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| RBOC to Recommended Standard-232, 422, and 423 (RS-232, RS-422, RS-423) |
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R March 2002 • Vol.6 Issue 3 |
RBOC to Recommended Standard-232, 422, and 423 (RS-232, RS-422, RS-423) | ||
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Encyclopedia entries in this article: RBOC RC2, RC4, RC5, and RC6 RDRAM README file read-only read-only memory (ROM) read/write real mode REALmagic RealNetworks real-time reboot Recommended Standard-232, 422, and 423 (RS-232, RS-422, RS-423) RBOC See Regional Bell Operating Company.
RC2, RC4, RC5, and RC6 These are proprietary encryption ciphers named after Dr. Ronald Rivest of RSA Data Security (now RSA Security). The ciphers encrypt messages using an algorithm based on random number combinations. People speculate that RC stands for either Ron Code or Rivest's Cipher. RC2 is a block cipher that uses a variable key size. It can be made more or less secure than the National Security Agency's DES (data encryption standard) by changing the key size. It's also about two to three times faster than the DES. RSA Security placed RC2 in the public domain in 1998. RC4 is also a variable key size using a fast stream cipher algorithm. Its key size ranges from 40 to 256 bits. A stream cipher is a method of encrypting data by applying a cryptographic formula and primer key to the data stream. There is a certain vulnerability to this method of encryption in that if two messages are encrypted with the same RC4 primer key, a hacker may decipher their encryption and recover both messages. Another vulnerability RC4 has is that it does not offer any data integrity checks, so if a hacker is able to decipher the message, he could modify the message and re-encrypt it without the recipient's knowledge that it was altered. For these reasons, RC4 is often used in conjunction with SSL (secure sockets layer) encryption, which offers another layer of security on top of RC4. Unlike RC2, RC4 is a trade secret of RSA Security and is not part of the public domain. RC2 and RC4 have been granted special U.S. export status in their 40-bit key versions. A 56-bit key size for RC4 is allowed for foreign subsidiaries and overseas offices of U.S. companies. The Software Publishers Association and the U.S. government initiated a control policy saying that any encryption technology needed to be reviewed before being allowed for use outside (exported out) of the United States. The control policy has three conditions that need to be met before export will be allowed: A technical review of the encryption product needs to be conducted, a post-export reporting system needs to be created for the encryption product, and the U.S. government needs to have the ability to review the export of strong encryption products to foreign governments. The key size is sometimes appended to the name of the encryption cipher, such as RC4-40 and RC4-128. RC5 uses a fast block cipher for encryption. Its algorithm uses three parameters: block size, primer key size, and number of rounds. The block size may be 32, 64, or 128 bits long. The primer key size may be from 0 to 2,048 bits. The number of rounds may be from 0 to 255. Due to the range of choices for each parameter, RC5 offers many different ways a message can be encrypted, which provides many different levels of security. Because of the complexity of the algorithm RC5 uses, RSA Security doesn't claim it to be as fast as RC2 or RC4. RC6 is a block cipher based on RC5 and designed by Rivest and other researchers at RSA Security. RC6 is a parameterized algorithm, like RC5, where the block size, key size, and number of rounds are variable. RC6 differs from RC5 in that it operates in units of four instead of two, and integer multiplication is now an additional primitive operation. Integer multiplication works by multiplying two 32-bit source values and produces a 64-bit result. The use of this type of multiplication greatly increases the diffusion achieved per round, which allows for greater security and increased encryption throughput. The main goal for RC6 was to meet the requirements of the AES (Advanced Encryption Standard). AES is a FIPS (Federal Information Processing Standard) publication that specifies a cryptographic algorithm for use by U.S. government agencies to protect unclassified, sensitive information. AES was designed to replace DES. The NIST (National Institute of Standards and Technology) enforces FIPS, which is an agency of the U.S. Commerce Department's Technology Administration. The AES was a worldwide competition to develop a new encryption technique for protecting electronic information. It was a three-year competition, and leaders in the area of cryptography were invited to participate. To determine how sound the submitted algorithms were, NIST invited the worldwide cryptographic community to try and attack, or hack, the encryption algorithms. From all the submissions, the selection was narrowed down to five finalists. When the five were selected, the