Network Working Group                                        L. Dunbar
Internet Draft                                               Futurewei
Intended status: Informational                              A. Sajassi
Expires: March 5, 2024                                         Cisco
                                                             J. Drake
                                                             B. Najem
                                                          Bell Canada
                                                         April 5, 2024

                  BGP Usage for SD-WAN Overlay Networks

   This document explores the complexities involved in managing large
   scale Software Defined WAN (SD-WAN) overlay networks, along with
   various SD-WAN scenarios. Its objective is to illustrate how the
   BGP-based control plane can effectively manage large-scale SD-WAN
   overlay networks with minimal manual intervention.

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

   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

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors. All rights reserved.

xxx, et al.                                                   [Page 1]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( 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. Conventions used in this document..............................4
   3. SD-WAN Scenarios and Their Requirements........................5
      3.1. Requirements..............................................6
         3.1.1. Supporting SD-WAN Segmentation.......................6
         3.1.2. Client Service Requirement...........................6
         3.1.3. SD-WAN Traffic Segmentation..........................7
         3.1.4. Zero Touch Provisioning..............................8
         3.1.5. Constrained Propagation of SD-WAN Edge Properties....8
      3.2. Scenario #1: Homogeneous Encrypted SD-WAN................10
      3.3. Scenario #2: Differential Encrypted SD-WAN...............11
      3.4. Scenario #3: Private VPN PE based SD-WAN.................13
   4. Provisioning Model............................................14
      4.1. Client Service Provisioning Model........................14
      4.2. Policy Configuration.....................................14
      4.3. IPsec Related Parameters Provisioning....................14
   5. BGP Controlled SD-WAN.........................................15
      5.1. Why BGP as Control Plane for SD-WAN?.....................15
      5.2. BGP Walk Through for Homogeneous Encrypted SD-WAN........15
      5.3. BGP Walk Through for Differential Encrypted SD-WAN.......18
      5.4. BGP Walk Through for Application Flow-Based Segmentation.19
      5.5. Benefit of Using Recursive Next Hop Resolution...........20
   6. SD-WAN Forwarding Model.......................................20
      6.1. Forwarding Model for Homogeneous Encrypted SD-WAN........21
         6.1.1. Network and Service Startup Procedures..............21
         6.1.2. Packet Walk-Through.................................21
      6.2. Forwarding Model for Hybrid Underlay SD-WAN..............22
         6.2.1. Network and Service Startup Procedures..............22
         6.2.2. Packet Walk-Through.................................23
      6.3. Forwarding Model for PE based SD-WAN.....................24
         6.3.1. Network and Service Startup Procedures..............24
         6.3.2. Packet Walk-Through.................................24
   7. Manageability Considerations..................................25
   8. Security Considerations.......................................25

Dunbar, et al.                                                [Page 2]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   9. IANA Considerations...........................................26
   10. References...................................................26
      10.1. Normative References....................................26
      10.2. Informative References..................................28
   11. Acknowledgments..............................................29

1. Introduction

   Software Defined Wide Area Network (SD-WAN), as described in
   [MEF70.1] [MEF70.2], provides overlay connectivity services that
   optimize the transport of IP packets over one or more underlay
   connectivity services by recognizing applications and determining
   forwarding behavior by applying policies to them. Here are some of
   the main characteristics of "SD-WAN" networks:

     - Transport Augmentation, referring to utilizing paths over
       different underlay networks. There are often multiple parallel
       overlay paths between any two SD-WAN edges; some are private
       networks over which traffic can traverse with or without
       encryption; others require encryption, e.g., over untrusted
       public networks.
     - Instead of all traffic hauled to corporate headquarters for
       centralized policy control, direct Internet breakout from
       remote branch offices is allowed.
     - Some traffic can be steered onto specific overlay paths based
       on the packets matching a predefined condition instead of
       destination IP addresses [RFC9522]. The matching condition can
       be one or multiple fields of the IP header of the packets.
       More detailed attributes for steering traffic are described in
       the Table7 and Table 8 of [MEF70.1]. Using IPv6 [RFC8200]
       packets as an example, the Flow Label, the source address, a
       specific extension header field, or a combination of multiple
       IP header fields can be used to steer traffic.
     - The traffic forwarding can also be based on specific
       performance criteria (e.g., packet delay, packet loss, jitter)
       to provide better performance by choosing the underlay that
       meets or exceeds the specified policies.

   This document describes the SD-WAN use cases and explores the
   complexities of managing large-scale SD-WAN overlay networks, a
   component of [Net2Cloud-Problem]. It aims to illustrate how the

Dunbar, et al.                                                [Page 3]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   BGP-based control plane can effectively manage large-scale SD-WAN
   overlay networks with minimal manual intervention.

   It's important to distinguish the BGP instance as the control
   plane for SD-WAN overlay from the BGP instances governing the
   underlay networks. Additionally, it assumes the existence of a
   secure channel between the SD-WAN controller and the SD-WAN edges
   for BGP Control Plane communication.

2. Conventions used in this document

   Cloud DC:   Third party data centers that host applications and
               workloads owned by different organizations or tenants.

   Controller: Used interchangeably with SD-WAN controller to manage
               SD-WAN overlay networks in this document. In the
               specific context of BGP-controlled SD-WAN, the
               controller functions as an integral component of the
               BGP Route Reflector.

   Client prefix: In this document, client prefix means IP prefix
               attached to a client port of an SD-WAN edge.

   CPE:        Customer Premise Equipment

   C-PE:       For SD-WAN network expanded from an existing VPN, the
               term C-PE refers to the PE (or CPE) of the existing
               VPN that has added WAN ports to other networks.

   Homogeneous Encrypted SD-WAN: An SD-WAN network in which all
               traffic to/from the SD-WAN edges are carried by IPsec
               tunnels regardless of underlay networks. I.e., the
               client traffic is carried by IPsec tunnel even over
               MPLS private networks.

   MP-NLRI:    In this document, the term "MP-NLRI" serves as a
               concise reference for "MP_REACH_NLRI".

   NSP:        Network Service Provider.

   PE:         Provider Edge

Dunbar, et al.                                                [Page 4]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   SD-WAN Edge Node: An edge node, which can be physical or virtual,
               maps the attached clients' traffic to the wide area
               network (WAN) overlay tunnels.

