Internet-Draft Gateway Info Exchange in SDWAN February 2024
Sheng, et al. Expires 1 September 2024 [Page]
Inter-Domain Routing
Intended Status:
Standards Track
C. Sheng
H. Shi, Ed.
L. Dunbar
G. Mishra

Associated Gateway Exchange in Multi-segment SD-WAN


The document describes the control plane enhancement for multi-segment SD-WAN to exchange the associated GW information between edges.

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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|
    +-----+               +-----+
Figure 1: Multi-segment SD-WAN

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:

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].

3.1. 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:

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

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:

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

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.

3.2. 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:

    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                             |

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.

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.

7. Normative References

Majumdar, K., Dunbar, L., Kasiviswanathan, V., and A. Ramchandra, "Multi-segment SD-WAN via Cloud DCs", Work in Progress, Internet-Draft, draft-dmk-rtgwg-multisegment-sdwan-07, , <>.
Gross, J., Ed., Ganga, I., Ed., and T. Sridhar, Ed., "Geneve: Generic Network Virtualization Encapsulation", RFC 8926, DOI 10.17487/RFC8926, , <>.
Dunbar, L., Hares, S., Raszuk, R., Majumdar, K., Mishra, G. S., and V. Kasiviswanathan, "BGP UPDATE for SD-WAN Edge Discovery", Work in Progress, Internet-Draft, draft-ietf-idr-sdwan-edge-discovery-12, , <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.

Authors' Addresses

Cheng Sheng
Beiqing Road
Hang Shi (editor)
Beiqing Road
Linda Dunbar
Gyan Mishra