[nSLUG] sprint.ca blocks mail from eastlink cable modems

Peter Cordes peter at llama.nslug.ns.ca
Sat Aug 10 02:38:28 ADT 2002

On Fri, Aug 09, 2002 at 01:06:09PM -0300, Jamie Fifield wrote:
> Haha, maybe it's just Peter they've blocked! :)

 They're blocking TCP SYN packets that have the ECN bit set in the TCP
flags.  I usually compile ECN into my kernel, but then I put a line in
sysctl.conf to disable it.  I forgot to turn it off on llama, and it looks
like it caught up with me.   I disabled /proc/sys/net/ipv4/tcp_ecn, and I
can connect to sprint now.  (ECN == explicit congestion notification.
there's an RFC about it.  It's a way for routers to tell end nodes about
congestion in the network.  It increases throughput for TCP connections.)

 It's lamers like sprint who prevent the Internet from making progress.  As
long as there are sites out there that choke on ECN like that, nobody can
realistically enable it.  If Linux supported a lamer list of sites to not
use ECN for, or a whitelist of sites that also used ECN, then it could be

For a while, I was confused by the ICMP messages they send back when you
ping them: type 3 (Destination unreachable), code 13 (Communication
administratively filtered).  I thought that was because I was blocked,
personally, but they probably do that for everyone's pings.

> Peter, have you been advertising pr0n sites? :)
 No, I keep my pr0n to myself ;-)

#define X(x,y) x##y
Peter Cordes ;  e-mail: X(peter at llama.nslug. , ns.ca)

"The gods confound the man who first found out how to distinguish the hours!
 Confound him, too, who in this place set up a sundial, to cut and hack
 my day so wretchedly into small pieces!" -- Plautus, 200 BCE

More information about the nSLUG mailing list