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Versions: 00 01 02

BESS Workgroup                                           A. Sajassi, Ed.
INTERNET-DRAFT                                               A. Banerjee
Intended Status: Standards Track                               S. Thoria
                                                               D. Carrel
                                                                   Cisco
                                                                 B. Weis
                                                              Individual
                                                                J. Drake
                                                                 Juniper

Expires: January 8, 2020                                    July 8, 2019


                              Secure EVPN
                   draft-sajassi-bess-secure-evpn-02


Abstract

   The applications of EVPN-based solutions ([RFC7432] and [RFC8365])
   have become pervasive in Data Center, Service Provider, and
   Enterprise segments. It is being used for fabric overlays and inter-
   site connectivity in the Data Center market segment, for Layer-2,
   Layer-3, and IRB VPN services in the Service Provider market segment,
   and for fabric overlay and WAN connectivity in Enterprise networks.
   For Data Center and Enterprise applications, there is a need to
   provide inter-site and WAN connectivity over public Internet in a
   secured manner with same level of privacy, integrity, and
   authentication for tenant's traffic as IPsec tunneling using IKEv2.
   This document presents a solution where BGP point-to-multipoint
   signaling is leveraged for key and policy exchange among PE devices
   to create private pair-wise IPsec Security Associations without IKEv2
   point-to-point signaling or any other direct peer-to-peer session
   establishment messages.



Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months



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   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
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Copyright and License Notice

   Copyright (c) 2014 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  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     2.1 Tenant's Layer-2 and Layer-3 data & control traffic  . . . .  7
     2.2 Tenant's Unicast & Multicast Data Protection . . . . . . . .  7
     2.3 P2MP Signaling for SA setup and Maintenance  . . . . . . . .  7
     2.4 Granularity of Security Association Tunnels  . . . . . . . .  7
     2.5 Support for Policy and DH-Group List . . . . . . . . . . . .  8
   3  BGP Component . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1 Zero Touch Bring-up (ZTB)  . . . . . . . . . . . . . . . . .  8
     3.2 Configuration Management . . . . . . . . . . . . . . . . . .  8
     3.3 Orchestration  . . . . . . . . . . . . . . . . . . . . . . .  9
     3.4 Signaling  . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4  Solution Description  . . . . . . . . . . . . . . . . . . . . .  9
     4.1 Inheritance of Security Policies . . . . . . . . . . . . . . 10
     4.2  Distribution of Public Keys and Policies  . . . . . . . . . 11
       4.2.1  Minimal DIM . . . . . . . . . . . . . . . . . . . . . . 11
       4.2.2  Multiple Policies . . . . . . . . . . . . . . . . . . . 12
         4.2.2.1  Multiple DH-groups  . . . . . . . . . . . . . . . . 12



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         4.2.2.2  Multiple or Single ESP SA policies  . . . . . . . . 12
     4.3  Initial IPsec SAs Generation  . . . . . . . . . . . . . . . 13
     4.4  Re-Keying . . . . . . . . . . . . . . . . . . . . . . . . . 13
     4.5  IPsec Databases . . . . . . . . . . . . . . . . . . . . . . 13
   5 Encapsulation  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.1 Standard ESP Encapsulation . . . . . . . . . . . . . . . . . 14
     5.2 ESP Encapsulation within UDP packet  . . . . . . . . . . . . 15
   6 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     6.1 The Base (Minimal Set) DIM Sub-TLV . . . . . . . . . . . . . 16
     6.2 Key Exchange Sub-TLV . . . . . . . . . . . . . . . . . . . . 17
     6.3 ESP SA Proposals Sub-TLV . . . . . . . . . . . . . . . . . . 18
       6.3.1 Transform Substructure . . . . . . . . . . . . . . . . . 19
   7  Applicability to other VPN types  . . . . . . . . . . . . . . . 19
   8  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 20
   9  Security Considerations . . . . . . . . . . . . . . . . . . . . 20
   10  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   10  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     11.1  Normative References . . . . . . . . . . . . . . . . . . . 20
     11.2  Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22


Terminology

   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.

   AC: Attachment Circuit.

   ARP: Address Resolution Protocol.

   BD: Broadcast Domain. As per [RFC7432], an EVI consists of a single
   or multiple BDs. In case of VLAN-bundle and VLAN-based service models
   (see [RFC7432]), a BD is equivalent to an EVI. In case of VLAN-aware
   bundle service model, an EVI contains multiple BDs. Also, in this
   document, BD and subnet are equivalent terms.

   BD Route Target: refers to the Broadcast Domain assigned Route Target
   [RFC4364]. In case of VLAN-aware bundle service model, all the BD
   instances in the MAC-VRF share the same Route Target.

   BT: Bridge Table. The instantiation of a BD in a MAC-VRF, as per
   [RFC7432].

   DGW: Data Center Gateway.



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   Ethernet A-D route: Ethernet Auto-Discovery (A-D) route, as per
   [RFC7432].

