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1994-04 MBone Provides Audio and Video Across the Internet
Macedonia, Michael R.
http://hdl.handle.net/10945/40136 MBone Provides Audio and Video Across the Internet
Michael R. Macedonia and Donald P. Brutzman Naval Postgraduate School
he joy of science is in the discovery. In March 1993, our group at the Naval Postgraduate School heard that the Jason Project, an underwater explo ration and educational program supported by Woods Hole Oceanographic IIInstitution in Massachusetts, was showing live video over the Internet from an under water robot in waters off Baja, Mexico. We worked furiously to figure out how to re ceive that video signal, laboring diligently to gather the right equipment, contact the appropriate network managers, and obtain hardware permissions from local bu reaucrats. After several days of effort, we learned that a satellite antenna uplink ca ble on the Jason support ship had become flooded with seawater a few hours before we became operational. Despite this disappointment, we remained enthusiastic because, during our ef forts, we discovered how to use the Internet's most unique network, MBone. Short for Multicast Backbone, 1 MBone is a virtual network that has been in existence since early 1992. It was named by Steve Casner1 of the University of Southern California Information Sciences Institute and originated from an effort to multicast audio and video from meetings of the Internet Engineering Task Force. Today, hundreds of re searchers use MBone to develop protocols and applications for group communi cation. Multicast provides one-to-many and many-to-many network delivery ser Researchers have vices for applications such as videoconferencing and audio where several hosts need to communicate simultaneously. produced the Multicast This article describes the network concepts underlying MBone, the importance of bandwidth considerations, various application tools, MBone events, interesting Backbone, which MBone uses (see the two sidebars), and provides guidance on how to connect your provides audio and Internet site to the MBone. video connectivity from outer space to Multicast networks under water - and Multicasting has existed for several years on local area networks such as Ethernet and Fiber Distributed Data Interface. However, with Internet Protocol multicast ad virtually everyplace in dressing at the network layer, group communication can be established across the In between. Anyone ternet. IP multicast addressing2 is an Internet standard (Request For Comment 1112) developed by Steve Deering3 of the Xerox Palo Alto Research Center and is sup can use it. ported by numerous workstation vendors, including Sun, Silicon Graphics, Digital
30 US govcrnmcnl work is no! pro!cctcJ by US copyright. COMPUTER MBone and distance learning at the Naval Postgraduate School Mike Mccann, NCAA and the lab at NPS, and could ask questions ()f the Naval Postgraduate Schoof Visualization Laboratory NCAA instructor over the network. Advar1ced preparation, good audio, and a camera operator in the NCARclassroom In March 1993, the W.R. Church Computer Center at the gave us a real. feeling of presence inBot.llder. "It wa$ justlike Naval Postgraduate School dedicated a Sun Sparcstation 2 being there," one of my classmates said. . to act as a Multicast Backbone (MBone) router for the cam Paul Hyder of NCAR was. instrumental in helping set up a pus and the Monterey Bay research community. This router direct "backup" tunnel betw~en NPS and NCAR, where the and an IP-encapsulated tunnel from Stanford University slowest I.ink is the T1 line between NPS and Stanford. During provides the NPS backbone with real-time audio, video; and the course, there was only one 30-minute period of br:oken other MBone data feeds. up audio. We later determined that this interruption was The MBone is an excellent tool for those doing research in caused by congestion on NCAR'sEther.net LAN. networks and video teleconferencing technology. Although it For much of 1993, the NPS Visualization lab loaned a Sun is not generally thought of as "ready for prime time" (audio Sparcstation 10 to the Monterey Bay Aquariurn Research dropouts may be frequent and video, at best, is only 3 Institute for testing and incorporation into the live audio/video frames per second over the Internet), NPS successfully used link to the research vessel Point Lobos and the remotely it to provide training in Cray Fortran optimization from the operated vehicle Ventana that explbre the Monterey subma National Center for Atmospheric Research in Boulder, rine canyon each day (see Figure A). Local res.earchers in Colorado. oceanography, virtual reality, and autonomous underwater Five people who would not have been able to afford to vehicles continue to take advantage of the. collaboration travel to Boulder remotely "attended" the three-day training opportunities that this technology makes possible. course at the NPS Computer Center's Visualization Labora It might not be too long before MBone enables us to video. tory. For the session, students - including myself - en conference with a classroom or a colleague half way around joyed two-way audio and video between the classroom at the world - directly from our desktop workstations.
