802.1d Spanning Tree Protocol
The access point, the wireless network transceiver, the wireless access point is a hub that supports 802.11a or 802.11b, or both, and allows multiple wireless clients to connect to the local network or the Internet.
ACK abbr. from acknowledgment
Notification of successful data reception, generated by the packet receiver.
Symmetric algorithm of block encryption (block size 128 bits, key 128/192/256 bits). This algorithm is well analyzed and is now widely used, as it was with its predecessor DES. As of 2009, AES is one of the most common symmetric encryption algorithms.
Automatic restoration of bandwidth parameters.
Bandwidth management (for the rational use of network resources).
BGP (Border Gateway Protocol)
Border Gateway Protocol, BGP protocol IP-routing protocol. Described in RFC 1163.
BOOTP (The Bootstrap Protocol)
The protocol of initial bootstrapping. Used to load diskless workstations. Its extension is DHCP .
A link portal, a portal for activating a user's connection to HotSpot.
Manipulation of additional code - the type of modulation used in the protocol 802.11b. Allows you to transfer data at a speed of 1 to 11 Mbit / s. Currently used very rarely due to the transition of modern devices to OFDM modulation .
Authentication Protocol [Handshake] by the method "challenge-greeting", mutual authentication protocol, CHAP protocol type of signal authentication when establishing communication between network devices (password exchange) using a pair of secret codes, including up to 16 characters. Used by communication devices at both ends of the line.
CSMA / CA
The mechanism of random access to the environment. At the channel layer of the IEEE 802.11 protocols, the fundamental mechanism for accessing the wireless environment is the DCF distributed control function, which implements the CSMA / CA method (multiple access to a carrier listening environment and avoid collisions). This method is similar in many respects to that used by Ethernet in wired networks. Each station, subject to the discipline of DCF and the basic access mechanism, independently determines the moment of its broadcasting and occupations of the environment, before the broadcast is listened to by the station and, in case it is free, the station starts transmitting. Consecutive attempts to transmit data of each station are separated by a delay interval, as well as by a random delayed time (Backoff time). In case of a collision, when two stations are simultaneously broadcasting, the collision avoidance mechanism is implemented. Both stations stop transmitting, each of them waiting for a random period of time, listening to the environment. Then the station, in which the interval was less, again goes on the air. Since the probability of coincidence of a random time interval for different stations is small, this method allows to reduce the probability of occurrence of repeated collisions many times.
Antenna gain or isotropic decibels. The antenna directivity pattern can be characterized by decibels, choosing as the reference diagram an isotropic source.
cm. also isotropic antenna
The logarithmic unit of measuring the signal power in relation to 1 milliwatt (1 mW = 0 dbm, 0.001 mW = -30 dbm).
A unique data transfer protocol in the point-to-point channels, developed on the basis of computer simulation data and significantly increasing the real throughput of the wireless connection. A special benefit from the use of DenFlow ™ is achieved when working in a noisy environment. In this case, the channel operates in a "preemptive" mode in relation to other systems operating on the basis of the CDMA / CA algorithm competing for the environment.
The Dynamic Host Configuration Protocol, the DHCP protocol, developed by the IETF to dynamically assign IP addresses to LAN hosts (workstations) while they are browsing the Internet to mitigate the 32-bit IP address shortage. Since assigning addresses to nodes is made from a centralized address pool, their uniqueness and, consequently, the absence of conflicting addresses are guaranteed. Implemented on different platforms (for example, in Windows 9x, Windows NT / 2000), is an extension of the BOOTP protocol.
Intermediate time interval. In the case of DIFS, the station listens to the broadcast before starting transmission. If it does not fix the signal of another station for a period of time exceeding the interframe gap, DIFS, then it starts transmitting. If the broadcast is busy, then it postpones its transmission until the end of the current transmission, selects a random time interval (the so-called rollback interval), and initializes the rollback timer. The rollback timer is reduced only when the broadcast is free, and freezes when it is busy. After releasing the ether, the timer decrease resumes only if the medium remains free for at least DIFS. If the timer is zeroed, the station can start transmitting.
see also SIFS
DNS (Domain Name System)
Domain Name System [names], Domain Name Service The Internet service, which is a distributed database for the hierarchical system of names of networks and computers connected to the Network, as well as a method for converting the string addresses of Internet servers to numeric IP addresses.