   Ethernet NVO tunnel: refers to Network Virtualization Overlay tunnels
   with Ethernet payload. Examples of this type of tunnels are VXLAN or
   GENEVE.

   EVI: EVPN Instance spanning the NVE/PE devices that are participating
   on that EVPN, as per [RFC7432].

   EVPN: Ethernet Virtual Private Networks, as per [RFC7432].

   GRE: Generic Routing Encapsulation.

   GW IP: Gateway IP Address.

   IPL: IP Prefix Length.

   IP NVO tunnel: it refers to Network Virtualization Overlay tunnels
   with IP payload (no MAC header in the payload).

   IP-VRF: A VPN Routing and Forwarding table for IP routes on an
   NVE/PE. The IP routes could be populated by EVPN and IP-VPN address
   families. An IP-VRF is also an instantiation of a layer 3 VPN in an
   NVE/PE.

   IRB: Integrated Routing and Bridging interface. It connects an IP-VRF
   to a BD (or subnet).

   MAC-VRF: A Virtual Routing and Forwarding table for Media Access
   Control (MAC) addresses on an NVE/PE, as per [RFC7432]. A MAC-VRF is
   also an instantiation of an EVI in an NVE/PE.

   ML: MAC address length.

   ND: Neighbor Discovery Protocol.

   NVE: Network Virtualization Edge.

   GENEVE: Generic Network Virtualization Encapsulation, [GENEVE].

   NVO: Network Virtualization Overlays.

   RT-2: EVPN route type 2, i.e., MAC/IP advertisement route, as defined
   in [RFC7432].

   RT-5: EVPN route type 5, i.e., IP Prefix route. As defined in Section
   3 of [EVPN-PREFIX].



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   SBD: Supplementary Broadcast Domain. A BD that does not have any ACs,
   only IRB interfaces, and it is used to provide connectivity among all
   the IP-VRFs of the tenant. The SBD is only required in IP-VRF- to-IP-
   VRF use-cases (see Section 4.4.).

   SN: Subnet.

   TS: Tenant System.

   VA: Virtual Appliance.

   VNI: Virtual Network Identifier. As in [RFC8365], the term is used as
   a representation of a 24-bit NVO instance identifier, with the
   understanding that VNI will refer to a VXLAN Network Identifier in
   VXLAN, or Virtual Network Identifier in GENEVE, etc. unless it is
   stated otherwise.

   VTEP: VXLAN Termination End Point, as in [RFC7348].

   VXLAN: Virtual Extensible LAN, as in [RFC7348].

   This document also assumes familiarity with the terminology of
   [RFC7432], [RFC8365] and [RFC7365].




























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1  Introduction

   The applications of EVPN-based solutions have become pervasive in
   Data Center, Service Provider, and Enterprise segments. It is being
   used for fabric overlays and inter-site connectivity in the Data
   Center market segment, for Layer-2, Layer-3, and IRB VPN services in
   the Service Provider market segment, and for fabric overlay and WAN
   connectivity in the Enterprise networks. For Data Center and
   Enterprise applications, there is a need to provide inter-site and
   WAN connectivity over public Internet in a secured manner with the
   same level of privacy, integrity, and authentication for tenant's
   traffic as used in IPsec tunneling using IKEv2. This document
   presents a solution where BGP point-to-multipoint signaling is
   leveraged for key and policy exchange among PE devices to create
   private pair-wise IPsec Security Associations without IKEv2 point-to-
   point signaling or any other direct peer-to-peer session
   establishment messages.

   EVPN uses BGP as control-plane protocol for distribution of
   information needed for discovery of PEs participating in a VPN,
   discovery of PEs participating in a redundancy group, customer MAC
   addresses and IP prefixes/addresses, aliasing information, tunnel
   encapsulation types, multicast tunnel types, multicast group
   memberships, and other info. The advantages of using BGP control
   plane in EVPN are well understood including the following:

   1) A full mesh of BGP sessions among PE devices can be avoided by
   using Route Reflector (RR) where a PE only needs to setup a single
   BGP session between itself and the RR as opposed to setting up N BGP
   sessions to N other remote PEs; therefore, reducing number of BGP
   sessions from O(N^2) to O(N) in the network. Furthermore, RR
   hierarchy can be leveraged to scale the number of BGP routes on the
   RR.

   2) MP-BGP route filtering and constrained route distribution can be
   leveraged to ensure that the control-plane traffic for a given VPN is
   only distributed to the PEs participating in that VPN.

   For setting up point-to-point security association (i.e., IPsec
   tunnel) between a pair of EVPN PEs, it is important to leverage BGP
   point-to-multipoint singling architecture using the RR along with its
   route filtering and constrain mechanisms to achieve the performance
   and the scale needed for large number of security associations (IPsec
   tunnels) along with their frequent re-keying requirements. Using BGP
   signaling along with the RR (instead of peer-to-peer protocol such as
   IKEv2) reduces number of message exchanges needed for SAs
   establishment and maintenance from O(N^2) to O(N) in the network.




