| Internet-Draft | SDWAN Edge Discovery | October 2023 |
| Dunbar, et al. | Expires 5 April 2024 | [Page] |
The document describes the encoding of BGP UPDATE messages for the SD-WAN edge node property discovery.¶
In the context of this document, BGP Route Reflector (RR) is the component of the SD-WAN Controller that receives the BGP UPDATE from SD-WAN edges and in turns propagates the information to the intended peers that are authorized to communicate via the SD-WAN overlay network.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
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 https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 5 April 2024.¶
Copyright (c) 2023 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
[SD-WAN-BGP-USAGE] illustrates how BGP [RFC4271] is used as a control plane for a SD-WAN network. SD-WAN network refers to a policy-driven network over multiple heterogeneous underlay networks to get better WAN bandwidth management, visibility, and control.¶
The document describes BGP UPDATE messages for an SD-WAN edge node to advertise its properties to its RR which then propagates that information to the authorized peers.¶
The following acronyms and terms are used in this document:¶
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 [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The objectives of SD-WAN edge discovery are for an SD-WAN edge node to discover its authorized peers and their associated properties to establish secure overlay tunnels [Net2Cloud]. The attributes to be propagated includes:¶
Some SD-WAN peers are connected by both trusted VPNs and untrusted public networks. Some SD-WAN peers are connected only by untrusted public networks. For the traffic over untrusted networks, IPsec Security Associations (IPsec SA) must be established and maintained. If an edge node has network ports behind a NAT, the NAT properties need to be discovered by the authorized SD-WAN peers.¶
Like any VPN networks, the attached client routes belonging to specific SD-WAN VPNs can only be exchanged with the SD-WAN peer nodes authorized to communicate.¶
A pure IPsec VPN has IPsec tunnels connecting all edge nodes over public networks. Therefore, it requires stringent authentication and authorization (i.e., IKE Phase 1) before other properties of IPsec SA can be exchanged. The IPsec Security Association (SA) between two untrusted nodes typically requires the following configurations and message exchanges:¶
Establish IPsec SA:¶
Attached client prefixes discovery, which is achieved by:¶
In a BGP-controlled SD-WAN network over hybrid MPLS VPN and public internet underlay networks, all edge nodes and RRs are already connected by private secure paths. The RRs have the policies to manage the authentication of all peer nodes. More importantly, when an edge node needs to establish multiple IPsec tunnels to many edge nodes, all the management information can be multiplexed into the secure management tunnel between RR and the edge node. Therefore, the amount of authentication in a BGP-Controlled SD-WAN network can be significantly reduced.¶
Client VPNs are configured via VRFs, just like the configuration of the existing MPLS VPN. The IPsec equivalent traffic selectors for local and remote routes are achieved by importing/exporting VPN Route Targets. The binding of client routes to IPsec SA is dictated by policies. As a result, the IPsec configuration for a BGP controlled SD-WAN (with mixed MPLS VPN) can be simplified:¶
BGP UPDATE: Announces the client route reachability for all permitted parallel tunnels/paths.¶
As described in [SD-WAN-BGP-USAGE], two separate BGP UPDATE messages are used for SD-WAN Edge Discovery:¶
In the following figure, four overlay paths between C-PE1 and C-PE2 are established for illustration purpose. More overlay paths are possible. One physical port on C-PE2 can terminate multiple overlay paths from different ports on C-PE1.¶
+---+
+--------------|RR |----------+
/ Untrusted +-+-+ \
/ \
/ \
+---------+ MPLS Path +-------+
11.1.1.x| C-PE1 A1-------------------------------B1 C-PE2 |10.1.1.x
| | | |
21.1.1.x| A2(192.10.0.10)------( 192.0.0.1)B2 |20.1.1.x
| | | |
| Addr A3(160.0.0.1) --------(170.0.0.1)B3 Addr |
| 1.1.1.1 | |2.2.2.2|
+---------+ +-------+
C-PE2 advertises the attached client routes as below:¶
The basic scheme of SD-WAN edge node discovery using BGP consists of the following:¶
For an SD-WAN deployment with multiple RRs, it is assumed that there are secure connections among those RRs. How secure connections are established among those RRs is out of the scope of this document. The existing BGP UPDATE propagation mechanisms control the edge properties propagation among the RRs.¶
