Suppression  . . . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   9
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   12. Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     13.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     13.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11




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1.  Introduction

   Ethernet Virtual Private Network (EVPN) solution is becoming
   pervasive for Network Virtualization Overlay (NVO) services in data
   center (DC) applications and as the next generation virtual private
   LAN services in service provider (SP) applications.

   With EVPN, providing any-to-any connectivity among sites of a given
   EVPN Instance (EVI) would require each Provider Edge (PE) router
   connected to one or more of these sites to hold all the host MAC and
   IP addresses for that EVI.  The use of host IP default route and host
   unknown MAC route within a DC is well understood in order to
   alleviate the learning of host MAC and IP addresses to only leaf
   nodes (PEs) within that DC.  All other host MAC and IP addresses from
   remote DCs are learned and stored in DC GW nodes thus alleviating
   leaf nodes from learning host MAC and IP addresses from the remote
   DCs.

   This draft further optimizes the MAC and IP address learning at the
   leaf nodes such that a leaf node within a DC only needs to learn and
   store MAC and IP addresses associated with the sites directly
   connected to it.  A leaf node does not need to learn and store MAC
   and IP addresses from any other leaf nodes thus reducing the number
   of learned MACs and IP addresses per EVI substantially.

   [RFC7024] provides rules for Hub and Spoke VPNs for BGP L3VPNs.  This
   draft updates and extends [RFC7024] for BGP EVPN Address Family.
   This draft provides rules for Originating and Processing of the EVPN
   host unknown MAC route and host default IP route by EVPN Virtual Hub
   (V-HUB).  This draft also provides rules for the handling of the BUM
   traffic in Hub and Spoke EVPNs and handling of ARP suppression.

   The leaf nodes and DC GW nodes in a data center are referred to as
   Virtual Spokes (V-spokes) and Virtual Hubs (V-hubs) respectively.  A
   set of V-spoke can be associated with one or more V-hubs.  If a V-
   spokes is associated with more than one V-hubs, then it can load
   balanced traffic among these V-hubs.  Different V-spokes can be
   associated with different sets of V-hubs such that at one extreme
   each V-spoke can have a different V-hub set although this may not be
   desirable and a more typical scenario may be to associate a set of V-
   spokes to a set of V-hubs - e.g., topology for a DC POD where a set
   of V-spokes are associated with a set of spine nodes or DC GW nodes.

   In order to avoid repeating many of the materials covered in
   [RFC7024], this draft is written as a delta document with its
   sections organized to follow those of that RFC with only delta
   description pertinent to EVPN operation in each section.  Therefore,




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   it is assumed that the readers are very familiar with [RFC7024] and
   EVPN.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
   be interpreted as described in [RFC2119] only when they appear in all
   upper case.  They may also appear in lower or mixed case as English
   words, without any normative meaning.

3.  Terminology

         ARP: Address Resolution Protocol
         BEB: Backbone Edge Bridge
         B-MAC: Backbone MAC Address
         CE: Customer Edge
         C-MAC: Customer/Client MAC Address
         ES: Ethernet Segment
         ESI: Ethernet Segment Identifier
         IRB: Integrated Routing and Bridging
         LSP: Label Switched Path
         MP2MP: Multipoint to Multipoint
         MP2P: Multipoint to Point
         ND: Neighbor Discovery
         NA: Neighbor Advertisement
         P2MP: Point to Multipoint
         P2P: Point to Point
         PE: Provider Edge
         EVPN: Ethernet VPN
         EVI: EVPN Instance
         RT: Route Target

   Single-Active Redundancy Mode: When only a single PE, among a group
   of PEs attached to an Ethernet segment, is allowed to forward traffic
   to/from that Ethernet Segment, then the Ethernet segment is defined
   to be operating in Single-Active redundancy mode.

   All-Active Redundancy Mode: When all PEs attached to an Ethernet
   segment are allowed to forward traffic to/from that Ethernet Segment,
   then the Ethernet segment is defined to be operating in All-Active
   redundancy mode.

4.  Routing Information Exchange for EVPN routes

   [RFC7024] defines multiple Route Types NLRI along with procedures for
   advertisements and processing of these routes.  Some of these
   procedures are impacted as the result of hub-and-spoke architecture.