   SD-WAN:     An overlay connectivity service that optimizes the
               transport of IP packets over one or more Underlay
               connectivity services by recognizing applications and
               determining forwarding behavior by applying policies
               to them. [MEF-70.1].

   SD-WAN IPsec SA: IPsec Security Association between two WAN ports
               of the SD-WAN edge nodes or between two SD-WAN edge

   SD-WAN over Hybrid Underlay Networks: SD-WAN over Hybrid Underlay
               Networks typically have edge nodes utilizing bandwidth
               resources from different types of underlay networks,
               some being private networks and others being public

   WAN Port:   A Port or Interface facing a Network Service Provider
               (NSP), with an address allocated by the NSP.

   C-PE:       SD-WAN Edge node, which can be Customer Premises
               Equipment (CPE) for customer-managed SD-WAN, or
               Provider Edge (PE) for provider-managed SD-WAN

   Private VPN: refers to a VPN that is supported wholly by a single
               network service provider without using any elements of
               the public Internet and without any traffic passing
               out of the immediate control of that service provider.

   ZTP:        Zero Touch Provisioning

3. SD-WAN Scenarios and Their Requirements

   This section outlines the fundamental requirements for SD-WAN
   overlay networks and introduces various SD-WAN scenarios. These
   scenarios serve as examples that are further explored in

Dunbar, et al.                                                [Page 5]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   subsequent sections to demonstrate the application of the BGP
   control plane.

3.1. Requirements

3.1.1. Supporting SD-WAN Segmentation

   "SD-WAN Segmentation" is a frequently used term in SD-WAN
   deployment, referring to policy-driven network partitioning. An
   SD-WAN segment is a virtual private network (SD-WAN VPN)
   consisting of a set of edge nodes interconnected by tunnels, such
   as IPsec tunnels and MPLS VPN tunnels.

   This document assumes that SD-WAN VPN configuration on PE devices
   will, as with MPLS VPN [RFC4364] [RFC4659], make use of VRFs
   [RFC4364] [RFC4659]. It is important to highlight that a single
   SD-WAN VPN can be mapped to one or multiple virtual topologies
   governed by the SD-WAN controller's policies.

   When using BGP for SD-WAN, the Client Prefix UPDATE is the same as
   MPLS VPN. Route Target in the BGP Extended Community [RFC4360] can
   be used to differentiate the routes belonging to different SD-WAN

   As SD-WAN is an overlay network arching over multiple types of
   networks, MPLS L2VPN[RFC4761] [RFC4762]/L3VPN[RFC4364] [RFC4659]
   or pure L2 underlay can continue using the VPN ID (Virtual Private
   Network Identifier), VN-ID (Virtual Network Identifier), or VLAN
   (Virtual LAN) in the data plane to differentiate packets belonging
   to different SD-WAN VPNs. To convey the SD-WAN VPN identifier
   within packets transported through an IPsec tunnel, an extra layer
   of encapsulation, like GRE [RFC2784] or VxLAN [RFC7348], is needed
   before inserting the packet into the IPsec ESP header.

3.1.2. Client Service Requirement

   The client service requirements describe the SD-WAN edge's ports,
   also known as SD-WAN client interfaces, which connect the client
   network to the SD-WAN service.

   The SD-WAN client interface should support IPv4 & IPv6 address
   prefixes and Ethernet (as described in [IEEE802.3] standard).

   It is worth noting that the "SD-WAN client interface" is called
   SD-WAN UNI (User Network Interface) in [MEF 70.1] with a set of
   attributes (described in Section 11 in MEF 70.1); these attributes
   (in MEF 70.1) describe the expected behavior and requirements to
   support the connectivity to the client network.

Dunbar, et al.                                                [Page 6]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   The client service should support the SD-WAN UNI service
   attributes at the SD-WAN edge as described in MEF 70.1, Section

3.1.3. SD-WAN Traffic Segmentation

   SD-WAN Traffic Segmentation enables the separation of the traffic
   based on the business and the security needs of different user
   groups and/or application requirements. Each user group and/or
   application may need different isolated topologies and/or policies
   to fulfill the business and security requirements.

   For example, if a retail business requires the point-of-sales
   (PoS) application to be on a different topology from other
   applications, the PoS application is routed only to the payment
   processing entity at a hub site; other applications can be routed
   to all other sites.

   The traffic from the PoS application follows a tree topology
   (denoted as "----" in the figure below), whereas other traffic can
   follow a multipoint-to-multipoint topology (denoted as "===").

              Payment traffic |Payment |
                +------+----+-+gateway +------+----+-----+
               /      /     | +----+---+      |     \     \
              /      /      |      |          |      \     \
           +-+--+  +-+--+  +-+--+  |   +-+--+  +-+--+  +-+--+
           |Site|  |Site|  |Site|  |   |Site|  |Site|  |Site|
           | 1  |  |  2 |  | 3  |  |   |4   |  |  5 |  | 6  |
           +--+-+  +--+-+  +--|-+  |   +--|-+  +--|-+  +--|-+
              |       |       |    |      |       |       |
            Multi-point connection for non-payment traffic

   Another example is an enterprise that wants to isolate the traffic
   from different departments, with each department having its unique
   topology and policy. The HR department may need to access specific
   applications that are not accessible by the engineering
   department. Also, contractors may have limited access to the
   enterprise resources.

Dunbar, et al.                                                [Page 7]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

3.1.4. Zero Touch Provisioning

   SD-WAN Zero-Touch Provisioning (ZTP) allows devices to be
   configured and provisioned centrally without the need to dispatch
   a network engineer to the field to configure the remote devices.
   When an SD-WAN edge is installed at a remote location, ZTP
   automates follow-up steps, including updates to the OS, software
   version, and configuration, before client traffic is forwarded.
   The ZTP can bootstrap a remote SD-WAN edge and establish a secure
   connection to the local SD-WAN Controller, making it convenient to
   add or delete an SD-WAN edge node (virtual or physical). ZTP for a
   remote SD-WAN edge usually includes the following steps:

     - The SD-WAN edge's customer information and its device
     identifier, such as the device serial number, are added to the
     SD-WAN Central Controller.

