bgp blackhole lists and transit providers

Mike Tancsa mike at
Wed Nov 10 03:21:24 UTC 1999

Lately, we have been running into this problem more and more.  One of our
upstreams AT&T buys transit from Teleglobe. Teleglobe it seems subscribes
to the realtime blackhole list via BGP.  Now, I am all for
limiting SPAM and such, but its starting to be an operational headache
having to deal with customers asking our support staff why they cannot get
to a certain web site.  The one that hit our support lines the most was which was  It can be a challenge explaining
the simplest of issues to end users, let alone upstream transit providers
using bgp to blackhole a host.  The customer just wants to get to the
granny's knitting guild!  At least with SMTP blocking, one end gets a
message stating "their mail is unwelcome, see .... for details", where as
when an intermediary is dropping all data, the end user just gets a vague

My questions is, if you were buying transit from an upstream, and that
upstream decided to partake in some sort of content filtering, how would
you feel ? Do you think its right for transit providers to do so ? Its one
thing if I choose to use this facility, but I feel a little helpless if two
ASs away from me uses it... i.e. upstream says, "this way to",
but then drops data going to  I dont want to have to fill me
router with a bunch of /32s so I can exit out UUnet to get around this.

Yes, sure I want a proactive upstream to stop network abuse... particularly
abuse issues, where I need their cooperation such as smurf attacks and
such.  But on issues, where I have all the necessary tools and choice to
deal with said issue (in this case SPAM), I would prefer it be left up to
me on how I deal with foreign SPAM sites.

Mike Tancsa, Network Admin        *  mike at
Sentex Communications Corp,       *
Cambridge, Ontario                *  01.519.651.3400
Canada                            *

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