Network Working Group J. Van Bokkelen
Request for Comments: 1173 FTP Software, Inc.
August 1990
Responsibilities of Host and Network Managers
A Summary of the "Oral Tradition" of the Internet
Status of this Memo
This informational RFC describes the conventions to be followed by
those in charge of networks and hosts in the Internet. It is a
summary of the "oral tradition" of the Internet on this subject.
[RFC Editor's note: This memo is a contribution by the author of his
view of these conventions. It is expected that this RFC will provide
a basis for the development of official policies in the future.]
These conventions may be supplemented or amended by the policies of
specific local and regional components of the Internet. This RFC
does not specify a standard, or a policy of the IAB. Distribution of
this memo is unlimited.
Table of Contents
Status of this Memo .............................................. 11. Basic Responsibilities......................................... 12. Responsibilities of Network Managers........................... 23. Responsibilities of Host System Managers....................... 24. Postmaster@foo.bar.baz......................................... 35. Problems and Resolutions....................................... 36. The Illusion of Security....................................... 47. Summary........................................................ 58. Security Considerations........................................ 59. Author's Address............................................... 5
The Internet is a co-operative endeavor, and its usefulness depends
on reasonable behaviour from every user, host and router in the
Internet. It follows that people in charge of the components of the
Internet MUST be aware of their responsibilities and attentive to
local conditions. Furthermore, they MUST be accessible via both
Internet mail and telephone, and responsive to problem reports and
diagnostic initiatives from other participants.
Even local problems as simple and transient as system crashes or
power failures may have widespread effects elsewhere in the net.
Problems which require co-operation between two or more responsible
individuals to diagnose and correct are relatively common. Likewise,
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RFC 1173 Responsibilities of Host and Network Managers August 1990
the tools, access and experience needed for efficient analysis may
not all exist at a single site.
This communal approach to Internet management and maintenance is
dictated by the present decentralized organizational structure. The
structure, in turn, exists because it is inexpensive and responsive
to diverse local needs. Furthermore, for the near term, it is our
only choice; I don't see any prospect of either the government or
private enterprise building a monolithic, centralized, ubiquitous "Ma
Datagram" network provider in this century.
One or more individuals are responsible for every IP net or subnet
which is connected to the Internet. Their names, phone numbers and
postal addresses MUST be supplied to the Internet NIC (or to the
local or regional transit network's NIC) prior to the network's
initial connection to the Internet, and updates and corrections MUST
be provided in a timely manner for as long as the net remains
connected.
In order to adequately deal with problems that may arise, a network
manager must have either:
A. System management access privileges on every host and router
connected to the local network, or:
B. The authority and access to either power off, re-boot,
physically disconnect or disable forwarding IP datagrams from
any individual host system that may be misbehaving.
For all networks, a network manager capable of exercising this level
of control MUST be accessible via telephone 8 hours a day, 5 days a
week. For nets carrying transit traffic, a network manager SHOULD be
accessible via telephone 24 hours a day.
One or more individuals must be responsible for every host connected
to the Internet. This person MUST have the authority, access and
tools necessary to configure, operate and control access to the
system. For important timesharing hosts, primary domain name servers
and mail relays or gateways, responsible individual(s) SHOULD be
accessible via telephone 24 hours a day, 7 days a week.
For less-important timesharing hosts or single-user PCs or
workstations, the responsible individual(s) MUST be prepared for the
possiblity that their network manager may have to intervene in their
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absence, should the resolution of an Internet problem require it.
Every Internet host that handles mail beyond the local network MUST
maintain a mailbox named "postmaster". In general, this should not
simply forward mail elsewhere, but instead be read by a system
maintainer logged in to the machine. This mailbox SHOULD be read at
least 5 days a week, and arrangements MUST be made to handle incoming
mail in the event of the absence of the normal maintainer.