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   The routing information exchange among the hub, spoke, and vanilla
   PEs are subject to the same rules as described in section 3 of
   [RFC7024].  Furthermore, if there are any changes to the EVPN route
   advisements and processing from advertisements and processing from
   [RFC7024], they are described below.

5.  EVPN unknown MAC Route

   Section 3 of [RFC7024] talks about how a V-hub of a given VPN must
   export a VPN-IP default route for that VPN and this route must be
   exported to only the V-spokes of that VPN associated with that V-hub.
   [I-D.EVPN-overlay] defines the notion of the unknown MAC route for an
   EVI which is analogous to a VPN-IP default route for a VPN.  This
   unknown MAC route is exported by a V-hub to its associated V-spokes.
   If multiple V-hubs are associated with a set of V-spokes, then each
   V- hub advertises it with a distinct RD when originating this route.
   If a V-spoke imports several of these unknown MAC routes and they all
   have the same preference, then traffic from the V-spoke to other
   sites of that EVI would be load balanced among the V-hubs.

5.1.  Originating EVPN Unknown MAC Route by a V-Hub

   Section 7.3 of the [RFC7024] defines procedures for originating a
   VPN-IP default route for a VPN.  The same procuedures apply when a
   V-hub wants to originate EVPN unknown MAC route for a given EVI.  The
   V-hub MUST announce unknown MAC route using the MAC/IP advertisement
   route along with the Default Gateway extended community as defined in
   section 10.1 of the [RFC7432].

5.2.  Processing VPN-MAC EVPN unknown Route by a V-SPOKE

   Within a given EVPN, a V-spoke MUST import all the unknown MAC routes
   unless the route-target mismatch happens.  The processing of the
   received VPN-MAC EVPN default route follows the rules explained in
   the section 3 of the [RFC7024].  The unknown MAC route MUST be
   installed according to the rules of MAC/IP Advertisement route
   installation rules in section 9.2.2 of [RFC7024].

   In absense of any more specific VPN-MAC EVPN routes, V-spokes
   installing the unknown MAC route MUST use the route when performing
   ARP proxy.  This behavior would allow V-Spokes to forward the traffic
   towards V-Hub.

5.3.  Aliasing

   [RFC7432] describes the concept and procedures for Aliasing where a
   station is multi-homed to multiple PEs operating in an All-Active
   redundancy mode, it is possible that only a single PE learns a set of



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   MAC addresses associated with traffic transmitted by the station.
   [RFC7432] describes the concepts and procedures for Aliasing, which
   occurs when a CE is multi-homed to multiple PE nodes, operating in
   all-active redundancy mode, but not all of the PEs learn the CE's set
   of MAC addresses.  This leads to a situation where remote PEs receive
   MAC advertisement routes, for these addresses, from a single NVE even
   though multiple NVEs are connected to the multi-homed station.  As a
   result, the remote NVEs are not able to effectively load-balance
   traffic among the NVEs connected to the multi-homed Ethernet segment.

   To alleviate this issue, EVPN introduces the concept of Aliasing.
   This refers to the ability of a PE to signal that it has reachability
   to a given locally attached Ethernet segment, even when it has learnt
   no MAC addresses from that segment.  The Ethernet A-D per-EVI route
   is used to that end.  Remote PEs which receive MAC advertisement
   routes with non-zero ESI SHOULD consider the MAC address as reachable
   via all NVEs that advertise reachability to the relevant Segment
   using Ethernet A-D routes with the same ESI and with the Single-
   Active flag reset.

   This procedure is impacted for virtual hub-and-spoke topology because
   a given V-spoke does not receive any MAC/IP advertisements from
   remote V-spokes; therefore, there is no point in propagating Ethernet
   A-D per-EVI route to the remote V-spokes.  In this solution, the V-
   hubs terminate the Ethernet A-D per-EVI route (used for Aliasing) and
   follows the procedures described in [RFC7432] for handling this
   route.

   There are scenarios for which it is desirable to establish direct
   communication path between a pair of V-spokes for a given host MAC
   address.  In such scenario, the advertising V-spoke advertises both
   the MAC/IP route and Ethernet A-D per-EVI route with the RT of V-hub
   (RT-VH) per section 3 of [RFC7024].  The use of RT-VH, ensures that
   these routes are received by the V-spokes associated with that V-hub
   set and thus enables the V-spokes to perform the Aliasing procedure.