megrez3telnethp8502001 Trying134.89.2.200 ... Connect«! to hp850.mbartotg. E1capecharacteri:1 '"'l'. Troll control login: teto Pauword: Type? for help.qto quit 10:24Vt6G299.8 -Hi 34.4 3.4280.40.530023Ll299.5 Time Pol Az El LYI Sp PL Dir Sen Ct Rng Bmg 10:24Vt6G299.8 -1.6 34.4 3.4280.40.5300230299.5 az270 10:24Vt6G299.8 -1.6 35.2 3.4280.40.5350231)299.5 10:24Vt6G299.8 -1.6 35.2 3.428tt40.535023Jl299.S g 1o :25 Vt 6G 271.6 -1.6 6.8 1.6 272.20.5 350 23.0 299.5 10:25Vt6G271.6 -1.6 6.8 1.627220.530023..0299.5 10:25Vt6G271.6 -1.6 6.8 1.627220.535023Jl299.5 10 :25 Vt 6G 271.6 -1.6 6.8 1.6 27220.5 350 23.0 299.5 10:25Vt6G271.6 -1.6 6.8 1.627220.530023»299.5 10:26 Vt 6G27Ui -Hi 6.8 0.7 22810.5 35023.0299.5 10:26Vt6G271.6 -1.6 10.3 0.7228.10.535123.0299.5 q Conneclioodosedby fotll!igohost megrez% telnet hp8502000 Tryirg 134.892.200 ... Connectedto hp850mbali.or9
' . Figure A. MBone session at the Monterey Bay Aquarium Research Institute showing application tools nv(network video), vat (visual audio tool), wb (whiteboard), and sd (session directory).
April 1994 31 Equipment Corporation, and Hewlett among the islands of MBone subnets Thus, a 128-kilobit per second video Packard. Categorized officially as an IP through Internet IP routers that (typi stream (typically 1-4 frames per second) Class D address, an IP multicast address cally) do not support IP multicast. This uses the same bandwidth whether it is re is mapped to the underlying hardware is done by encapsulating the multicast ceived by one workstation or 20. That is multicast services of a LAN. Two things packets inside regular IP packets. As in good. However, that same multicast make multicasting feasible on a world stalled commercial hardware is upgraded packet is ordinarily prevented from cross wide scale: to support multicast traffic, this mixed ing network boundaries such as routers. system of specially dedicated mrouters The reasons for this current restriction (1) installation of high bandwidth In and tunnels will no longer be necessary. are religious and obvious from a net ternet backbone connections, and We expect that most commercial routers working standpoint. If a multicast stream (2) widespread availability of worksta will support multicast in the near future, that can touch every workstation could tions with adequate processing eliminating the inefficiencies and man jump from network to network without power and built-in audio capability. agemenfheadaches of duplicate routers controls, the entire Internet would quickly and tunnels. become saturated by such streams. That The reason MBone became a virtual would be disastrous! Therefore, controls network is that it shares the same physi are necessary. cal media as the Internet. It uses a net MBone can control multicast packet work of routers ( mrouters) that can sup Bandwidth distribution across the Internet in two port multicast. These mrouters are either constraints ways: upgraded commercial routers, or dedi cated workstations running with modi The key to understanding the con (1) It can limit the lifetime of multicast fied kernels in parallel with standard straints of MBone is thinking about band packets, and routers. width. The reason a multicast stream is (2) It can use sophisticated pruning al MBone is augmented by "tunneling," a bandwidth-efficient is that one packet can gorithms to adaptively restrict multi scheme to forward multicast packets touch all workstations on a network. cast transmission. This is being tested.
