3Com Corporation was an American digital electronics manufacturer best known for its computer network products. The company was co-founded in 1979 by Robert Metcalfe , Howard Charney and others. Bill Krause joined as President in 1981. Metcalfe explained the name 3Com was a contraction of "Computer Communication Compatibility", with its focus on Ethernet technology that he had co-invented, which enabled the networking of computers.
115-634: Ethernet ( / ˈ iː θ ər n ɛ t / EE -thər-net ) is a family of wired 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 . The original 10BASE5 Ethernet uses
230-448: A time to live (TTL) value, if a frame is sent into a looped topology, it can loop forever. A physical topology that contains switching or bridge loops is attractive for redundancy reasons, yet a switched network must not have loops. The solution is to allow physical loops, but create a loop-free logical topology using the SPB protocol or the older STP on the network switches. A node that
345-458: A datagram is called a packet or frame . Packet is used to describe the overall transmission unit and includes the preamble , start frame delimiter (SFD) and carrier extension (if present). The frame begins after the start frame delimiter with a frame header featuring source and destination MAC addresses and the EtherType field giving either the protocol type for the payload protocol or
460-756: A protocol stack , often constructed per the OSI model, communications functions are divided up into protocol layers, where each layer leverages the services of the layer below it until the lowest layer controls the hardware that sends information across the media. The use of protocol layering is ubiquitous across the field of computer networking. An important example of a protocol stack is HTTP (the World Wide Web protocol) running over TCP over IP (the Internet protocols) over IEEE 802.11 (the Wi-Fi protocol). This stack
575-513: A buffer on the switch in its entirety, its frame check sequence verified and only then the packet is forwarded. In modern network equipment, this process is typically done using application-specific integrated circuits allowing packets to be forwarded at wire speed . When a twisted pair or fiber link segment is used and neither end is connected to a repeater, full-duplex Ethernet becomes possible over that segment. In full-duplex mode, both devices can transmit and receive to and from each other at
690-513: A coaxial cable 0.375 inches (9.5 mm) in diameter, later called thick Ethernet or thicknet . Its successor, 10BASE2 , called thin Ethernet or thinnet , used the RG-58 coaxial cable. The emphasis was on making installation of the cable easier and less costly. Since all communication happens on the same wire, any information sent by one computer is received by all, even if that information
805-503: A diverse set of networking capabilities. The protocols have a flat addressing scheme. They operate mostly at layers 1 and 2 of the OSI model. For example, MAC bridging ( IEEE 802.1D ) deals with the routing of Ethernet packets using a Spanning Tree Protocol . IEEE 802.1Q describes VLANs , and IEEE 802.1X defines a port-based network access control protocol, which forms the basis for the authentication mechanisms used in VLANs (but it
920-580: A doubling of network size. Once repeaters with more than two ports became available, it was possible to wire the network in a star topology . Early experiments with star topologies (called Fibernet ) using optical fiber were published by 1978. Shared cable Ethernet is always hard to install in offices because its bus topology is in conflict with the star topology cable plans designed into buildings for telephony. Modifying Ethernet to conform to twisted-pair telephone wiring already installed in commercial buildings provided another opportunity to lower costs, expand
1035-845: A joint venture with China-based Huawei Technologies —3Com achieved a market presence in China , and a significant networking market share in Europe , Asia , and the Americas. 3Com products were sold under the brands 3Com, H3C, and TippingPoint. On April 12, 2010, Hewlett-Packard completed the acquisition of 3Com, and it no longer exists as a separate entity. 3Com's products, support, and technologies were eventually merged into HPE's Aruba Networks business unit following HP's acquisition of Aruba in 2015 and subsequent split into HPE later that same year. After reading an article on ALOHAnet , Robert Metcalfe became interested in computer networking. ALOHAnet
1150-440: A large, congested network into an aggregation of smaller, more efficient networks. A router is an internetworking device that forwards packets between networks by processing the addressing or routing information included in the packet. The routing information is often processed in conjunction with the routing table . A router uses its routing table to determine where to forward packets and does not require broadcasting packets which
1265-440: A multi-port bridge. Switches normally have numerous ports, facilitating a star topology for devices, and for cascading additional switches. Bridges and switches operate at the data link layer (layer 2) of the OSI model and bridge traffic between two or more network segments to form a single local network. Both are devices that forward frames of data between ports based on the destination MAC address in each frame. They learn
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#17327729451631380-454: A networking protocol known as PARC Universal Packet (PuP), with the entire system ready for build-out by late 1974. At this point, Xerox management did nothing with it, even after being approached by prospective customers. Increasingly upset by management's lack of interest, Metcalfe left Xerox in 1975, but he was lured back again the next year. Further development followed, resulting in the seminal Xerox Network Systems (XNS) protocol, which
1495-418: A public company via an initial public offering (IPO) in 1984. The company's network software products included: 3Com's expansion beyond its original base of PC and thin Ethernet products began in 1987 when it merged with Bridge Communications. This provided a range of equipment based on Motorola 68000 processors and using XNS protocols compatibly with 3Com's Etherterm PC software. By 1995, 3Com's status
1610-457: A repeater hub assists with collision detection and fault isolation for the network. Hubs and repeaters in LANs have been largely obsoleted by modern network switches. Network bridges and network switches are distinct from a hub in that they only forward frames to the ports involved in the communication whereas a hub forwards to all ports. Bridges only have two ports but a switch can be thought of as
