Hi, Bob, This approach seems to assume an integrated implementation of multiple protocol layers.
There are other cases where the "shim" is added indirectly, as a packet is "tunneled" independently over multiple protocols. I scanned the draft and didn't see this addressed explicitly (maybe I missed it). It's implied throughout 3.2 but never stated as a MAY, e.g., systems MAY support ECN across shim layers but are NOT REQUIRED to do so. Can that sort of explicit caveat be included? This case might be added as a final bullet in the list at the end of section 3.2. Joe On 6/16/2017 7:25 AM, Bob Briscoe wrote: > Fabio, Larry, Uri, > > I notice VXLAN-GPE is on the IETF standards track. > It will need to specify support for propagation of the ECN field > between inner and outer for cases when there is (or might be) an IP > header (v4 or v6) within the L2 encapsulation, and when the outer is > IP (v4 or v6). > > I believe ECN propagation between inner and outer is already in the > Linux code for VXLAN, but it's not specified in RFC7348, so other > implementations might overlook it. Given that ECN is heavily used in > DCs (e.g. for DCTCP), this is a significant omission. > > Please refer to draft-ietf-tsvwg-rfc6040update-shim > <https://tools.ietf.org/html/draft-ietf-tsvwg-rfc6040update-shim> and > RFC6040. > > I will warn you that, unless you believe that all existing VXLAN > implementations already support ECN, this will not be just a > straightforward case of referencing the appropriate RFCs. If there > might be non-ECN VXLAN decapsulators out there, the tunnel ingress > will have to know (by config or capability negotiation) whether the > egress supports ECN propagation, and if not, switch to 'compatibility > mode' (zeroing the outer ECN field). That could require definition of > a capability parameter during tunnel set-up (unless you envisage > tunnel set up will always be by administrative config). > > Cheers > > > > Bob > > > -- > ________________________________________________________________ > Bob Briscoe http://bobbriscoe.net/ > > > _______________________________________________ > nvo3 mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/nvo3
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