-- ' -- ... ·- .. .·:·~C~~~t~··~qieuce pver the MBone during the JasonPro~(!t~~L ,·- ·~ Ah~~M¥t:~1; W()ods Hole Oceanographic Institution anyone on the MBone who'fia~~·~o1~thefllouLAs sonar surveys progressedduringJ~.~xpedition,gatawas )J~$on~e~eais ?Jemotely ?Pe~ated, dual-vehicle sys transmitted back to shore, and tile :detaifeifmoctels were < 'tern dev~loped ~y the Woods Hole Oceanographic Institu updated and then distrlbutedoveJ:lhelntemet . ~()ll for u~d~rwatef .s?ience and exploration. The Jason A workstation on board the LanejCfi~$tgenerated •·Foundation f?r r::o~cation uses this system as part of an multicast packets containing navigatlorran
32 COMPUTER Responsible daily use of the MBone net Table 1. Electronic mail addresses for requesting addition to the MBone mail lists. work consists merely of making sure you don't overload your local or regional bandwidth capacity. Electronic Mail Address MBone protocol developers are ex Mail List for Subscription Requests Region perimenting with automatically pruning and grafting subtrees, but for the most mbone-eu: [email protected] Europe part MBone uses thresholds to truncate mbone-jp: [email protected] Japan broadcasts to the leaf routers. The trun mbone-korea [email protected] Korea cation is based on the setting for the time mbone-na: [email protected] North America to-live (ttl) field in a packet that is decre mbone-nz: [email protected] New Zealand mented each time the packet passes mbone-oz: [email protected] Australia though an mrouter. A ttl value of 16 mbone-sg: [email protected] Singapore would limit multicast to a campus, as op mbone: [email protected] Others posed to values of 128 or 255, which might send a multicast stream to every rem-conf [email protected] Worldwide subnet on the MBone (currently about 13 countries). A ttl field is sometimes de cremented by large values under a global thresholding scheme provided to limit Table 2. Electronic mail addresses for putting messages on the mailing lists. multicasts to sites and regions if desired. These issues can have a major impact on network performance. For example, a Electronic Mail Address default video stream consumes about 128 Mail List for Posting Messages Purpose Kbps of bandwidth, or nearly 10 percent of a Tl line (a common site-to-site link on MBone [email protected] Network configuration the Internet). Several simultaneous high and tool development bandwidth sessions might easily saturate rem-conf [email protected] Conference announcements network links and routers. This problem and general discussion is compounded by the fact that general purpose workstation routers that MBone typically uses are normally not as fast or robust as the dedicated hardware routers used in most of the Internet. ing Group5 has proposed a Multicast ex nounces itself to the MBone mail list, and tension to the Open Shortest Path link the nearest potential providers decide state protocol that addresses this issue us who can establish the most logical con Networking details ing an algorithm developed by Deering.5 nection path to minimize regional Inter With both protocols, mrouters must dy net loading. When a host on an MBone-equipped namically compute a source tree for each Scheduling MBone events is handled subnet establishes or joins a common participant in a multicast group. similarly. Special programs are announced shared session, it announces that event via MBone is small enough that this tech in advance on an MBone event electronic the Internet Group Management Proto nique is not a problem. However, some mail list (for example, [email protected] col. The mrouter on the subnet forwards researchers speculate that, for a larger for messages and rem-conf-request@es. that announcement to the other mrouters network with frequently changing group net for subscription requests) (see Tables in the network. Groups are disbanded memberships, these routing techniques 1 and 2). Advance announcements usu when everyone leaves, freeing up the IP will be computationally inefficient. Re ally prevent overloaded scheduling of In multicast address for reuse. The routers search efforts on these issues are on ternet-wide events and alert potential occasionally poll hosts on the subnets to going, since every bottleneck conquered participants. determine if any are still group members. results in a new bottleneck revealed. Cooperation is key. Many people are If there is no reply by a host, the router surprised to learn that no single person or stops advertising that host's group mem entity is "in charge" of either local topol bership to the