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Loopback
Loopback (also written loop-back) is the routing of electronic signals or digital data streams back to their source without intentional processing or modification. It is primarily a means of testing the communications infrastructure. There are many example applications. It may be a communication channel with only one communication endpoint. Any message transmitted by such a channel is immediately and only received by that same channel. In telecommunications, loopback devices perform transmission tests of access lines from the serving switching center, which usually does not require the assistance of personnel at the served terminal. Loop around is a method of testing between stations that are not necessarily adjacent, wherein two lines are used, with the test being done at one station and the two lines are interconnected at the distant station. A patch cable may also function as loopback, when applied manually or automatically, remotely or locally, facilitating a loop-back ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Localhost
In computer networking, localhost is a hostname that refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses any local network interface hardware. Loopback The local loopback mechanism may be used to run a network service on a host without requiring a physical network interface, or without making the service accessible from the networks the computer may be connected to. For example, a locally installed website may be accessed from a Web browser by the URL it is mainly used for web development purposes ''http://localhost'' to display its home page. The name ''localhost'' normally resolves to the IPv4 loopback address , and to the IPv6 loopback address . Name resolution IPv4 network standards reserve the entire address block 127.0.0.0/8 (more than 16 million addresses) for loopback purposes. Updated by RFC 8190. That means any packet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RS-232
In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' ('' data terminal equipment'') such as a computer terminal, and a ''DCE'' ('' data circuit-terminating equipment'' or '' data communication equipment''), such as a modem. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is ''TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange'', issued in 1997. The RS-232 standard had been commonly used in computer serial ports and is still widely used in industrial communication devices. A serial port complying with the RS-232 standard was once a standard feature of many types of computers. Personal computers used them for co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bogon Filtering
Bogon filtering is the practice of filtering bogons, which are bogus (fake) IP addresses of a computer network. Bogons include IP packets on the public Internet that contain addresses that are not in any range allocated or delegated by the Internet Assigned Numbers Authority (IANA) or a delegated regional Internet registry (RIR) and allowed for public Internet use. The areas of unallocated address space are called the bogon space. Bogons also include some address ranges from allocated space, also known as Martian packets, mainly when they are being used as source address. Addresses reserved for private networks, such as those in , , and , loopback interfaces like and , and link-local addresses like and are part of it. Also addresses for Carrier-grade NAT, Teredo, and 6to4 and documentation prefixes fall into this category. Many ISPs and end-user firewalls filter and block bogons, because they have no legitimate use, and usually are the result of accidental misconfigurati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CIDR Notation
Classless Inter-Domain Routing (CIDR ) is a method for allocating IP addresses and for IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous classful network addressing architecture on the Internet. Its goal was to slow the growth of routing tables on routers across the Internet, and to help slow the rapid exhaustion of IPv4 addresses. IP addresses are described as consisting of two groups of bits in the address: the most significant bits are the network prefix, which identifies a whole network or subnet, and the least significant set forms the ''host identifier'', which specifies a particular interface of a host on that network. This division is used as the basis of traffic routing between IP networks and for address allocation policies. Whereas classful network design for IPv4 sized the network prefix as one or more 8-bit groups, resulting in the blocks of Class A, B, or C addresses, under CIDR address space is allocated to Internet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bit Error Rate Test
In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors. The bit error rate (BER) is the number of bit errors per unit time. The bit error ratio (also BER) is the number of bit errors divided by the total number of transferred bits during a studied time interval. Bit error ratio is a unitless performance measure, often expressed as a percentage. The bit error probability ''pe'' is the expected value of the bit error ratio. The bit error ratio can be considered as an approximate estimate of the bit error probability. This estimate is accurate for a long time interval and a high number of bit errors. Example As an example, assume this transmitted bit sequence: 1 1 0 0 0 1 0 1 1 and the following received bit sequence: 0 1 0 1 0 1 0 0 1, The number of bit errors (the underlined bits) is, in this case, 3. The BER is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communication Endpoint
A communication endpoint is a type of communication network node. It is an interface exposed by a communicating party or by a communication channel. An example of the latter type of a communication endpoint is a publish-subscribe topic or a group in group communication systems. See also *Node (networking) *Terminal (telecommunication) *Connection-oriented communication *Data terminal equipment *Dial peer *End system *Host (network) A network host is a computer or other device connected to a computer network. A host may work as a server offering information resources, services, and applications to users or other hosts on the network. Hosts are assigned at least one network ... References Computing terminology Telecommunications {{compu-network-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Network Interface