     - Upon power-up, the SD-WAN edge can establish the transport
     layer secure connection [BCP195] to its controller, whose URL
     (or IP address) and credential for connection request can be
     preconfigured on the edge device by the manufacture, external
     USB drive or secure Email given to the installer. The external
     USB method involves providing the installer with a pre-
     configured USB flash drive containing the necessary
     configuration files and settings for the SD-WAN device. The
     secure Email approach entails sending a secure email containing
     the configuration details for the SD-WAN device.

     - The SD-WAN Controller authenticates the ZTP request from the
     remote SD-WAN edge with its configurations. Once the
     authentication is successful, it can designate a local network
     controller near the SD-WAN edge to pass down the initial
     configurations via the secure channel. The local network
     controller manages and monitors the communication policies for
     traffic to/from the edge node.

3.1.5. Constrained Propagation of SD-WAN Edge Properties

   For an SD-WAN Edge to establish an IPsec tunnel to another one and
   announce the attached client prefixes to each other, both edges
   need to know each other's network properties, such as the IP
   addresses of the WAN ports, the edges' loopback addresses, the
   attached client prefixes, the supported encryption methods, etc.

Dunbar, et al.                                                [Page 8]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   One SD-WAN edge node may only be authorized to communicate with a
   small number of other SD-WAN edge nodes. In this circumstance, the
   property of the SD-WAN edge node should not be propagated to other
   nodes that are not authorized to communicate. But a remote SD-WAN
   edge node, upon powering up, may not have the right policies to
   know which peers are authorized to communicate. Therefore, SD-WAN
   deployment needs to have a central point to distribute the
   properties of an SD-WAN edge node to its authorized peers.

   BGP is well suited for this purpose. RFC4684 has specified the
   procedure to constrain the distribution of BGP UPDATE to only a
   subset of nodes. Route-Reflector (RR) [RFC4456], as an integral
   part of the SD-WAN controller, has the policy governing
   communication among peers. The RR only propagates the BGP UPDATE
   from an edge to others within the same SD-WAN VPN.

   As the connection between an SD-WAN edge and its RR can be over an
   insecure network, an SD-WAN edge must establish a secure
   connection to its designated RR upon power-up. The BGP UPDATE
   messages must be sent over the secure channel to the RR.

          Authorized Peers G1 |RR |   Authorized Peer G2
                +======+====+=+   +======+====+=====+
               /      /     | +---+      |     \     \
              /      /      |            |      \     \
           +-+--+  +-+--+  +-+--+      +-+--+  +-+--+  +-+--+
           |C-PE|  |C-PE|  |C-PE|      |C-PE|  |C-PE|  |C-PE|
           | 1  |  |  2 |  | 3  |      |4   |  |  5 |  | 6  |
           +----+  +----+  +----+      +----+  +----+  +----+
                Tenant 1                   Tenant 2
          Figure 1: Authorized Peer Groups managed by RR

   Tenant separation is achieved by the SD-WAN VPN identifiers
   represented in the control plane and data plane, respectively.

Dunbar, et al.                                                [Page 9]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

3.2. Scenario #1: Homogeneous Encrypted SD-WAN

   Homogeneous Encrypted SD-WAN refers to an SD-WAN network with edge
   nodes encrypting all traffic over the WAN underlay to other edge
   nodes, regardless of whether the underlay is private or public, as
   shown in Figure 2 below. For lack of better terminology, we call
   this Homogeneous Encrypted SD-WAN throughout this document.

   Here are some typical scenarios for using Homogeneous Encryption:

   -  A small branch office connecting to its HQ offices via the
   Internet. All traffic to/from this small branch office must be
   encrypted, usually achieved by IPsec Tunnels [RFC6071].

   -  A store in a shopping mall may need to securely connect to its
   applications in one or more Cloud DCs via the Internet. A common
   way of achieving this is to establish IPsec SAs to the Cloud DC
   gateway to carry the sensitive data to/from the store.

   The granularity of the IPsec SAs for Homogeneous Encryption can be
   per site, per subnet, per tenant, or per address. Once the IPsec
   SA is established for a specific subnet/tenant/site, all traffic
   to/from the subnet/tenant/site is encrypted.

                      +--------------|RR |------------+
                     /  Untrusted    +-+-+             \
                    /                                   \
                   /                                     \
     +----+  +---------+                             +------+  +----+
     | CN3|--|         P1-----+ -------------+------ P1     |--| CN3|
     +----+  | C-PE1   P2-----+              |       | C-PE2|  +----+
     +----+  |         P3-----+     Wide     +------ P2     |  +----+
     | CN2|--|         |      |     area     +------ P3     |--| CN1|
      +-+--+  +---------+      |   network    |       +------+  +-+--+
        \                     |              |                  /
         \   +---------+      | all packets  |       +------+  /
          +--|         P1-----+ encrypted    +------ P1     |-+
              | C-PE3   P2-----+     by       |       | C-PE4|
     +----+  |         P3-----+ IPsec SAs    +------ P2     |  +----+
      | CN1|--|         P4-----+--------------+       |      |--| CN2|
      +----+  +---------+                             +------+  +----+

   CN: Client Networks, which is same as Tenant Networks used by NVo3

                Figure 2: Homogeneous Encrypted SD-WAN

Dunbar, et al.                                               [Page 10]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   One of the properties of Homogeneous Encryption is that the SD-WAN
   Local Network Controller, e.g., RR in BGP-controlled SD-WAN, might
   be connected to C-PEs via an untrusted public network, therefore,
   requiring a secure connection between RR and C-PEs.

   A Homogeneous Encrypted SD-WAN shares certain characteristics with
   the widely deployed IPsec VPN. However, while IPsec VPNs typically
   operate in a point-to-point manner among a limited number of
   nodes, SD-WAN networks can comprise a large number of edge nodes
   and a centralized controller responsible for managing
   configurations across these nodes.

