Lbl scientists are probing the properties of fullerenesña family of molecules with immense industrial potential




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This latter undertaking involves a collaboration between Zettl's group and the femtosecond laser research group of LBL Director Charles V. Shank. Fullerene samples will be flashed with a succession of visible light


pulses only 12 femtoseconds long (a femtosecond is a millionth of a billionth of a second). Spectroscopic analysis, led by MSD's Robert Schoenlein, will subsequently allow the researchers to follow the photoexcitation process step by step.


Another effort underway at LBL, led by MSD physicist Yuen-Ron Shen, will explore the nonlinear optical properties of fullerenes (see sidebar).


Zettl and Cohen would like to establish a central fullerene research program at LBL. ''The program will take advantage of the initial lead Berkeley presently has in many areas of fullerene-derivative synthesis, single crystal growth, and superconductivity," says Zettl.


In addition to their staff positions at LBL, Zettl and Cohen are both professors at UC Berkeley. Their proposed fullerene program would thus be able to bring together several strong physics and chemistry research groups from both institutions.


ÑLYNN YARRIS


9


BUILDING THE SUPERHIGHWAY


RESEARCHERS AT LBL ARE

MAKING KEY CONTRIBUTIONS

TO NETWORK CONFERENCING

AND SCIENTIFIC IMAGING


[BEN - THIS STUFF IS UNSCANNABLE. I LEFT IT IN IN CASE YOU WANT TO CLEAN IT UP RATHER THAN RETYPE IT.]


IN 1989, LB] Johnston was U.S. Senate h plore the potent) superhighway.


Johnston an Washington the computer demons fore a Senate heari sibilities of a trig computer netwo in a computer an analyzed, and asse tific ''movies" by tributed thousa demonstrated hov netic resonance i ers, data-storag workstations cou together, linking i ways never befo


Four years let and Vice Presiden had chaired th California's Silico Graphics Inc., the of the emerging i and, in turn, share Gore has champio infancy.


On the eve o Silicon Graphics


tRS AT LBE ARE ~ ~ ~ ~ : :C2ONTRIB:WIONtS


C',tONFERENC,~ING


: : : :


$19i'7IC; 7MAGI\G


;RESEARC'HER BIl ~ ~; ailed to Waslnington~for~a~ ~ ~;~ aring. Its purpose: to ex- ~ ;~;~ of a nationa l information


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hiss colleagues showed~ sure.; 1)llring~rthe first live~


. . ; , :, ~;. ~ S; ~ ~ ~


ratnon ever conholuctea oe ~ ~:


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displaycod data;~ rocessed,: bled inmto anminnated scien-evices;~a~nd ~researchers ~ dis'ds of wiles;~apart. I hey equ~prnent~stuch~as a magagnng wmnt, supercomput~deviccs, and coomp~ter bc tempo>rarily bridged olividwals and resolirces in~


ossil~le.


r, Presidellt Bill (,linton Al Gore who, as senator, 1989 ~h~earing, fleww too Valley. Meetiilg at Silicon were bricted on the status~^ ~ ~;'~ tornnation superlnnghway their vision for its future ncd this proJect snnce;~its


:


the Clinton-Gore visit,; Andrew Cherenson sen t


F ~RHIGHW,


out;a spur-of-tlne-moment message on a spreading,~ spiderwveb-like computer net­sviork that nnow links many academic and research institutions around the world: Alnybody interested in the Clinton/Gore conference? Logging in later, he checked


,


tlne response.


Tlne~ next nhorning, Cherenson plugged in a Sony nninicamera and tagged along with~Glinmton and Gore during their br~annstorming sessnon with the planners and players who are l~elping build the in~forma;tionn~:superlnighway. Around the world, 200 rapt "participants" sat at their desks in tronlt of connputer workstations, watching tine events at Silicon Graphics while com;menting ;among themselves. Cherenson's innprolmptu video confer­enceÑa lnarbinger of the ease with which we will~be fable to talk, visit together, and share~information in the near futureÑwas broadcast in 11 countries and 22 time


zones. ~ ~ ; ;


A decade ago, such communication wvas conventional witlmin the world of sci­ence fiction; but new and alien as a nation­al policy goal.;~lleginning in 1968, the federal goverlhment through its Defense Advanced~ Research Projects Agency (DARPA) provided ~seed money to estab­fish fi~rst one; and tlne~ several experimental networks that coul' move data between researc~ln institutions~at high speed. These prototype network.s ll ave evolved, prolifer­ated,~and rapidly linked. Today, a fused