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2 Requirements

   The requirements for secured EVPN are captured in the following
   subsections.

2.1 Tenant's Layer-2 and Layer-3 data & control traffic

   Tenant's layer-2 and layer-3 data and control traffic must be
   protected by IPsec cryptographic methods. This implies not only
   tenant's data traffic must be protected by IPsec but also tenant's
   control and routing information that are advertised in BGP must also
   be protected by IPsec. This in turn implies that BGP session must be
   protected by IPsec.

2.2 Tenant's Unicast & Multicast Data Protection

   Tenant's layer-2 and layer-3 unicast traffic must be protected by
   IPsec. In addition to that, tenant's layer-2 broadcast, unknown
   unicast, and multicast traffic as well as tenant's layer-3 multicast
   traffic must be protected by IPsec when ingress replication or
   assisted replication are used. The use of BGP P2MP signaling for
   setting up P2MP SAs in P2MP multicast tunnels is for future study.

2.3 P2MP Signaling for SA setup and Maintenance

   BGP P2MP signaling must be used for IPsec SAs setup and maintenance.
   The BGP signaling must follow P2MP signaling framework per
   [CONTROLLER-IKE] for IPsec SAs setup and maintenance in order to
   reduce the number of message exchanges from O(N^2) to O(N) among the
   participant PE devices.

2.4 Granularity of Security Association Tunnels

   The solution must support the setup and maintenance of IPsec SAs at
   the following level of granularities:

   1) Per PE: A single IPsec tunnel between a pair of PEs to be used for
   all tenants' traffic supported by the pair of PEs.

   2) Per tenant: A single IPsec tunnel per tenant per pair of PEs. For
   example, if there are 1000 tenants supported on a pair of PEs, then
   1000 IPsec tunnels are required between that pair of PEs.

   3) Per subnet: A single IPsec tunnel per subnet (e.g., per VLAN/EVI)
   of a tenant on a pair of PEs.

   4) Per IP address: A single IPsec tunnel per pair of IP addresses of
   a tenant on a pair of PEs.



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   5) Per MAC address: A single IPsec tunnel per pair of MAC addresses
   of a tenant on a pair of PEs.

   6) Per Attachment Circuit: A single IPsec tunnel per pair of
   Attachment Circuits between a pair of PEs.


2.5 Support for Policy and DH-Group List

   The solution must support a single policy and DH group for all SAs as
   well as supporting multiple policies and DH groups among the SAs.


3  BGP Component

   The architecture that encompasses device-to-controller trust model,
   has several components among which is the signaling component. Secure
   EVPN Signaling, as defined in this document, is the BGP signaling
   component of the overall Architecture. We will briefly describe this
   Architecture here to further facilitate understanding how Secure EVPN
   fits into the overall architecture. The Architecture describes the
   components needed to create BGP based SD-WANs and how these
   components work together. Our intention is to list these components
   here along with their brief description and to describe this
   Architecture in details in a separate document where to specify the
   details for other parts of this architecture besides the BGP
   signaling component which is described in this document.

   The Architecture consists of four components.  These components are
   Zero Touch Bring-up, Configuration Management, Orchestration, and
   Signaling.  In addition to these components, secure communications
   must be provided between the edge nodes and all servers/devices
   providing the architecture components.


3.1 Zero Touch Bring-up (ZTB)

   The first component is a zero touch capability that allows an edge
   device to find and join its SD-WAN with little to no assistance other
   than power and network connectivity.  The goal is to use existing
   work in this area.  The requirements are that an edge device can
   locate its ZTB server/component of its SD-WAN controller in a secure
   manner and to proceed to receive its configuration.


3.2 Configuration Management

   After an edge device joins its SD-WAN, it needs to be configured.



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   Configuration covers all device configuration, not just the
   configuration related to Secure EVPN.  The previous Zero Touch Bring-
   up component will have directed the edge device, either directly or
   indirectly, to its configuration server/component.  One example of a
   configuration server is the I2NSF Controller. After a device has been
   configured, it can engage in the next two components.  Configuration
   may include updates over time and is not a one time only component.


3.3 Orchestration

   This component is optional.  It allows for more dynamic updates of
   configuration and statistics information.  Orchestration can be more
   dynamic than configuration.


3.4 Signaling

   Signaling is the component described in this document.  The
   functionality of a Route Reflector is well understood.  Here we
   describe the signaling component of BGP SD-WAN Architecture and the
   BGP extension/signaling for IPsec key management and policy.



4  Solution Description

   This solution uses BGP P2MP signaling where an originating PE only
   send a message to the Route Reflector (RR) and then the RR reflects
   that message to the interested recipient PEs. The framework for such
   signaling is described in [CONTROLLER-IKE] and it is referred to as
   device-to-controller trust model. This trust model is significantly
   different than the traditional peer-to-peer trust model where a P2P
   signaling protocol such as IKEv2 [RFC7296] is used in which the PE
   devices directly authenticate each other and agree upon security
   policy and keying material to protect communications between
   themselves. The device-to-controller trust model leverages P2MP
   signaling via the controller (e.g., the RR) to achieve much better
   scale and performance for establishment and maintenance of large
   number of pair-wise Security Associations (SAs) among the PEs.