   Existing private VPNs (e.g., MPLS based) can use Homogeneous
   Encrypted SD-WAN to extend over the public network to remote sites
   to which the VPN operator does not own or lease infrastructural

3.3. Scenario #2: Differential Encrypted SD-WAN

   The Differential Encrypted SD-WAN refers to an SD-WAN network in
   which traffic over the existing VPN is forwarded natively without
   encryption, and the traffic over the Public Internet is encrypted.
   Differential Encrypted SD-WAN is over hybrid private VPN and
   public Internet underlays. Since IPsec requires additional
   processing power and the encrypted traffic over the Internet does
   not have the premium SLA (Service Lever Agreement) commonly
   offered by Private VPNs, especially over a long distance, current
   practice is for traffic over a private VPN to be forwarded without

   One C-PE might have the Internet-facing WAN ports managed by
   different NSPs with the WAN ports' addresses assigned by the
   corresponding NSPs. Clients might have policies to specify:

   1) Some flows can only be forwarded over private VPNs.
   2) Some flows can be forwarded over either private VPNs or the
     public Internet. The packets over the public Internet are
   3) Some flows, especially Internet-bound browsing ones, can be
     handed off to the Internet without further encryption.

   Suppose a flow traversing multiple segments, such as A<->B, B<->C,
   C<->D, has Policy 2) above. The flow can cross different underlays
   in different segments, such as over Private underlay between A<->B
   without encryption or over the public Internet between B<->C
   protected by an IPsec SA.

Dunbar, et al.                                               [Page 11]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   As shown in the figure below, C-PE-1 has two different types of
   interfaces (A1 to Internet and A2 & A3 to VPN). The C-PE's
   loopback address and the attached client addresses may or may not
   be visible to the NSPs. The WAN ports' addresses can be allocated
   by the service providers or dynamically assigned (e.g., by DHCP).

                        +--------------|RR |----------+
                       /  Untrusted    +-+-+           \
                      /                                 \
                     /                                   \
     +----+  +---------+  packets encrypted over     +------+  +----+
     | CN3|--|         A1-----+ Untrusted    +------ B1     |--| CN1|
     +----+  | C-PE1   A2-\                          | C-PE2|  +----+
     +----+  |         A3--+--+              +---+---B2     |  +----+
     | CN2|--|         |   |PE+--------------+PE |---B3     |--| CN3|
     +----+  +---------+   +--+   trusted    +---+   +------+  +----+
                              |      WAN     |
     +----+  +---------+   +--+   packets    +---+   +------+  +----+
     | CN1|--|         C1--|PE| go natively  |PE |-- D1     |--| CN1|
     +----+  | C-PE3   C2--+--+ without encry+---+   | C-PE4|  +----+
             |         |      +--------------+       |      |
             |         |                             |      |
     +----+  |         |      without encrypt over   |      |  +----+
     | CN2|--|         C3--+---- Untrusted  --+------D2     |--| CN2|
     +----+  +---------+                             +------+  +----+

     CN: Client Network
                Figure 3: SD-WAN with Hybrid Underlays

     Also, the connection between C-PEs and their Controller (RR)
     might be via the untrusted public network. It is necessary to
     have secure channel for communication between RR and C-PEs.

     There could be multiple SD-WAN edges (C-PEs) sharing common
     property, such as a geographic location. Some applications over
     SD-WAN may need to traverse specific geographic areas for
     various reasons, such as to comply with regulatory rules, to
     utilize specific value-added services, or others.

     Services may not be congruent, i.e., the packets from A-> B may
     traverse one underlay network, and the packets from B -> A may
     go over a different underlay.

Dunbar, et al.                                               [Page 12]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

3.4. Scenario #3: Private VPN PE based SD-WAN

   This scenario refers to an existing VPN (e.g., EVPN[RFC7432] or
   IPVPN) being expanded by adding extra ports facing the public
   Internet to accommodate any additional bandwidth requirement
   between two PEs.

   Here are some differences from the Hybrid Underlay scenario
   (Section 3.3):

       - For MPLS-based VPN, PEs would have MPLS as payload
          encapsulated within the IPsec tunnel egressing the Internet
          WAN ports, MPLS-in-IP/GRE-in-IPsec.
       - The BGP RR is connected to PEs in the same way as the VPN,
          i.e., via a trusted network.

   PE-based SD-WAN can be used by VPN service providers to
   temporarily increase bandwidth between sites when not sure if the
   demand will sustain for an extended period or as a temporary
   solution prior to building or leasing a permanent infrastructure.

                         //        +---+
                        //          ^
                       //           || VPN
                      //     VPN    v
                      |PE1| <====> |RR| <=>   |PE3|
                      +-+-+        +--+       +-+-+
                        |                       |
                        +--- Public Internet -- +

          Figure 4: Additional Internet paths added to the VPN

     For Ethernet-based client traffic, Private VPN PE based SD-WAN
     should support VLAN-based service interfaces (EVPN Instances),
     VLAN bundle service interfaces, or VLAN-Aware bundling service
     interfaces. EVPN service requirement as described in Section 3.1
     of [RFC8388] are applicable to the SD-WAN Ethernet-based Client
     services. For IP-based client interfaces, L3VPN service
     requirements are applicable.

Dunbar, et al.                                               [Page 13]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

4. Provisioning Model

4.1. Client Service Provisioning Model

   Client service provisioning can follow the same approach as MPLS
   VRFs (Virtual Routing and Forwarding) [RFC4364][RFC4659]. A client
   VPN can establish the communication policy by specifying the BGP
   Route Targets to be imported and exported. Alternatively,
   conventional Match and Action ACLs (Access Control List) can
   identify the specific routes allowed or denied to or from the
   client VPN.

   When an SD-WAN edge node is dedicated to one client with a single
   virtual network, all prefixes attached to the client port(s) on
   the edge node can be considered to be inside a single VRF, and the
   RR can manage the policies for import/export policies for that

4.2. Policy Configuration

   One of the characteristics of an SD-WAN service is that packets
   can be forwarded over multiple types of underlays. Policies are
   needed to govern which underlay paths can carry a flow, as
   described by Section 8 of [MEF70.1]. A flow is a collection of
   packets between the same source and destination pair that are
   subject to the same forwarding and policy decisions at the ingress
   SD-WAN edge node, and are identified by the settings of one or
   more fields in the packet headers. For example, client-prefix-x
   can only be mapped to a MPLS topology.

4.3. IPsec Related Parameters Provisioning

   SD-WAN edge nodes must negotiate various cryptographic parameters
   to establish IPsec tunnels between them. Alternatively, the edges
   can retrieve the attribute values from their controller, thereby
   streamlining the configuration process. In the context of a BGP-
   controlled SD-WAN, BGP UPDATE messages can be extended to
   propagate the IPsec-related attribute values for each node,
   facilitating peer selection of mutually supported values-instead
   of the process facilitated by IPsec IKEv2 [RFC7296].