cryptographic community was asked to intensify its hacks on the finalists. In the end, NIST did not choose RC6 for the standard; it chose the Rijndael, which was submitted by Joan Daemen of Proton World International and Vincent Rijmen of Katholieke Universiteit Leuven. In 1997, RSA initiated the Secret-Key Challenge to demonstrate the modest level of security in the encryption technology currently allowed to be exported under past and current U.S. government policy. Prior to 2000, the U.S. policy on cryptography allowed the export of only 40-bit encryption technology, with exceptions possible for 56-bit algorithms. Now, 128-bit encryption technology has been made available outside of the United States. Because the challenge was initiated, very determined hackers have cracked the 56-bit encryption code after countless hours of computation. RC5 using 128-bit encryption is still considered one of the safest encryption methods. Back to top RDRAM See Rambus dynamic random-access memory. Back to top README file A README file is a small text file that comes with many software packages. It contains last-minute information about the software that was not included in the printed documentation or online help. Sometimes these files contain information on anomalies or bugs discovered in the program. The format of README files is plain ASCII (American Standard Code for Information Interchange), which means any text editor, such as Notepad, can view it. If the CD, floppy diskette, or compressed file your software came on contains a README file, it's a good idea to review it before installing the new program. Don't be surprised if there is no README file, though. Not every program needs one. You can find README files in the root directory of the media a program is shipped on (CD-ROM or floppy diskette). If the program is part of a file you downloaded from the Internet, you will find the README file within the downloaded file. Some programs might have more than one README file associated with them. If that's the case, you'll see files such as README.1ST, README.TXT, and README.LST. If you see a file named README.1ST, it's a good idea to read that one before any of the others; many times it has instructions about the other README files. Back to top read-only Read-only is a term used to reference data that can be retrieved from memory or storage but can't be altered. A read-only file or document can be displayed or printed but not altered in any way. Read-only access is a term used to refer to a type of access privilege that permits the reader to view a file but not alter it. For example, users on a network may be granted read-only access to files in a company database so they can't change the information without permission. This is also known as read-only permission. A read-only terminal, also known as a receive-only terminal, is a device that can accept and display data but cannot form it itself. A printer would be considered a read-only terminal, as would an airport display terminal. Back to top read-only memory (ROM) A semiconductor-based memory module that contains instructions or data that is permanently recorded by the chip manufacturer. A user cannot remove or overwrite the instructions or data; he can only read them. Because the information is permanent, it stays on the chip even if the computer is turned off. ROM is often referred to as firmware because it never changes. ROM is essential to your computer and many video games because it contains the basic instructions for how a system is supposed to operate. Relating to ROM in human terms, you could consider the instructions for breathing part of a person's ROM: Even if you lose your memory, you'll always remember how to carry out fundamental functions such as breathing. Just like RAM, there are different types of ROM, including PROM (programmable ROM), EPROM (erasable programmable ROM), and EEPROM (electronically erasable programmable ROM). A ROM chip's instructions are recorded onto the integrated circuits within the chip. PROM is a blank ROM chip that can only be programmed once through a PROM programming device. This device electrically alters the connectors within the chip with instructions and data. Only a manufacturer can program ROM, but consumers can write data to PROM. Users can rewrite data to EPROM chips many times, but EPROM chips require a special EPROM programming device that can erase the contents of the ROM and write the new instructions. This type of memory is typical in smart cards, modems, and digital cameras. Manufacturers like to use this type of memory when they need something malleable. Unlike PROM and EPROM chips, EEPROM chips don't have to be removed from the device to be overwritten; specific instructions of the ROM can be overwritten rather than the entire ROM, and there is no need for a special programming device. EEPROM is often used for the computer's BIOS. You'll need a special program and associated data file to change data in EEPROM. When the program is run, an instruction is sent to the EEPROM's controller to give it a very low