In message <431DD3BD(_dot_)9090108(_at_)cisco(_dot_)com>, Eliot Lear writes:
More and more voice over ip (VoIP) has gained acceptance in the market
place. However, the ability to debug end points real time is limited.
Wouldn't it be nice for a manager to query a phone to determine how
many data packets it thinks it has sent to a far end and then follow
that stream to determine who is dropping? In order to accomplish this
task, the manager has to have access to a phone which, if remote, may
well be sitting behind a firewall such as the one you have at home.
Eliot, I have very grave reservations about this. Quite frankly, I
don't think that arbitrary management stations should have any right
whatsoever to connect to my devices.
I agree that the functionality you suggest is useful. The trick is to
permit that without permitting misbehavior. (I'll note here that the
interests of vendors and the interests of users are not identical.
More and more, vendors like subscription-based models, where users keep
on paying, to give just one example.) This requires not just a
view-based access control model -- where the view might be "MIB
variables for this call only" -- but an express intent by the user to
permit the access for that particular call. This demands a different
notion of "view" than has been traditional; it also implies a user
interface issue and -- given the existence of firewalls -- a multi-
party protocol: my endpoint, your endpoint, my management proxy (which
is accessible through the firewall), your management proxy, and the
vendor's diagnostic station. I'd be hard-pressed to see this as within
scope for ISMS. It may, however, be a very nice subject for a separate
working group.
Furthermore, if the phone wants to send a notification to a manager, it
too is likely to reside behind a firewall.
Not if the site is properly managed. The manager's port should be
exposed to the outside. Just as web servers have to permit inbound
port 80 and mail servers have to permit inbound port 25, a management
station has to accept its own traffic. A firewall can, at best,
protect the other ports on the machine -- but those should be turned
off anyway.
--Steven M. Bellovin, http://www.cs.columbia.edu/~smb
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