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Re: ECN and issue 58

Black_David@xxxxxxx wrote:


My proposed text:

When IPsec tunnels behave as originally specified in [RFC 2401], ECN


is not appropriate for the outer IP headers because tunnel decapsulation
processing discards ECN congestion indications to the detriment of the
network.  ECN support for IPsec tunnels for IKEv1-based IPsec requires
multiple  operating modes and negotiation (see [RFC 3168]).  IKEv2
simplifies this situation requiring that ECN be usable in the outer IP
headers of all tunnel-mode IPsec SAs created by IKEv2.  Specifically,
tunnel encapsulators and decapsulators for all tunnel-mode Security
Associations (SAs) created by IKEv2 MUST support the ECN


option for tunnels specified in [RFC3168] and MUST implement the tunnel
encapsulation and decapsulation processing specified in [RFC2401bis] to
prevent discarding of ECN congestion indications.

NB: [RFC 2401] reference is informative, [RFC 3168] and [2401bis] are

It might be useful to consider that RFC2168 already specifies how ECN interacts with IP in IP (RFC2003) tunneling (sec 9.1), and that IPsec tunnels should follow that convention.

Yes, that was considered, and the latter reference to [RFC3168] in my text
is to sec 9.1 -  it would be good to make that explicit (i.e., "... ECN
full-functionality option for tunnels specified in Section 9.1 of


This is keeping with another goal, i.e., having 2401bis point to RFC2003 excepting only security caveats, rather than (largely) respecifying an existing specification.

If 2401bis goes that route, that would be ok, but 2401bis has to do
something to override RFC2401 and Section 9.2 of RFC3168.  I would
prefer to not point to RFC2003 from IKEv2, and leave it to 2401bis to
decide whether to say that this is realized by reference to RFC2003
(... provided that you can convince Steve Kent that the result doesn't
 break any IPsec security properties ... ).

Sure - it's probably better to have all that info in one place - in 2401bis.