Corresponding Gateway Exchange in Multi-segment SD-WAN

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Table of Contents

1. Introduction

To interconnect geographically faraway branches or SASE resources, multi-segment SD-WAN is often deployed via cloud backbone[I-D.draft-dmk-rtgwg-multisegment-sdwan]. As shown in Figure 1, CPE 1 and CPE 2 are connected to the nearest Cloud GW in different regions. For the traffic from CPE 1 to CPE 2, the CPE 1 will encapsulate the address of the egress GW(GW3) and destination CPE(CPE2) in the dataplane(see Section 5.2 of [I-D.draft-dmk-rtgwg-multisegment-sdwan]). To accomplish that, CPE needs to know their peers' corresponding GW addresses. This document proposes an control plane enhancement based on [I-D.draft-ietf-idr-sdwan-edge-discovery] to exchange the corresponding GW address between 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.¶

3. Corresponding GW Sub-TLV

Corresponding GW Sub-TLV within the Hybrid Underlay Tunnel UPDATE indicates the address of the corresponding GW. The following is the structure of the Corresponding 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=TBD2 (C-GW  subTLV)     |  Length (2 Octets)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Corresponding GW Addr Family  | Address                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ (variable)                    +
   ~                                                               ~
   |             Corresponding GW Address                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4. Security Considerations

This document does not introduce any new security considerations.¶

5. IANA Considerations

TBD.¶

Authors' Addresses