other multicast routers. ogy changes or event scheduling. MBone routing protocols are still im Topology and event mature and their ongoing design is a cen scheduling tral part of this network experiment. Protocols Most MBone routers use the Distance The MBone community must manage Vector Multicast Routing Protocol, the MBone topology and the scheduling The magic of MBone is that telecon which some network researchers com of multicast sessions to minimize conges ferencing can be done in the hostile world monly consider inadequate for rapidly tion. By the beginning of 1994, some 750 of the Internet where variable packet de changing network topologies because subnets were already connected world livery delays and limited bandwidth play routing information propagates too wide. Topology changes for new nodes havoc with applications that require some slowly.4 The Open Shortest Path Work- are added by consensus: A new site an- real-time guarantees. Limited experi-
April 1994 33 ments demonstrated the feasibility of au Windows versions are available, although dio over the ARPAnet as early as 1973. ported tools can be found for 386 boxes However, only a few years ago, transmit running the (free) 386BSD Unix. Point ting video across the Internet was con ers to all public.application tools are in sidered impossible. Development of cluded in the Frequently Asked Ques effective multicast protocols disproved tions section.1 Mirror FTP sites are that widespread opinion. In this respect, available overseas. MBone is like the proverbial talking dog: Additional tools are also available or It's not so much what the dog has to say under development. Winston Dang of that is amazing, it's more that the dog can the University of Hawaii has created imm talk at all! (Image Multicaster Client), a low-band The key network concepts that make width image server. It typically provides MBone possible are IP multicast and real live images of Earth from various geo time stream delivery via adaptive re stationary satellites at half-hour intervals ceivers. For example, in addition to the in either visible or infrared spectra. multicast protocols, many MBone appli Henning Schulzrinne of AT&T/Bell cations are using the draft Real-Time Pro Laboratories developed nevot, a network tocol on top of the User Datagram Pro voice terminal providing multiple party tocol and Internet Protocol. RTP,6 being Figure 1. The sd (session directory) of conferences with a choice of transport developed by the Audio-Video Transport MBone events. protocols. Eve Schooler of the Informa Working Group of the Internet Engi tion Sciences Institute is part of a team neering Task Force, provides timing and developing mmcc, a session orchestration sequencing services, permitting the appli tool and multimedia conference control cation to adapt and smooth out network may have different audio processing hard program. induced latencies and errors. ware (for example, different microphones Mike Macedonia of the Naval Postgrad Related real-time delivery schemes are and amplifiers). Audio also generates lots uate School, coauthor of this article, has also being evaluated. The end result is that of relatively small packets, which are the created a multicast version of NPSNet,7 a even with a time-critical application such bane of network routers. 3D distributed virtual environment that as an audio tool, participants normally uses the IEEE Distributed Interactive perceive conversations as if they are in real Simulation (DIS) application protocol.8 time. This is because there is actually a Application tools Stephen Lau of SRI International small buffering delay to synchronize and is experimenting with using graphics resequence the arriving voice packets. Besides basic networking technology, workstation windows as image drivers. Protocol development continues. Al MBone researchers are developing new Kurt Lid! of UUnet Technologies, Falls though operation is usually acceptable in applications that typify many of the Church, Virginia, is working on a net practice, many aspects of MBone are still goals associated with the information work news distribution application that considered experimental. superhighway. Session availability is dy uses multicast to reduce overall Internet namically announced using a tool called loading and expedite news delivery. sd (session directory), which displays ac (Their goal is 120 ms total propagation Data compression tive multicast groups (see Figure 1). The coast to coast - which is amazing since sd tool also launches multicast applica light takes about 16 ms to make