   This device-to-controller trust model first secures the control
   channel between each device and the controller using peer-to-peer
   protocol such as IKEv2 [RFC7296] to establish P2P SAs between each PE
   and the RR. It then uses this secured control channel for P2MP
   signaling in establishment of P2P SAs between each pair of PE
   devices.




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   Each PE advertises to other PEs via the RR the information needed in
   establishment of pair-wise SAs between itself an every other remote
   PEs. These pieces of information are sent as Sub-TLVs of IPSec tunnel
   type in BGP Tunnel Encapsulation attribute. These Sub-TLVs are
   detailed in section 5 and are based on the DIM message components
   from [CONTROLLER-IKE] and the IKEv2 specification [RFC7296]. The
   IPsec tunnel TLVs along with its Sub-TLVs are sent along with the BGP
   route (NLRI) for a given level of granularity.

   If only a single SA is required per pair of PE devices to multiplex
   user traffic for all tenants, then IPsec tunnel TLV is advertised
   along with IPv4 or IPv6 NLRI representing loopback address of the
   originating PE. It should be noted that this is not a VPN route but
   rather an IPv4 or IPv6 route.

   If a SA is required per tenant between a pair of PE devices, then
   IPsec tunnel TLV can be advertised along with EVPN IMET route
   representing the tenant or can be advertised along with a new EVPN
   route representing the tenant.

   If a SA is required per tenant's subnet (e.g., per VLAN) between a
   pair of PE devices, then IPsec tunnel TLV is advertised along with
   EVPN IMET route.

   If a SA is required between a pair of tenant's devices represented by
   a pair of IP addresses, then IPsec tunnel TLV is advertised along
   with EVPN IP Prefix Advertisement Route or EVPN MAC/IP Advertisement
   route.

   If a SA is required between a pair of tenant's devices represented by
   a pair of MAC addresses, then IPsec tunnel TLV is advertised along
   with EVPN MAC/IP Advertisement route.

   If a SA is required between a pair of Attachment Circuits (ACs) on
   two PE devices (where an AC can be represented by <VLAN, port>), then
   IPsec tunnel TLV is advertised along with EVPN Ethernet AD route.

4.1 Inheritance of Security Policies

   Operationally, it is easy to configure a security association between
   a pair of PEs using BGP signaling. This is the default security
   association that is used for traffic that flows between peers.
   However, in the event more finer granularity of security association
   is desired on the traffic flows, it is possible to set up SAs between
   a pair of tenants, a pair of subnets within a tenant, a pair of IPs
   between a subnet, and a pair of MACs between a subnet using the
   appropriate EVPN routes as described above. In the event, there are
   no security TLVs associated with an EVPN route, there is a strict



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   order in the manner security associations are inherited for such a
   route. This results in an EVPN route inheriting the security
   associations of the parent in a hierarchical fashion. For example,
   traffic between an IP pair is protected using security TLVs announced
   along with the EVPN IP Prefix Advertisement Route or EVPN MAC/IP
   Advertisement route as a first choice. If such TLVs are missing with
   the associated route, then one checks to see if the subnets the IPs
   are associated with has security TLVs with the EVPN IMET route. If
   they are present, those associations are used in securing the
   traffic. In the absence of them, the peer security associations are
   used. The order in which security associations are inherited are from
   the granular to the coarser, namely, IP/MAC associated TLVs with the
   EVPN route being the first preference, and the subnet, the tenant,
   and the peer associations preferred in that fashion.

   It should be noted that when a security association is made it is
   possible for it to be re-used by a large number of traffic flows. For
   example, a tenant security association may be associated with a
   number of child subnet routes. Clearly it is mandatory to keep a
   tenant security association alive, if there are one or more subnet
   routes that want to use that association. Logically, the security
   associations between a pair of entities creates a single secure
   tunnel. It is thus possible to classify the incoming traffic in the
   most granular sense {IP/MAC, subnet, tenant, peer} to a particular
   secure tunnel that falls within its route hierarchy. The policy that
   is applied to such traffic is independent from its use of an existing
   or a new secure tunnel. It is clear that since any number of
   classified traffic flows can use a security association, such a
   security association will not be torn down, if at least there is one
   policy using such a secure tunnel.

4.2  Distribution of Public Keys and Policies

   One of the requirements for this solution is to support a single DH
   group and a single policy for all SAs as well as to support multiple
   DH groups and policies among the SAs. The following subsections
   describe what pieces of information (what Sub-TLVs) are needed to be
   exchanged to support a single DH group and a single policy versus
   multiple DH groups and multiple policies.