An Ethernet network transmitting a LAN environment with a bus architecture developed at the Xerox PARC research center (Robert Metcalf, May 22, 1973), and then adapted by DEC and Intel. It is regulated by the IEEE 802.3 and ISO 8802.3 standards. Regulates as a transmitting medium coaxial cable, access control method CSMA / CD, data transfer rate 10 Mbit / s, packet size from 72 to 1526 bytes, as well as data encoding method. In one Ethernet network, up to 1024 workstations can work. The development of this technology for 100 Mbit / s networks was called Fast Ethernet and 1 Gb / s - Gigabit Ethernet.
Combining short frames. Several consecutive short data packets are combined into one wireless frame of the maximum length for the most efficient transmission. On the receiving side, the long frame is fragmented.
A firewall, a firewall, a security system, a firewall, a firewall system (hardware or software), or a combination of systems that protects the boundary between two or more networks, in order to protect against unauthorized entry into the network or preventing an exit from her data packets. It is also used to distinguish access within the corporate network, if there are sites in it with information that requires secrecy. Usually it works on routers or dedicated servers. The network layer firewall (or packet filter) examines the network traffic at the packet level of the network protocol. They can, in particular, remove packets from circulation based on their TCP and UDP port numbers, to allow certain types of connections to trusted servers. The application-level firewall examines application-level traffic such as FTP, e-mail, or Telnet. Often also redirects outgoing traffic, giving it the appearance of the firewall itself, not the internal host system.
Group transfer of personnel.
File transfer protocol, client-server protocol from the set of IP protocols, providing search and transfer of files between two, possibly, heterogeneous machines over the TCP / IP network . It is defined in RFC 959. It is used on the Internet to work with ftp-servers.
Public wireless LANs have a small coverage radius. Organized in the places of the greatest congestion of the owners of portable computers, which allows you to quickly and effectively organize the connection to the Internet by private users.
Council on Internet architecture, the IAB is one of the governing bodies of the Internet, which is part of the ISOC. Approves new protocols, standards, network development projects, rules for issuing addresses, etc. It works on a voluntary basis, but only qualified individuals can become members of the IAB.
Internet Engineering Support Task Force, Internet Engineering Committee, IETF Committee IAB is an open public organization of the Internet that discusses the technical problems of the Network and its architecture and creates working groups to solve them. Develops standards and protocols Internet, produces RFC . This committee arose on the initiative of the IAB in 1986.
The protocol of internal gateways is used to exchange information about routing on the Internet.
The degree of protection of the shell is a system for classifying the degrees of protection of electrical equipment from penetration of solid objects and water in accordance with the international standard IEC 60529 (DIN 40050, GOST 14254-96). The marking of the degree of protection of the electrical equipment envelope is carried out with the help of an international protection sign (IP) and two digits, the first of which means protection from solid objects, the second - from penetration of water. The code looks like IPXX, where the X positions are numbers, or the symbol X, if the degree is not defined. Numbers can be followed by one or two letters giving auxiliary information. For example, the degree of protection IP67 - the first digit means that the dust can not get into the device + full protection from contact, the second figure means the possibility of a short-term immersion of the device in water to a depth of up to 1 meter.
IP address A network address in the Internet is a 4-byte (32-bit) number that specifies the unique number of the host computer on the Internet (IP Number). IP addresses are divided into five classes: A, B, C, D, and E; class D, in particular, specifies a stream of information of the type "point - many points". Each class of network addresses is allocated a certain number of host addresses ( RFC 1918). Since addresses for some classes are already exhausted, a new protocol with extended 128-bit addressing (IPng) will be introduced. When using the SLIP protocol, IP addresses are assigned dynamically at the beginning of the session.
