Associated Gateway Exchange in Multi-segment SD-WAN

Introduction describes how enterprises leverage Cloud Providers’ backbone infrastructure to interconnect their branch offices. As illustrated in Figure 1, CPE-1 and CPE-2 establish connections to their respective Cloud Gateways (GW) in distinct regions. CPE-1 and CPE-2 maintain the pairwise IPsec Security Associations (SAs). The IPsec encrypted traffic from CPE-1 to CPE-2 is encapsulated by the GENEVE header [RFC8926], with the outer destination address being the GW1. specifies a set of sub-TLVs to convey information about the GWs associated with the destination branches, such as GW3 for CPE-2, along with additional attributes. To accomplish this, CPE-1 must be aware of the associated GW addresses of their peers. This document proposes a BGP extension, building upon , enabling a CPE to advertise its directly connected GW address to other CPEs .

Multi-segment SD-WAN

Requirements Language 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 when, and only when, they appear in all capitals, as shown here. The following acronyms and terms are used in this document:

Cloud DC: Off-Premises Data Center, managed by 3rd party, that hosts applications, services, and workload for different organizations or tenants.
CPE: Customer (Edge) Premises Equipment.
OnPrem: On Premises data centers and branch offices.
RR Route Reflector.
SD-WAN: Software Defined Wide Area Network. In this document, “SD-WAN” refers to a policy-driven transporting of IP packets over multiple underlay networks for better WAN bandwidth management, visibility, and control.
VPN Virtual Private Network.

Extension to SD-WAN Underlay UPDATE for Associated GWs The Client Routes Update is the same as described in .

NLRI SD-WAN SAFI Route Type For GW Adding a new attribute (Associated-Gateway Sub-TLV) to the SD-WAN-Hybrid Tunnel Encoding which is included in the SD-WAN SAFI (=74) Underlay Tunnel Update: NLRI Route-Type = 2: For advertising the detailed properties of the transit gateways for the edge. The SD-WAN NLRI Route-Type =2 has the following encoding: SD-WAN-Color: To represent a group of tunnels that correlate with the Color-Extended-community included in a client route UPDATE. When multiple SD-WAN edges can reach a client route 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 represents the site. SD-WAN Node ID: The node's IPv4 or IPv6 address.

Associated GW Sub-TLV The Associated GW Sub-TLV, within the SD-WAN-Hybrid Tunnel TLV (code point 25), carries the associated GW address(es) with which the SD-WAN edge is associated. The following is the structure of the associated GW Sub-TLV: Priority (1-255) indicate the preference of the GW. The higher the value, the more preference is the GW. Priority = 0 represents that the connection exists but request Cloud Backbone not to choose the GW if possible.

Manageability Considerations Effective management of SD-WAN edge nodes and the exchange of associated cloud gateway information are critical aspects in ensuring a robust and scalable SD-WAN deployment.

Security Considerations This document does not introduce any new security considerations.

IANA Considerations Need IANA to assign a new Sub-TLV Type under the SD-WAN-Hybrid Tunnel TLV. - SD-WAN Associated GW Sub-TLV.