🚀 go-pugleaf

[Changed followup-to: because I assume the filtering issue is more or
 less EPFL-specific.  If you want to follow up from outside EPFL,
 please change the Newsgroups: header back to ch.network.]

saouli@di.epfl.ch (Karim Saouli) writes:

   Is there any filtering done either in broadcast or reception of
   talk protocols?

There are in fact sites whose policy it is to filter packets to
specific ports.  Since you are posting from EPFL, I assume that this
is the problem you experience.  UDP packets with a port number of 517
(talk) or 518 (ntalk) are dropped by the router between SWITCH and
EPNET.  The same is true for TCP packets with a destination port of 79
(FINGER).

   Is it really wyse to do such a thing?

Good question.  As you have said in your IRC example, port
restrictions can often be circumvented by recompiling or reconfiguring
programs to use non-standard ports.  For talk and FINGER, filtering
does a much better job at making these services unusable.  (Reason:
Talk and FINGER are contacted by user programs, rather than specific
servers that have to be explicitly configured anyway, like for IRC.)

Personally I think that these particular policy decisions do more harm
than good, but then I could be wrong.  One thing I'd like to get
clarified, however, is *who* makes such policy decisions and on which
basis.  Has there been excessive abuse of Talk? Are there security
considerations which led to the filtering policies? If so, do these
security problems still exist? Couldn't the filtering be made more
specific? Finally, is it considered good manners to forbid FINGER
requests to our machines, while our local users can finger other hosts
all over the world?

Just wondering,
-- 
Simon Leinen.
Laboratoire d'Intelligence Artificielle
Ecole Polytechnique Federale de Lausanne
IN-Ecublens
1015 Lausanne
Tel.: (021) 693-5277
Office: INR 237