ECN

Mikael Abrahamsson swmike at swm.pp.se
Fri Nov 7 01:27:58 CST 2008


Hi,

On LKML (Linux Kernel Mailing List) there is talk 
<http://lkml.org/lkml/2008/11/4/151> about shipping the Linux kernel with 
ECN turned on by default (it was on by default a few years back but that 
change was reverted due to too many sites dropping ECN enabled SYNs).

Recent investigations <http://www.imperialviolet.org/binary/ecntest.pdf> 
shows that 0.5% of end hosts will drop SYN packets with ECN turned on. 
This is approximately the same rate I have seen for A/AAAA adoption in 
this tread <http://www.ops.ietf.org/lists/v6ops/v6ops.2008/msg01585.html>.

Do we in the operational ISP community have an opinion on ECN adoption 
that we want to voice? As far as I can discern from 
<http://www.cisco.com/en/US/docs/ios/12_2t/12_2t8/feature/guide/ftwrdecn.html> 
for ECN to actually be useful, we (the ISPs) have to turn this option on 
in the routers as well. Is anyone doing this today? What vendors support 
it?

When I thought about it, the IP core (10G links etc) first came to mind, 
and there it's fairly easy to roll out (since I guess a lot of us do WRED 
already), but what about on slower links? Would it make sense to have our 
DSLAMs do this? What about DSL/cable modems (well, vendors should first 
realise that FIFO is not great to begin with :P) ?

<http://www.icir.org/tbit/> is a summary page I found on ECN that looks 
like a good resource for further reading. Is anyone looking into including 
ECN configuration into some BCP document?

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se




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