The IPSec protocol, proposed by the IETF protocol suite for the transmission of information in virtual private networks. Provides authentication, integrity checking and encryption of IP packets
ISOC (Internet Society)
Internet community, ISOC committee, international public organization, one of the governing bodies of the Internet. It was established in 1992, it monitors the development of network standards and protocols. It includes more than 150 organizations, including IETF , IAB .
L2TP is a network layer-layer tunneling protocol that combines the L2F (Layer 2 Forwarding) protocol developed by Cisco and the Microsoft PPTP protocol. The IETF standard allows the ISP to organize a VPN with the specified access priorities, but does not include encryption and authentication mechanisms (to create a secure VPN it is used in conjunction with IPSec ). Supported by Cisco in the OS IOS.
LAN (Local Area Network)
A local [computing] network, LAN is one of several types of geographically limited communications networks. LAN connects computers, printers and other electronic equipment, allowing you to exchange various types of information at high speed and share resources common to the network (for example, printers, modems). The distance between computers in the LAN, as a rule, is not more than 300 m. Local networks can have gateways in switched public networks or other local networks. LAN is characterized by the topology of the network (bus topology, star topology), used by network protocols and the transmission medium (wired and wireless networks).
LLID (Logical Link Identificator) - 2 bytes, indicating the individual identifier of the EPON (Ethernet PON ) node . Required for the emulation of point-to-point and point-to-multipoint connections in a passive optical network. The first bit of the field indicates the frame transfer mode (unicast or multicast). The following 15 bits indicate the individual address of the PON node.
Abbreviation: Within line of sight. In the context of telecommunications, it is most common to describe a radio channel when the base and client points are within line of sight relative to each other.
The hardware address of a device attached to a networked environment. 48-bit number used by the medium access system, which allows to uniquely identify the device in the local network.
The MPPE protocol, an encryption protocol that can be used with PPTP to obtain a secure connection.
Network address translation technology that mitigates the problem of the lack of 32-bit IP addresses on the Internet. Allows you to use any IP addresses for the internal network (intranet or local network), with only one IP address visible from the outside, usually controlled by the firewall.
Abbreviation: Out of line of sight. In the context of telecommunications, it is most common when describing a radio channel, when the base and client points are out of scope vis-à-vis each other.
OLT (optical line terminal)
A subscriber terminal used in the PON network .
Orthogonal frequency division multiplexing- is a digital modulation scheme that uses a large number of closely spaced orthogonal subcarriers. Each subcarrier is modulated in a conventional modulation scheme (eg, quadrature amplitude modulation) at a low symbol rate, while maintaining the overall data rate, as with conventional single carrier modulation schemes in the same passband. In practice, OFDM signals are obtained by using a fast Fourier transform. The main advantage of OFDM in comparison with the single-carrier scheme is its ability to withstand complex conditions in the channel. For example, to combat attenuation in the high-frequency region in long copper conductors, narrow-band interference, and frequency-selective damping caused by the multipath nature of propagation, without the use of sophisticated equalizer filters. Channel EQ is simplified due to the fact that the OFDM signal can be considered as a set of slowly modulated narrowband signals, rather than as one rapidly modulated broadband signal. A low symbol rate makes it possible to use a guard interval between characters, which allows you to cope with temporal scattering and eliminate intersignal distortion.
Open Systems Interconnection, OSI Reference Model The seven-level model of data transfer protocols, approved by ISO in 1984, to ensure the interaction of open systems. In the OSI model, all network functions are divided into layers in such a way that all the higher layers use the services of the underlying ones through standardized interfaces. This structure allows you to modify any of the levels without affecting the others. OSI levels from the bottom up: physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer. Since the first through third levels control the physical delivery of data over the network, they are sometimes referred to as media layer layers.
