COMPUTER ARCHITECHTUREDATA COMMPC NETWORKINGa) What are microprocessor? A microprocessor or processing unit (CPU) is an integrated circuit built on a tiny piece of silicon. In order to function as a computer, the processor requires a power supply, a clock and memory. It contains thousands, or even millions, of transistors, which are interconnected via superfine traces of aluminum. The transistors work together to store and manipulate data so that the microprocessor can perform a wide variety of useful functions. The particular functions a microprocessor performs are dictated by software. The microprocessor is comprised of a single integrated circuit, which is a matrix of transistors and other electrical circuit. These are design like a “legs” to fastern the chip to the fiberglass circuit board which sits inside the computer and to carry electrical impulses into and out of the chip . The type of CPU determine its processing power,how fast it can execute various instructions. Most of the processor and CPU today can executes millions of instruction per second. It also determines the precise repertoire of instruction the computer understand and therefore which it can run. The speed of microprocessor depend on it value. For example a 32 bit microprocessor that run at 50 MHz is more power than 16 bit microprocessor that run at 25 MHz. b) Why do we need them? ENIAC was the first computer invented in 1946 and weighed 30 tons. Its used around 160 kW power to start the computer. One of the reason why we need microprocessor is to reduce the size of computer, inexpensive and easily replaceable design component. The most important reason is to reduce power supply implemented. The first microprocessor Intel 4004 is develop only take 5 volt. One of the most common tasks microprocessors perform is to serve as the "brains" inside personal computers, but they deliver "intelligence" to countless other devices as well. c) When did they come about? In the late 1960s, many scientist had discussed the possibility of the computer on a chip, but nearly everyone felt that integreted circuit technology was not yet ready to support such a chip . Intel’s Ted Hoff felt differently; he was the first person to recognize that the new silicon –gated MOS technology might make a single chip CPU possible . Hoff and the intel team developed such an architecture with just over 2,300 transistors in an area of only 3 by 4 milimetres. With its 4 bit CPU , command register , decoder , decoding control , control monitoring of machine commands and interim register , it can performed about 60,000 calculations in a second. Intels introduced the worlds first commercial microprocessor the 4004 , in November 1971 . The Pioneer 10 spacecraft used the 4004 microprocessor , it was launched on March 2, 1972 and was the first spacecraft and microprocessor to enter the Asteroid Belt. d) Who invented and manufactured them? The microprocessor was invented by Ted Hoff at Intel. The 4-bit 4004 processor, released in November 1971 was revolutionary because for the first time most of the logic elements used in a computer we placed on a single chip. In addition, it was programmable. The 8086, the progenitor of the x86 architecture, was released in June, 1978. It was a 16 bit microprocessor with 29,000 transistors, it has gone through several iterations in the 80286, 80386, 80486 to the present day flagship processor, the Pentium. The 60 MHz Pentium delivers roughly 380 times the performance of a 4.77MHz 8086 with only 100 times transistor count, a four-fold improvement in the process technology. e) How it works? The Bus Unit is the place where instructions flow in and out of the microprocessor from the computer's main memory. Here on this tiny silicon chip are millions of switches and pathways that help your computer make important decisions and perform helpful tasks. To help you understand how the microprocessor does its job, you will go step by step through a simple task on the chip. For the purpose of this demonstration, you will add two numbers together while watching the microprocessor do its magic. You will complete this task in four easy steps and you may review each step as many times as you want. Remember, each part of the processor has a special task. For the basic Intel 386 microprecessor it comprised of six main components, namely prefect unit, paging unit, segment unit, decode unit, bus interface unit and execution unit. Each performing a saperate task. Prefect Unit it accused up next software instruction for the CPU. When CPU finished its screen test,the prefect ask for the next instruction. The second and third components are called a paging and segments unit. They know the exact memory location of the next instruction and it is retreived by asking the bus interface unit to find it from rims. Let say ADD 2+2 instruction, the bus interface unit passed the instruction to prefetch unit than from prefetch unit route to decode unit which translate it into language of the processor can understand. Finally the instruction is transferred to the execution unit which carry up the results of the software commond . The results is then sent back to paging unit or segment unit and bus unit finally to it correct location in the PC memory. f) How Chips Are Made PreparationThe images below represent just some of the ingredients used to build microprocessors. Read the description of each image to learn more about important ingredients like silicon, which is