1725-418: A single failure can cause the network to fail entirely. In general, the more interconnections there are, the more robust the network is; but the more expensive it is to install. Therefore, most network diagrams are arranged by their network topology which is the map of logical interconnections of network hosts. Common topologies are: The physical layout of the nodes in a network may not necessarily reflect
1840-576: A standard for CSMA/CD based on the IEEE 802 draft. Because the DIX proposal was most technically complete and because of the speedy action taken by ECMA which decisively contributed to the conciliation of opinions within IEEE, the IEEE 802.3 CSMA/CD standard was approved in December 1982. IEEE published the 802.3 standard as a draft in 1983 and as a standard in 1985. Approval of Ethernet on the international level
1955-403: A standard voice telephone line. Modems are still commonly used for telephone lines, using a digital subscriber line technology and cable television systems using DOCSIS technology. A firewall is a network device or software for controlling network security and access rules. Firewalls are inserted in connections between secure internal networks and potentially insecure external networks such as
2070-422: A standard. As part of that process Xerox agreed to relinquish their 'Ethernet' trademark. The first standard was published on September 30, 1980, as "The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications". This so-called DIX standard (Digital Intel Xerox) specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and a global 16-bit Ethertype -type field. Version 2
2185-401: A thick coaxial cable as a shared medium . This was largely superseded by 10BASE2 , which used a thinner and more flexible cable that was both cheaper and easier to use. More modern Ethernet variants use twisted pair and fiber optic links in conjunction with switches . Over the course of its history, Ethernet data transfer rates have been increased from the original 2.94 Mbit/s to
2300-877: A transmission medium. Power line communication uses a building's power cabling to transmit data. The following classes of wired technologies are used in computer networking. Network connections can be established wirelessly using radio or other electromagnetic means of communication. The last two cases have a large round-trip delay time , which gives slow two-way communication but does not prevent sending large amounts of information (they can have high throughput). Apart from any physical transmission media, networks are built from additional basic system building blocks, such as network interface controllers , repeaters , hubs , bridges , switches , routers , modems, and firewalls . Any particular piece of equipment will frequently contain multiple building blocks and so may perform multiple functions. A network interface controller (NIC)
2415-406: A variety of network topologies . The nodes of a computer network can include personal computers , servers , networking hardware , or other specialized or general-purpose hosts . They are identified by network addresses and may have hostnames . Hostnames serve as memorable labels for the nodes and are rarely changed after initial assignment. Network addresses serve for locating and identifying
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#17327729451632530-495: A variety of different sources, primarily to support circuit-switched digital telephony . However, due to its protocol neutrality and transport-oriented features, SONET/SDH also was the obvious choice for transporting Asynchronous Transfer Mode (ATM) frames. Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous time-division multiplexing and encodes data into small, fixed-sized cells . This differs from other protocols such as
2645-657: A virtual system of links that run on top of the Internet . Overlay networks have been used since the early days of networking, back when computers were connected via telephone lines using modems, even before data networks were developed. The most striking example of an overlay network is the Internet itself. The Internet itself was initially built as an overlay on the telephone network . Even today, each Internet node can communicate with virtually any other through an underlying mesh of sub-networks of wildly different topologies and technologies. Address resolution and routing are
2760-410: A wide range of networking technologies. On November 11, 2009, 3Com and Hewlett-Packard announced that Hewlett-Packard would acquire 3Com for $ 2.7 billion in cash. On April 12, 2010, Hewlett-Packard completed its acquisition. When Hewlett-Packard split into Hewlett Packard Enterprise and Hewlett-Packard Inc., the 3Com unit continued with HPE and was ultimately integrated into Aruba Networks along with
2875-522: Is computer hardware that connects the computer to the network media and has the ability to process low-level network information. For example, the NIC may have a connector for plugging in a cable, or an aerial for wireless transmission and reception, and the associated circuitry. In Ethernet networks, each NIC has a unique Media Access Control (MAC) address —usually stored in the controller's permanent memory. To avoid address conflicts between network devices,
2990-422: Is a virtual network that is built on top of another network. Nodes in the overlay network are connected by virtual or logical links. Each link corresponds to a path, perhaps through many physical links, in the underlying network. The topology of the overlay network may (and often does) differ from that of the underlying one. For example, many peer-to-peer networks are overlay networks. They are organized as nodes of
3105-566: Is also found in WLANs ) – it is what the home user sees when the user has to enter a "wireless access key". Ethernet is a family of technologies used in wired LANs. It is described by a set of standards together called IEEE 802.3 published by the Institute of Electrical and Electronics Engineers. Wireless LAN based on the IEEE 802.11 standards, also widely known as WLAN or WiFi, is probably
3220-478: Is an electronic device that receives a network signal , cleans it of unnecessary noise and regenerates it. The signal is retransmitted at a higher power level, or to the other side of obstruction so that the signal can cover longer distances without degradation. In most twisted-pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. With fiber optics, repeaters can be tens or even hundreds of kilometers apart. Repeaters work on
3335-482: Is commonly carried over Ethernet and so it is considered one of the key technologies that make up the Internet . Ethernet was developed at Xerox PARC between 1973 and 1974 as a means to allow Alto computers to communicate with each other. It was inspired by ALOHAnet , which Robert Metcalfe had studied as part of his PhD dissertation and was originally called the Alto Aloha Network. Metcalfe's idea
