IDR experts:

https://datatracker.ietf.org/doc/draft-dunbar-idr-sdwan-edge-discovery/ 
proposes using two separate BGP UPDATE messages for SDWAN Edge Discovery:


  *   UPDATE U1 for advertising the attached client routes,
This UPDATE is exactly the same as the BGP edge client route UDPDATE. It  uses 
the Encapsulation Extended Community and the Color Extended Community to link 
with the Underlay Tunnels UPDATE Message.


  *   UPDATE U2 advertises the properties of the various tunnels, including 
IPsec, terminated at the edge node.

Since there are many parameters associated with an IPsec SA, IPsec SA 
identifiers are used in the Tunnel Encap Path Attribute, instead  of listing 
all the detailed attributes of the IPsec SA.

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= IPsec-SA-ID subTLV      |  Length (2 Octets)            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      IPsec SA Identifier #1                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      IPsec SA Identifier #2                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

If the client traffic needs to be encapsulated in a specific type within the 
IPsec ESP Tunnel, such as GRE or VxLAN, etc., the corresponding Tunnel-Encap 
Sub-TLV needs to be prepend right before the IPsec-SA-ID Sub-TLV.

Using 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.

Do people see any issues of this proposed encoding?

Thank you very much.
Linda Dunbar
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