fundamental to making microprocessors. Silicon Wafers cut from an ingot of pure silicon, are used by Intel to make microprocessors. Silicon, the primary ingredient of beach sand, is a semiconductor of electricity. Semiconductors are materials that can be altered to be either a conductor or an insulator. Chemicals and gases are used throughout the chip-making process. Some, like hexamethyldisilazane, are complex and difficult to pronounce. Others, such as boron, are simple elements found in the Periodic Table of the Elements. Metals, such as aluminum and copper, are used to conduct the electricity throughout the microprocessor. Gold is also used to connect the actual chip to its package. Ultraviolet (UV) Light has very short wavelengths and is just beyond the violet end of the visible spectrum. UV light is used to expose patterns on the layers of the microprocessor in a process much like photography. Masks used in the chip-making process are like stencils. When used with UV light, masks create the various circuit patterns on each layer of the microprocessor. FabricationMicroprocessors are built in layers on a silicon wafer through various processes using chemicals, gases, and light. Although several microprocessors are built on a single wafer, our demonstration will build only a small piece of a microprocessor. Let's take a closer look... On the wafer, the first layer of silicon dioxide is grown by exposing it to extreme heat and gas. This growth is similar to the way rust grows on metal when exposed to water. The silicon dioxide on the wafer, however, grows much faster and is too thin to be seen by the naked eye. The wafer is then coated with a substance called photoresist. Photoresist becomes soluble when exposed to ultraviolet light. Layering In a process called photolithography, ultraviolet light is then passed through a patterned mask, or stencil, onto the silicon wafer. The mask protects parts of the wafer from the light. The light turns the exposed areas into a gooey layer of photoresist. Each layer on the microprocessor uses a mask with a different pattern. Etching The gooey photoresist is completely dissolved by a solvent. This reveals a pattern of photoresist made by the mask on the silicon dioxide. The revealed silicon dioxide is etched away with chemicals. The rest of the photoresist is removed. This process leaves ridges of silicon dioxide on the silicon wafer base. LayersTo begin another layer, a second, thinner layer of silicon dioxide is grown over the ridges and etched areas of the wafer base. Then, a layer of polysilicon and another layer of photoresist are applied. Ultraviolet light is then passed through a second mask, exposing a new pattern on the photoresist. The photoresist is dissolved with solvent to expose the polysilicon and silicon dioxide, which are then etched away with chemicals. The remaining photoresist is removed, leaving ridges of polysilicon and silicon dioxide. Ion ImplantationThrough a process called ion implantation (also called doping), the exposed areas of the silicon wafer are bombarded with various chemical impurities called ions. Ions are implanted in the silicon wafer to alter the way silicon in these areas conducts electricity. Layers upon LayersThe layering and masking processes are repeated, creating windows that allow for connections to be made between the layers. Atoms of metal are deposited on the wafer, filling the windows. Another masking and etching stage leaves strips of the metal that make the electrical connections. Roughly 20 layers are connected to form the microprocessor's circuitry in a 3-dimensional structure. The exact number of layers on a wafer depends on the design of the microprocessor. Multiple ProcessorsSo far, we've built only a tiny portion of a microprocessor. In reality, making microprocessors is much more complex, demanding more than 250 steps. Consequently, hundreds of identical microprocessors are created in batches on a single wafer. g) Comparison between market leader Pentium-4 was released for production on Nov 20, 2000. The Pentium-4 is fabricated in Intel's 0.18 micron CMOS process. Its die size is 217 mm2, power consumption is 50W. The Pentium 4 is available in 1.4GHz and 1.5Hz bins. At 1.5GHz the microprocessor delivers 535 SPECint2000 and 558 SPECfp2000 of performance. Pentium-4 is the first completely new x86-processor design from Intel since the Pentium PRO processor, with its P6 micro-architecture, was introduced in 1995. Pentium-4' micro-architecture is known as NetBurst. It has many interesting features.- Compared to the Intel Pentium-III processor, Intel's NetBurst micro-architecture doubles the pipeline depth to 20 stages. In addition to the L1 8 KB data cache, the Pentium 4 processor includes an Execution Trace Cache that stores up to 12 K decoded micro-ops in the order of program execution. The on-die 256KB L2-cache is non-blocking, 8-way set associative. It employs 256-bit interface that delivers data transfer rate of 48 GB/s at 1.5 GHz. The Pentium 4 processor expands the floating-point registers to a full 128-bit and adds an additional register for data movement. Pentium-4' NetBurst micro-architecture introduces Internet Streaming SIMD Extensions 2 (SSE2). This extends the SIMD capabilities that MMX technology and SSE technology delivered by adding 144 new instructions. These instructions include 128-bit SIMD integer arithmetic and 128-bit SIMD double-precision floating-point operations. Pentium 4 