electrical charge, about 10 to 13 volts, which erases the EEPROM's programmable memory. The program then downloads the new instruction set in the chip. Once the instruction download is complete, another charge is sent to the chip, returning it to a read-only state. The program to update an EEPROM should come from the manufacturer of the device. If it doesn't, you might cause damage to the chip by writing the wrong instruction set to it and thus rendering the chip useless. Updates are usually shipped on bootable floppy disks. This is because you will want to update the device without the intervention of an operating system. Back to top read/write Read/write is a term used to describe a device that users can read from and write to. A hard drive is a good example: a user can read from it (such as when you access a document file stored on the drive) and write to it (such as when you save new or modified files to the drive). Rewriteable CDs are different from CD-ROMs (CD-read-only memory) or CD-Rs (CD-recordable) in that users can read information from and write information to rewriteable CDs many times. Unlike CD-Rs, which contain a dye that can only be changed once, CD-RWs (CD-rewriteable) contain a dye that can be changed back and forth from opaque to transparent, thus making it possible to write and rewrite data on the disc as many as 1,000 times. Rewriteable drives use a laser to heat a disc to one temperature so when the disc cools, its dye is transformed into a transparent state. It can then be used to heat the dye so it cools into a cloudy state. Back to top real mode An operational state of the early Intel CPUs (80286) that limited the processor to 1MB of memory. In real mode, the microprocessor imitated the Intel 8086 and 8088 microprocessors. This mode is also referred to as protected mode. In this mode, programs can access extended memory and virtual memory. Protected mode also supports multitasking, which is the ability to execute more than one task (program) at the same time. When the Intel microprocessors 80386 and later were built, they included support of an operational state called virtual 8086 mode. This mode let microprocessors run several real-mode programs at once. The original IBM PC could only address 1MB of memory, and DOS was created to work with that memory model. As personal computers' memory capacity grew past the 1MB range, many devices required that their drivers could only be loaded below the 1MB range because they weren't designed to reside in the memory space above 1MB. These devices could have been for sound cards, CD-ROM drivers, and game adapters. Drivers loaded below the 1MB range are called real-mode drivers.
REALmagic REALmagic is a registered trademark of Sigma Designs; it refers to the company's MPEG (Moving Pictures Experts Group; a digital video compression standard and file format developed by the group. MPEG-based video files require either special hardware or software to decode the compressed information) decoder chipset used for video streaming. Sigma Designs has included this technology in all of its commercial and retail products. On the commercial side, the company offers chipsets and PCBs (printed circuit boards) for third-party companies to use in set-top boxes or streaming video network devices for VOD (video-on-demand). VOD refers to technology that lets users select video from a central server to be viewed on a television or computer monitor. Sigma Designs' add-ins for consumers are built using the REALmagic chipsets for use with DVD and MPEG-2 video playback on to a computer monitor or television. The company also makes a PC add-in card (the REALmagic Xcard) that will help you turn your personal computer into a digital video recorder like TiVo, Panasonic's ReplayTV, or Microsoft's UltimateTV set-top boxes. Back to top RealNetworks Because the Internet was originally intended to deal with text-based information, not audio or video, users were initially stuck using file formats such as WAV (Waveform Audio), AVI (Audio-Video Interleaved), and MOV (Apple QuickTime Audio) to transmit sound and video over the Web. The problem with these file formats is that they are often very large and take time to download before they start to play. RealNetworks changed all that by pioneering the technology known as streaming media. Rather than waiting for an entire multimedia file to download to a target computer before viewing the file, the information is transferred to the target in a continuous stream and stored in a buffer. When enough information has been received in the buffer, the media player associated with the streaming media starts to play, even before the whole file is downloaded. RealAudio is RealNetworks' brand name for streaming, prerecorded, or live audio; RealVideo is the company's brand name for streaming, prerecorded, or live video. RealServer is the company's software program that allows the streaming of audio, video, and rich media files. According to RealNetworks, its media player, RealPlayer, is currently installed on over 90% of all U.S. home