Dunbar, et al.                                               [Page 14]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

5. BGP Controlled SD-WAN

5.1. Why BGP as Control Plane for SD-WAN?

   In the case of a modest-sized SD-WAN network with a limited number
   of nodes, the hub-and-spoke model, employing Next Hop Resolution
   Protocol (NHRP)[RFC2332] or a centralized hub managing edge nodes,
   including the mapping of local and public addresses along with
   tunnel identifiers, has proven effective. However, when dealing
   with a larger SD-WAN network, exceeding 100 nodes and encompassing
   diverse underlays, the conventional approach becomes notably
   intricate, convoluted, and susceptible to errors.

   Here are some of the compelling reasons for using BGP:

   -  Simplified peer authentication process:

     With a secure management channel established between an edge
     node and an RR, the RR can perform peer authentication on behalf
     of the edge node. The RR has policies on peer communication and
     the built-in capability to constrain the propagation of the
     UPDATE messages to the authorized edge nodes [RFC4684].

   - Scalable IPsec tunnel management

     When multiple IPsec tunnels are established between two edge
     nodes, BGP Tunnel Attribute Update can associate multiple IPsec
     tunnels with the client prefixes. In an IPsec VPN, separate
     IPsec Tunnels between two edge nodes are treated as parallel
     links requiring duplicated control plane messages exchanged on
     all those parallel tunnels if the client prefixes need be load
     shared among the IPsec tunnels.

   - Simplified IPsec tunnel traffic selection configurations

     The IPsec tunnel's traffic selector or admission control can be
     inherently realized by specifying importing/exporting the Route
     Targets representing the SD-WAN VPNs.

5.2. BGP Walk Through for Homogeneous Encrypted SD-WAN

   For the BGP-controlled Homogeneous Encrypted SD-WAN, a C-PE can
   advertise its attached client prefixes and the properties of the
   IPsec SA in one BGP UPDATE message.

   In the figure below, the BGP UPDATE message from C-PE2 to RR can
   have the client prefixes encoded in the MP-NLRI Path Attribute and

Dunbar, et al.                                               [Page 15]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   the IPsec Tunnel associated information encoded in the Tunnel-
   Encapsulation [RFC9012] Attributes.

                        +---------|RR |----------+
                       / Untrusted+---+           \
                      /                            \
                     /                              \
             +---------+                       +---------+
           --+         |-----------------------|         |-
             |         |                       | C-PE2   |- VLAN = 15
             | C-PE1   |                     +-||
           --||                     | |         |-
             +---------+                     | +---------+
             +---------+                     |
           --|         |---------------------+
             |         |
             | C-PE3   |
                Figure 5: Homogeneous Encrypted SD-WAN

   Alternatively, the C-PE2 can use two separate BGP UPDATE messages:

  - Update 1 for advertising the attached client prefixes.
  - Update 2 for advertising the underlay properties.

   This approach significantly reduces the size of BGP UPDATE
   messages, especially for IPsec tunnels terminated at edge nodes or
   WAN ports. IPsec SA tunnels have various attributes that may
   change at frequencies different from those of client prefix
   updates, such as periodic changes in IPsec SA nonce. Furthermore,
   multiple client prefixes can be transported over a single underlay
   IPsec SA tunnel.

   When using two separate BGP UPDATE messages, which is described by
   Section 4 and 8 of [RFC9012], UPDATE U1 has its Nexthop to the
   node loopback address and is recursively resolved to the IPsec SA
   tunnel type advertised by the UPDATE U2.

   Here are the details of the UPDATE messages:

     - Suppose that a given packet, denoted as "C", destined towards
       the client addresses attached to C-PE2 (e.g., prefix

Dunbar, et al.                                               [Page 16]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024 can be carried by any IPsec tunnels terminated
       at C-PE2.
     - The path along which "C" is to be forwarded is determined by
       BGP UPDATE U1.
     - UPDATE U1 does not have a Tunnel Encapsulation attribute.
     - UPDATE U1 can include the Encapsulation Extended Community
       with the option to have the Color Extended Community.
     - The address of the next-hop of UPDATE U1 is router C-PE2.
     - UPDATE U2 is for advertising the SD-WAN underlay path that has
       a Tunnel Encapsulation attribute to describe the IPsec SA
       detailed attributes.

   UPDATE U1 (client prefix advertisement):

     - MP-NLRI Path Attribute:
     - Nexthop: (C-PE2)
     - Encapsulation Extended Community: TYPE = IPsec

     Note: The IPsec Tunnel Type specified in RFC5566 is obsolete. A
     new tunnel type is needed to represent the IPsec Tunnel underlay

   UPDATE U2 (Underlay tunnel advertisement):
     - MP-NLRI Path Attribute: (C-PE2)
     - Tunnel Encapsulation Path Attributes for IPsec SA detailed
     attributes, including the WAN address to be used as the IP
     address of the IPsec encrypted packets.

   If different client prefixes attached to C-PE2 need to be reached
   by separate underlay IPsec tunnels, the Color Extended Community
   [RFC9012] can be used to associate the prefixes with the tunnels.
   See Section 8 of [RFC9012].

   Suppose C-PE2 does not have a policy on the authorized peers for
   the specific client prefixes. Then, the RR then needs to check the
   client prefixes' policies to constrain the BGP UPDATE message
   propagation only to the remote authorized edge nodes.

Dunbar, et al.                                               [Page 17]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

5.3. BGP Walk Through for Differential Encrypted SD-WAN

   In this scenario, some client prefixes can be forwarded over any
   one of the tunnels terminating at the edge node. Some client
   prefixes can only be forwarded over specific tunnels (such as only

   An edge node can use the Color Extended Community (Section 4 & 8
   of [RFC9012]) in its BGP UPDATE message to associate the client
   prefixes with the specific tunnels.