that trip.) Other aspects of this research include tions and automatically selects unused the related needs to compress a variety of addresses for any new groups. Steve media and optionally provide privacy McCanne and Van Jacobson of the Uni Events through encryption. Several techniques versity of California Lawrence Berkeley to reduce bandwidth include Joint Pho Laboratory developed sd. Many of the most exciting events on tographic Experts Group compression, Video, audio, and a shared drawing the Internet appear on MBone first. Per wavelet-based encoding, and the ISO whiteboard are the principal MBone haps the most popular is NASA Select, standard H.261 for video. Visually, this applications, provided by software pack the in-house cable channel broadcast dur translates to "velocity compression"; ages called nv (net video), vat (visual au ing space shuttle missions. It's exciting rapidly changing screen blocks are up dio tool), and wb (whiteboard). The prin seeing an astronaut positioning another dated much more frequently than slowly cipal authors of these tools are Ron astronaut by the boots to repair a satellite changing blocks. Frederick of Xerox Palo Alto Research - live on your desktop from 150 miles Encodings for audio include Pulse Center for nv, and McCanne and Jacob above the surface of the planet. Coded Modulation and Group Speciale son for vat and wb. Each program is avail Conferences on supercomputing, the Mobile (the name of the standardization able in executable form without charge Internet Engineering Task Force, scien group for the European digital cellular from various anonymous File-Transfer tific visualization, and many other topics telephony standard). Besides concerns for Protocol sites on the Internet. Working have appeared - often accompanied by real-time delivery, audio is a difficult me versions are available for Sun, Silicon directions on how to download PostScript dia for both MBone and teleconferencing Graphics, DEC, and Hewlett-Packard copies of presented papers and slides in general. This is because of the need to architectures, with ports in progress for from anonymous FTP sites. balance signal levels for all parties, who Macintosh. No DOS, OS-2, Amiga, or Radio Free VAT is a community radio
34 COMPUTER station whose DJs sign up for air time via Given adequate network bandwidth, an automated server (vat-radiorequest@ you next need a designated MBone net Caveats aplenty elxr.jpl.nasa.gov). Xerox PARC occa work administrator. Working part-time, Problems still exist and a lot of work is sionally broadcasts lectures by dis it typically takes one to three weeks for a in progress. The audio interface takes tinguished speakers. Internet Talk Radio network-knowledgeable person to es coaching and practice. Leaving your mi (Carl Malamud, [email protected]) has tablish MBone at a new site. Setup is not crophone on by mistake can disrupt a ses presented talks by US Vice President Al for the faint of heart, but all the tools are sion since typically only one person can Gore, talk-show host Larry King, and documented, and help is available from be understood at a time. You will need a others. the MBone list. video capture board in your workstation Another new area is remote learning, You should read the Frequently Asked to transmit video, but no special hard which can use MBone to bring expertise Questions a few times, ensure that soft ware is needed to receive video. One-to over long distances and multiply training ware tools and multicast-compatible ker four frames per second video seems benefits. Finally, default MBone audio nels are available for your target work pretty slow (standard video is 30 frames and video channels are provided so that stations, and subscribe to the mail list in per second), but in practice it is sur new users can experiment and get advice advance to enable you to ask questions prisingly effective when combined with from more experienced users. and receive answers. Table 1 shows the phone-quality voice. various worldwide MBone list sub There is one big danger: One user scription request addresses. After sub blasting a high-bandwidth video signal scribing, review the FAQ. (greater than 128 Kbps) can cause severe Groupwork on These tools can also work in isolation and widespread network problems. Con group ware between workstations on a single LAN trols on access to tools are rudimentary without an mrouter. We recommend that and security is minimal; for example, a The MBone community is active and you test the application tools locally in local user might figure out how to listen