For some environments where the communication to RR is highly secured, [RFC9016] IKE-less can be deployed to simplify IPsec SA establishment among edge nodes.¶
In SD-WAN deployment, SD-WAN Segmentation is a frequently used term, referring to partitioning a network into multiple subnetworks, just like MPLS VPNs. SD-WAN Segmentation is achieved by creating SD-WAN virtual topologies and SD-WAN VPNs. An SD-WAN virtual topology consists of a set of edge nodes and the tunnels (a.k.a. underlay paths), including both IPsec tunnels and/or MPLS VPN tunnels, interconnecting those edge nodes.¶
An SD-WAN VPN is configured in the same way as the VRFs of an MPLS VPN. One SD-WAN client VPN can be mapped to multiple SD-WAN virtual topologies. SD-WAN Controller governs the policies of mapping a client VPN to SD-WAN virtual topologies.¶
Each SD-WAN edge node may need to support multiple VPNs. Route Target is used to differentiate the SD-WAN VPNs. For example, in the picture below, the Payment-Flow on C-PE2 is only mapped to the virtual topology of C-PEs to/from Payment Gateway, whereas other flows can be mapped to a multipoint-to-multipoint virtual topology.¶
+---+
+--------------|RR |----------+
/ Untrusted +-+-+ \
/ \
/ \
+---------+ MPLS Path +-------+
11.1.1.x| C-PE1 A1-------------------------------B1 C-PE2 |10.1.1.x
| | | |
21.1.1.x| A2(192.10.0.10)------( 192.0.0.1)B2 |20.1.1.x
| | | |
| Addr A3(160.0.0.1) --------(170.0.0.1)B3 Addr |11.2.2.x
| 1.1.1.1 | / |2.2.2.2|
+---------+ / +-------+
\ /
\ /PaymentFlow
\ /
\ +----+----+
+---------------| payment |
| Gateway |
+---------+
BGP has a built-in mechanism [RFC4684] to dynamically achieve the constrained distribution of edge information. In a nutshell, an SD-WAN edge sends RT Constraint (RTC) NLRI to the RR for the RR to install an outbound route filter, as shown in the figure below:¶
RT Constraint RT constraint
NLRI={SD-WAN#1, SD-WAN#2} NLRI={SD-WAN#1, SD-WAN#3}
-----> +---+ <-----------
+--------------------|RR1|------------------+
| Outbound Filter +---+ Outbound Filter |
| Permit SD-WAN#1,#2 Permit SD-WAN#1,#3|
| Deny all Deny all |
| <------- ---------> |
| |
+-----+---+ MPLS Path +-----+-+
11.1.1.x| C-PE1 A1-------------------------------B1 C-PE2 |10.1.1.x
| | | |
21.1.1.x| A2(192.10.0.10)------( 192.0.0.1)B2 |20.1.1.x
| | | |
| Addr A3(160.0.0.1) --------(170.0.0.1)B3 Addr |
| 1.1.1.1 | |2.2.2.2|
+---------+ +-------+
SD-WAN VPN #1 SD-WAN VPN #1
SD-WAN VPN #2 SD-WAN VPN #3
However, a SD-WAN overlay network can span across untrusted networks, RR cannot trust the RT Constraint (RTC) NLRI BGP UPDATE from any nodes. RR can only process the RTC NLRI from authorized peers for a SD-WAN VPN.¶
It is out of the scope of this document on how RR is configured with the policies to filter out unauthorized nodes for specific SD-WAN VPNs.¶
When the RR receives BGP UPDATE from an edge node, it propagates the received UPDATE message to the nodes that are in the Outbound Route filter for the specific SD-WAN VPN.¶
The SD-WAN network's Client Route UPDATE message is the same as the L3 VPN or EVPN client route UDPATE message. The SD-WAN Client Route UPDATE message uses the Encapsulation Extended Community and the Color Extended Community to link with the SD-WAN Underlay UPDATE Message.¶
An SD-WAN VPN is same as a client VPN in a BGP controlled SD-WAN network. The Route Target Extended Community should be included in a Client Route UPDATE message to differentiate the client routes from routes belonging to other VPNs.¶
For an SD-WAN edge node which can be reached by both MPLS and IPsec paths, the client packets reached by MPLS network will be encoded with the MPLS Labels based on the scheme specified by [RFC8277].¶
For GRE Encapsulation within an IPsec tunnel, the GRE key field can be used to carry the SD-WAN VPN ID. For network virtual overlay (VxLAN, GENEVE, etc.) encapsulation within the IPsec tunnel, the Virtual Network Identifier (VNI) field is used to carry the SD-WAN VPN ID.¶
The hybrid underlay tunnel UPDATE is to advertise the detailed properties associated with the public facing WAN ports and IPsec tunnels.¶
A new NLRI SAFI [RFC5521], SD-WAN-SAFI=74, is introduced within the MP_REACH_NLRI Path Attribute of RFC4760 for advertising the detailed properties of the SD-WAN tunnels terminated at the edge node:¶
+------------------+ | Route Type | 2 octet +------------------+ | Length | 2 Octet +------------------+ | Type Specific | ~ Value (Variable) ~ | | +------------------+
Where¶
This document defines the following SD-WAN Route type:¶