OSPF (Open Shortest Path First)
Routing by the shortest path. Inner Routing Protocol ( IGP ). Unlike RIP , which routes routes by one conditional metric (the "weight" of the route), OSPF defines the network topology and evaluates each channel between routers based on a whole set of characteristics, truly optimal routes.
Authentication protocol by password authentication method, implemented by exchanging pairs of identifiers / passwords between two devices.
see also CHAP
Utility for testing connections in networks based on the TCP / IP protocol. The utility sends requests (ICMP Echo-Request) of the ICMP protocol to the specified network node and captures incoming responses (ICMP Echo-Reply). The time between sending the request and receiving a response (RTT, from the English. Round Trip Time ) allows to determine the round trip delay (RTT) along the route and the packet loss frequency, i.e. to determine the load indirectly on the data transmission channels and intermediate devices.
PoE (Power over Ethernet)
Power over Ethernet power for wireless adapters (access points) via a standard Category 5 cable.
At the root of this tree is the basic equipment of the provider (OLT - Optical Line Terminal), and it ends with the subscriber equipment (ONU - Optical Network Unit). This topology resembles the propagation of a signal on the radio, when a signal sent from the root device reaches each subscriber unit. Unlike active passive networks, this solution does not use intermediate active equipment (optical repeaters, media converters, routers), which makes it much easier to structure the optical network without reducing its functionality.
The technology of organizing PPTP channels in a network based on the 802.3 standard. PPPoE technology, starts a PPP session, over an Ethernet network.
At the same time, user authentication through PAP and CHAP protocols is supported , dynamic allocation of IP addresses to users, assignment of the gateway address, DNS server, etc.
The principle of PPPoE is to establish a point-to-point connection over a common Ethernet environment. The functioning of PPPoE is divided into two stages. In the first stage, the two devices communicate their addresses to each other and establish the initial connection. In the second stage, the PPP session starts. All clients are allocated private addresses, and are offered to be authorized by PPPoE. With correct authorization, the client is also given a private ip address, which will then work through NAT .
PPTP (Point-to-Point Tunneling Protocol)
The tunnel-to-peer protocol, PPTP, is one of four protocols used in virtual private networks ( L2TP , RSVP , VPN ). Provides the creation of cryptographically secure connections by encapsulating PPP packets encrypted with public keys, as well as data flow control and multiprotocol tunneling based on IP . Developed and promoted by corporations 3Com, ECI Telematics International, Microsoft.
Intermediary server, server-representative, proxy-server program for caching responses to Internet application requests sent to the Internet or to WWW requests of client application parts, working at the application level. Copies of received Web pages, files, etc. some time is stored on the server, and when receiving subsequent similar requests, the proxy server itself sends out the available copies, which reduces the response time and the amount of network traffic. In addition, the proxy server can filter requests, blocking access to sites of a certain type. Structurally, the proxy server consists of a number of specific intermediaries for specific applications: an intermediary for Web pages, for ftp, for e-mail, for RealAudio, and so on.
Console program for managing other computers, which supports the following protocols: Telnet, SSH, Rlogin, Raw.
QoS (Quality of Service)
Quality and class of data transmission services provided to the user by the network.
R2 ( R2-AP1-F5060-PTP-PA600-T, R2-AP2-F5060-PTMP-PA600-T, R2-AP1-F2425-PTP-PA400, R2-AP1-F2425-PTMP-PA400 ...)
A series of routers R2 was released in the period from 2007 to 2011. At the moment, replaced by a compatible, but more modern series of RS3.
Radius server (Remote Authentication Dial-In User Service)
Remote dial-in user authentication service over dial-up lines, RADIUS protocol is the Internet standard, which provides passwords connectivity of various systems (server databases) for authentication and user account management systems.
Request for comment. A series of IETF documents (standards, instructions, workgroup reports, etc.) that define the "device" of the Internet, in particular, TCP / IP standards. Any member of the ISOC can submit a paper for its publication in the RFC. When publishing, the document receives a number. The published version never changes, the changed version gets a new number, so there is a problem of finding the latest RFC of this standard. There are already several thousand such documents since the beginning of their release in 1969. RFCs are free and available to all. RFC 1543 contains an instruction to the authors of RFC. The document considered as a standard goes through all stages of the development of the standard, its testing and approval.