   In summary, PE devices (V-hubs in general and V-spokes occasionally)
   that receive EVPN MAC/IP route advertisements (associated with a
   multi-homed site) need to also receive the associated Ethernet A-D
   per-EVI route advertisement(s) in order for them to perform Aliasing
   procedure.

5.4.  Split-Horizon And Mass Withdraw

   [RFC7432] uses Ethernet A-D per-ES route to a) signal to remote PEs
   the multi-homing redundancy type (Single-Active versus All-Active),
   b) advertise ESI label for split-horizon filtering when MPLS
   encapsulation is used, and c) advertise mass-withdraw when a failure



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   of an access interface impacts many MAC addresses.  This route does
   not need to be advertise from a V-spoke to any remote V-spoke unless
   a direct communication path between a pair of spoke is needed for a
   given flow.

   Even if communication between a pair of V-spoke is needed for just a
   single flow, the Ethernet A-D per ES route needs to be advertised
   from the originating V-spoke for that ES which may handle tens or
   hundreds of thousands of flows.  This is because in order to perform
   Aliasing function for a given flow, the Ethernet A-D per-EVI route is
   needed and this route itself is dependent on the Ethernet A-D per-ES
   route.  In such scenario, the advertising V-spoke advertises the
   Ethernet A-D per-ES route with the RT of V-hub (RT-VH) per section 3
   of [RFC7024].

   In summary, PE devices (V-hubs in general and V-spokes occasionally)
   that receive EVPN MAC/IP route advertisements (associated with a
   multi-homed site) need to also receive the associated Ethernet A-D
   per-ES route advertisement(s).

6.  Forwarding Considerations

6.1.  IP-only Forwarding

   When EVPN operates in IP-only forwarding mode using EVPN Route Type
   5, then all forwarding considerations in section 4 of [RFC7024] are
   directly applicable here.

6.2.  MAC-only Forwarding - Bridging

   When EVPN operates in MAC-only forwarding mode (i.e., bridging mode),
   then for a given EVI, the MPLS label that a V-hub advertises with an
   Unknown MAC address MUST be the label that identifies the MAC-VRF of
   the V-hub in absense of a more specific MAC route.  When the V-hub
   receives a packet with such label, the V- hub pops the label and
   determines further disposition of the packet based on the lookup in
   the MAC-VRF.  Otherwise, the MPLS label of the matching more specific
   route is used and packet is is forwarded towards the associated
   NEXTHOP of the more specific route.

6.3.  MAC and IP Forwarding - IRB

   When a EVPN speaker operates in IRB mode, it implements both the "IP
   and MAC forwarding Modes" (aka Integrated Routing and Bridging -
   IRB).  On a packet by packet basis, the V-spoke decides whether to do
   forwarding based on a MAC address lookup (bridge) or based on a IP
   address lookup (route).  If the host destination MAC address is that
   of the IRB interface (i.e., if the traffic is inter-subnet), then the



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   V-spoke performs an additional IP lookup in the IP-VRF.  However, if
   the host destination MAC address is that of an actual host MAC
   address (i.e., the traffic is intra-subnet) , then the V-spoke only
   performs a MAC lookup in the MAC-VRF.  The procedure specified in
   Section 6.1 and Section 6.2 are applicable to inter-subnet and intra-
   subnet forwarding respectively.  For intra-subnet traffic, if the MAC
   address is not found in the MAC-VRF, then the V-spoke forwards the
   traffic to the V-hub with the MPLS label received from the V-hub for
   the unknown MAC address.  For the Inter-subnet traffic, if the IP
   prefix is not found in the IP-VRF, then the V-spoke forwards the
   traffic to the V-hub with the MPLS label received from the V-hub for
   the default IP address.

7.  Handling of the Broadcast and Multicast traffic

   The handling of the Broadcast and Multicast traffic should be done
   according to the EVPN rules described in [RFC7432].

8.  ARP/ND Suppression

   [RFC7432] defines the procedures for ARP/ND suppression where a PE
   can terminate gratuitous ARP/ND request message from directly
   connected site and advertises the associated MAC and IP addresses in
   an EVPN MAC/IP advertisement route to all other remote PEs.  The
   remote PEs that receive this EVPN route advertisement, install the
   MAC/IP pair in their ARP/ND cache table thus enabling them to
   terminate ARP/ND requests and generate ARP/ND responses locally thus
   suppressing the flooding of ARP/ND requests over the EVPN network.