4.2.1  Minimal DIM

   For SA establishment, at the minimum, a PE needs to advertise to
   other PEs, its DIM values as specified in [CONTROLLER-IKE].  These
   include:

      ID   Tunnel ID
      N    Nonce



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      RC   Rekey Counter
      I    Indication of initial policy distribution
      KE   DH public value.

   When this minimal set of DIM values is sent, then it is assumed that
   all peer PEs share the same policy for which DH group to use, as well
   as which IPSec SA policy to employ. Section 5.1 defines the Minimal
   DIM sub-TLV as part of IPsec tunnel TLV in BGP Tunnel Encapsulation
   Attribute.

4.2.2  Multiple Policies

   There can be scenarios for which there is a need to have multiple
   policy options.  This can happen when there is a need for policy
   change and smooth migration among all PE devices to the new policy is
   required. It can also happen if different PE devices have different
   capabilities within the network. In these scenarios, PE devices need
   to be able to choose the correct policy to use for each other. This
   multi-policy scheme is described in section 6 of [CONTROLLER-IKE]. In
   order to support this multi-policy feature, a PE device MUST
   distribute a policy list. This list consists of multiple distinct
   policies in order of preference, where the first policy is the most
   preferred one.  The receiving PE selects the policy by taking the
   received list (starting with the first policy) and comparing that
   against its own list and choosing the first one found in common. If
   there is no match, this indicates a configuration error and the PEs
   MUST NOT establish new SAs until a message is received that does
   produce a match.


4.2.2.1  Multiple DH-groups

   It can be the case that not all peers use the same DH group.  When
   multiple DH groups are supported, the peer may include multiple KE
   Sub-TLVs.  The order of the KE Sub-TLVs determines the preference.
   The preference and selection methods are specified in Section 6 of
   [CONTROLLER-IKE].

4.2.2.2  Multiple or Single ESP SA policies

   In order to specify an ESP SA Policy, a DIM may include one or more
   SA Sub-TLVs. When all peers are configured by a controller with the
   same ESP SA policy, they MAY leave the SA out of the DIM.  This
   minimizes messaging when group configuration is static and known.
   However, it may also be desirable to include the SA.  If a single SA
   is included, the peer is indicating what ESP SA policy it uses, but
   is not willing to negotiate.  If multiple SA Sub-TLVs are included,
   the peer is indicating that it is willing to negotiate.  The order of



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   the SA Sub-TLVs determines the preference.  The preference and
   selection methods are specified in Section 6 of [CONTROLLER-IKE].


4.3  Initial IPsec SAs Generation

   The procedure for generation of initial IPsec SAs is described in
   section 3 of [CONTROLLER-IKE]. This section gives a summary of it in
   context of BGP signaling. When a PE device first comes up and wants
   to setup an IPsec SA between itself and each of the interested remote
   PEs, it generates a DH pair along for each [what word here?
   "tennant"?] using an algorithm defined in the IKEv2 Diffie-Hellman
   Group Transform IDs [IKEv2-IANA]. The originating PE distributes the
   DH public value along with the other values in the DIM (using IPsec
   Tunnel TLV in Tunnel Encapsulation Attribute) to other remote PEs via
   the RR. Each receiving PE uses this DH public number and the
   corresponding nonce in creation of IPsec SA pair to the originating
   PE - i.e., an outbound SA and an inbound SA. The detail procedures
   are described in section 5.2 of [CONTROLLER-IKE].


4.4  Re-Keying

   A PE can initiate re-keying at any time due to local time or volume
   based policy or due to the result of cipher counter nearing its final
   value. The rekey process is performed individually for each remote
   PE. If rekeying is performed with multiple PEs simultaneously, then
   the decision process and rules described in this rekey are performed
   independently for each PE. Section 4 of [CONTROLLER-IKE] describes
   this rekeying process in details and gives examples for a single
   IPsec device (e.g., a single PE) rekey versus multiple PE devices
   rekey simultaneously.


4.5  IPsec Databases

   The Peer Authorization Database (PAD), the Security Policy Database
   (SPD), and the Security Association Database (SAD) all need to be
   setup as defined in the IPsec Security Architecture [RFC4301].
   Section 5 of [CONTROLLER-IKE] gives a summary description of how
   these databases are setup for the controller-based model where key is
   exchanged via P2MP signaling via the controller (i.e., the RR) and
   the policy can be either signaled via the RR (in case of multiple
   policies) or configured by the management station (in case of single
   policy).


5 Encapsulation



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   Vast majority of Encapsulation for Network Virtualization Overlay
   (NVO) networks in deployment are based on UDP/IP with UDP destination
   port ID indicating the type of NVO encapsulation (e.g., VxLAN, GPE,
   GENEVE, GUE) and UDP source port ID representing flow entropy for
   load-balancing of the traffic within the fabric based on n-tuple that
   includes UDP header. When encrypting NVO encapsulated packets using
   IP Encapsulating Security Payload (ESP), the following two options
   can be used:  a) adding a UDP header before ESP header (e.g., UDP
   header in clear) and b) no UDP header before ESP header (e.g.,
   standard ESP encapsulation). The following subsection describe these
   encapsulation in further details.