NLRI Route-Type = 1: For advertising the detailed properties of the SD-WAN tunnels terminated at the edge, where the transport network port can be uniquely identified by a tuple of three values (Port-Local-ID, SD-WAN-Color, SD-WAN-Node-ID). The SD-WAN NLRI Route-Type =1 has the following encoding:¶
+------------------+
| Route Type = 1 | 2 octet
+------------------+
| Length | 2 Octet
+------------------+
| Port-Local-ID | 4 octets
+------------------+
| SD-WAN-Color | 4 octets
+------------------+
| SD-WAN-Node-ID | 4 or 16 octets
+------------------+
o Port local ID: SD-WAN edge node Port identifier, which is locally significant. If the SD-WAN NLRI applies to multiple WAN ports, this field is NULL.¶
o SD-WAN-Color: to represent a group of tunnels, which correlate with the Color-Extended-community included in the client routes UPDATE. When a client route can be reached by multiple SD-WAN edges co-located at one site, the SD-WAN- Color can represent a group of tunnels terminated at those SD-WAN edges co-located at the site, which effectively represent the site.¶
o SD-WAN Node ID: The node's IPv4 or IPv6 address.¶
A new BGP Tunnel-Type=SD-WAN-Hybrid (code point 25) is to indicate hybrid underlay tunnels.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tunnel-Type=25(SD-WAN-Hybrid )| Length (2 Octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPsec-SA-ID Sub-TLV within the Hybrid Underlay Tunnel UPDATE indicates one or more pre-established IPsec SAs by using their identifiers, instead of listing all the detailed attributes of the IPsec SAs.¶
Using an IPsec-SA-ID Sub-TLV not only greatly reduces the size of BGP UPDATE messages, but also allows the pairwise IPsec rekeying process to be performed independently.¶
The following is the structure of the IPsec-SA-ID sub-TLV:¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Type=64 (IPsec-SA-ID subTLV) | Length (2 Octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPsec SA Identifier #1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPsec SA Identifier #2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Extended Port Attribute Sub-TLV is to advertise the properties associated with a public Internet-facing WAN port that might be behind NAT. An SD-WAN edge node can query a STUN Server (Session Traversal of UDP through Network address translation [RFC8489]) to get the NAT properties, including the public IP address and the Public Port number, to pass to its peers.¶
The location of a NAT device can be:¶
The initiator's address and/or responder's address can be dynamically assigned by an ISP or when their connection crosses a dynamic NAT device that allocates addresses from a dynamic address pool.¶
As one SD-WAN edge can connect to multiple peers, the pair-wise NAT exchange as IPsec's IKE[RFC7296] is not efficient. In the BGP Controlled SD-WAN, NAT properties for a WAN port are encoded in the Extended Port Attribute sub-TLV, which the following format:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=65(extPort| ExtPort Length| Reserved |I|O|R|R|R|R|R|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAT Type | Encap-Type |Trans networkID| RD ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local IP Address |
32-bits for IPv4, 128-bits for Ipv6
~~~~~~~~~~~~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public IP |
32-bits for IPv4, 128-bits for Ipv6
~~~~~~~~~~~~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Public Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended SubSub-TLV |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where¶
Flags:¶
Two types of the Extended SubSub-TLVs are specified in this document: Underlay Network Transport SubSub-TLV and the underlay Geo Location SubSub-TLV.¶
The Underlay Network Transport SubSub-TLV is an optional Sub-TLV to carry the WAN port connection types and bandwidth, such as LTE, DSL, Ethernet, etc.¶
The format of this Sub-TLV is as follows:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UnderlayType | Length | Flag | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Connection Type| Port Type | Port Speed |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where¶
Connection Type: are listed below as:¶
Port Type: There are different types of ports. They are listed Below as:¶
For a large SD-WAN heterogeneous deployment where SD-WAN Node-ID is not enough to identify the exact location of an SD-WAN edge, the geolocation Sub-TLV specified in the [LISP-GEOLOC] can be appended to the Extended Port Attribute Sub-TLV to describe the accurate location of the transport network node.¶
[Note: get the detailed number from the LIST draft to be reused here]¶
