|Known for||Network and security protocols; computer books|
|Thesis||Network layer protocols with Byzantine robustness (1988)|
|Doctoral advisor||David D. Clark|
Radia Joy Perlman (born December 18, 1951) is an American computer programmer and network engineer. She is most famous for her invention of the spanning-tree protocol (STP), which is fundamental to the operation of network bridges, while working for Digital Equipment Corporation. She also made large contributions to many other areas of network design and standardization, such as link-state routing protocols.
More recently she has invented the TRILL protocol to correct some of the shortcomings of spanning-trees. She is currently employed by Dell EMC.
Perlman grew up near Asbury Park, New Jersey. She is Jewish.Both of her parents worked as engineers for the US government. Her father worked on radar and her mother was a mathematician by training who worked as a computer programmer. During her school years Perlman found math and science to be “effortless and fascinating”, but had no problem achieving top grades in other subjects as well. She enjoyed playing the piano and French horn. While her mother helped her with her math homework, they mainly talked about literature and music.
Despite being the best science and math student in her school it was only when Perlman took a programming class in high school that she started to consider a career that involved computers. She was the only woman in the class and later reflected "I was not a hands-on type person. It never occurred to me to take anything apart. I assumed I'd either get electrocuted, or I'd break something".
As an undergraduate at MIT Perlman learned programming for a physics class. She was given her first paid job in 1971 as part-time programmer for the LOGO Lab at the (then) MIT Artificial Intelligence Laboratory, programming system software such as debuggers.
Working under the supervision of Seymour Papert, she developed a child-friendly version of the educational robotics language LOGO, called TORTIS ("Toddler's Own Recursive Turtle Interpreter System"). During research performed in 1974–76, young children—the youngest aged 3½ years, programmed a LOGO educational robot called a Turtle. Perlman has been described as a pioneer of teaching young children computer programming.
As a math grad at MIT she needed to find an adviser for her thesis, and joined the MIT group at BBN Technologies. There she first got involved with designing network protocols.Perlman obtained a B.S. and M.S. in Mathematics and a Ph.D. in Computer Science from MIT in 1988. Her doctoral thesis at MIT addressed the issue of routing in the presence of malicious network failures.
When studying at MIT in the late 60s she was one among the 50 or so women students, in a class of about 1,000 students. To begin with MIT only had one women’s dorm, limiting the number of women students that could study. When the men’s dorms at MIT became coed Perlman moved out of the women’s dorm into a mixed dorm, where she became the "resident female". She later said that she was so used to the gender imbalance, that it became normal. Only when she saw other women students among a crowd of men she noticed that "it kind of looked weird".
She is most famous for her invention of the Spanning Tree Protocol (STP), which is fundamental to the operation of network bridges, while working for Digital Equipment Corporation. Perlman is the author of a textbook on networking and coauthor of another on network security. She holds more than 100 issued patents.She was a Fellow at Sun Microsystems and has taught courses at the University of Washington, Harvard University and MIT, and has been the keynote speaker at events all over the world. Perlman is the recipient of awards such as Lifetime Achievement awards from Usenix and the Association for Computing Machinery’s Special Interest Group on Data Communication (SIGCOMM).
Perlman invented the spanning tree algorithm and the Spanning Tree Protocol (STP). While working as a consulting engineer at Digital Equipment Corporation (DEC) in 1984 she was tasked with developing a straightforward protocol which enabled network bridges to locate loops in a local area network (LAN). It was required that the protocol should use a constant amount of memory when implemented on the network devices, regardless of how large the network was. Building and expanding bridged networks was difficult because loops, where more than one path leads to the same destination, could result in the collapse of the network. Redundant paths in the network meant that a bridge could forward a frame in multiple directions. Therefore loops could cause Ethernet frames to fail to reach their destination, thus flooding the network. Perlman utilised the fact that bridges had unique 48 bit MAC addresses, and devised a network protocol so that bridges within the LAN communicated with one another. The algorithm implemented on all bridges in the network allowed the bridges to designate one root bridge in the network. Each bridge then mapped the network and determined the shortest path to the root bridge, deactivating other redundant paths. Despite Perlman's concerns that it took the spanning tree protocol about a minute to react when changes in the network topology occurred, during which time a loop could bring down the network, it was standardised as 802.1d by the Institute of Electrical and Electronics Engineers (IEEE). Perlman said that the benefits of the protocol amount to the fact that "you don't have to worry about topology" when changing the way a LAN is interconnected. Perlman has however criticised changes which were made in the course of the standardisation of the protocol.
From the paper "An Algorithm for Distributed Computation of a Spanning Tree in an Extended LAN":
Perlman was the principal designer of the DECnet IV and V protocols, which are part of the DECnet network protocol suite for peer-to-peer network architectures. She also made major contributions to the Connectionless Network Protocol (CLNP). Perlman has collaborated with Yakov Rekhter on developing network routing standards, such as the Open System Interconnection Routing Protocol (IDRP), which allows routers in packet switching networks to communicate with one another across broadcast domains. At DEC she also oversaw the transition from distance vector to link-state routing protocols. Link-state routing protocols had the advantage that they adapted to changes in the network topology faster, and DEC's link-state routing protocol was second only to the link-state routing protocol of the Advanced Research Projects Agency Network (ARPANET). While working on the DECnet project Perlman also helped to improve the intermediate-system to intermediate-system routing protocol, known as IS-IS, so that it could route the Internet Protocol (IP), AppleTalk and the Internetwork Packet Exchange (IPX) protocol.The Open Shortest Path First (OSPF) protocol relied in part on Perlman's research on fault-tolerant broadcasting of routing information.