3450-406: Is either dropped or forwarded to another segment. This reduces the forwarding latency. One drawback of this method is that it does not readily allow a mixture of different link speeds. Another is that packets that have been corrupted are still propagated through the network. The eventual remedy for this was a return to the original store and forward approach of bridging, where the packet is read into
3565-432: Is in turn connected to the cable (with thin Ethernet the transceiver is usually integrated into the network adapter). While a simple passive wire is highly reliable for small networks, it is not reliable for large extended networks, where damage to the wire in a single place, or a single bad connector, can make the whole Ethernet segment unusable. Through the first half of the 1980s, Ethernet's 10BASE5 implementation used
Ethernet - Misplaced Pages Continue
3680-412: Is inefficient for very big networks. Modems (modulator-demodulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this one or more carrier signals are modulated by the digital signal to produce an analog signal that can be tailored to give the required properties for transmission. Early modems modulated audio signals sent over
3795-476: Is intended for just one destination. The network interface card interrupts the CPU only when applicable packets are received: the card ignores information not addressed to it. Use of a single cable also means that the data bandwidth is shared, such that, for example, available data bandwidth to each device is halved when two stations are simultaneously active. A collision happens when two stations attempt to transmit at
3910-484: Is more than one Layer 2 ( OSI model ) path between two endpoints (e.g. multiple connections between two network switches or two ports on the same switch connected to each other). The loop creates broadcast storms as broadcasts and multicasts are forwarded by switches out every port , the switch or switches will repeatedly rebroadcast the broadcast messages flooding the network. Since the Layer 2 header does not support
4025-404: Is not sending packets, the link can be filled with packets from other users, and so the cost can be shared, with relatively little interference, provided the link is not overused. Often the route a packet needs to take through a network is not immediately available. In that case, the packet is queued and waits until a link is free. The physical link technologies of packet networks typically limit
4140-616: Is now used to interconnect appliances and other personal devices . As Industrial Ethernet it is used in industrial applications and is quickly replacing legacy data transmission systems in the world's telecommunications networks. By 2010, the market for Ethernet equipment amounted to over $ 16 billion per year. In February 1980, the Institute of Electrical and Electronics Engineers (IEEE) started project 802 to standardize local area networks (LAN). The DIX group with Gary Robinson (DEC), Phil Arst (Intel), and Bob Printis (Xerox) submitted
4255-619: Is sending longer than the maximum transmission window for an Ethernet packet is considered to be jabbering . Depending on the physical topology, jabber detection and remedy differ somewhat. Computer network A computer network is a set of computers sharing resources located on or provided by network nodes . Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical , and wireless radio-frequency methods that may be arranged in
4370-435: Is significantly better. In a modern Ethernet, the stations do not all share one channel through a shared cable or a simple repeater hub ; instead, each station communicates with a switch, which in turn forwards that traffic to the destination station. In this topology, collisions are only possible if station and switch attempt to communicate with each other at the same time, and collisions are limited to this link. Furthermore,
4485-480: Is the procedure by which two connected devices choose common transmission parameters, e.g. speed and duplex mode. Autonegotiation was initially an optional feature, first introduced with 100BASE-TX (1995 IEEE 802.3u Fast Ethernet standard), and is backward compatible with 10BASE-T. The specification was improved in the 1998 release of IEEE 802.3. Autonegotiation is mandatory for 1000BASE-T and faster. A switching loop or bridge loop occurs in computer networks when there
4600-586: Is the process of selecting network paths to carry network traffic. Routing is performed for many kinds of networks, including circuit switching networks and packet switched networks. 3Com 3Com provided network interface controller and switches , routers , wireless access points and controllers, IP voice systems, and intrusion prevention systems . The company was based in Santa Clara, California . From its 2007 acquisition of 100 percent ownership of H3C Technologies Co., Limited (H3C) —initially
4715-459: Is used between the wireless router and the home user's personal computer when the user is surfing the web. There are many communication protocols, a few of which are described below. The Internet protocol suite , also called TCP/IP, is the foundation of all modern networking. It offers connection-less and connection-oriented services over an inherently unreliable network traversed by datagram transmission using Internet protocol (IP). At its core,
Ethernet - Misplaced Pages Continue
4830-411: Is used by the operating system on the receiving station to select the appropriate protocol module (e.g., an Internet Protocol version such as IPv4 ). Ethernet frames are said to be self-identifying , because of the EtherType field. Self-identifying frames make it possible to intermix multiple protocols on the same physical network and allow a single computer to use multiple protocols together. Despite
4945-517: The 10BASE-T standard introduced a full duplex mode of operation which became common with Fast Ethernet and the de facto standard with Gigabit Ethernet . In full duplex, switch and station can send and receive simultaneously, and therefore modern Ethernets are completely collision-free. For signal degradation and timing reasons, coaxial Ethernet segments have a restricted size. Somewhat larger networks can be built by using an Ethernet repeater . Early repeaters had only two ports, allowing, at most,
5060-554: The DEC LSI-11 , DEC VAX-11 , Sun-2 and the IBM PC . In the mid-1980s, 3Com branded their Ethernet technology as EtherSeries, while introducing a range of software and PC -based equipment to provide shared services over a local area network (LAN) using XNS protocols. These protocols were branded EtherShare (for file sharing), EtherPrint (for printing), EtherMail (for email ), and Ether- 3270 (for IBM host emulation). 3Com became