Routing Information Protocol. The simplest protocol for dynamic internal routing ( IGP ) for local networks. The first version of RIP, described in RFC 1058, does not support the network mask in routes and applies a standard mask for the desired address range (network class). RIP v2 is free from this shortcoming and is endowed with additional features, such as simple authentication. RIP v1 uses broadcast broadcasts, and v2 - multicast; both work through port 520 / udp, but are incompatible with each other.
Router (on the network). A hardware / software device physically combining two or more computer networks together, transmitting packets from one network to another by means of special software (it receives the packet into its buffer via one of the input channels and sends it through one of its output communication channels.) The need for waiting the end of packet reception leads to the delay of the packet in the router, proportional to the length of the packet). A router can connect networks that use different topologies and protocols. Reduces network traffic by passing only those packets that must go to the attached LAN (filtering function). The router is running on the network layer of the OSI model. Unlike bridges, routers are suitable for large networks with multiple circuits that have redundant paths for communication. Routers are protocol-oriented, they are static and dynamic. In static - the network administrator manually sets routing tables, and in dynamic - the router creates them himself. A dynamic router continuously exchanges packages with other routers to track the appearance of new nodes and workstations to properly adjust their routing tables. Dynamic routers detect overloads in networks and defective chains. One of the advantages over bridges is that the router does not automatically replicate all broadcast messages.
Routing, a process, or a method for determining and assigning a path for delivering packets (messages) through one or more networks along the most appropriate route.
see also Router
Resource reservation protocol, RSVP protocol, IETF standard . Works on the IP protocol. Serves to transmit traffic over the Internet, sensitive to time delays. Responsible for assigning priorities to different types of traffic, thereby increasing the quality of communication services. The resource reservation process is initialized by the receiver: it tells the sending nodes the desired packet flow parameters.
Short interframe time interval. The successful reception of each data frame is immediately verified by sending a positive acknowledgment. The receiving station transmits a frame with acknowledgment after receiving the frame after the expiration of the SIFS, which is shorter than the DIFS . When sending a confirmation, the receiving party does not resort to listening to the broadcast in advance. If the acknowledgment is not received, the transmitting side repeats the transmission of the frame.
A simple network management protocol is a protocol for managing communication networks based on the UDP architecture. Devices that normally support SNMP are routers, switches, servers, workstations, printers, modems, etc. The protocol is designed to provide management and control of devices and applications in the communication network by exchanging control information between agents located on network devices and managers located at control stations. SNMP defines a network as a collection of network control stations and network elements (master machines, gateways and routers, terminal servers) that together provide administrative communications between network management stations and network agents.
The protocol of secure access to the console based on the system of encoding with public keys.
The protocol of the covering [binding] tree [network]. Allows you to avoid sending parallel data packets over independent parallel routes.
A utility that allows you to transfer information about events occurring in the system to a specified remote port.
A utility that allows you to intercept and analyze network traffic passing through the router.
Transmission Control Protocol / Internet Protocol. A platform-independent set of protocols for communication in global computer networks, local networks or in interconnected network complexes (TCP, IP). It consists of three basic sets of protocols: IP (lower-level service), TCP (data transfer), and UDP. Provides end-users with two types of services: a service with establishing a logical connection (TCP) and without establishing a logical connection ( UDP ).
TDM (Time-Division Multiplexing)
Temporal of th Multiplexing (seal) - technology combining the information supplied by several low-speed lines, for its transmission over one high speed communications channel. Sealing is carried out by allocating for each line its time interval.