:: ~ :: ~ :; ~ ;: ;


^illfrastructure~;of more than 11,000 net­~vorks ltnown as the Internet, or just ''the net," joins upwards of 10 million people arounm;d time world. ~ ~; : ~ :~:From;ittie:outse I.aboratony has bee ; architects~of lhetwo


``tf~r~`r thP net`~r


Lawrence Berkeley one of the principal computing, helping " since 1972. LBL "went on;the air" in;L975, becoming one of a handful of institutions connected to the netwvork.~ When the Internet overload­ed, bogged down, a~1 was on the verge of self-destructionn in ~86, LBL researcher


~T ~ :- ~'t of a two-man team


that helped rescue it, saving it from those who recommended that it should be abandoned. More recently, Jacobson and his team have made other key contributions, engineering the metamorphosis of what had been a data and e-mail pipeline into a network that now allows many people to speak and interact instantly via audio and video network conferencing. Today, this formerly mail-dominated culture is flourishing, allowing people around the world to interact routinely, just as they did during the Clinton/Gore Silicon Graphics visit. LBL also is a pioneer in distributed scientific computing, forging new links that make the location of expensive computing resources immaterial.


Looking at what has been accomplished and what is in the works, LBL Information and Computing Sciences Division Director Stu Loken says we are at the dawn of a new Information Age.


''The federal government has a long history of investment in the nation's infrastructure," notes Loken. ''It built canals in the 18th century, railroads in the 19th century, and interstate highways in the 20th century. Then, about 10 years ago, it began the construction of high-speed computer networks. These networks are the highways of the Information Age."


Loken and almost every other researcher in the field say the information superhighways will result in the inevitable convergence of television, telephone, cable television, computer, consumer electronics, publishing and information enterprises into a single interactive information industry. Vice President Gore predicts this will be ''the most important and lucrative marketplace of the 21st century." AT&T says it expects the global information market to be worth $1.4 trillion by 1996; Apple Computer estimates the market will grow to $3.5 trillion by the year 2001.


The vision of information superhighways almost crashed in 1986.


12


Then almost two decades old, the Internet had 10,000 users. They had come to rely on the network for it had already become much more than just a means to exchange electronic mail and move data. The network served as a virtual office hallway, intimately connecting distant collaborators.


In October of 1986, the Internet experienced what its many designers diagnosed as ''congestion collapse." CommunicationsÑa digital data-stream consisting of everything from written messages to raw scientific dataÑhad been flowing through the system at up to 56 kilobits per second (56,000 bits, or about two typed pages, per second). Then one day, this 21st-century information system suddenly slowed to the pace of the telegraph. That day, the transmission rate between Lawrence Berkeley Laboratory and the University of California at Berkeley only a quarter-mile away slowed to 320 bits per second. Users of the system were mystified and dismayed.


Internet users all over the country, as reliant on the network as most of us are on our telephones, puzzled over how to revive it. Van Jacobson from LBL's Engineering Division was among those who became involved.


''The network had slowed by a factor of a thousand," recalls Jacobson. ''Mail that had gone through in minutes now took a full day. People started giving up on this. The whole idea of network communication was imperiled.


''I was working with Mike Karels (of the Berkeley Unix development group at the University of California at Berkeley). For six months, we had been asking why the Internet was failing, beating our heads against a brick wall. Then one night in a Berkeley coffee house, there was a moment of enlightenment. We turned the question around. The real question was, 'How had the Internet ever worked?'


"Think about it," says Jacobson: A workstation can transmit data at 10 megabits per second (10 million bits) and a router puts it on the Internet, which has a capacity of 56 kilobits per second. You


start with this bottleneck and then must contend with thousands of people using the network simultaneously. Given this, he says, a traffic jam on the Internet was inevitable.


As the traffic had increased on the Internet, the system's many users had relied on what amounted to self-destructive behavior in their attempts to break through the network gridlock. Packets of information would be transmitted to the network by a computer and subsequently returned to the sender because of the congestion. Computers had been programmed to deal with this by immediately trying again, repeatedly resending the message until it went through. Jacobson likens the situation to pouring gasoline on


a fire.


The solution, he says, was to make the network users more polite.