5175-406: The Institute of Electrical and Electronics Engineers (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six octets . The three most significant octets are reserved to identify NIC manufacturers. These manufacturers, using only their assigned prefixes, uniquely assign the three least-significant octets of every Ethernet interface they produce. A repeater
5290-558: The OSI model , Ethernet provides services up to and including the data link layer . The 48-bit MAC address was adopted by other IEEE 802 networking standards, including IEEE 802.11 ( Wi-Fi ), as well as by FDDI . EtherType values are also used in Subnetwork Access Protocol (SNAP) headers. Ethernet is widely used in homes and industry, and interworks well with wireless Wi-Fi technologies. The Internet Protocol
5405-582: The Spanning Tree Protocol (STP) to maintain a loop-free, meshed network, allowing physical loops for redundancy (STP) or load-balancing (SPB). Shortest Path Bridging includes the use of the link-state routing protocol IS-IS to allow larger networks with shortest path routes between devices. Advanced networking features also ensure port security, provide protection features such as MAC lockdown and broadcast radiation filtering, use VLANs to keep different classes of users separate while using
5520-477: The World Wide Web , digital video and audio , shared use of application and storage servers , printers and fax machines , and use of email and instant messaging applications. Computer networking may be considered a branch of computer science , computer engineering , and telecommunications , since it relies on the theoretical and practical application of the related disciplines. Computer networking
5635-587: The Audrey and Kerbango products less than a year later. In March 2000, in a highly public and criticized move, 3Com exited the high-end core routers and switch market to focus on other areas of the business. The CoreBuilder Ethernet and ATM LAN switches, PathBuilder and NetBuilder WAN Routers were all discontinued June 2000. CoreBuilder products and the customer base was migrated over to Extreme Networks . The PathBuilder and NetBuilder were transitioned to Motorola. 3Com focused its efforts from 2000 to 2003 on building up
5750-534: The HomeConnect, OfficeConnect, SuperStack, NBX and Total Control product lines. Due to this perceived exit from the Enterprise market, 3Com would never gain momentum with large customers or carriers again. In July 2000, 3Com spun off Palm as an independent company. Following Palm's IPO, 3Com continued to own 80 percent of Palm, but 3Com's market capitalization was smaller than Palm's. U.S. Robotics
5865-440: The Internet protocol suite or Ethernet that use variable-sized packets or frames . ATM has similarities with both circuit and packet switched networking. This makes it a good choice for a network that must handle both traditional high-throughput data traffic, and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before
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#17327729451635980-574: The Internet. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in cyber attacks . A communication protocol is a set of rules for exchanging information over a network. Communication protocols have various characteristics. They may be connection-oriented or connectionless , they may use circuit mode or packet switching, and they may use hierarchical addressing or flat addressing. In
6095-486: The LAN was observed. This is in contrast with token passing LANs (Token Ring, Token Bus), all of which suffer throughput degradation as each new node comes into the LAN, due to token waits. This report was controversial, as modeling showed that collision-based networks theoretically became unstable under loads as low as 37% of nominal capacity. Many early researchers failed to understand these results. Performance on real networks
6210-607: The LEC's ingress CLASS 5 switch to the Total Control 1000 media gateway, where it was converted from TDM to IP and transported across AT&T's WorldNet IP backbone. When it reached the destination, it was passed to the egress LEC's CLASS 5 switch as an untariffed data call. CommWorks modified the gateway and softswitch software to support SIP for MCI/WorldCom's hosted business offering in 2000. Although 3Com sold CommWorks to UTStarcom, they retained intellectual property rights to
6325-627: The actual data exchange begins. ATM still plays a role in the last mile , which is the connection between an Internet service provider and the home user. There are a number of different digital cellular standards, including: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), cdmaOne , CDMA2000 , Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS (IS-136/TDMA), and Integrated Digital Enhanced Network (iDEN). Routing
6440-468: The association of physical ports to MAC addresses by examining the source addresses of received frames and only forward the frame when necessary. If an unknown destination MAC is targeted, the device broadcasts the request to all ports except the source, and discovers the location from the reply. Bridges and switches divide the network's collision domain but maintain a single broadcast domain. Network segmentation through bridging and switching helps break down
6555-478: The beginning of the end of 3Com. In addition to consumer network electronics, USRobotics was a well-known manufacturer of a dialup access server, the "Total Control Hub", rebadged by 3Com as the "Total Control 1000", based largely on its Courier modem technology. This key business product competed against Cisco's AS5200 access server line in the mid-1990s as the explosion of the Internet led to service provider investment in dialup access server equipment. 3Com continued
6670-607: The company for $ 2.2 billion, with minority equity financing from Huawei Technologies. However, the deal met with US government regulatory opposition and it fell through early in 2008, following concerns over Huawei's risk of conducting cyber security attacks against the United States and its allies, Huawei's former dealings in Iran, and Huawei being operated by a former engineer in China's People's Liberation Army . Edgar Masri left
6785-504: The company in April 2008, partially as a result of the failed Bain transaction. In April 2008, Robert Mao was named chief executive, and Ron Sege president and chief operating officer. In fiscal year 2008 ended May 30, 2008, 3Com had annual revenue of $ 1.3 billion and more than 6,000 employees in over 40 countries. In September 2008, 3Com reported financial results for its fiscal 2009 first quarter, which ended August 29, 2008. Revenue in