PCs and is the most commonly used form of streaming media. The latest version of RealNetworks' player is called RealOne Player. Not only does it play streaming media using RealNetworks' format, but it can also play Windows AVI, MP3 audio files, and MPEG files. In addition to being able to play other media formats, RealOne also broadcasts radio talk and music shows over the Internet. Radio stations are hoping this alliance will broaden their listener bases. Many media companies, such as ABC News, FOXSports, and The Wall Street Journal, offer special broadcasts made available exclusively to RealOne subscribers. In order to view and listen to these special broadcasts, you will need to purchase the RealOne Player Plus and pay a monthly subscription service fee. RealNetworks offers two versions of its RealOne player: One is free and the other is subscription-based. The free version lets a user access all of RealOne Player's playback features and the media jukebox and play other media formats as mentioned above. With the media jukebox, users can play and record digital audio files on their PCs. RealNetworks has partnered with several third-party software manufacturers to provide the best level of support for creating your own streaming media. The minimum system requirement to make any RealNetworks streaming media files is a personal computer with a sound card. If you wish to make a streaming video media file, your computer will need a video capture card and a VCR or camcorder. In order to broadcast your streaming media, you can host your material on a Web hosting service that offers RealNetworks support, such as Interland.Com or DellHost.Com or use RealNetworks' RealSystem Server solutions to host your own stream media server over the Internet or across your intranet.
The other technology that's part of RealSystems iQ is called NeuralCast technology. NeuralCast technology lets RealServer interact with other RealServer systems on a company's network. When a streaming broadcast consumes too many resources for the RealServer that is broadcasting, the NeuralCast technology will create a bridge to another RealServer on the network, and it will synchronize and transmit the broadcast using the other server, as well. As demand for the broadcast continues, the NeuralCast technology will use as many RealServer systems it can find within the network to help offset the streaming load. As the demand lessens, the NeuralCast will start releasing the servers it was using. Rob Glaser, a former Microsoft vice president in charge of Multimedia and Consumer Systems, founded the company in 1994. At that time, RealNetworks was known as Progressive Networks. Back to top real-time A term used to describe an action that occurs within a time frame imposed by external conditions. The term "real-time" is usually used before many different computer features or in reference to simulated action. For example, real-time transaction processing means that the transaction occurs in a human's perception of the normal passage of time it would take to process a transaction. In computer games, real-time refers to actions that would occur at the same speed as they would in the real world. Terms associated with real-time: real-time animation: This is a term used to describe computer animation where the images of objects are computed and updated on the screen at the same rate as their real-world counterparts. Real-time animation allows dynamic involvement by users because the computer can accept and incorporate movement comments as it's drawing the next image in the visible space. Simulation games such as flight simulators utilize real-time animation techniques.
RTSP (Real-Time Streaming Protocol): This is a client-server multimedia presentation control protocol for sending streaming audio and video, regardless of the format, across the Internet. RTSP's foundation is based on using the existing Internet and World Wide Web infrastructure and scaled to work with large audiences, as well as single-viewer media on-demand. Netscape Communications and RealNetworks, with the backing of more than 40 media companies, proposed the standard to the IETF (Internet Engineering Task Force) in 1996. That draft underwent development by such groups as RealNetworks, Netscape Communications, Columbia University, and the IETF MMUSIC (Multiparty Multimedia Session Control) working group. In April 1998, RTSP was published as an IETF Proposed Standard. Microsoft has a competing protocol called ASF (Advanced Streaming Format) created by its Windows Media technology group. ASF is a replacement file format to Microsoft's original AVI (Audio-Video Interleaved) media format. In many ways, ASF performs like RTSP, but RTSP is not part of the ASF specification. Apple Computers has its own streaming technology called QuickTime. Unlike Microsoft's streaming media protocol, QuickTime is built on the RTSP specifications. RTP (Real-Time Transport Protocol): RTSP provides VCR-style control functionality such as fast-forward, pause, reverse, and absolute positioning, which is beyond the