   For example, in Figure 5 above, suppose that Route
   can be carried by either MPLS or IPsec and Route can
   only be carried by MPLS; C-PE2 can use the following UPDATE

   UPDATE #1a for the client prefix

     - MP-NLRI Path Attribute:
         Nexthop: (C-PE2)
     - Encapsulation Extended Community: TYPE = IPsec
     - Color Extended Community: RED

   UPDATE #1b for the client prefix
     - MP-NLRI Path Attribute:
         Nexthop: (C-PE2)
     - Encapsulation Extended Community: TYPE = MPLS [RFC8365]

   UPDATE #2: for the underlay IPsec tunnel terminated at the node:
     - MP-NLRI Path Attribute: (C-PE2)
     - Tunnel Encapsulation Path Attributes: TYPE=SD-WAN-Hybrid
      Including the information about the WAN ports for receiving
      IPsec encrypted packets, the IPsec properties, etc.
     - Color Extended Community: RED

Dunbar, et al.                                               [Page 18]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

5.4. BGP Walk Through for Application Flow-Based Segmentation

   Suppose an application flow is identified by source or destination
   IP addresses. Application Flow-based Segmentation described in
   3.1.2 can be realized by constraining the BGP UPDATE messages,
   such that only the nodes that meet the criteria of the application
   flow receive these updates. The following BGP Update messages can
   be advertised to ensure that the Payment Application only
   communicates with the Payment Gateway shown in Figure 6:

   BGP UPDATE #1a from C-PE2 to RR for the P2P topology that is only
   propagated to Payment GW node:

      - MP-NLRI Path Attribute:
            - Nexthop:
      - Encapsulation extended community: TYPE = IPsec
      - Color Extended Community: BLUE

   BGP UPDATE #1b from C-PE2 to RR is propagated to C-PE1 & C-PE3 for
   the prefixes to be reached by C-PE1 and C-PE3:

      - MP-NLRI Path Attribute:
            - Nexthop:
       - Encapsulation extended community: TYPE =IPsec
       - Color Extended Community: RED

   BGP UPDATE #2a for the underlay IPsec Tunnel Path attributes
   terminated at C-PE2 that are propagated to C-PE1 & C-

     - MP-NLRI Path Attribute: (C-PE2)
     - Tunnel Encapsulation Path Attributes: TYPE=IPsec (for all
     IPsec SAs)
     - Color Extended Community: RED

   UPDATE #2b for the IPsec SA to the Payment GW that is only
   propagated to Payment GW:
     - MP-NLRI Path Attribute:

Dunbar, et al.                                               [Page 19]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024
     - Tunnel Encapsulation Path Attributes: TYPE=IPsec (for the
     IPsec SA to Payment GW).
     - Color Extended Community: Blue

                       +------->|  GW   |<----+
                      /         +-------+      \
                     /        Blue Tunnel       \
                    /for Payment App:\
                   /                              \
           +------/--+                        +----\----+
         --|-----+   |                        |     +---|
           |         |     Red Tunnels        |         |
         --| C-PE1   |------------------------|         |-
           ||                        |  C-PE2  |
         --|         |------------------------||-
           |   ------+                       +|         |- VLAN=25;
                                            / |         |
           +---------+                     /  +---------+
         --|         |--------------------+
           | C-PE3   |                   /
           ||                  /
         --|         |-----------------+
         Figure 6: Application Based SD-WAN Segmentation

5.5. Benefit of Using Recursive Next Hop Resolution

   Using the Recursive Next Hop Resolution described in Section 8 of
   [RFC9012], the clients' route UPDATE messages become very compact,
   and any attribute changes of the underlay network tunnels, such as
   IPsec key refreshing, can be advertised independently of the
   client prefixes update. This method is handy when the underlay
   paths are IPsec tunnels, which requires periodic message exchange
   for the pairwise re-keying process.

6. SD-WAN Forwarding Model

   This section describes how client traffic is forwarded in BGP
   Controlled SD-WAN for the use cases described in Section 3.

Dunbar, et al.                                               [Page 20]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   The procedures described in Section 6 of RFC8388 are applicable
   for the SD-WAN client traffic. Like the BGP-based VPN/EVPN client
   prefixes UPDATE message, Route Target can distinguish routes from
   different clients.

6.1. Forwarding Model for Homogeneous Encrypted SD-WAN

6.1.1. Network and Service Startup Procedures

   A single IPsec security association (SA) protects data in one
   direction. In the Homogeneous Encrypted SD-WAN Scenario, two SAs
   must be present to secure traffic in both directions between two
   C-PE nodes, two client ports, or two prefixes. Using Figure 2 of
   Section 3.2 as an example, for client CN2 attached to C-PE1, C-
   PE3, and C-PE4 to have a full-mesh connection, six one-directional
   IPsec SAs must be established: C-PE1 <-> C-PE3; C-PE1 <-> C-PE4;
   C-PE3 <-> C-PE4.

   SD-WAN services to clients can be IP-based or Ethernet-based. An
   SD-WAN edge can learn client prefixes from the client-facing ports
   via OSPF, RIP, BGP, or static configuration for its IP-based
   services. For Layer-2 SD-WAN services, the relevant EVPN
   parameters, such as the ESI (Ethernet Segment Identifier), EVI,
   and CE-VID (Customer Edge Virtual Instance Identifier) to EVI
   mapping, can be configured similarly to EVPN described in RFC8388.

   Instead of running IGP within each IPsec tunnel done by the IPsec
   VPN, BGP RR can propagate UPDATE messages of the client prefixes
   attached to an SD-WAN edge node to its authorized peers.

   The controller manages how clients' routes are associated with
   individual IPsec SA. Therefore, it is no longer necessary to
   manually configure the IPsec tunnel's endpoint addresses on each
   SD-WAN edge node and set up policies for the allowed client

6.1.2. Packet Walk-Through

   For unicast packets forwarding:

     An IPsec SA terminated at a C-PE node can have multiple client
     prefixes multiplexed in the IPsec SA (or tunnel). Packets
     to/from the client prefixes are encapsulated in an inner tunnel,
     such as GRE or VxLAN. Different client traffic can be
     differentiated by a unique value in the inner encapsulation key
     or ID field. The GRE or VxLAN tunnel is encapsulated by an outer
     IP header whose destination & source addresses are the C-PE

Dunbar, et al.                                               [Page 21]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

     nodes loopback addresses and most likely has the Protocol-code =
     ESP (50).

     C-PE Node-based IPsec tunnel is inherently protected when the C-
     PE has multiple WAN ports to different underlay paths. As shown
     in Figure 2, when one of the underlay paths fails, the IPsec
     traffic can be forwarded to or received from a different
     physical port.

