Dr. Dobb's Journal December 2002
Funded by a new grant from the National Science Foundation, scientists from five universities and research institutes are working together on the Infrastructure for Resilient Internet Systems (IRIS) project (http://iris.lcs.mit.edu/software.html). Seeking to transcend the limitations of scalability and security that have plagued other distributed networks such as Gnutella, the IRIS project has two goals: Add a capacity for secure, highly fault-tolerant data storage to the Internet, and provide an infrastructure upon which other distributed applications might be built.
IRIS relies on the properties of distributed hash tables (also known as "lookup services" or "location-independent routing services"). In a DHT-based network, each document or piece of data is associated with a key; nodes in the network each store some part of the address index, though the stored data changes on a dynamic basis.
The NSF grant money partially goes toward building prototype networks to test the IRIS software. The first, a small network of 100 nodes, is expected to be online within a year. Then, with the help of Intel's PlanetLab testbed (http://www.planet-lab.org/), project members plan to build a prototype of 1000 nodes. By the end of the five-year grant period, they hope to have a usable, publicly available network in place.
The J Consortium, a group of companies challenging Sun Microsystem's control of the Java specifications, has released a reference generator and dumper for its JEFF file format. JEFF, an ISO standard (published in July, 2002) intended for use in embedded devices, lets Java programs be executed from storage memory, and reduces the size of Java files. The generator and dumper were created by Silicomp, and are published both in source and binary form by the JEFF Working Groups (http://www.j-consortium .org/jeffwg/index.shtml).
The Educational Testing Service (ETS) has canceled two scheduled testing dates for the GRE Computer Science Subject Test, leaving only the December 2002 testing date open, and has announced that the subject test will not be offered at all in India or China during the 2002-2003 academic year. According to the GRE board, "significant numbers" of questions from the subject test have been posted to the Internet in China and India, throwing the validity of the scores into question. ETS believes that the questions were memorized by students during early administrations of the test (see http://www.ets.org/news/grecsqa.html).
In 2002, 862 students from China and 388 students from India took the Computer Science subject test. According to ETS, "applicants to graduate programs in computer science from those countries are urged to highlight their other key credentials like grade point average in relevant courses, work experience, and letters of recommendation."
The computer science test is expected to return to China and India in 2003, presumably once additional security measures have been implemented. The ETS says, however, that the security problem is not occurring in other regions of the world, nor has it affected other subject tests.
The first two Voyager spacecraft were launched 25 years ago this year. While their primary missions—close flybys of the gas giant planets—were completed in 1989, the two spacecraft remain in daily contact with NASA scientists. Communications are conducted over NASA's Deep Space Network (http://deepspace.jpl.nasa .gov/dsn/), though it now takes almost 12 hours for a command signal from Earth to reach Voyager 1 (http://voyager.jpl.nasa .gov/index.html).
The Voyagers' onboard Computer Command Systems (CSS), which carry out commands and respond to malfunctions, are limited in power by today's technological standards: They are 18-bit, interrupt-type processors with 4096 words of nonvolatile memory. Their resilient and flexible design, however, has let them remain in working order as the mission expands and evolves. Ten percent of CSS memory is occupied by fault-protection algorithms; the Voyagers can go into a "safe state" in a matter of seconds. The memory also contains both fixed routines and a reprogrammable section. (All programming is done in assembly language.)
Voyager 1 has now traveled more than 84 times the distance between the Earth and the sun, making it the farthest-flung man-made object in the universe. Voyager 2 is traveling more slowly, but both spacecraft passed the orbit of Pluto a decade ago, and are now seeking the outer edges of our solar system. They have enough power to fly until the year 2020.