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Sub: ECRT Advisory - EA-95:01 Sever


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Subject: ECRT Advisory - EA-95:01 Severe Bit Shortage
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Since this has significant impact to Internet services, I felt I should
pass this along as quickly as possible.


chuq
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Date: Sat, 1 Apr 1995 16:25:23 -0600
From: ecrt-advisory@ecrt.org (ECRT Advisory) (by way of werner@cs.utexas.edu (Werner Uhrig))
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 num ber 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 from unused software and data being stored on disk or other magnetic media. ECRT 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.

Chuq Von Rospach (PlaidSoft: Writing, Editing, and Damage Control for Hire)
chuqui@netcom.com * GEnie:chuq * AOL:chuqui * CIS:75141,1242
chuq@abs.apple.com * Apple Business Systems * Software Gnome
{Member Science Fiction & Fantasy Writers of America}
Home page: http://abs.apple.com/~chuq/chuqui.html


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