Bob, Any encaps/decaps implementation in userspace is by default non-propagating for ECN.
Userspace switches, directly attached transports for type 2 hypervisors, etc. In fact, it cannot be - this is strictly "kernel business" - a userspace implementation is not entitled to arbitrarily set or clear the ECN bit on an outgoing packet. It has no means to do so. IMHO, propagation of ECN and Diff-Serv markings should be purely a matter of configuration and administrative decision without the IETF mandating it left right and center. We can recommend it (it is nice to have), but we should not mandate it because that gets us into the realm of prohibiting perfectly valid (and quite useful) classes of implementations. A. On 16/06/17 15:25, 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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