This section describes the detailed IPsec SA properties sub-TLVs. When the IPsec SA properties are associated with the node, any of the node's WAN ports can be the outer destination address of the IPsec encapsulated data packets.¶
The Nonce Sub-TLV is based on the Base DIM sub-TLV as described the Section 10.1 of [SECURE-EVPN]. The following fields are removed because:¶
The format of this Sub-TLV is as follows:¶
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 |
+---------------------------------------------------------------+
| IPsec SA Identifier |
+---------------------------------------------------------------+
| |
~ Nonce Data ~
| |
+---------------------------------------------------------------+
IPsec SA ID - The 4 bytes IPSec SA ID is to differentiate multiple IPsec SAs terminated at the edge. The IPsec SA ID can be used in the IPsec-SA-ID subTLV of a different BGP UPDATE message to refer to all the values carried in the IPsec Public Key SubTLV and the IPsec SA Proposal Sub-TLV that are in the same BGP UPDATE message as the IPsec SA Nonce sub-TLV.¶
The IPsec Public Key Sub-TLV is derived from the Key Exchange Sub-TLV described in [SECURE-EVPN] with an addition of Duration filed to define the IPSec SA life span. The edge nodes would pick the shortest duration value advertised by the peers.¶
The format of this Sub-TLV is as follows:¶
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 ~
| |
+---------------------------------------------------------------+
| Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The IPsec SA Proposal Sub-TLV is to indicate the number of Transform Sub-TLVs. This Sub-TLV aligns with the sub-TLV structure from [SECURE-EVPN].¶
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 ~ | | +---------------------------------------------------------------+
The Transform Type and the Transform Attributes Sub-sub-TLV are taken from the section 3.3.2 and 3.3.5 of RFC7296, respectively.¶
For a simple SD-WAN network with edge nodes supporting only a few pre-defined encryption algorithms, a simple IPsec sub-TLV can be used to encode the pre-defined algorithms, as below:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IPsec-simType |IPsecSA Length | Flag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transform | Mode | AH algorithms |ESP algorithms |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ReKey Counter (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| key1 length | Key 1 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| key2 length | Key 2 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| key-i length | Nonce ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:¶
- Transform (1 Byte):¶
- IPsec Mode (1 byte):¶
- ESP algorithms (1 byte): ESP authentication algorithms supported, which can be md5 | sha1 | sha2-256 | sha2-384 | sha2-512 | sm3. Each SD-WAN edge node can have multiple authentication algorithms; send to its peers to negotiate the strongest one. Default algorithm is AES-256.¶
When a node supports multiple authentication algorithms, the initial UPDATE needs to include the "Transform Sub-TLV" described by [SECURE-EVPN] to describe all of the algorithms supported by the node.¶
When an SD-WAN edge receives a client route BGP UPDATE from a peer with a color that does not match with any of the tunnels advertised by the peer, the client route UPDATE should be ignored, and an error message (e.g., Syslog) should be generated to its management system per[RFC7606].¶
For example, for two peers, PA and PB, both PA and PB will first advertise their SD-WAN properties (i.e., tunnel properties). Say PA advertises two SD-WAN tunnels (Red and Green), and PB advertises two SD-WAN tunnels (Yellow and Purple). PB should report a mismatch error message when PB receives a Client Update from PA with a color NOT Red or Green. PA should report a Mismatch Error when PA receives a Client Update from PB with a color that is not Yellow and Purple.¶
Upon receiving a Tunnel Update that includes the IPsec-SA-ID subTLV from a peer, the BGP node should report Mismatch error if the IPsec SA has not been established yet.¶
Moreover, if the encap-Types, in the Extended Port Attributes Sub-TLV, in the received SDWAN update is not supported by the local ports, the corresponding ports between the remote edge and local edge will not establish an overlay tunnel. Overlay tunnels would only be established between two ports belonging to different edges, if their attributes are compatible. For instance, the encap Types should match. Policies and configurations outside the scope of this document could allow for mismatched attributes to be present and allow establishing overlay tunnels.¶