processor's 400 MHz (100 MHz "quadpumped") system bus provides up to 3.2 GB/s of bandwidth. The bus is fed by dual PC800 Rambus channel. This compares to 1.06 GB/s delivered on the Pentium-III processor's 133-MHz system bus. Two Arithmetic Logic Units (ALUs) on the Pentium 4 processor are clocked at twice the core processor frequency. This allows basic integer instructions such as Add, Subtract, Logical AND, Logical OR, etc. to execute in a half clock cycle. The integer register file runs also runs at the double frequency. Reference: · www.chip.com.my · Tabak,D.,multiprocessor, Eaglewood Cliffs, NJ:Prentice Hall, 1990 · http://ece.uprm.edu/~micro2/history/links.htm · http://www.intel.com.education/teachtech/learning/chips/ · http://inventors.about.com/library/inventors/blmicroprocessor.htm · http://www.toplink/eletronicl/computer.html · J.R Gibson, Electronic Logic Circuits,Edward Arnold Ltd,London,1993 ATAS DATA COMM
- Bluetooth Technology Bluetooth technology revolutionizes the personal connectivity market by providing freedom from wired connections that enabling links between mobile computers, mobile phones, portable handheld devices, and connectivity to the Internet. Interface, synchronize, and exchange. As a wireless, Bluetooth technology redefines the very way in experience connectivity. Bluetooth wireless technology is supported by product and application development in a wide range of market segments, including software developers, silicon vendors, peripheral and camera manufacturers, mobile PC manufacturers and handheld device developers, consumer electronics manufacturers, car manufacturers, and test and measurement equipment manufacturers. Bluetooth wireless technology can works everywhere. Hardware that complies with the Bluetooth wireless specification ensures communication compatibility worldwide. As a low-cost, low-power solution with industry-wide support, Bluetooth wireless technology allows you to bring connectivity everywhere. 1.1 Bluetooth History Bluetooth was invented in 1994 by L. M. Ericsson of Sweden. The standard is named after Harald Blaatand "Bluetooth" II, king of Denmark 940-981A. The Bluetooth Special Interest Group (SIG)was founded by Ericsson,IBM,Intel,Nokia and Toshiba in February 1998, to develop an open specification for short-range wireless connectivity . The group is now promoted by 3COM, Microsoft, Lucent and Motorola also . More than 1900 companies have joined the SIG. 2.0 What is Bluetooth Bluetooth is the name given to a new technology standard using short-range radio links, intended to replace the cable(s) connecting portable and/or fixed electronic devices. The standard defines a uniform structure for a wide range of devices to communicate with each other, with minimal user effort. Its key features are robustness, low complexity, low power and low cost. The technology also offers wireless access to LANs, PSTN, the mobile phone network and the internet for a host of home appliances and portable handheld interfaces. The standard is aimed at achieving global acceptance such that any Bluetooth device, anywhere in the world, can connect to other Bluetooth devices in its proximity, regardless of brand. Bluetooth enabled electronic devices connect and communicate wirelessly via short-range, ad hoc networks called piconets. Each unit can simultaneously communicate with up to seven other units per piconet. Moreover, each unit can simultaneously belong to several piconets. These piconets are established dynamically and automatically as Bluetooth devices enter and leave the radio proximity. 2.1 Bluetooth Wireless Technology Bluetooth wireless technology is a worldwide specification for a small-form factor, low-cost radio solution that provides links between mobile computers, mobile phones, other portable handheld devices, and connectivity to the Internet. The specification is developed, published and promoted by the Bluetooth Special Interest Group (SIG). 2.2 Bluetooth SIG The Bluetooth Special Interest Group (SIG), a trade association comprised of leaders in the telecommunications, computing, and network industries, is driving development of the technology and bringing it to market. The Bluetooth SIG promoters include 3Com, Agere, Ericsson, IBM, Intel, Microsoft, Motorola, Nokia and Toshiba, and hundreds of Associate and Adopter member companies. 3.0 Bluetooth Wireless-capable Product While the possibilities are nearly endless for the applications of the technology, some of the current capabilities include: . Eliminating the need for wired connections between electronic products and accessories. . Exchanging files, business cards, calendar appointments, etc. with of Bluetooth users. . Transfering and synchronizing files between devices. . Connecting to localized content services in public areas. . Functioning as remote controls, keys, tickets and e-cash wallets 4.0 Bluetooth wireless specification The Bluetooth wireless specification defines a low-power, low-cost technology that provides a standardized platform for eliminating cables between mobile devices and facilitating connections between products. Unlike many other wireless standards, the Bluetooth wireless specification includes both link layer and application layer definitions for product developers. Radios that comply with the Bluetooth wireless specification operate in the unlicensed, 2.4 GHz radio spectrum ensuring communication compatibility worldwide. These radios use a spread spectrum, frequency