6900-566: The company moved its Silicon Valley Santa Clara headquarters to Marlborough , Massachusetts. It also formed a venture called H3C with Huawei , whereby 3Com would sell and rebrand products under the joint venture. In 2003, 3Com sold its CommWorks Corporation subsidiary to UTStarcom, Inc. CommWorks was based in Rolling Meadows, Illinois , and developed wireline telecommunications and wireless infrastructure technologies. In January 2006, Claflin announced he would be leaving
7015-571: The company. In January 2006, R Scott Murray became CEO of 3Com and chairman of H3C Technology in China, the joint venture with Huawei Technologies. Murray voluntarily resigned from the company in August 2006 over his concerns about the questionable business ethics of Huawei and potential cyber security risks posed by Huawei. Edgar Masri returned to 3Com to head as president and CEO following Murray's departure. In September 2007, Bain Capital agreed to buy
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#17327729451637130-453: The destination and the source of each data packet. Ethernet establishes link-level connections, which can be defined using both the destination and source addresses. On reception of a transmission, the receiver uses the destination address to determine whether the transmission is relevant to the station or should be ignored. A network interface normally does not accept packets addressed to other Ethernet stations. An EtherType field in each frame
7245-610: The development of the Total Control line until it was eventually spun off as a part of Commworks, which was then acquired by UTStarcom. In August 1998, Bruce Claflin was named chief operating officer . The modem business was rapidly shrinking. 3Com attempted to enter the DSL business, but was not successful. In the lucrative server network interface card (NIC) business, 3Com dominated market share, with Intel only able to break past 3Com after dramatic price slashing. It started developing Gigabit Ethernet cards in-house but later scrapped
7360-562: The elimination of the chaining limits inherent in non-switched Ethernet have made switched Ethernet the dominant network technology. Simple switched Ethernet networks, while a great improvement over repeater-based Ethernet, suffer from single points of failure, attacks that trick switches or hosts into sending data to a machine even if it is not intended for it, scalability and security issues with regard to switching loops , broadcast radiation , and multicast traffic. Advanced networking features in switches use Shortest Path Bridging (SPB) or
7475-487: The emerging office communication market, including Siemens' support for the international standardization of Ethernet (April 10, 1981). Ingrid Fromm, Siemens' representative to IEEE 802, quickly achieved broader support for Ethernet beyond IEEE by the establishment of a competing Task Group "Local Networks" within the European standards body ECMA TC24. In March 1982, ECMA TC24 with its corporate members reached an agreement on
7590-447: The evolution of Ethernet technology, all generations of Ethernet (excluding early experimental versions) use the same frame formats. Mixed-speed networks can be built using Ethernet switches and repeaters supporting the desired Ethernet variants. Due to the ubiquity of Ethernet, and the ever-decreasing cost of the hardware needed to support it, by 2004 most manufacturers built Ethernet interfaces directly into PC motherboards , eliminating
7705-611: The farthest nodes and creates practical limits on how many machines can communicate on an Ethernet network. Segments joined by repeaters have to all operate at the same speed, making phased-in upgrades impossible. To alleviate these problems, bridging was created to communicate at the data link layer while isolating the physical layer. With bridging, only well-formed Ethernet packets are forwarded from one Ethernet segment to another; collisions and packet errors are isolated. At initial startup, Ethernet bridges work somewhat like Ethernet repeaters, passing all traffic between segments. By observing
7820-585: The first companies to deliver a complete networked phone system, and increased its distribution channel with larger telephony partners such as Southwestern Bell and Metropark Communications , 3Com helped make VoIP into a safe and practical technology with wide adoption. 3Com then tried to move into the smart consumer appliances business and in June 2000, 3Com acquired internet radio startup Kerbango for $ 80 million. It developed its Audrey appliance, which made an appearance on The Oprah Winfrey Show . It scrapped
7935-509: The group was split into three subgroups, and standardization proceeded separately for each proposal. Delays in the standards process put at risk the market introduction of the Xerox Star workstation and 3Com's Ethernet LAN products. With such business implications in mind, David Liddle (General Manager, Xerox Office Systems) and Metcalfe (3Com) strongly supported a proposal of Fritz Röscheisen ( Siemens Private Networks) for an alliance in
8050-435: The installed base, and leverage building design, and, thus, twisted-pair Ethernet was the next logical development in the mid-1980s. Ethernet on unshielded twisted-pair cables (UTP) began with StarLAN at 1 Mbit/s in the mid-1980s. In 1987 SynOptics introduced the first twisted-pair Ethernet at 10 Mbit/s in a star-wired cabling topology with a central hub, later called LattisNet . These evolved into 10BASE-T, which
8165-545: The largest computer networks in the world at that time. An Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. In the 1980s, IBM's own PC Network product competed with Ethernet for the PC, and through the 1980s, LAN hardware, in general, was not common on PCs. However, in the mid to late 1980s, PC networking did become popular in offices and schools for printer and fileserver sharing, and among
8280-502: The latest 400 Gbit/s , with rates up to 1.6 Tbit/s under development. The Ethernet standards include several wiring and signaling variants of the OSI physical layer . Systems communicating over Ethernet divide a stream of data into shorter pieces called frames . Each frame contains source and destination addresses, and error-checking data so that damaged frames can be detected and discarded; most often, higher-layer protocols trigger retransmission of lost frames. Per
8395-433: The length of the payload. The middle section of the frame consists of payload data including any headers for other protocols (for example, Internet Protocol) carried in the frame. The frame ends with a 32-bit cyclic redundancy check , which is used to detect corruption of data in transit . Notably, Ethernet packets have no time-to-live field , leading to possible problems in the presence of a switching loop. Autonegotiation
