Messages in this thread |  | | Date | Sat, 9 Sep 2000 12:32:34 +0200 | From | Jamie Lokier <> | Subject | Re: ECN & cisco firewall |
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Graham Murray wrote: > "David S. Miller" <davem@redhat.com> writes: > > > The authors of rfc793 probably, in all honesty, really meant > > "must be set to zero by current implementations". > > I agree, to me it seems obvious that the reason is so that these bits > could be used at some time in the future for some, then unknown, > purpose. Now that RFC 2481 has defined the bits, only implementations > which grok and support ECN should be setting these bits, older > implementations will (following RFC793) set them to zero and thus old > and new implementations should correctly interwork.
The RFC 793 authors really should have stated that non-zero bits on incoming packets are reserved for future protocol extensions, and should be silently accepted and ignored.
RFC 793 predates modern firewalls AFAIK. There just wasn't a need for protection from things like DDOS's, teardrop etc.
Now, for how to deal with firewalls that block ECN. Perhaps it's a _good_ thing that they send RSTs. Presumably the RSTs don't have ECN bits set. So our TCP stack can observe this and say "ah, that route doesn't do ECN; let's retry without ECN and see if we get a better response".
-- Jamie - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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