     When a C-PE receives an IPsec encrypted packet from its WAN
     ports, it decrypts the packet and forwards the inner packet to
     the client port based on the inner packet's destination address.

   For multicast packets forwarding:

     IPsec was created to be a security protocol between two and only
     two devices, so multicast service using IPsec is problematic. An
     IPsec peer encrypts a packet so that only one other IPsec peer
     can successfully perform the de-encryption. A straightforward
     way to forward a multicast packet for the Homogeneous Encrypted
     SD-WAN is to encapsulate the multicast packet in separate
     unicast IPsec SA tunnels. More optimized forwarding multicast
     packets for the Homogeneous Encrypted SD-WAN is out of the scope
     of this document.

6.2. Forwarding Model for Hybrid Underlay SD-WAN

   In this scenario, as shown in Figure 3 of Section 3.3, traffic
   forwarded over the trusted VPN paths can be native (i.e.,
   unencrypted). The traffic forwarded over untrusted networks need
   to be protected by IPsec SA.

6.2.1. Network and Service Startup Procedures

   Infrastructure setup: The proper MPLS infrastructure must be
   configured among the edge nodes, i.e., the C-PE1/C-PE2/C-PE3/C-PE4
   of Figure 3. The IPsec SA between wAN ports or nodes must be set
   up as well. IPsec SA related attributes on edge nodes can be
   distributed by BGP UPDATE messages as described in Section 5.

   There could be policies governing how flows can be forwarded, as
   specified by [MEF70.1].  For example, "Private-only" indicates
   that the flows can only traverse the MPLS VPN underlay paths.

Dunbar, et al.                                               [Page 22]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

6.2.2. Packet Walk-Through

   For unicast packets forwarding:

     When the C-PE-a in Figure 7 receives a packet from a client
     port, if the packet belongs to a flow that can only be forwarded
     over the MPLS VPN, the forwarding processing is the same as the
     MPLS VPN. Otherwise, the C-PE node can make the local decision
     in choosing the least cost path, including the previously
     established MPLS paths and IPsec Tunnels, to forward the packet.
     Packets forwarded over the trusted MPLS VPN can be native
     without additional encryption, while the packets sent over the
     untrusted networks must be encrypted by IPsec SA.

     For a c-PE with multiple WAN ports provided by different NSPs,
     separate IPsec SAs can be established for the different WAN
     ports. In this case, the C-PE have multiple IPsec tunnels in
     addition to the MPLS path to choose from to forward the packets
     from the client ports.

     If the IPsec SA is chosen, the packet is encapsulated by the
     IPsec header and encrypted by the IPsec SA before forwarding it
     to the WAN.

     For packets received from an MPLS path, processing is the same
     as MPLS VPN.

     For IPsec SA encrypted packets received from the WAN ports, the
     packets are decrypted, and the inner payload is decapsulated and
     forwarded per the forwarding table of the C-PE. For all packets
     from the Internet-facing WAN ports, the additional anti-DDoS
     mechanism has to be enabled to prevent potential attacks from
     the Internet-facing ports. The anti-DDoS mechanism comprises
     numerous components, and their detailed discussion is beyond the
     scope of this document. Control Plane should not learn routes
     from the Internet-facing WAN ports.

Dunbar, et al.                                               [Page 23]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

                        +--------------|RR |----------+
                       /               +-+-+           \
                      /                                 \
                     /                                   \
     +----+  +---------+  packets encrypted over    +---------+  +----+
     | CN3|--|         A1-----+ Untrusted    +----- B1        |--| CN1|
     +----+  | C-PE-a  A2-----+              +------B2 C-PE-b |  +----+
             ||                            ||
     +----+  |         A3  |PE+--------------+PE |--B3        |--| CN3|
     +----+  +---------+   +--+   trusted    +---+  +---------+  +----+
                              |     VPN      |
                      Figure 7: Over hybrid SD-WAN

   For multicast packets forwarding:

     For multicast traffic, MPLS multicast [RFC6513, RFC6514, or
     RFC7988] can be used to forward multicast traffic.

     If IPsec tunnels are chosen for a multicast packet, the packet
     is encapsulated and encrypted by multiple separate IPsec tunnels
     to the desired destinations.

6.3. Forwarding Model for PE based SD-WAN

6.3.1. Network and Service Startup Procedures

   In this scenario, all PEs have secure interfaces facing the
   clients and facing the MPLS backbone, with some PEs having extra
   ports to the untrusted public Internet. The public Internet paths
   are for offloading low priority traffic when the MPLS paths get
   congested. The PEs are already connected to their RRs, and the
   configurations for the clients and policies are already

6.3.2. Packet Walk-Through

   For PEs to offload some MPLS packets to the Internet path, each
   MPLS packet is wrapped by an outer IP header as MPLS-in-IP or
   MPLS-in-GRE [RFC4023]. The outer IP address can be an interface
   address or the PE's loopback address.

   When IPsec Tunnel mode is used to protect an MPLS-in-IP packet,
   the entire MPLS-in-IP packet is placed after the IPsec tunnel

   When IPsec transport mode is used to protect the MPLS packet, the
   MPLS-in-IP packet's IP header becomes the outer IP header of the

Dunbar, et al.                                               [Page 24]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   IPsec packet, followed by an IPsec header, and then followed by
   the MPLS label stack. The IPsec header must set the payload type
   to MPLS by using the IP protocol number specified in section 3 of

   If IPsec transport mode is applied to an MPLS-in-GRE packet, the
   GRE header follows the IPsec header.

   The IPsec SA's endpoints should not be the client-facing interface
   addresses unless the traffic to/from those clients always goes
   through the IPsec SA even when the MPLS backbone has enough
   capacity to transport the traffic.

   When the PEs' Internet-facing ports are behind the NAT [RFC3715],
   an outer UDP field can be added outside the encrypted payload
   [RFC3948]. Three UDP ports must be open on the PEs: UDP port 4500
   (used for NAT traversal), UDP port 500 (used for IKE), and IP
   protocol 50 (ESP). IPsec IKE (Internet Key Exchange) between the
   two PEs would be over the NAT [RFC3947] as well.

   Upon receiving a packet from a client port, the forwarding
   processing is the same as the MPLS VPN. If the MPLS backbone path
   to the destination is deemed congested, the IPsec tunnel towards
   the target Pes is used to encrypt the MPLS-in-IP packet.