scope of RTP. RTP is an IETF proposed standard and an ITU (International Telecommunications Union) standard. It is a packet format for transmitting streaming data (audio and video) in real-time across a network. RTP is used by many standard protocols, such as RTSP, for streaming applications. RTP offers only one-way communication between the streaming server and the client. Back to top reboot A term that refers to having to restart a computer and reload the OS (operating system). Many types of computers reboot when a user presses the CTRL-ALT-DELETE key combination. In Windows 95 and newer, a user can also reboot by selecting Shut Down from the Start menu, then clicking the Restart The Computer choice. On Apple Macintosh computers, you reboot your computer by selecting the Restart option from the Special menu. Rebooting a computer is sometimes the only way to regain control over a computer that is frozen due to an error. Rebooting a computer, however, causes all unsaved data in open applications to be lost. Reboot is also commonly known as a warm boot because the system is reset while the power is still on. There are times when a computer has erred so badly that a warm boot is not possible and requires a cold boot. A cold boot refers to restarting your computer by turning off the power and then turning it back on in 30 seconds or so. Sometimes you can't reboot your computer by pressing a combination of keys or through menu options. This occasionally happens because there's a system failure from which the OS can't recover. In this case, the computer won't respond to keyboard combinations and the pointer may stop moving across the screen. If this happens, you may have to press the computer's reset button, often located near the power button on the front of the computer. Some computers don't have reset buttons. If this is the case with your computer, you will have to perform a cold boot. Back to top Recommended Standard-232, 422, and 423 (RS-232, RS-422, RS-423) This is a standard connection interface approved by the EIA (Electronic Industries Association) in 1969 for communication through PC serial ports. This standard enables connections between such things as modems or other devices that use serial communication ports and personal computers or VDTs (video display terminals). The standard evolved over the years, and PC manufacturers adopted its third revision, referred to as RS-232C. In the PC industry, RS-232C was used for connecting computers to printers, plotters, backup tape devices, VDTs, programmed equipment, and other computers. Most equipment using RS-232 serial ports use a 9- or 25-pin D-type connector. Each pin connects to a wire within the cable, which is used to carry a signal from one port to the other. In today's personal computers, the 9-pin connector is the common port size for RS-232 connectivity. RS-232C can only support data transfer rates of 20Kbps (kilobits per second) and travel a distance of about 50 feet. These limitations are mostly due to the fact when the standard was conceived, 20Kbps was considered a very high line speed and cables were thick and had high capacitance. Two new recommended standards were designed to transmit data for greater distances at higher rates: RS-422 and RS-423. RS-422 defines the electrical characteristics of how the signal is transmitted through the serial connection. RS-422 is also called a differential, or balanced, interface because each communication signal is transferred over twisted pair wires. One of the twisted pair wires is for data transmission and the other is for reception. RS-422 can obtain data transfer rates of as fast as 10Mbps (megabits per second) and travel distances as far as 4,000 feet. The RS-422 standard is backward-compatible with RS-232 devices. RS-422 is commonly used to exchange data between two or more points, or nodes, on a network. RS-423 is similar to RS-422 in that it's designed for 10Mbps transfer rates and can travel as far as 4,000 feet. But unlike RS-422, RS-423 is an unbalanced interface where all signals are returned on one signal ground, or common, wire. RS-423 uses twisted pair wires, like RS-422, but data only travels along one of them. The other wire is tied to the ground wire. RS-423 is also defined as a unidirectional interface between one transmitting source and many data receivers. For example, a computer system may need to update a number of VDTs that are displaying information at multiple locations throughout an organization. Data always travels in one direction using RS-423. Though these new standards are available, many PC manufacturers have opted to continue to use the RS-232C standard. All Apple Macintosh computers contain an RS-422 port that RS-232C communication utilizes. RS-423 is most often used for sending data to terminals or receiving data from card readers. In 1991, the EIA merged with the TIA (Telecommunications Industry Association) and the RS-232C standard was renamed EIA/TIA-232-E, but RS-232C is still the common name. Back to top |
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