8510-620: The literature as the physical medium ) used to link devices to form a computer network include electrical cable , optical fiber , and free space. In the OSI model , the software to handle the media is defined at layers 1 and 2 — the physical layer and the data link layer. A widely adopted family that uses copper and fiber media in local area network (LAN) technology are collectively known as Ethernet. The media and protocol standards that enable communication between networked devices over Ethernet are defined by IEEE 802.3 . Wireless LAN standards use radio waves , others use infrared signals as
8625-629: The many diverse competing LAN technologies of that decade, Ethernet was one of the most popular. Parallel port based Ethernet adapters were produced for a time, with drivers for DOS and Windows. By the early 1990s, Ethernet became so prevalent that Ethernet ports began to appear on some PCs and most workstations . This process was greatly sped up with the introduction of 10BASE-T and its relatively small modular connector , at which point Ethernet ports appeared even on low-end motherboards. Since then, Ethernet technology has evolved to meet new bandwidth and market requirements. In addition to computers, Ethernet
8740-665: The means that allow mapping of a fully connected IP overlay network to its underlying network. Another example of an overlay network is a distributed hash table , which maps keys to nodes in the network. In this case, the underlying network is an IP network, and the overlay network is a table (actually a map ) indexed by keys. Overlay networks have also been proposed as a way to improve Internet routing, such as through quality of service guarantees achieve higher-quality streaming media . Previous proposals such as IntServ , DiffServ , and IP multicast have not seen wide acceptance largely because they require modification of all routers in
8855-399: The mixing of speeds, both of which are critical to the incremental deployment of faster Ethernet variants. In 1989, Motorola Codex introduced their 6310 EtherSpan, and Kalpana introduced their EtherSwitch; these were examples of the first commercial Ethernet switches. Early switches such as this used cut-through switching where only the header of the incoming packet is examined before it
8970-415: The most well-known member of the IEEE 802 protocol family for home users today. IEEE 802.11 shares many properties with wired Ethernet. Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers. They were originally designed to transport circuit mode communications from
9085-474: The need for a separate network card. Ethernet was originally based on the idea of computers communicating over a shared coaxial cable acting as a broadcast transmission medium. The method used was similar to those used in radio systems, with the common cable providing the communication channel likened to the Luminiferous aether in 19th-century physics, and it was from this reference that the name Ethernet
9200-412: The network needs to deliver the user data, for example, source and destination network addresses , error detection codes, and sequencing information. Typically, control information is found in packet headers and trailers , with payload data in between. With packets, the bandwidth of the transmission medium can be better shared among users than if the network were circuit switched . When one user
9315-420: The network topology. As an example, with FDDI , the network topology is a ring, but the physical topology is often a star, because all neighboring connections can be routed via a central physical location. Physical layout is not completely irrelevant, however, as common ducting and equipment locations can represent single points of failure due to issues like fires, power failures and flooding. An overlay network
9430-469: The network. Despite the physical star topology and the presence of separate transmit and receive channels in the twisted pair and fiber media, repeater-based Ethernet networks still use half-duplex and CSMA/CD, with only minimal activity by the repeater, primarily generation of the jam signal in dealing with packet collisions. Every packet is sent to every other port on the repeater, so bandwidth and security problems are not addressed. The total throughput of
9545-729: The network. On the other hand, an overlay network can be incrementally deployed on end-hosts running the overlay protocol software, without cooperation from Internet service providers . The overlay network has no control over how packets are routed in the underlying network between two overlay nodes, but it can control, for example, the sequence of overlay nodes that a message traverses before it reaches its destination . For example, Akamai Technologies manages an overlay network that provides reliable, efficient content delivery (a kind of multicast ). Academic research includes end system multicast, resilient routing and quality of service studies, among others. The transmission media (often referred to in
9660-494: The nodes by communication protocols such as the Internet Protocol . Computer networks may be classified by many criteria, including the transmission medium used to carry signals, bandwidth , communications protocols to organize network traffic , the network size, the topology, traffic control mechanisms, and organizational intent. Computer networks support many applications and services , such as access to
9775-626: The now-ubiquitous twisted pair with 10BASE-T. By the end of the 1980s, Ethernet was clearly the dominant network technology. In the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 NIC in March 1981, and that year started selling adapters for PDP-11s and VAXes , as well as Multibus -based Intel and Sun Microsystems computers. This was followed quickly by DEC's Unibus to Ethernet adapter, which DEC sold and used internally to build its own corporate network, which reached over 10,000 nodes by 1986, making it one of
9890-464: The physical layer of the OSI model but still require a small amount of time to regenerate the signal. This can cause a propagation delay that affects network performance and may affect proper function. As a result, many network architectures limit the number of repeaters used in a network, e.g., the Ethernet 5-4-3 rule . An Ethernet repeater with multiple ports is known as an Ethernet hub . In addition to reconditioning and distributing network signals,
10005-403: The plans. Later, it formed a joint venture with Broadcom , where Broadcom would develop the main integrated circuit component and the NIC would be 3Com branded. In 1999, 3Com acquired NBX, a Boston company with an Ethernet-based phone system for small and medium-sized businesses. This product proved popular with 3Com's existing distribution channel and saw rapid growth and adoption. As one of