hopping, full-duplex signal at up to 1600 hops/sec. The signal hops among 79 frequencies at 1 MHz intervals to give a high degree of interference immunity. While point-to-point connections are supported, the specification allows up to seven simultaneous connections to be established and maintained by a single radio. The intergration of Bluetooth wireless technology brings new functionality to an entire range of familiar product while also setting the stage for entirely unique applications with Revolutionary Connectivity implications. Devices enabled with Bluetooth wireless technology will be able to: .Free electronic accessories and peripherals from wired connections. .Exchange files, business cards, and calendar appointments. .Transfer and synchronize data wirelessly. .Take advantage of localized content services in public areas. .Function as remote controls, keys, tickets and e-cash wallets. 5.0 System Requirements The Bluetooth system is now recognized more than just a cable replacement technology. Varous innovative usage models have openned up new areas where Bluetooth can be used. These also impose many requirements on the system, some of which are: There should be a universal framework that offers means to access information across a diverse set of devices (for example, PDA's, laptops, PC's, mobile phones, home appliances etc.)in a seamless, user friendly and efficient manner. Available for collaboration between devices, in the proximity of one another, where every device provides its inherent function based on its form, user interface,cost and power. The standard must enable the devices to establish ad hoc connections. Also, introduced is the the ünconscious connectivity" paradigm , where devices can connect to those in proximity almost without any user command or interaction. This shall allow utilization of various information recourses for the benefit of the user. Support for both data and voice is expected as these are two most important kinds of information being transmitted over networks today. (The requirements of video and streaming multimedia are also being imposed on the future versions of Bluetooth). The communications should offer similar protection as in cables. There should not be any compromises on security in switching over to wireless. 6.0 System Architecture The system architecture for Bluetooth has been segmented into various almost independent layers for conceptual ease of description. These layers are described in detail in the core Bluetooth specifications. The design specifications also describe certain properties for certain common classes of applications to be implemented over Bluetooth to achieve uniformity across diverse manufacturers. These are described in profiles of the Bluetooth Specification. The figure shows that the protocol stack consists of a radio layer at the bottom which forms the physical connection interface. The baseband and Link Manager Protocol(LMP) that reside over it are basically meant to establish and control links between Bluetooth devices. These three bottom layers are typically implemented in hardware/firmware. The Host Controller layer is required to interface the Bluetooth hardware to the upper protocol-L2CAP(Logical Link Control and Adaptation Protocol). The host controller is required only when the L2CAP resides in software in the host. If the L2CAP is also on the Bluetooth module, this layer may not be required as then the L2CAP can directly communicate with the LMP and baseband. Applications reside above L2CAP. The following subsections give a brief description of each layer. 8.0 Baseband The baseband is the layer that controls the radio. The frequency hopsequences are provided by this layer. Baseband also takes care of lower level encryption for secure links. The packet handling over the wireless link is the responsibility of Baseband. Two types of links can be established: SCO: Synchronous Connection Oriented. These links are meant for synchronous data-typically voice. ACL: Asynchronous Connection less. These links may be used for data transfer applications, which do not require a synchronous link. The baseband provides the functionalities required for devices to synchronize their clocks and establish connections. Inquiry procedures for discovering the addresses of devices in proximity are also provided. Error correction for packets is provided depending on the type of packet. Various packet types are specified for some common applications, differing in their data capacity and error correction. 9.0 Logical Link Control and Adaptation Protocol This is the protocol with which most applications would interact unless a host controller is used. The basic functions of the L2CAP are: 9.1 Multiplexing The protocol must allow multiple applications to use a link between two devices simultaneously. 9.2 Segmentation and Reassembly The protocol must reduce the size of packets provided by applications to the size of packets accepted by Baseband. L2CAP itself accepts packet sizes upto 64kb but the baseband packets can accept a payload of at most 2745 bits. The reverse procedure, that of combining the segmented packets in the proper order, has to be carried out for received packets. 