5.1 Standard ESP Encapsulation

   When standard IP Encapsulating Security Payload (ESP) is used
   (without outer UDP header) for encryption of NVO packets, it is used
   in transport mode as depicted below. When such encapsulation is used,
   for BGP signaling, the Tunnel Type of Tunnel Encapsulation TLV is set
   to ESP-Transport and the Tunnel Type of Encapsulation Extended
   Community is set to NVO encapsulation type (e.g., VxLAN, GENEVE, GPE,
   etc.). This implies that the customer packets are first encapsulated
   using NVO encapsulation type and then it is further encapsulated &
   encrypted using ESP-Transport mode.



























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       +-+-+-+-+-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+-+-+-+-+
       |       MAC Header      |          |      MAC Header       |
       +-+-+-+-+-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+-+-+-+-+
       | Eth Type = IPv4/IPv6  |          | Eth Type = IPv4/IPv6  |
       +-+-+-+-+-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+-+-+-+-+
       |    IP Header          |          |    IP Header          |
       |    Protocol = UDP     |          |    Protocol = ESP     |
       +-----------------------+          +-----------------------+
       |      UDP Header       |          |    ESP Header         |
       | Dest Port = VxLAN     |          +-----------------------+
       +-----------------------+          |     UDP Header        |
       |     VxLAN Header      |          | Dest Port = VxLAN     |
       +-----------------------+          +-----------------------+
       |    Inner MAC Header   |          |   VxLAN Header        |
       +-----------------------+          +-----------------------+
       |    Inner Eth Payload  |          |   Inner MAC Header    |
       +-----------------------+          +-----------------------+
       |        CRC            |          |   Inner Eth Payload   |
       +-----------------------+          +-----------------------+
                                          |  ESP Trailer (NP=UDP) |
                                          +-----------------------+
                                          |        CRC            |
                                          +-----------------------+



               Figure 3: VxLAN Encapsulation within ESP


5.2 ESP Encapsulation within UDP packet

   In scenarios where NAT traversal is required ([RFC3948]) or where
   load balancing using UDP header is required, then ESP encapsulation
   within UDP packet as depicted in the following figure is used. The
   ESP for NVO applications is in transport mode. The outer UDP header
   (before the ESP header) has its source port set to flow entropy and
   its destination port set to 4500 (indicating ESP header follows). A
   non-zero SPI value in ESP header implies that this is a data packet
   (i.e., it is not an IKE packet). The Next Protocol field in the ESP
   trailer indicates what follows the ESP header, is a UDP header. This
   inner UDP header has a destination port ID that identifies NVO
   encapsulation type (e.g., VxLAN). Optimization of this packet format
   where only a single UDP header is used (only the outer UDP header) is
   for future study.

   When such encapsulation is used, for BGP signaling, the Tunnel Type
   of Tunnel Encapsulation TLV is set to ESP-in-UDP-Transport and the
   Tunnel Type of Encapsulation Extended Community is set to NVO



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   encapsulation type (e.g., VxLAN, GENEVE, GPE, etc.). This implies
   that the customer packets are first encapsulated using NVO
   encapsulation type and then it is further encapsulated & encrypted
   using ESP-in-UDP with Transport mode.


   [RFC3948]


       +-+-+-+-+-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+-+-+-+-+
       |       MAC Header      |          |      MAC Header       |
       +-+-+-+-+-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+-+-+-+-+
       | Eth Type = IPv4/IPv6  |          | Eth Type = IPv4/IPv6  |
       +-+-+-+-+-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+-+-+-+-+
       |    IP Header          |          |    IP Header          |
       |    Protocol = UDP     |          |    Protocol = UDP     |
       +-----------------------+          +-----------------------+
       |      UDP Header       |          |    UDP Header         |
       | Dest Port = VxLAN     |          | Dest Port = 4500(ESP) |
       +-----------------------+          +-----------------------+
       |     VxLAN Header      |          |    ESP Header         |
       +-----------------------+          +-----------------------+
       |    Inner MAC Header   |          |     UDP Header        |
       +-----------------------+          | Dest Port = VxLAN     |
       |    Inner Eth Payload  |          +-----------------------+
       +-----------------------+          |   VxLAN Header        |
       |        CRC            |          +-----------------------+
       +-----------------------+          |   Inner MAC Header    |
                                          +-----------------------+
                                          |   Inner Eth Payload   |
                                          +-----------------------+
                                          |  ESP Trailer (NP=UDP) |
                                          +-----------------------+
                                          |        CRC            |
                                          +-----------------------+
          Figure 4: VxLAN Encapsulation within ESP Within UDP


6 BGP Encoding

   This document defines two new Tunnel Types along with its associated
   sub-TLVs for The Tunnel Encapsulation Attribute [TUNNEL-ENCAP]. These
   tunnel types correspond to ESP-Transport and ESP-in-UDP-Transport as
   described in section 4. The following sub-TLVs apply to both tunnel
   types unless stated otherwise.