Each C-PE device advertises a SD-WAN SAFI Underlay NLRI to the other C-PE devices via a BGP Route Reflector to establish pairwise SAs between itself and every other remote C-PEs. During the SAFI NLRI advertisement, the BGP originator would include either simple IPSec Security Association properties defined in IPSec SA Sub-TLV based on IPSec-SA-Type = 1 or full-set of IPSec Sub-TLVs including Nonce, Public Key, Proposal and number of Transform Sub-TLVs based on IPSec-SA-Type = 2.¶
The C-PE devices compare the IPSec SA attributes between the local and remote WAN ports. If there is a match on the SA Attributes between the two ports, the IPSec Tunnel is established.¶
The C-PE devices would not try to negotiate the base IPSec-SA parameters between the local and the remote ports in the case of simple IPSec SA exchange or the Transform sets between local and remote ports if there is a mismatch on the Transform sets in the case of full-set of IPSec SA Sub-TLVs.¶
Here is an example of using Figure 1 in Section 3 to establish an IPsec Tunnel between C-PE1 and C-PE2 WAN Ports A2 and B2 (A2: 192.10.0.10 - B2:192.0.0.1).¶
C-PE1 needs to advertise the following attributes for establishing the IPsec SA:¶
C-PE2 needs to advertise the following attributes for establishing IPsec SA:¶
As there is no matching transform between the WAN ports A2 and B2 in C-PE1 and C-PE2, respectively, no IPsec Tunnel will be established.¶
The C-PE2 of Figure 1 can send the following SD-WAN UPDATE messages to advertise the properties associated with WAN Port 192.0.0.1 and WAN Port 170.0.0.1, respectively:¶
The C-PE2 of the Figure 1 can send the following SD-WAN UPDATE messages to advertise node level IPsec SA:¶
SD-WAN NLRI: AFI=IPv4/IPv6 and SAFI = SD-WAN¶
Tunnel-Type = Hybrid-SD-WAN¶
IPsec-SA-ID Sub-TLV or IPsec SA Property Sub-TLVs¶
Here is an encoding example of four IPsec SAs terminated at the same node.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tunnel-Type =SD-WAN-Hybrid | Length = | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tunnel-end-point sub-TLV | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | subTLV-Type = IPsec-SA-ID | Length = | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPsec SA Identifier = 1 | +---------------------------------------------------------------+ | IPsec SA Identifier = 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPsec SA Identifier = 3 | +-------------------------------+-------------------------------+ | IPsec SA Identifier = 4 | +---------------------------------------------------------------+
The Length of the Tunnel-Type = SDDWAN-Hybrid is the sum of the following:¶
Unlike MPLS VPN whose PE nodes are all controlled by the network operators, SD-WAN edge nodes can be installed anywhere, in shopping malls, in 3rd party Cloud DCs, etc.¶
It is very important to ensure that client routes advertisement from an SD-WAN edge node are legitimate. The RR needs to drop all the BGP Update messages from an SD-WAN edge nodes that have invalid Route Targets.¶
The document describes the encoding for SD-WAN edge nodes to advertise its properties to their peers to its RR, which propagates to the intended peers via untrusted networks.¶
The secure propagation is achieved by secure channels, such as TLS, SSL, or IPsec, between the SD-WAN edge nodes and the local controller RR.¶
SD-WAN edge nodes might not have secure channels with the RR. In this case, BGP connection has be established over IPsec or TLS.¶
IANA has assigned SAFI = 74 as the Hybrid (SD-WAN) SAFI.¶
IANA is requested to assign a type from the BGP Tunnel Encapsulation Attribute Tunnel Types as follows [RFC8126]:¶
Value Description Reference ----- ------------ --------- 25 SD-WAN-Hybrid (this document)¶
IANA is requested to assign the following sub-Types in the BGP Tunnel Encapsulation Attribute Sub-TLVs registry:¶
Value Type Description Reference
----- ----------------------- ---------------
64 IPSEC-SA-ID Sub-TLV (Section 6.3)
65 Extended Port Property Sub-TLV (Section 6.4)
66 Underlay Transport Sub-TLV (Section 6.5)
67 IPsec SA Nonce Sub-TLV (Section 7.1)
68 IPsec Public Key Sub-TLV (Section 7.2)
69 IPsec SA Proposal Sub-TLV (Section 7.3)
70 Simplified IPsec SA sub-TLV (Section 7.4)
¶
Acknowledgements to Wang Haibo, Shunwan Zhuang, Hao Weiguo, and ShengCheng for implementation contribution; Many thanks to Yoav Nir, Graham Bartlett, Jim Guichard, John Scudder, and Donald Eastlake for their review and suggestions.¶
This document was prepared using 2-Word-v2.0.template.dot.¶
Below is a list of other contributing authors:¶