''If too many people try to communicate at once," explains Jacobson, ''the network can't deal with that and rejects the packets, sending them back. When a workstation retransmits immediately, this aggravates the situation. What we did was write polite protocols that require a slight wait before a packet is retransmitted. Everybody has to use these polite protocols or the Internet doesn't work for anybody."


Jacobson and Karels' protocols, now a universal part of the Internet, are called ''Slow Start." Slow Start avoids congestion by monitoring the network and, when congestion appears imminent, delaying the transmission of packets anywhere from milliseconds to a second. Slow Start delays transmission rates based on factors that include the current available capacity of the network as well as a multiple of the round-trip transmission time (essentially, distance) between the sender and the chosen destination. Six years after it was introduced, Slow Start continues to avoid network congestion even though both the speed of the network and the number of users have grown a thousand-fold.


About two years ago, Jacobson and researchers at Xerox's Palo Alto Research Center (PARC) took on a project to add audio and video conferencing to the Internet. As with telephone systems, audio/video conferencing between multiple parties via computer was an old, yet unattained, vision.


13


In terms of conferencing, a computer network starts with an inherent advantage over a telephone system. Whereas a telephone line connects two points and carries one conversation, the Internet connects each party on the line and carries multiple simultaneous "conversations." To support this huge flow of information, it breaks communications down into small packets which are mixed into the ongoing stream of packets traversing the network. Each packet is wrapped with shipping and assembly instructions (called protocols), which give the destination, return address, and how the receiving computer can reorder all the packets back into the original communication.


Because of the slight delays inherent in the Internet, several research groups charged with bringing audio and video conferencing to the network concluded that they had been given an impossible mission. They advised that a new network be built.


''We felt this was ridiculous," recalls Jacobson. ''The Internet supported communication between two Cray supercom


14


puters, which transmit at one gigabit per second (one billion bits). It also worked for somebody sitting at a keyboard, typing at 20 bits per second. This robustness and dynamic range seemed too good to abandon. So we looked hard. There should have been no reason why we couldn't do audio and video."


Delays actually are more disruptive to people talking than they are to video conferencing. Conferees can tolerate an occasional still picture during a video transmission whereas voices heard in uneven staccato bursts sound like gibberish. Jacobson and Steve Deering of Xerox PARC concentrated on devising a system that would preserve the global connectivity of the Internet yet also allow a smooth and prompt audio flow.


To allow the listener to hear continuous speech, Jacobson and Deering first added a time-stamp to each audio packet. The receiver reads the time-stamps, chronologically orders the packets, and then plays them while continuing to receive and order additional incoming packets for subsequent replay. That averts inside-out Pig Latin speech, but it does not deal with the uneven nature of network packet-flow and the bursts of audio that result.


To remedy this, the two researchers took advantage of the difference between the incredible speed at which the network moves packets and the relatively long two-tenths to half-second delay that humans can handle without conversation being disrupted. They created an algorithm that computes how long packets are taking to arrive and then slows down the voice replay enough to allow even the slowest packets sufficient time to arrive. The playback delays introduced by the algorithm actually are very short, typically less than one-tenth of a second. Thanks to the imperceptible controlled delays introduced by Jacobson and Deering, voice conferencing between Internet users with microphones and computer speakers now is commonplace.


Seated in his office at LBL, Jacobson demonstrated how he is connected with


DATA DICTIONARY


Science is a domain where knowledge often leapfrogs ahead of language As new knowledge or techniques arise, scientists neologizeÑinvent new wordsÑproviding a vocabulary th at allows others to know and exchange ideas about what is new. By necessity computer scientists are particularly prolific coiners of words. They also are very imaginative.


Here is a sampling:

ackÑin data communications, ack is a character transmitted by a receiver of data to acknowledge that information has been received from a sender


ARPAnetÑthe mother of all high speed networks, developed by engineers under contract to the Pentagon's Advanced Research Projects Agency in the early 1970s. It was a testbed for early network research, pioneered packet-switching technology, and was the original backbone for the Internet


ATMÑasynchronous transfer mode, a new, very high-speed standard telecommunications transmission protocol recently adopted by telecommunications and computer industries for a new commercial high- speed computer network providing integrated voice-video-data communication


bandwithÑrate at which bits can be transmitted over a networkÑ i.e., at 2 million bits/second


bounceÑthe return of a piece of electronic mail because of an error in delivery
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