6.1 The Base (Minimal Set) DIM Sub-TLV




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   The Base DIM is described in 3.2.1. One and only one Base DIM may be
   sent in the IPSec Tunnel TLV.


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   ID Length   |       Nonce Length            |I|   Flags     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                             Rekey                             |
       |                            Counter                            |
       +---------------------------------------------------------------+
       |                                                               |
       ~  Originator ID + (Tenant ID) + (Subnet ID) + (Tenant Address) ~
       |                                                               |
       +---------------------------------------------------------------+
       |                                                               |
       ~                          Nonce Data                           ~
       |                                                               |
       +---------------------------------------------------------------+

                    Figure 5: The Base DIM Sub-TLV

   ID Length (16 bits) is the length of the Originator ID + (Tenant ID)
   + (Subnet ID) + (Tenant Address) in bytes.

   Nonce Length (8 bits) is the length of the Nonce Data in bytes

   I (1 bit) is the initial contact flag from [CONTROLLER-IKE]

   Flags (7 bits) are reserved and MUST be set to zero on transmit and
   ignored on receipt.

   The Rekey Counter is a 64 bit rekey counter as specified in
   [CONTROLLER-IKE]

   The Originator ID + (Tenant ID) + (Subnet ID) + (Tenant Address) is
   the tunnel identifier and uniquely identifies the tunnel. Depending
   on the granularity of the tunnel, the fields in () may not be used -
   i.e., for a tunnel at the PE level of granularity, only Originator ID
   is required.

   The Nonce Data is the nonce described in [CONTROLLER-IKE].  Its
   length is a multiple of 32 bits.  Nonce lengths should be chosen to
   meet minimum requirements described in IKEv2 [RFC7296].


6.2 Key Exchange Sub-TLV



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   The KE Sub-TLV is described in 3.2.1 and 3.2.2.1.  A KE is always
   required.  One or more KE Sub-TLVs may be included in the IPSec
   Tunnel TLV.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Diffie-Hellman Group Num    |          Reserved             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~                       Key Exchange Data                       ~
       |                                                               |
       +---------------------------------------------------------------+

                    Figure 6: Key Exchange Sub-TLV

   Diffie-Hellman Group Num 916 bits) identifies the Diffie-Hellman
   group in the Key Exchange Data was computed.  Diffie-Hellman group
   numbers are discussed in IKEv2 [RFC7296] Appendix B and [RFC5114].

   The Key Exchange payload is constructed by copying one's Diffie-
   Hellman public value into the "Key Exchange Data" portion of the
   payload. The length of the Diffie-Hellman public value is described
   for MOPD groups in [RFC7296] and for ECP groups in [RFC4753].


6.3 ESP SA Proposals Sub-TLV

   The SA Sub-TLV is described in 3.2.2.2.  Zero or more SA Sub-TLVs may
   be included in the IPSec Tunnel TLV.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ||Num Transforms|               Reserved                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~                           Transforms                          ~
       |                                                               |
       +---------------------------------------------------------------+


                 Figure 8: ESP SA Proposals Sub-TLV

   Num Transforms is the number of transforms included.

   Reserved is not used and MUST be set to zero on transmit and MUST be
   ignored on receipt.



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6.3.1 Transform Substructure

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Transform Attr Length       |Transform Type |    Reserved.  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Transform ID         |            Reserved           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~                     Transform Attributes                      ~
       |                                                               |
       +---------------------------------------------------------------+


                Figure 9: Transform Substructure Sub-TLV

   The Transform Attr Length is the length of the Transform Attributes
   field.

   The Transform Type is from Section 3.3.2 of [RFC7296] and
   [IKEV2IANA].  Only the values ENCR, INTEG, and ESN are allowed.

   The Transform ID specifies the transform identification value from
   [IKEV2IANA].

   Reserved is unused and MUST be zero on transmit and MUST be ignored
   on receipt.

   The Transform Attributes are taken directly from 3.3.5 of [RFC7296].

7  Applicability to other VPN types

   Although P2MP BGP signaling for establishment and maintenance of SAs
   among PE devices is described in this document in context of EVPN,
   there is no reason why it cannot be extended to other VPN
   technologies such as IP-VPN [RFC4364], VPLS [RFC4761] & [RFC4762],
   and MVPN [RFC6513] & [RFC6514] with ingress replication. The reason
   EVPN has been chosen is because of its pervasiveness in DC, SP, and
   Enterprise applications and because of its ability to support SA
   establishment at different granularity levels such as: per PE, Per
   tenant, per subnet, per Ethernet Segment, per IP address, and per
   MAC. For other VPN technology types, a much smaller granularity
   levels can be supported. For example for VPLS, only the granularity
   of per PE and per subnet can be supported. For per-PE granularity
   level, the mechanism is the same among all the VPN technologies as
   IPsec tunnel type (and its associated TLV and sub-TLVs) are sent
   along with the PE's loopback IPv4 (or IPv6) address. For VPLS, if



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   per-subnet (per bridge domain) granularity level needs to be
   supported, then the IPsec tunnel type and TLV are sent along with
   VPLS AD route.