open. Work on tools, protocols, stan advance (before going through the dedi through your workstation mike (unless dards, applications, and events is very cated mrouter effort) to see if they are you unplug it). much a cooperative and international ef compatible with your system and match Audio broadcast preparations are of fort. Feedback and suggestions are often your expectations. ten overlooked but can be just as in relayed to the entire MBone electronic To receive multicast packets on your volved as video broadcast preparations. mail list. (As an example, the article you LAN, you will need to configure an Network monitoring tools are not yet are reading was previewed by that group.) mrouter. This can be either a single work convenient to use. There is no guaran Cooperation is essential due to the lim station on a LAN, or a host dedicated as teed delivery: Lost packets stay lost. In ited bandwidth of many networks - in a parallel mrouter. A nondedicated single ternet bandwidth is still inadequate for particular, transoceanic links. So far, no workstation can receive and pass multi MBone in many countries. hierarchical scheme has been necessary cast to its LAN neighbors, but this ar On one occasion, an unusual topology for resolving potentially contentious is rangement can place double MBone traf change caused a feedback loop that over sues such as topology changes or event fic on that LAN. rode the NASA Select audio track. Al scheduling. Interestingly, distributed A more practical approach is to dedi though plenty of people were willing to problem solving and decision making has cate an old unused workstation as an point out the symptoms of our error, it worked on a human level just as success mrouter and equip it with two Ethernet was not possible for the rest of the net fully as on the network protocol level. We cards, which are needed so this mrouter work to cut off the offending workstation hope this decentralized approach will can act independently and in parallel with cleanly. continue to be successful, even with the your standard IP router. (NPS uses both More situations will undoubtedly oc rapid addition of new users. approaches.) After deciding on your cur as MB one developers and users learn mrouter configuration, obtain and load more. Unpleasant surprises usually trig the application software tools. You are ger a flurry of discussion and a corre Cost of admission now ready to put multicast on your LAN. sponding improvement in the tools. Once connected, you should pass along Expect to spend some time if you want The cost of equipment is often relatively any lessons learned to the tool authors or to be an MBone user. It is time-consum low, but to get on MBone, you need the the MBone list. When the opportunity ing because learning and fixing are in willingness to study and learn how to use presents itself, show your overall network volved and because it is lots of fun! these new and fast-moving tools, you site administrator something spectacular need bandwidth, and you need some on MB one (such as a live space walk) and hardware. NPS runs MBone tools on make sure your site is budgeting funds to tis not every day that someone says workstations connected via Ethernet (10 increase your network bandwidth. to you, "Here is a multimedia tele Mbps). Off-campus links are via Tl lines Demands on network bandwidth are I vision station that you can use to (1.5 Mbps). significant and getting more critical. You broadcast from your desktop to the We found that bandwidth capacities might consider Tengdin's First (and world." These are powerful concepts lower than Tl are generally unsuitable Only) Law of Telecommunications: "The and powerful tools that extend our abil for MBone video, although some users jump from zero to whatever baud rate is ity to communicate and collaborate tre - sometimes entire countries! - on spe the most important jump you can make. mendously. They have already changed cially configured networks have managed After that, everyone always wants to go the way people work and interact on to make the tools work at 56 and 64 Kbps. straight to the speed of light." the net.•
April 1994 35 Acknowledgments Further reading We thank the originators of the MBone tools and dozens of MBone Baker, S., "Multicasting for Sound and Video," Unix Rev., Feb. 1994, users who provided essential contributions to this article. pp. 23-29.
Casner, S., and S. Deering, "First IETF Internet Audiocast," ACM SIG Comm Computer Comm. Rev., July 1992, pp. 92-97; also as file:// References venera.isi.edu/pub/ietf-audiocast.article.ps.
