Re: [Idr] Tunnel-Encap Gaps for SD-WAN described in draft-ietf-rtgwg-net2cloud-gap-analysis-02.txt

Linda Dunbar <> Thu, 20 June 2019 22:07 UTC

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From: Linda Dunbar <>
To: John E Drake <>, "" <>, "" <>
Thread-Topic: Tunnel-Encap Gaps for SD-WAN described in draft-ietf-rtgwg-net2cloud-gap-analysis-02.txt
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Date: Thu, 20 Jun 2019 22:07:38 +0000
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Subject: Re: [Idr] Tunnel-Encap Gaps for SD-WAN described in draft-ietf-rtgwg-net2cloud-gap-analysis-02.txt
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Thank you very much for the feedback.
Comments are inserted below:

From: John E Drake <>


-       [Tunnel-Encap] doesn't have the functionality that would help the C-PE to register its WAN Port properties.

-       A SD-WAN tunnel, e.g. IPsec-based, requires a negotiation between the tunnel's end points for supported encryption algorithms and tunnel types before it can be properly established, whereas [Tunnel-Encap]  only allow the announcement of one endpoint's supported encapsulation capabilities for specific attached routes and no negotiation between tunnel end points is needed.

[JD]  What you need to do is implement the model described in  the Secure EVPN draft (<>).  Viz, the SD-WAN C-PEs are attached to a route reflector and each uses the route reflector to advertise its security-related  information the other C-PEs.  As we discussed in Prague the tunnel encapsulation attribute is not associated with client routes.  Rather it is associated with the loopback or interface addresses of the advertising SD-WAN C-PE.  I.e., IPv4/IPv6 addresses rather than VPN IPv4/IPv6 addresses

[Linda]Yes, using Loopback address would be a good way for tunnel, but that is not what Tunnel-Encap specified. The draft Tunnel-Encap is to advertise supported Encap capabilities for specified routes.
I have another section (4.3) on the gap analysis for SECURE-EVPN, specifically, Secure-EVPN does not address the scenario of C-PE having some ports facing trusted MPLS VPN and other ports facing the untrusted public Internet. The document assumes that a client route is either forwarded all encrypted through one tunnel, or not encrypted at all through a different tunnel. In SD-WAN, one client route can be forwarded encrypted at one time through the untrusted network and be forwarded unencrypted at different time through MPLS VPN.
If you think the secure-evpn has addressed those scenarios, can you please indicate which section? Thank you.

The establishment of a SD-WAN tunnel can fail, e.g., in case the two endpoints support different encryption algorithms. That is why a SD-WAN tunnel needs to be established and maintained independently from advertising client routes attached to the edge node.

[JD]  See above

-       [Tunnel-Encap] requires all tunnels updates are associated with routes. There can be many client routes associated with the SD-WAN IPsec tunnel between two C-PEs' WAN ports; the corresponding destination prefixes (as announced by the aforementioned routes) may also be reached through the VPN underlay without any encryption.. A more realistic approach to separate SD-WAN tunnel management from client routes association with the SD-WAN tunnels.

[JD]  See above

-       When SD-WAN tunnel and clients routes are separate, the SD-WAN Tunnel establishment may not have routes associated.
There is a suggestion on using a "Fake Route" for a SD-WAN node to use [Tunnel-Encap] to advertise its SD-WAN tunnel end-points properties. However, using "Fake Route" can raise some design complexity for large SD-WAN networks with many tunnels. For example, for a SD-WAN network with hundreds of nodes, with each node having many ports & many endpoints to establish SD-WAN tunnels with their corresponding peers, the node would need as many "fake addresses". For large SD-WAN networks (such as those comprised of more than 10000 nodes), each node might need 10's thousands of "fake addresses", which is very difficult to manage and requires lots of configuration tasks to get the nodes properly set up.

[JD]  There is no need for a 'Fake Route'.  We advertise a tunnel encapsulation attribute with security-related information for a specific SD-WAN port on the C-PE as identified by its IPv4/IPv6 interface address.  If a set of SD-WAN ports have common security-related information a tunnel encapsulation attribute can be advertised with a C-PE's loopback address.

[Linda] this section is for Tunnel-Encap, which doesn't allow Loopback address to be associated with the tunnel. If you think it does, can you please indicate which section? Thank you.