   In this hub-and-spoke approach, the ARP suppression needs to be
   performed by both the EVPN V-hubs as well V-spokes as follow.  When a
   V-Spoke receives a gratuitous ARP/ND request, it terminates it and
   stores the source MAC/IP pair in its ARP/ND cache table.  Then, it
   advertises the source MAC/IP pair to its associated V-Hubs using EVPN
   MAC/IP advertisement route.  The V-Hubs upon receiving this EVPN
   route advertisement, create an entry in their ARP/ND cache table for
   this MAC/IP pair.

   Now when a V-Spoke receives an ARP/ND request, it first looks up its
   ARP cache table, if an entry for that MAC/IP pair is found, then an
   ARP/ND response is generated locally and sent to the CE.  However, if
   an entry is not found, then the ARP/ND request is unicasted to one of
   the V-hub associated with this V-spoke.  Since, the associated V-hub
   keeps all the MAC/IP ARP entries in its cache table, it can formulate
   and ARP/ND response and forward it to that CE via the corresponding
   V-spoke.





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9.  IANA Considerations

   This document does NOT make any new requests for IANA allocations.

10.  Security Considerations

   All the security considerations in [RFC7432] apply directly to this
   document because this document leverages [RFC7432] control plane and
   their associated procedures - although not the complete set but
   rather a subset.

   This draft does not introduce any new security considerations beyond
   that of [RFC7432] and [RFC4761] because advertisements and processing
   of B-MAC addresses follow that of [RFC7432] and processing of C-MAC
   addresses follow that of [RFC4761] - i.e, B-MAC addresses are learned
   in control plane and C-MAC addresses are learned in data plane.

11.  Acknowledgements

   The authors would like to thank Yakov Rekhter for initial idea
   discussions.

12.  Change Log

   Initial Version:  Sep 21 2014

13.  References

13.1.  Normative References

   [I-D.ietf-l2vpn-evpn]
              Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., and J.
              Uttaro, "BGP MPLS Based Ethernet VPN", draft-ietf-l2vpn-
              evpn-11 (work in progress), October 2014.

   [RFC1771]  Rekhter, Y. and T. Li, "A Border Gateway Protocol 4 (BGP-
              4)", RFC 1771, March 1995.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              March 2000.

   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484, February 2003.




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   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4374]  McCobb, G., "The application/xv+xml Media Type", RFC 4374,
              January 2006.

   [RFC6459]  Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
              Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, January 2012.

   [RFC7024]  Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter,
              Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS
              VPNs", RFC 7024, October 2013.

   [RFC7432]  Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., Uttaro,
              J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
              VPN", RFC 7432, February 2015.

13.2.  Informative References

   [I-D.drao-bgp-l3vpn-virtual-network-overlays]
              Rao, D., Mullooly, J., and R. Fernando, "Layer-3 virtual
              network overlays based on BGP Layer-3 VPNs", draft-drao-
              bgp-l3vpn-virtual-network-overlays-03 (work in progress),
              July 2014.

   [I-D.ietf-bess-evpn-overlay]
              Sajassi, A., Drake, J., Bitar, N., Isaac, A., Uttaro, J.,
              and W. Henderickx, "A Network Virtualization Overlay
              Solution using EVPN", draft-ietf-bess-evpn-overlay-01
              (work in progress), February 2015.

   [RFC4389]  Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
              Proxies (ND Proxy)", RFC 4389, April 2006.

   [RFC4761]  Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
              (VPLS) Using BGP for Auto-Discovery and Signaling", RFC
              4761, January 2007.






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   [RFC7080]  Sajassi, A., Salam, S., Bitar, N., and F. Balus, "Virtual
              Private LAN Service (VPLS) Interoperability with Provider
              Backbone Bridges", RFC 7080, December 2013.

   [RFC7209]  Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
              Henderickx, W., and A. Isaac, "Requirements for Ethernet
              VPN (EVPN)", RFC 7209, May 2014.

Authors' Addresses

   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA 95124  95134
   USA

   Email: keyupate@cisco.com


   Ali Sajassi
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA 95124  95134
   USA

   Email: sajassi@cisco.com


   John E. Drake
   Juniper Networks, Inc.

   Email: jdrake@juniper.net


   Wim Henderickx
   Alcatel-Lucent

   Email: wim.henderickx@alcatel-lucent.com













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