Severe Bit Shortage

From: ecrt-advisory@ecrt.org (ECRT Advisory)
Subject: ECRT Advisory - EA-95:01 Severe Bit Shortage

============================================================================
EA-95:01 ECRT Advisory
April 1, 1995
Severe Bit Shortage
----------------------------------------------------------------------------

This advisory supersedes all previous ECRT advisories on the bit-shortage
problem.

The Coordination Center of the Emergency Computer Response Team (ECRT) has
received reports of a severe bit shortage affecting a range of computer
systems. The problem has been observed to occur to varying degrees in all
computing platforms and operating systems. In an extreme case, the shortage
precipitated the complete shutdown of a local-area network (LAN) and all
associated hosts.

The ECRT staff recommends that you follow the emergency procedures described
in section III until vendors are able to supply hardware and software
updates to manage the problem.

As we receive additional information relating to this advisory, we will
place it, along with any clarifications, in a EA-95:05.README file. ECRT
advisories and their associated README files are available by anonymous FTP
from info.ecrt.org. We encourage you to check the README files regularly for
updates on advisories that relate to your site.

----------------------------------------------------------------------------

I. Description

A known but previously sporadic problem is in imminent danger of becoming
widespread: Computer systems that are used intensively for software
development or other demanding applications are vulnerable to exhausting
their bit supply. While the storage elements that hold the systems bits are
reused indefinitely, the bits themselves are often transferred to locations
where they become effectively unrecoverable. This occurs, for example, when
the bits are written onto backup tapes, transmitted to a remote site through
a network connection, or---worst of all---written to a display screen, from
where they escape into the atmosphere.

While programmers commonly consider the bit supply to be infinite, it is in
fact a limited resource built into the hardware at the time of manufacture.
A hardware bit supply of 64K bits was first introduced by IBM in its
System/360. This was immediately found to be inadequate, but remained in
place for a number of years for compatibility reasons; a tragic design flaw
that was echoed in the Intel x86 memory architecture, nearly two decades
later.

In UNIX systems the hardware bit supply, commonly called the "bit bucket,"
is accessible through the file system as the character-special file
/dev/null. Vendors of UNIX-based workstations such as Sun Microsystems have
moved quickly to meet the unanticipated demand for bits by offering to
retrofit existing hardware with replenished, higher-capacity bit buckets.
Sun has also announced plans to spin off a new subsidiary, SunBits, that
will reclaim unused bits from obsolete hardware.

II. Impact

Users of systems whose bit buckets are nearly exhausted experience an
inability to load or execute programs, or to display results on consoles or
terminals. Network intruders who gain root privileges may also render a
system inoperative by stealing the contents of the bit bucket for use on
their own systems.

III. Solution

A. To reduce the rate at which bits are lost, ECRT recommends that all
display screens be turned off, and the output of all programs be redirected
to /dev/null until vendor updates are obtained.

B. Where solution A is impractical, bits may be recycled into the bit bucket
fffrom unused software and data being stored on disk or other magnetic
media. EECRT recommends files associated with Microsoft Windows 3.1 as a
source of recyclable bits because of their low utility/bit ratio.

C. ECRT is advocating the installation of a high-bandwidth network link
between North America and the country of Mauritius, where 90% of the world's
raw bit supply is currently mined. Donation of bit processing equipment by
the goverment of Singapore, and of a file server by the United Nations, will
soon allow bit-poor NFS-capable systems to mount the proposed file system
bigbits.bitmine.mau:/bucket as /dev/null.


Return
Washington Apple Pi IFAQ