   Upon receiving a packet from the Internet-facing WAN port, the
   packet is decrypted, and the inner MPLS payload is extracted to be
   sent to the MPLS VPN engine.

   Same as Scenario #2, the additional anti-DDoS mechanism must be
   enabled to prevent potential attacks from the Internet-facing
   port. Control Plane should not learn routes from the Internet-
   facing WAN ports.

7. Manageability Considerations

     BGP-controlled SD-WAN utilizes the BGP RR to facilitate the
     routes and underlay properties distribution among the authorized
     edge nodes. With RR having the preconfigured policies about the
     authorized peers, the peer-wise authentications of the IPsec IKE
     (Internet Key Exchange) are significantly simplified.

8. Security Considerations

   Adding an Internet-facing WAN port to a C-PE can introduce the
   following security risks:

Dunbar, et al.                                               [Page 25]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   1) Potential DDoS attacks from the Internet-facing ports.

   2) Potential risk of malicious traffic being injected via the
   Internet-facing WAN ports.

   3) For the Differential Encrypted SD-WAN deployment model, there
   is a risk of unauthorized traffic injected into the Internet-
   facing WAN ports being leaked to the L2/L3 VPN networks.

   Therefore, the additional anti-DDoS mechanism must be enabled on
   all Internet-facing ports to prevent potential attacks from those
   ports. Control Plane should not learn any routes from the
   Internet-facing WAN ports.

   In SD-WAN deployments where no secure management channel exists
   between the SD-WAN controller and the SD-WAN edges, TLS or IPsec
   can be established to bridge the gap. BGP is a TCP-based protocol
   that can be easily aligned with TLS-based security.

9. IANA Considerations

       No Action is needed.

10. References

10.1. Normative References

   [BCP195]  Consists of RFC8996 and RFC9325.

   [RFC2332] J. Luciani, et al, "NBMA Next Hop Resolution Protocol
             (NHRP)", RFC2332, April 1998.

   [RFC2784] D. Farinacci, et al, "Generic Routing Encapsulation
             (GRE)" RFC2784, March 2000.

   [RFC3715] B. Aboba, W. Dixon, "IPsec-Network Address Translation
             (NAT) Compatibility Requirements", March 2004.

Dunbar, et al.                                               [Page 26]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   [RFC3947] T. Kivinen, et al, "Negotiation of NAT Traversal in the
             IKE", Jan. 2005.

   [RFC3948] A. Huttunen, et al, "UDP Encapsulation of IPsec ESP
             Packets", Jan 2005.

   [RFC4023] T. Worster, Y. Rekhter, E. Rosen, "Encapsulating MPLS in
             IP or Generic Routing Encapsulation (GRE)", March 2005.

   [RFC4360] S. Sangli, et al, "BGP Extended Communities Attribute",
             RFC4360, Feb. 2006.

   [RFC4364] E. Rosen, Y. Rekhter, "BGP/MPLS IP Virtual Private
             networks (VPNs)", Feb 2006.

   [RFC4456] T. Bates, E. Chen, R. Chandra, "BGP Route Reflection: An
             Alternative to Full Mesh Internal BGP (IBGP)", April

   [RFC4659] J. De clercq, et al, "BGP-MPLS IP Virtual Private
             Network (VPN) Extension for IPv6 VPN", RFC4659, Sept

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

   [RFC4762] M. Lasserre and V. Kompella, "Virtual Private LAN
             Service (VPLS) Using Label Distribution Protocol (LDP)
             Signaling", RFC4762, Jan. 2007.

   [RFC4684] P. Marques, et al, "Constrained Route Distribution for
             BGP/MPLS IP VPNs", November 2006.

   [RFC6071] S. Frankel, S. Krishan, "IP Security (IPsec) and
             Internet Key Exchange (IKE) Document Roadmap", Feb 2011.

   [RFC7296] C. Kaufman, et al, "Internet Key Exchange Protocol
             Version 2 (IKEv2)", Oct 2014.

Dunbar, et al.                                               [Page 27]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   [RFC7348] M. Mahalingam, et al, "Virtual eXtensible Local Area
             Network (VXLAN): A Framework for Overlaying Virtualized
             Layer 2 Networks over Layer 3 Networks", RFC7348, Aug

   [RFC7432] A. Sajassi, et al, "BGP MPLS-Based Ethernet VPN",
             RFC7432, Feb 2015.

   [RFC8200] S. Deering and R. Hinden, "Internet Protocol, Version 6
             (IPv6) Specification". July 2017.

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

   [RFC8388] J. Rabadan, et al, "Usage and Applicability of BGP MPLS-
             Based Ethernet VPN", RFC8388, May 2018.

   [RFC9012] K.Patel, et al "The BGP Tunnel Encapsulation Attribute",
             RFC9012, April 2021.

   [RFC9522] A. Farrel, "Overview and Principles of Internet Traffic
             Engineering", RFC9522, Jan. 2024.

10.2. Informative References

   [Net2Cloud-Problem] L. Dunbar and A. Malis, "Dynamic Networks to
             Hybrid Cloud DCs: Problems and Mitigation Practices",
             draft-ietf-rtgwg-net2cloud-problem-statement-37, March.

   [IEEE802.3] "IEEE Standard for Ethernet" by The Institute of
             Electrical and Electronics Engineers (IEEE) 802.3.

   [MEF70.1] SD-WAN Service Attributes and Service Framework,
             attributes-and-service-framework/. Nov 2021.

Dunbar, et al.                                               [Page 28]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

   [MEF70.2] "SD-WAN Service Attributes and Service Framework" by
             service-attributes-and-service-framework/. Oct 2023.

11. Acknowledgments

   Acknowledgements to Andrew Alston, Adrian Farrel, Jim Guichard,
   Joel Halpern, John Scudder, Darren Dukes, Andy Malis, Donald
   Eastlake, Stephen Farrell, and Victo Sheng for their review and

   This document was prepared using

Dunbar, et al.                                               [Page 29]

Internet-Draft           BGP Usage for SD-WAN           April 5, 2024

Authors' Addresses

   Linda Dunbar

   Ali Sajassi

   John Drake

   Basil Najem
   Bell Canada

Contributor's Addresses

   David Carrel

   Ayan Banerjee

Dunbar, et al.                                               [Page 30]