10120-448: The port they are intended for, traffic on a switched Ethernet is less public than on shared-medium Ethernet. Despite this, switched Ethernet should still be regarded as an insecure network technology, because it is easy to subvert switched Ethernet systems by means such as ARP spoofing and MAC flooding . The bandwidth advantages, the improved isolation of devices from each other, the ability to easily mix different speeds of devices and
10235-456: The protocol suite defines the addressing, identification, and routing specifications for Internet Protocol Version 4 (IPv4) and for IPv6 , the next generation of the protocol with a much enlarged addressing capability. The Internet protocol suite is the defining set of protocols for the Internet. IEEE 802 is a family of IEEE standards dealing with local area networks and metropolitan area networks. The complete IEEE 802 protocol suite provides
10350-555: The quarter was $ 342.7 million compared to revenue of $ 319.4 million in the corresponding period in fiscal 2008, a 7 percent increase. Net income in the quarter was $ 79.8 million, compared with a net loss of $ 18.7 million in the first quarter of fiscal year 2008. The company reported that it had more than 2,700 engineers, with more than 1,400 United States patents and nearly 180 Chinese-issued patents, as well as more than 1050 pending Chinese applications. It also reported pending applications for 35 separate inventions outside of China covering
10465-409: The repeater is limited to that of a single link, and all links must operate at the same speed. While repeaters can isolate some aspects of Ethernet segments , such as cable breakages, they still forward all traffic to all Ethernet devices. The entire network is one collision domain , and all hosts have to be able to detect collisions anywhere on the network. This limits the number of repeaters between
10580-476: The rest of HP's networking portfolio. 3Com came close to merging with computer maker Convergent Technologies , abandoning the pact just two days before a vote was scheduled in March 1986. Later, 3Com went on to acquire the following: CommWorks Corporation was a subsidiary of 3Com Corporation, based in Rolling Meadows, Illinois . It was sold to UTStarcom of Alameda, California in 2003. CommWorks
10695-546: The same physical infrastructure, employ multilayer switching to route between different classes, and use link aggregation to add bandwidth to overloaded links and to provide some redundancy. In 2016, Ethernet replaced InfiniBand as the most popular system interconnect of TOP500 supercomputers. The Ethernet physical layer evolved over a considerable time span and encompasses coaxial, twisted pair and fiber-optic physical media interfaces, with speeds from 1 Mbit/s to 400 Gbit/s . The first introduction of twisted-pair CSMA/CD
10810-480: The same time, and there is no collision domain. This doubles the aggregate bandwidth of the link and is sometimes advertised as double the link speed (for example, 200 Mbit/s for Fast Ethernet). The elimination of the collision domain for these connections also means that all the link's bandwidth can be used by the two devices on that segment and that segment length is not limited by the constraints of collision detection. Since packets are typically delivered only to
10925-512: The same time. They corrupt transmitted data and require stations to re-transmit. The lost data and re-transmission reduces throughput. In the worst case, where multiple active hosts connected with maximum allowed cable length attempt to transmit many short frames, excessive collisions can reduce throughput dramatically. However, a Xerox report in 1980 studied performance of an existing Ethernet installation under both normal and artificially generated heavy load. The report claimed that 98% throughput on
11040-515: The sharing of files and information, giving authorized users access to data stored on other computers. Distributed computing leverages resources from multiple computers across a network to perform tasks collaboratively. Most modern computer networks use protocols based on packet-mode transmission. A network packet is a formatted unit of data carried by a packet-switched network . Packets consist of two types of data: control information and user data (payload). The control information provides data
11155-493: The size of packets to a certain maximum transmission unit (MTU). A longer message may be fragmented before it is transferred and once the packets arrive, they are reassembled to construct the original message. The physical or geographic locations of network nodes and links generally have relatively little effect on a network, but the topology of interconnections of a network can significantly affect its throughput and reliability. With many technologies, such as bus or star networks,
11270-412: The so-called Blue Book CSMA/CD specification as a candidate for the LAN specification. In addition to CSMA/CD, Token Ring (supported by IBM) and Token Bus (selected and henceforward supported by General Motors ) were also considered as candidates for a LAN standard. Competing proposals and broad interest in the initiative led to strong disagreement over which technology to standardize. In December 1980,
11385-411: The source addresses of incoming frames, the bridge then builds an address table associating addresses to segments. Once an address is learned, the bridge forwards network traffic destined for that address only to the associated segment, improving overall performance. Broadcast traffic is still forwarded to all network segments. Bridges also overcome the limits on total segments between two hosts and allow
11500-476: The system was deployed at PARC, Metcalfe and Boggs published a seminal paper. Ron Crane , Yogen Dalal , Robert Garner, Hal Murray, Roy Ogus, Dave Redell and John Shoch facilitated the upgrade from the original 2.94 Mbit/s protocol to the 10 Mbit/s protocol, which was released to the market in 1980. Metcalfe left Xerox in June 1979 to form 3Com . He convinced Digital Equipment Corporation (DEC), Intel , and Xerox to work together to promote Ethernet as
11615-761: Was StarLAN , standardized as 802.3 1BASE5. While 1BASE5 had little market penetration, it defined the physical apparatus (wire, plug/jack, pin-out, and wiring plan) that would be carried over to 10BASE-T through 10GBASE-T. The most common forms used are 10BASE-T, 100BASE-TX, and 1000BASE-T . All three use twisted-pair cables and 8P8C modular connectors . They run at 10 Mbit/s , 100 Mbit/s , and 1 Gbit/s , respectively. Fiber optic variants of Ethernet (that commonly use SFP modules ) are also very popular in larger networks, offering high performance, better electrical isolation and longer distance (tens of kilometers with some versions). In general, network protocol stack software will work similarly on all varieties. In IEEE 802.3,