9.3 Quality of Service L2CAP allows applications to demand QoS on certain parameters like peak bandwidth, latency and delay variation. L2CAP checks if the link is capable of providing it and provides it if possible. Basically, L2CAP provides the network layer functions to applications and higher protocols. Host Controller Interface 10.0 Conclusions The above sections described some of the important considerations in the design of the Bluetooth standard. There are however a lot of other considerations such as the avoidance of collisions and satisfying the radio spectrum regulations. Today in human technology, all communication become wireless and someday we will cannot find any communication using cable and it will make a lot of modernization in data communication. 11.0 References: 1. Bluetooth Special Interest Group, "Specifications of the Bluetooth System: Core", Version 1.0.B, July 1999. Bluetooth Special Interest Group, "Specifications of the Bluetooth System: Profiles", Version 1.0.B, July 1999. 2. Haartsen, Mahmoud Naghshineh, Jon Inouye, Olaf J. JOeressen and Warren Allen, Bluetooth: Vision Goals and Architechture , Mobile Computing and Communications Review, Vol. 1, Number 2,(1997). 3. Jaap Haartsen, BLUETOOTH-The universal radio interface for ad hoc, wireless connectivity,Ericsson Review, Number 3, 1998, pp 110-117. 4. Kris Fleming, Uma Gadamsetty, Robert J Hunter, Srikanth Kambhatla, Sridhar Rajagopal and Sundaram Ramakesavan, Architectural Overview of Intel's Bluetooth Software Stack, Intel Technology Journal, Q2 2000. 5. Jaap Haartsen, The Bluetooth Radio System,IEEE Personal Communications, February 2000. 6. http://www.bluetooth.com/dev/specifications.asp 7. http://www.bluetooth.com/util/faq4.asp 8. http://e-www.motorola.com/webapp/sps/site/homepage.jsp? nodeId=03M0ymVXlR5 9. http://www.nokia.com/bluetooth/whatis.html 10. http://www.zdnet.co.uk/news/specials/1999/04/bluetooth/ Simple Questions With Answers Q1: What is Bluetooth technology? Bluetooth wireless technology is a worldwide specification for a small-form factor, low-cost radio solution that provides links between mobile computers, mobile phones, other portable handheld devices, and connectivity to the Internet. The specification is developed, published and promoted by the Bluetooth Special Interest Group (SIG). Q2: What is the Bluetooth SIG? The Bluetooth Special Interest Group (SIG), a trade association comprised of leaders in the telecommunications, computing, and network industries, is driving development of the technology and bringing it to market. The Bluetooth SIG promoters include 3Com, Agere, Ericsson, IBM, Intel, Microsoft, Motorola, Nokia and Toshiba, and hundreds of Associate and Adopter member companies. Q3: What are the differences between Wi-Fi (IEEE 802.11b) and the Bluetooth wireless technology? The Bluetooth wireless technology and Wi-Fi are complementary technologies. The Bluetooth wireless technology is designed to replace cables between cell phones, laptops, and other computing and communication devices within a 10-meter range. Wi-Fi is wireless Ethernet; it provides an extension or replacement of wired networks for dozens of computing devices. Q4. What forms the host and what is the host controller in a Bluetooth device? The host is the device which wants to use Bluetooth for its communication requirements. It could be a laptop, a headphone, a PDA or any other device. The host controller is a special module on the Bluetooth hardware which formats the data packets being communicated from the host to the Bluetooth module into a format suitable for the link between the host and the module. Q5. How is the situaion handed if two devices launch an inquiry simultaneously? When two devices start an inquiry simultaneously, then they cannot discover each other in that inquiry sequence. (They do not cause collissions for other devices as the inquiry hop sequence is different for the two devices). To prevent the devices never being able to discover each other, the specification requires that the interval between two inquiries be random. This ensures that the two devices which collided once will not collide again in the next inquiry. ATAS PC NETWORKING
CCITT CCITT (Commite' Consultatif International de Telegraphique et Telephonique) CCITT adalah sebuah organisasi yang bekerjasama dengan organisai standard dalam mewujudkan satu bahasa standard yang diguna dalam sistem komunikasi. Antara standard yang di hasilkan ialah V.XX seperti V.21 dan V.24 juga standard X.n seperti X.25 . IEEE IEEE (Institute of Electrical and Electronics Engineers, Inc.) IEEE adalah Institut teknikal profesional yang terbesar di dunia. Ia membiayai persidangan teknikal , simposium dan mesyuarat di seluruh dunia . Mereka menerbitkan kertas kerja berkenaan elektrik, elektronik dan kejuruteraan komputer dan juga sains komputer di seluruh dunia. Antara bidang yang diterokai termasuklah Aeroangkasa, komputer dan komunikasi, teknologi bioperubatan, kuasa elektrik dan elektronik pengguna . DoD DoD (Department of Defence) DoD adalah satu badan ketenteraan Amerika Syarikat yang bertanggungjawab dalam menguruskan banyak standard perisiaan kejuruteraan. ANSI ANSI (American National Standards Institute) ANSI adalah sebuah pertubuhan kerajaan Amerika Syarikat yang bertanggungjawab untuk mengesahkan standard yang digunakan dalam berbagai bidang termasuk komputer dan komunikasi. Antara standard yang disahkan oleh ANSI adalah American Standard Code for Information Interchange (ASCII). EIA EIA (Electronic Industries Association) EIA terdiri daripada organisasi individu yang bersetuju dengan standard-standard penghantaran data seperti EIA/TIA-232 dahulu dikenali sebagai RS-232) SPX/IPX SPX/IPX (Sequenced Packet Exchange/ Internetwork Packet Exchange) Is a networking protocol develop by Novell that interconnects networks that use Novells NetWare environments client and servers.IPX is a datagram or packet protocols and is connectionless (that is it doesn’t reqire that a connection be maintained during an exchanged of packets).IPX uses the 48 bit MAC address to uniquely identify the machine.The SPX handles the packet once it is on the wire and manages packet acknowledgement.Microsoft calls their version of IPX/SPX “NWLink”.It is a very widely used today. TCP/IP TCP/IP (Transmission Control Protocol/Internet Protocol) Adalah bahasa komunikasi utama ataupun protokol kepada internet. Digunakan juga sebagai protokol komunikasi dalam rangkaian persendirian seperti intranet dan extranet. TCP/IP mempunyai 2 layer program. Layer pertama Transmission Control Protocol (TCP), menukarkan data atau fail kepada packets yang lebih kecil yang akan dihantar melalui internet dan kemudian diterima oleh TCP layer pada penerima yang akan menukar kembali packets tersebut kepada data atau fail asal. Layer kedua , Internet Protocol (IP), mengendali alamat pada setiap packet dan memandu packet kepada destinasi yang tepat. Setiap pintu laluan komputer pada sistem rangkaian memeriksa alamat ini untuk memastikan alamat untuk setiap data dihantar. Antara aplikasi yang menggunakan TCP/IP adalah TCP/IP adalah World Wide Web's Hypertext Transfer Protocol (HTTP) File Transfer Protocol (FTP), Telnet dan Simple Mail Transfer Protocol (SMTP). SMB SMB (Server Message Block) Satu protokol yang menyediakan satu kaedah untuk permohonan pelanggan(client) didalam komputer dimana pelanggan(client) boleh membaca, menulis kedalam fail dan juga memohon perkhidmatan daripada program server didalam rangkaian komputer. Boleh access ke dalam fail melalui pembekal kawalan seperti sumber-sumber yang lain termasuk mesin pencetak dan “mail slots”. Dari sini pelanggan akan dapat membuat, mencipta dan mengemaskini fail . Boleh berkomunikasi dengan sebarang program server yang telah diprogramkan untuk menerima permohonan pelanggan SMB. NetBIOS NetBIOS (Network Basic Input/Output System) NetBIOS adalah program yang membenarkan aplikasi-aplikasi pada komputer yang berlainan untuk berkomunikasi melalui Local Area Network LAN. Ia dicipta oleh syarikat IBM untuk rangkaian komputer generasi awal. NetBIOS digunakan dalam rangkaian Ethernet, token ring dan Windows NT NetBIOS juga termasuk session layer dan transport layer didalam (OSI) model. NetBIOS menyediakan 2 mod komunikasi Session Dua komputer menghasilkan sambungan untuk “conversation” , membenarkan mesej yang besar dikendalikan. Mempunyai “error detection” dan “recovery”. Datagram Datagram adalah "connectionless" (mesej dihantar secara bersendirian), mesej adalah lebih kecil dan aplikasi bertanggungjawab untuk error detection dan recovery. NetBEUI NetBEUI (NetBIOS Extended User Interface) Satu versi yang dihasilkan oleh NetBIOS yang membenarkan komputer berkomunikasi diantara Local Area Network. Ia merupakan versi baru NetBIOS dan pilihan terbaik untuk berkomunikasi diantara single LAN. Seperti NetBIOS, NetBEUI juga tidak menyokong untuk laluan mesej bagi rangkaian-rangkaian yang lain. Ia dibangunkan oleh IBM untuk LAN Manager dan telah diambil oleh Microsoft untuk Windows NT. Ia turut digunakan oleh Hewlett-Packard & DEC. ATAS What is Local Talk? All macintosh computers have had local talk hardware and software built into their system since1984. Local Talk is easy to set up and requires a minimal h/ware investrment for Macintoshes, but it has had little impact into the IBM world, making local talk cards expensive for computers. Hardware Connecting a macintosh to a local talk network are easy. All that’s is needed is an active network jack, a teleconnector, wire and resistor as well as documentation and other information. Software Just as local talk h/ware is built into Macintosh h/ware, the s/ware components are built into the MacOS. The following s/ware is required for local talk network connectivity. Network control panel : . MacTCP (needed for TCP/IP protocols) . Sharring set up . File Shariing Monitor (needed for file shatrring) . Users and groups (needed for several file sharring) Network Extension : . Apple Share . Network Extension . Apple Built-In Ethernet (needed for Enthernet) . Ether Talk Phase 2 (needed for Ethernet) Local Talk Daisy Chains A simple Local Talk network can be one computer connected to a printer or two computers connected together. Local Talk connects computers in a “daisy chain” , one network device is plugged into another, forming a long line of devices. The end of chains must be terminated and cannot be joint to make a circle. FDDI FDDI (Fiber Distributed Data Interface) is a standard for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol. In addition to being large geographically, an FDDI local area network can support thousands of users. An FDDI network contains two token rings, one for possible backup in case the primary ring fails. The primary ring offers up to 100 Mbps capacity. If the secondary ring is not needed for backup, it can also carry data, extending capacity to 200 Mbps. The single ring can extend the maximum distance; a dual ring can extend 100 km (62 miles). Today however, comparable speeds are available using cooper cable . The cooper version of FDDI is known as CDDI FDDI is a product of American National Standards Committee X3-T9 and conforms to the Open Systems Interconnection (OSI) model of functional layering. It can be used to interconnect LANs using other protocols. FDDI-II is a version of FDDI that adds the capability to add circuit-switched service to the network so that voice signals can also be handled. Work is underway to connect FDDI networks to the developing Synchronous Optical Network (SONET). In FDDI , access is limited by time . A station may send a many frames as it can within its allocated access period , with the provision that real- time data will sent first . To implement this access mechanism , FDDI differentiates between two types of data frames : synchronous and asynchronous . Synchronous here refers to information that is real-time , while asynchronous refers to information that is not . This frames usually called S-frames and A-frames . FDDI defines three times register to control circulation . The three registers is called synchronous allocation(SA) . target token rotation time (TTRT) and absolut maximum time (AMT). Terangkan secara ringkas tentang wireless LAN. . Advantage . Disadvantage A wireless LAN is one in which a mobile user can connect to a local area network (LAN) through a wireless (radio) connection. A standard, IEEE 802.11, specifies the technologies for wireless LANs. The standard includes an encryption method, the Wired Equivalent Privacy algorithm. High-bandwidth allocation for wireless will make possible a relatively low-cost wiring of classrooms in the United States. A similar frequency allocation has been made in Europe. Hospitals and businesses are also expected to install wireless LAN systems where existing LANs are not already in place. Using technology from the Symbionics Networks, Ltd., a wireless LAN adapter can be made to fit on a Personal Computer Memory Card Industry Association (PCMCIA) card for a laptop or notebook computer. Introduction A wireless local area network (LAN) is a flexible data communications system implemented as an extension to, or as an alternative for, a wired LAN. Using radio frequency (RF) technology, wireless LANs transmit and receive data over the air, minimizing the need for wired connections. Thus, wireless LANs combine data connectivity with user mobility. Wireless LANs have gained strong popularity in a number of vertical markets, including the health-care, retail, manufacturing, warehousing, and academia. These industries have profited from the productivity gains of using hand-held terminals and notebook computers to transmit real-time information to centralized hosts for processing. Today wireless LANs are becoming more widely recognized as a general-purpose connectivity alternative for a broad range of business customers. Business Research Group, a market research firm, predicts a sixfold expansion of the worldwide wireless LAN market by the year 2000, reaching more than $2 billion in revenues. WhyWireless? The widespread reliance on networking in business and the meteoric growth of the Internet and online services are strong testimonies to the benefits of shared data and shared resources. With wireless LANs, users can access shared information without looking for a place to plug in, and network managers can set up or augment networks without installing or moving wires. Wireless LANs offer the following productivity, convenience, and cost advantages over traditional wired networks: . Mobility: Wireless LAN systems can provide LAN users with access to real-time information anywhere in their organization. This mobility supports productivity and service opportunities not possible with wired networks. . Installation Speed and Simplicity: Installing a wireless LAN system can be fast and easy and can eliminate the need to pull cable through walls and ceilings. . Installation Flexibility: Wireless technology allows the network to go where wire cannot go. . Reduced Cost-of-Ownership: While the initial investment required for wireless LAN hardware can be higher than the cost of wired LAN hardware, overall installation expenses and life-cycle costs can be significantly lower. Long-term cost benefits are greatest in dynamic environments requiring frequent moves and changes. . Scalability: Wireless LAN systems can be configured in a variety of topologies to meet the needs of specific applications and installations. Configurations are easily changed and range from peer-to-peer networks suitable for a small number of users to full infrastructure networks of thousands of users that enable roaming over a broad area. How Wireless LANs Are Used in the Real World Wireless LANs frequently augment rather than replace wired LAN networks—often providing the final few meters of connectivity between a wired network and the mobile user. The following list describes some of the many applications made possible through the power and flexibility of wireless LANs: . Doctors and nurses in hospitals are more productive because hand-held or notebook computers with wireless LAN capability deliver patient information instantly. . Consulting or accounting audit teams or small workgroups increase productivity with quick network setup. . Students holding class on a campus greensward access the Internet to consult the catalog of the Library of Congress. . Network managers in dynamic environments minimize the overhead caused by moves, extensions to networks, and other changes with wireless LANs. . Training sites at corporations and students at universities use wireless connectivity to ease access to information, information