1. S. Casner, "Frequently Asked Questions (FAQ) on the Multicast Curtis, P., MBone map, available via anonymous FTP from file:// Backbone," May 6, 1993, file://venera.isi.edu/mbone/faq.txt. parcftp.xerox.com/pub/net-research/mbone-map-big.ps. 2. D.E. Comer, Internetworking with TCP/IP, Vol. 1, Prentice Hall, Englewood Cliffs, N.J., 1991. Deering, S., "MBone: The Multicast Backbone," CERFnet Semi nar, Mar. 3, 1993, file://parcftp.xerox.com/pub/net-research/cerfnet 3. S. Deering, "Host Extensions for IP Multicasting," Request For seminar-slides.ps. Comment 1112, Aug. 1989, file://nic.ddn.mil/rfc/rfclll2.txt. 4. R. Perlman, Interconnections: Bridges and Routers, Addison Wesley, New York, 1993, p. 258. FTP Availability 5. J. Moy, "Multicast Extensions to OSPF," Internet Eng. Task Force This article is available electronically via anonymous FTP to Draft, July 1993, file://nic.ddn.mil/internet-drafts/draft-ietf-mospf taurus.cs.nps.navy.mil in subdirectory pub/mbmg as mbone.hottopic.ps; multicast-04. txt. in Uniform Resource Locator (URL) format used above, this anony mous FTP request corresponds to file://taurus.cs.nps.navy.mil/pub/ 6. H. Schulzrinne and S. Casner, "RTP: A Transport Protocol for mbmg/mbone.hottopic.ps. Real-Time Applications," Internet Engineering Task Force Draft, Oct. 20, 1993, file://nic.ddn.mil/internet-drafts/draft-ietf-avt-rtp- 04.ps. 7. D.R. Pratt, M.J. Zyda, et al., NPSNet Ann. Lab Rev., Dec. 1993, available at file://taurus.cs.nps.navy.mil/pub/npsnet/npsnet.annual. report.ps. 8. IEEE Standard for Information Technology - Protocols for Dis tributed Interactive Simulation Applications, Version 2.0, Univ. of Central Florida, Inst. for Simulation and Training, Orlando, Florida, May28, 1993. Michael R. Macedonia is a US Army major and a PhD student in com puter science at the Naval Postgraduate School. His research is directed toward the development of software architectures supporting large scale distributed virtual environments. During Operations Desert ISTANCE EDUCATION Shield and Desert Storm, he Jed a team that designed and established LEADING TO computer communications between the Joint Electronic Warfare Cen A MASTER OF SCIENCE IN ter modeling network and US forces in the Middle East to provide elec tronic warfare analytical products for combat commanders. Macedonia received a BS from the US Military Academy in 1979 SOFTWARE and an MS from the University of Pittsburgh in 1989. He is a member ENGINEERING of the IEEE Computer and Communications Societies.
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The program is centered about the.problems facing the working professional in the field. Emphasis is Donald P. Brotzman is a lieutenant commander and submarine officer on both the fundamental principles of software and in the US Navy, and has served three submarine tours. His current doc system design, and the practical problems of commercialization. Much of the subject material of toral research investigates the design and construction of an underwa the core is based on the curriculum recommended ter virtual world that includes an operational autonomous underwater by the Software Engineering Institute. The elective robot. His research interests also include 3D real-time computer graph courses enable the student to focus on particular ics, virtual worlds, scientific visualization, underwater robotics, dis interests. tributed simulation, machine learning, and high-performance network applications. He is editor ofvideoconference proceedings for annual un e ADMISSION REQUIREMENTS: BS/BA in one of manned underwater vehicle conferences. the sciences or engineering disciplines with a Brotzman received a BSEE from the US Naval Academy in 1978 and 3.0/4.0 GPA and one year experience in software an MS in computer science from the Naval Postgraduate School in 1992. development or maintenance. He is a member of IEEE, the IEEE Computer Society, ACM, and the American Association for Artificial Intelligence. For complete information contact Michael Kirkpatrick Readers can contact the authors at the Computer Science Depart Southern Methodist University ment, Naval Postgraduate School, Monterey CA 93943-5000. Their (214) 768-1452 e-mail addresses are [email protected] and brutzman@nps. FAX: (214) 768-3845 navy.mil. e-mail: [email protected] SMU does not discriminate on tlle basis of race, cok1r, national or eUtic origin, sex or disability COMPUTER Reader Service Number 2