11730-485: Was achieved by a similar, cross- partisan action with Fromm as the liaison officer working to integrate with International Electrotechnical Commission (IEC) Technical Committee 83 and International Organization for Standardization (ISO) Technical Committee 97 Sub Committee 6. The ISO 8802-3 standard was published in 1989. Ethernet has evolved to include higher bandwidth, improved medium access control methods, and different physical media. The multidrop coaxial cable
11845-634: Was also spun out again as a separate company at this time. In January 2001, Claflin became chief executive officer , replacing Éric Benhamou , CEO from 1990 to 2000. He was criticized for the costly diversification in the mobile handheld computer market. At this point, the company's main line of business, selling addon network interface cards ("NICs"), was also shrinking rapidly, mainly because many new computers had NICs built in. The company started slashing or selling divisions and going through numerous rounds of layoffs . The company went from employing more than 12,000 employees to fewer than 2,000. In May 2003,
11960-549: Was an over-the-air wide area network system in Hawaii using ultra high frequency radios and made several assumptions that Metcalfe thought would not be correct in practice. He developed his own theories of how to manage traffic, and began to consider an "ALOHAnet in a wire" networking system. In 1972, he joined Xerox PARC to develop these ideas, and after pairing up with David Boggs , the two had early 3 Mbit/s versions of Ethernet working in 1973. They then went on to build up
12075-511: Was completed by 1978. Once again, Metcalfe found that management was unwilling to actually do anything with the product, and he threatened to leave and in 1979 he left the company. Metcalfe subsequently co-founded 3Com in 1979. The other co-founders were Metcalfe's college friend Howard Charney and two others. Bill Krause joined as President in 1981 and became CEO in 1982 and led 3Com until 1992 when he retired. 3Com began making Ethernet adapter cards for many early 1980s computer systems, including
12190-516: Was deployed in the United States, Japan , and Korea covering the 2G CDMA market sample carriers included Sprint. It led to follow on products that became core to CommWorks now UTStarcom offerings including the 2.5 and 3G packet data gateway products known as PDSN and Home Agents. CommWorks/3Com co-developed an H.323-based softswitch with AT&T in 1998 for use in a "transparent trunking" application for AT&T's residential long-distance customers. Long distance telephone calls were redirected from
12305-433: Was derived. Original Ethernet's shared coaxial cable (the shared medium) traversed a building or campus to every attached machine. A scheme known as carrier-sense multiple access with collision detection (CSMA/CD) governed the way the computers shared the channel. This scheme was simpler than competing Token Ring or Token Bus technologies. Computers are connected to an Attachment Unit Interface (AUI) transceiver , which
12420-446: Was designed for point-to-point links only, and all termination was built into the device. This changed repeaters from a specialist device used at the center of large networks to a device that every twisted pair-based network with more than two machines had to use. The tree structure that resulted from this made Ethernet networks easier to maintain by preventing most faults with one peer or its associated cable from affecting other devices on
12535-551: Was essentially to limit the Aloha-like signals inside a cable, instead of broadcasting into the air. The idea was first documented in a memo that Metcalfe wrote on May 22, 1973, where he named it after the luminiferous aether once postulated to exist as an "omnipresent, completely passive medium for the propagation of electromagnetic waves." In 1975, Xerox filed a patent application listing Metcalfe, David Boggs , Chuck Thacker , and Butler Lampson as inventors. In 1976, after
12650-661: Was formerly the Carrier Network Business unit of 3Com, comprising several acquired companies: U.S. Robotics (Rolling Meadows, Illinois), Call Technologies ( Reston, Virginia ), and LANsource ( Toronto , Ontario , Canada ). CommWorks was able to use technology from each company to create IP softswitch and IP communications software. U.S. Robotics provided media gateways (the Total Control 1000 product line, formerly used for dial-modem termination) and softswitch technology. Call Technologies provided Unified Messaging software. LANsource provided fax-over-IP software that
12765-462: Was influenced by a wide array of technological developments and historical milestones. Computer networks enhance how users communicate with each other by using various electronic methods like email, instant messaging, online chat, voice and video calls, and video conferencing. Networks also enable the sharing of computing resources. For example, a user can print a document on a shared printer or use shared storage devices. Additionally, networks allow for
12880-483: Was integrated with the Unified Messaging platform. The Carrier Network Business unit of 3Com developed an Inter-working function technology that became the first and dominant 2G CDMA wireless data gateway product. In partnership with Unwired Planet (now Openwave) and Qualcomm Quicknet connect allowed for 6 second connect times versus modems connecting the call in approximately 30 seconds. This product
12995-466: Was published in November 1982 and defines what has become known as Ethernet II . Formal standardization efforts proceeded at the same time and resulted in the publication of IEEE 802.3 on June 23, 1983. Ethernet initially competed with Token Ring and other proprietary protocols . Ethernet was able to adapt to market needs, and with 10BASE2 shift to inexpensive thin coaxial cable, and from 1990 to
13110-405: Was replaced with physical point-to-point links connected by Ethernet repeaters or switches . Ethernet stations communicate by sending each other data packets : blocks of data individually sent and delivered. As with other IEEE 802 LANs, adapters come programmed with globally unique 48-bit MAC address so that each Ethernet station has a unique address. The MAC addresses are used to specify both
13225-434: Was such that they were able to enter into an agreement with the city of San Francisco to pay $ 900,000 per year for the naming rights to Candlestick Park . That agreement ended in 2002. In 1997, 3Com merged with USRobotics (USR), a maker of dial-up modems, and owner of Palm, Inc. USRobotics was known for its Sportster line of consumer-oriented modems, as well as its Courier business-class modem line. This merger spelled
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