   The following table lists what level of granularity can be supported
   by a given VPN technology and with what BGP route.


    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Functionality |     EVPN    |   IP-VPN    |    MVPN   |   VPLS  |
    +---------------+-------------+-------------+-----------+---------+
    | per PE        |IPv4/v6 route|IPv4/v6 route|IPv4/v6 rte|IPv4/v6  |
    +---------------+-------------+-------------+-----------+---------+
    | per tenant    |IMET (or new)|lpbk (or new)|  I-PMSI   | N/A     |
    +---------------+-------------+-------------+-----------+---------+
    | per subnet    |   IMET      |     N/A     |    N/A    | VPLS AD |
    +---------------+-------------+-------------+-----------+---------+
    | per IP        |EVPN RT2/RT5 |  VPN IP rt  | *,G or S,G|  N/A    |
    +---------------+-------------+-------------+-----------+---------+
    | per MAC       |  EVPN RT2   |     N/A     |    N/A    |  N/A    |
    +---------------+-------------+-------------+-----------+---------+






8  Acknowledgements


9  Security Considerations


10  IANA Considerations

   A new transitive extended community Type of 0x06 and Sub-Type of TBD
   for EVPN Attachment Circuit Extended Community needs to be allocated
   by IANA.

10  References

11.1  Normative References

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


   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC2119



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              Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May
              2017.

   [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", RFC 7432,
              February, 2015.


   [RFC8365] Sajassi et al., "A Network Virtualization Overlay Solution
              Using Ethernet VPN (EVPN)", RFC 8365, March, 2018.

   [TUNNEL-ENCAP] Rosen et al., "The BGP Tunnel Encapsulation
              Attribute", draft-ietf-idr-tunnel-encaps-03, November
              2016.

   [CONTROLLER-IKE] Carrel et al., "IPsec Key Exchange using a
              Controller", draft-carrel-ipsecme-controller-ike-00, July,
              2018.

   [IKEV2IANA] IANA, "Internet Key Exchange Version 2 (IKEv2)
              Parameters", <http://www.iana.org/assignments/ikev2-
              parameters/>.

   [RFC3948] Huttunen et al., "UDP Encapsulation of IPsec ESP Packets",
              RFC 3948, January 2005.

   [IKEV2-IANA] IANA, "Internet Key Exchange Version 2 (IKEv2)
              Parameters", February 2016,
              www.iana.org/assignments/ikev2-parameters/ikev2-
              parameters.xhtml.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005.

11.2  Informative References


   [RFC4364] Rosen, E., et. al., "BGP/MPLS IP Virtual Private Networks
   (VPNs)", RFC 4364, February 2006.

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

   [RFC4762] Kompella, K., et. al., "Virtual Private LAN Service (VPLS)
   Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January
   2007.

   [RFC6513] Rosen, E., et. al., "Multicast in MPLS/BGP IP VPNs", RFC



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   6513, February 2012.

   [RFC6514] Rosen, E., et. al., "BGP Encodings and Procedures for
   Multicast in MPLS/BGP IP VPNs", RFC 6514, February 2012.

   [RFC7606]  Chen, E., Scudder, J., Mohapatra, P., and K. Patel,
   "Revised Error Handling for BGP UPDATE Messages", RFC 7606, August
   2015, <http://www.rfc-editor.org/info/rfc7606>.

   [802.1Q] "IEEE Standard for Local and metropolitan area networks -
   Media Access Control (MAC) Bridges and Virtual Bridged Local Area
   Networks", IEEE Std 802.1Q(tm), 2014 Edition, November 2014.

   [RFC7348]  Mahalingam, M., et al., "Virtual eXtensible Local Area
   Network (VXLAN): A Framework for Overlaying Virtualized Layer 2
   Networks over Layer 3 Networks", RFC 7348, DOI 10.17487/RFC7348,
   August 2014.

   [GENEVE]  Gross, J., et al., "Geneve: Generic Network Virtualization
   Encapsulation", Work in Progress, draft-ietf-nvo3-geneve-06, March
   2018.


Authors' Addresses


   Ali Sajassi
   Cisco
   Email: sajassi@cisco.com


   Ayan Banerjee
   Cisco
   Email: ayabaner@cisco.com


   Samir Thoria
   Cisco
   Email: sthoria@cisco.com


   David Carrel
   Cisco
   Email: carrel@cisco.com


   Brian Weis
   Individual



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   Email: bew.stds@gmail.com


   John Drake
   Juniper
   Email: jdrake@juniper.net













































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