exchanges, and learning. . Network managers installing networked computers in older buildings find that wireless LANs are a cost-effective network infrastructure solution. . Trade show and branch office workers minimize setup requirements by installing pre-configured wireless LANs needing no local MIS support. Wireless LAN Technology Manufacturers of wireless LANs have a range of technologies to choose from when designing a wireless LAN solution. Each technology comes with its own set of advantages and limitations. Narrowband Technology A narrowband radio system transmits and receives user information on a specific radio frequency. Narrowband radio keeps the radio signal frequency as narrow as possible just to pass the information. Undesirable crosstalk between communications channels is avoided by carefully coordinating different users on different channel frequencies. A private telephone line is much like a radio frequency. When each home in a neighborhood has its own private telephone line, people in one home cannot listen to calls made to other homes. In a radio system, privacy and noninterference are accomplished by the use of separate radio frequencies. The radio receiver filters out all radio signals except the ones on its designated frequency. From a customer standpoint, one drawback of narrowband technology is that the end-user must obtain an FCC license for each site where it is employed. Spread Spectrum Technology Most wireless LAN systems use spread-spectrum technology, a wideband radio frequency technique developed by the military for use in reliable, secure, mission-critical communications systems. Spread-spectrum is designed to trade off bandwidth efficiency for reliability, integrity, and security. In other words, more bandwidth is consumed than in the case of narrowband transmission, but the tradeoff produces a signal that is, in effect, louder and thus easier to detect, provided that the receiver knows the parameters of the spread-spectrum signal being broadcast. If a receiver is not tuned to the right frequency, a spread-spectrum signal looks like background noise. There are two types of spread spectrum radio: frequency hopping and direct sequence. Frequency-Hopping Spread Spectrum Technology Frequency-hopping spread-spectrum (FHSS) uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical channel. To an unintended receiver, FHSS appears to be short-duration impulse noise. Direct-Sequence Spread Spectrum Technology Direct-sequence spread-spectrum (DSSS) generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The longer the chip, the greater the probability that the original data can be recovered (and, of course, the more bandwidth required). Even if one or more bits in the chip are damaged during transmission, statistical techniques embedded in the radio can recover the original data without the need for retransmission. To an unintended receiver, DSSS appears as low-power wideband noise and is rejected (ignored) by most narrowband receivers. Infrared Technology A third technology, little used in commercial wireless LANs, is infrared. Infrared (IR) systems use very high frequencies, just below visible light in the electromagnetic spectrum, to carry data. Like light, IR cannot penetrate opaque objects; it is either directed (line-of-sight) or diffuse technology. Inexpensive directed systems provide very limited range (3 ft) and typically are used for personal area networks but occasionally are used in specific wireless LAN applications. High performance directed IR is impractical for mobile users and is therefore used only to implement fixed sub-networks. Diffuse (or reflective) IR wireless LAN systems do not require line-of-sight, but cells are limited to individual rooms. How Wireless LANs Work Wireless LANs use electromagnetic airwaves (radio or infrared) to communicate information from one point to another without relying on any physical connection. Radio waves are often referred to as radio carriers because they simply perform the function of delivering energy to a remote receiver. The data being transmitted is superimposed on the radio carrier so that it can be accurately extracted at the receiving end. This is generally referred to as modulation of the carrier by the information being transmitted. Once data is superimposed (modulated) onto the radio carrier, the radio signal occupies more than a single frequency, since the frequency or bit rate of the modulating information adds to the carrier. Multiple radio carriers can exist in the same space at the same time without interfering with each other if the radio waves are transmitted on different radio frequencies. To extract data, a radio receiver tunes in one radio frequency while rejecting all other frequencies. In a typical wireless LAN configuration, a transmitter/receiver (transceiver) device, called an access point, connects to the wired network from a fixed location using standard cabling. At a minimum, the access point receives, buffers, and transmits data between the wireless LAN and the wired network infrastructure. A single access point can support a small group of users and can function within a range of less than one hundred to several hundred feet. The access point (or the antenna attached to the access point) is usually mounted high but may be mounted essentially anywhere that is practical as long as the desired radio coverage is obtained. ATAS
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