A virtual network interface (VIF) is an abstract virtualized representation of a computer network interface that may or may not correspond directly to a network interface controller. Operating system level It is common for the operating system kernel to maintain a table of virtual network interfaces in memory. This may allow the system to store and operate on such information independently of the physical interface involved (or even whether it is a direct physical interface or for instance a tunnel or a bridged interface). It may also allow processes on the system to interact concerning network connections in a more granular fashion than simply to assume a single amorphous "Internet" (of unknown capacity or performance). W. Richard Stevens, in volume 2 of his treatise entitled TCP/IP Illustrated, refers to the kernel's Virtual Interface Table in his discussion of multicast routing. For example, a multicast router may operate differently on interfaces that represent tunnels t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advanced Linux Sound Architecture
Advanced Linux Sound Architecture (ALSA) is a software framework and part of the Linux kernel that provides an application programming interface (API) for sound card device drivers. Some of the goals of the ALSA project at its inception were automatic configuration of sound-card hardware and graceful handling of multiple sound devices in a system. ALSA is released under GPL-2.0-or-later and LGPL-2.1-or-later. On Linux, sound servers, like sndio, PulseAudio, JACK (low-latency professional-grade audio editing and mixing) and PipeWire, and higher-level APIs (e.g OpenAL, SDL audio, etc.) work on top of ALSA and its sound card device drivers. ALSA succeeded the older Linux port of the Open Sound System (OSS). History The project to develop ALSA was led by Jaroslav Kysela, and was based on the Linux device driver for the Gravis Ultrasound sound card. It started in 1998 and was developed separately from the Linux kernel until it was introduced in the 2.5 development series ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Sound System
The Open Sound System (OSS) is an interface for making and capturing sound in Unix and Unix-like operating systems. It is based on standard Unix devices system calls (i.e. POSIX read, write, ioctl, etc.). The term also sometimes refers to the software in a Unix kernel that provides the OSS interface; it can be thought of as a device driver (or a collection of device drivers) for sound controller hardware. The goal of OSS is to allow the writing of sound-based applications that are agnostic of the underlying sound hardware. OSS was created by Hannu Savolainen and is distributed under four license options, three of which are free software licences, thus making OSS free software. API The API is designed to use the traditional Unix framework of open(), read(), write(), and ioctl(), via special devices. For instance, the default device for sound input and output is /dev/dsp. Examples using the shell: cat /dev/random > /dev/dsp # plays white noise through the speaker cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing Protocol
A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets are forwarded through the networks of the internet from router to router until they reach their destination computer. Routing algorithms determine the specific choice of route. Each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the topology of the network. The ability of routing protocols to dynamically adjust to changing conditions such as disabled connections and components and route data around obstructions is what gives the Internet its fault tolerance and high availability. The specific characteristics of routing protocols include the manner in which they avoi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Martian Packet
A Martian packet is an IP packet seen on the public Internet that contains a source or destination address that is reserved for special-use by Internet Assigned Numbers Authority (IANA) as defined in , Appendix B Glossary (Martian Address Filtering). On the public Internet, such a packet either has a spoofed source address, and it cannot actually originate as claimed, or the packet cannot be delivered. The requirement to do this is found in , Section 5.3.7 (Martian Address Filtering). Martian packets commonly arise from IP address spoofing in denial-of-service attacks, but can also arise from network equipment malfunction or misconfiguration of a host. In Linux terminology, a martian packet is an IP packet received by the kernel on a specific interface, while routing tables indicate that the source IP is expected on another interface. The name is derived from ''packet from Mars'', meaning that packet seems to be not of this Earth. IPv4 and IPv6 In both IPv4 and IPv6, a Marti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Datagram
A datagram is a basic transfer unit associated with a packet-switched network. Datagrams are typically structured in header and payload sections. Datagrams provide a connectionless communication service across a packet-switched network. The delivery, arrival time, and order of arrival of datagrams need not be guaranteed by the network. History In the early 1970s, the term ''datagram'' was created by combining the words ''data'' and ''telegram'' by the CCITT rapporteur on packet switching, Halvor Bothner-By. While the word was new, the concept had already a long history. In 1962, Paul Baran described, in a RAND Corporation report, a hypothetical military network having to resist a nuclear attack. Small standardized "message blocks", bearing source and destination addresses, were stored and forwarded in computer nodes of a highly redundant meshed computer network. "The network user who has called up a "virtual connection" to an end station and has transmitted messages ... migh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
