Associated Gateway Exchange in Multi-segment SD-WAN

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Table of Contents

1. Introduction

[I-D.draft-dmk-rtgwg-multisegment-sdwan] 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.¶

[I-D.draft-dmk-rtgwg-multisegment-sdwan] 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 [I-D.draft-ietf-idr-sdwan-edge-discovery], enabling a CPE to advertise its directly connected GW address to other CPEs .¶

  (^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^)
  (            Region2             )
  (            +-----+             )
  (            | GW2 |             )
  (            +-----+             )
  (           /       \            )
  (          /  Cloud  \           )
  (         /  Backbone \          )
  ( Region1/             \Region3  )
  ( +-----+               +-----+  )
  ( | GW1 |---------------| GW3 |  )
  ( +--+--+               +--+--+  )
  (^^^^|^^^^^^^^^^^^^^^^^^^^^|^^^^^)
       |                     |
    +--+--+               +--+--+
    |CPE 1|               |CPE 2|
    +-----+               +-----+

2. 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 [RFC2119] [RFC8174] 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.¶

3. Extension to SD-WAN Underlay UPDATE for Associated GWs

The Client Routes Update is the same as described in Section 5 of [I-D.draft-ietf-idr-sdwan-edge-discovery].¶

+------------------+
|    Route Type    | 2 octet
+------------------+
|     Length       | 2 Octet
+------------------+
|   Type Specific  |
~ Value (Variable) ~
|                  |
+------------------+

+------------------+
|  Route Type = 2  | 2 octet
+------------------+
|     Length       | 2 Octet
+------------------+
|   SD-WAN Color   | 4 octets
+------------------+
|  SD-WAN-Node-ID  | 4 or 16 octets
+------------------+

    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=TBD    |    length     |  Priority         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Associated GW Addr Family     | Address                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ (variable)                    +
   ~                                                               ~
   |             Associated GW Address                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4. 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.¶

5. Security Considerations

This document does not introduce any new security considerations.¶

6. IANA Considerations

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

- SD-WAN Associated GW Sub-TLV.¶

Authors' Addresses