A machine's "postmaster" is the normal point of contact for problems
related to mail delivery. Because most traffic on the long-haul
segments of the Internet is in the form of mail messages, a local
problem can have significant effects elsewhere in the Internet. Some
problems may be system-wide, such as disk or file system full, or
mailer or domain name server hung, crashed or confused. Others may
be specific to a particular user or mailing list (incorrect aliasing
or forwarding, quota exceeded, etc.).
In either case, the maintainer of a remote machine will normally send
mail about delivery problems to "postmaster". Also, "postmaster" is
normally specified in the "reply-to:" field of automatically
generated mail error messages (unable to deliver due to nonexistent
user name, unable to forward, malformed header, etc.). If this
mailbox isn't read in a timely manner, significant quantities of mail
may be lost or returned to its senders.
Advances in network management tools may eventually make it possible
for a network maintainer to detect and address most problems before
they affect users, but for the present, day-to-day users of
networking services represent the front line. No responsible
individual should allow their "dumb-question" filter to become too
restrictive; reports of the form "I haven't gotten any mumblefrotz
mail for a week... " or "I could get there this morning, but not
now..." should always get timely attention.
There are three basic classes of problems that may have network-wide
scope: User-related, host-related and network-related.
A. User-related problems can range from bouncing mail or
uncivilized behaviour on mailing lists to more serious
issues like violation of privacy, break-in attempts or
vandalism.
B. Host-related problems may include mis-configured software,
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obsolete or buggy software and security holes.
C. Network-related problems are most frequently related to
routing: incorrect connectivity advertisements, routing
loops and black holes can all have major impacts.
Mechanisms are usually in place for handling failure of
routers or links, but problems short of outright failure
can also have severe effects.
Each class of problem has its own characteristics. User-related
problems can usually be solved by education, but system managers
should be aware of applicable federal and state law as well; Privacy
violations or "cracking" attempts have always been grounds for
pulling a user's account, but now they can also result in
prosecution. Host-related problems are usually resolvable by re-
configuration or upgrading the software, but sometimes the
manufacturer needs to be made aware of a bug, or jawboned into doing
something about it; Bugs that can't be fixed may be serious enough to
require partial or total denial of service to the offending system.
Similar levels of escalation exist for network-related problems, with
the solution of last resort being ostracism of the offending net.
Every host and network manager MUST be aware that the Internet as
presently constituted is NOT secure. At the protocol level, much
more effort has been put into interoperability, reliability and
convenience than has been devoted to security, although this is
changing. Recent events have made software developers and vendors
more sensitive to security, in both configuration and the underlying
implementation, but it remains to be demonstrated how much long-term
effect this will have. Meanwhile, the existing system survives
through the co-operation of all responsible individuals.
Security is subjective; one site might view as idle curiosity what
another would see as a hostile probe. Since ultimately the existence
of the Internet depends on its usefulness to all members of the
community, it is important for managers to be willing to accept and
act on other sites' security issues, warning or denying access to
offending users. The offended site, in turn, must be reasonable in
its demands (someone who set off an alarm while idly seeing if the
sendmail "DEBUG" hole was closed on a "sensitive" host probably
should be warned, rather than prosecuted).
Because Internet security issues may require that local management
people either get in touch with any of their users, or deny an
offending individual or group access to other sites, it is necessary
that mechanisms exist to allow this. Accordingly, Internet sites
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SHOULD NOT have "general use" accounts, or "open" (without password)
terminal servers that can access the rest of the Internet.
In turn, the "sensitive" sites MUST be aware that it is impossible in
the long term to deny Internet access to crackers, disgruntled former
employees, unscrupulous competitors or agents of other countries.
Getting an offender flushed is at best a stop-gap, providing a
breathing space of a day or an hour while the security holes under
attack are closed. It follows that each host's manager is ultimately
responsible for its security; the more "sensitive" the application or
data, the more intimate the manager must be with the host's operating
system and network software and their foibles.
The heart of the Internet is the unique community of interest
encompassing its users, operators, maintainers and suppliers.
Awareness and acceptance of the shared interest in a usable Internet
is vital to its survival and growth. The simple conventions
presented here should be supplemented by common sense as necessary to
achieve that end.