Perlman subsequently worked as network engineer for Sun Microsystems, now Oracle. She specialised on network and security protocols and while working for Oracle obtained more than 50 patents.
Ethernet is a family of computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET.
A network switch is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.
Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
DECnet is a suite of network protocols created by Digital Equipment Corporation. Originally released in 1975 in order to connect two PDP-11 minicomputers, it evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s. Initially built with three layers, it later (1982) evolved into a seven-layer OSI-compliant networking protocol.
The Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails.
Link-state routing protocols are one of the two main classes of routing protocols used in packet switching networks for computer communications, the other being distance-vector routing protocols. Examples of link-state routing protocols include Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS).
Dynamic routing, also called adaptive routing, is a process where a router can forward data via a different route or given destination based on the current conditions of the communication circuits within a system. The term is most commonly associated with data networking to describe the capability of a network to 'route around' damage, such as loss of a node or a connection between nodes, so long as other path choices are available. Dynamic routing allows as many routes as possible to remain valid in response to the change.
Protocol-Independent Multicast (PIM) is a family of multicast routing protocols for Internet Protocol (IP) networks that provide one-to-many and many-to-many distribution of data over a LAN, WAN or the Internet. It is termed protocol-independent because PIM does not include its own topology discovery mechanism, but instead uses routing information supplied by other routing protocols. PIM is not dependent on a specific unicast routing protocol; it can make use of any unicast routing protocol in use on the network. PIM does not build its own routing tables. PIM uses the unicast routing table for reverse path forwarding.
Virtual Private LAN Service (VPLS) is a way to provide Ethernet-based multipoint to multipoint communication over IP or MPLS networks. It allows geographically dispersed sites to share an Ethernet broadcast domain by connecting sites through pseudowires. The term 'sites' includes multiplicities of both servers and clients. The technologies that can be used as pseudo-wire can be Ethernet over MPLS, L2TPv3 or even GRE. There are two IETF standards track RFCs describing VPLS establishment.
Local Area Transport (LAT) is a non-routable networking technology developed by Digital Equipment Corporation to provide connection between the DECserver terminal servers and Digital's VAX and Alpha and MIPS host computers via Ethernet, giving communication between those hosts and serial devices such as video terminals and printers. The protocol itself was designed in such a manner as to maximize packet efficiency over Ethernet by bundling multiple characters from multiple ports into a single packet for Ethernet transport. Over time, other host implementations of the LAT protocol appeared allowing communications to a wide range of Unix and other non-Digital operating systems using the LAT protocol.
The Multiple Spanning Tree Protocol (MSTP) and algorithm, provides both simple and full connectivity assigned to any given Virtual LAN (VLAN) throughout a Bridged Local Area Network. MSTP uses BPDUs to exchange information between spanning-tree compatible devices, to prevent loops in each MSTI and in the CIST, by selecting active and blocked paths. This is done as well as in STP without the need of manually enabling backup links and getting rid of bridge loops danger.
A computer network is a group of computers that use a set of common communication protocols over digital interconnections for the purpose of sharing resources located on or provided by the network nodes. The interconnections between nodes are formed from a broad spectrum of telecommunication network technologies, based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.
George Varghese is a Principal Researcher at Microsoft Research. Before joining MSR's lab in Silicon Valley in 2013, he was a Professor of Computer Science at the University of California San Diego, where he led the Internet Algorithms Lab and also worked with the Center for Network Systems and the Center for Internet Epidemiology. He is the author of the textbook Network Algorithmics published by Morgan Kaufmann in 2004.
Data center bridging (DCB) is a set of enhancements to the Ethernet local area network communication protocol for use in data center environments, in particular for use with clustering and storage area networks.
TRILL is an Internet Standard implemented by devices called TRILL switches. TRILL combines techniques from bridging and routing and is the application of link-state routing to the VLAN-aware customer-bridging problem. RBridges are compatible with and can incrementally replace previous IEEE 802.1 customer bridges. They are also compatible with IPv4 and IPv6 routers and end nodes. They are invisible to current IP routers and, like routers, RBridges terminate the bridge spanning tree protocol.
A routing bridge or RBridge, also known as a TRILL switch, is a network device that implements the TRILL protocol, as specified by the IETF and should not be confused with BRouters. RBridges are compatible with previous IEEE 802.1 customer bridges as well as IPv4 and IPv6 routers and end nodes. They are invisible to current IP routers and, like routers, RBridges terminate the bridge spanning tree protocol.
Bridge Protocol Data Units (BPDUs) are frames that contain information about the spanning tree protocol (STP). A switch sends BPDUs using a unique source MAC address from its origin port to a multicast address with destination MAC.
Sylvia Ratnasamy is a Belgian-Indian computer scientist. She is best known as one of the inventors of the distributed hash table (DHT). Her doctoral dissertation proposed the content-addressable networks, one of the original DHTs, and she received the ACM Grace Murray Hopper Award in 2014 for this work. She is currently a professor at the University of California, Berkeley.
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