The protocol of the integrity of the temporary key in the WPA secure wireless access protocol . The Wi-Fi Alliance was proposed to replace the vulnerable WEP protocol in existing wireless equipment by updating the software. Although the same RC4 algorithm as WEP is used for encryption, the initialization vector is doubled (up to 48 bits), and the rules for changing the bit sequence of the initialization vector are implemented. In addition, for each packet transmitted, a new key is created, and the integrity is verified using a cryptographic checksum. All this allows successfully counteracting attacks such as replay (reusing keys) and forgery(changing the contents of the transmitted packets).
Transparent process, the application (execution) of which is invisible to the user or program.
Transparent query caching.
see also Proxy Server
A utility designed to determine the route of the data in TCP / IP networks . To determine the intermediate routers, traceroute sends to the target node a series of ICMP packets (3 packets by default), incrementing the TTL field by 1. Each field usually indicates the maximum number of routers that can be traversed by the packet. The first series of packets is sent with TTL equal to 1, and therefore the first router returns ICMP message "time exceeded in transit" , indicating the impossibility of data delivery. Traceroute captures the address of the router, as well as the time between sending the packet and receiving a response. Then tracerouterepeats sending a series of packets, but with a TTL of 2, which causes the first router to reduce TTL packets per unit and send them to the second router. The second router, having received packets with TTL = 1, also returns "time exceeded in transit" . The process is repeated until the packet reaches the target node. When a response is received from this node, the tracing process is considered complete. At the end host, the IP datagram with TTL = 1 is not discarded and does not call the ICMP message of the type expired , but should be given to the application. The achievement of the destination is determined as follows: the datagrams sent by the traceroute contain a UDP packet with a known unused port number on the addressed host. The port number will be 33434 +(the maximum number of transit sections to the node) is 1. At the destination, the UDP module, receiving similar datagrams, returns an ICMP "port not available" error message. Thus, to find out about the completion of the work, the traceroute program is sufficient to detect that an ICMP error message of this type has been received.
The protocol of user datagrams, protocol UDP - network transport layer protocol from the set of protocols TCP / IP . Individual packets are sent using IP without checking for the correct transmission and delivery guarantees, but as soon as possible. At the same time, some of the packets are lost, but, for example, when the voice is transmitted, the sound is not interrupted, which is important for ensuring its legibility.
URL (Uniform Resource Locator)
A unified index of the [information] resource, the URL, the address used by the Web browser to search for an Internet resource. Proposed by Tim Berners-Lee (Tim Berners-Lee). A URL is a standardized string of characters that indicates the location of a resource, document, or part of it on the Internet. It usually starts with the type of protocol (for example, FTP : if the document is on the FTP server or http: if it is on the Web site), followed by the identifier of the specific information, for example, the domain name to which the server belongs, the name of the organization or the file name path on this server. The suffix denotes the type of organization.
VDS (Virtual Distribution System)
A virtual network device used to organize a transparent bridge when encoding a channel.
A virtual local computer network is a group of hosts with a common set of requirements that interact as if they were connected to a broadcast domain, regardless of their physical location. A VLAN has the same properties as a physical local area network, but allows end stations to group together, even if they are not in the same physical network.
Virtual private network subnet of the corporate network, ensuring the safe entry into it of remote users. Subnets are used to securely transfer sensitive data through the Internet by encapsulating (tunneling) IP packets inside other packets, which are then routed.
WAN (Wide Area Network)
A global geographically distributed intranet covering a significant geographical area (region, country, a number of countries) and providing information transfer using dial-up and dedicated lines or special communication channels.
Algorithm for the security of Wi-Fi networks. It is used to ensure confidentiality and protection of the transmitted data of authorized wireless network users from listening. Currently, this technology is obsolete , since its hacking can be done in just a few minutes. Nevertheless, it continues to be widely used. For security in wireless networks, it is recommended to use WPA .
A new security standard for wireless LANs. WPA technology replaced wireless security technology WEP. The advantages of WPA are enhanced data security and tightened control over access to wireless networks. An important characteristic is the compatibility between the plurality of wireless devices, both at the hardware level and at the software level. WPA provides support for 802.1X standards, as well as for the EAP (Extensible Authentication Protocol) protocol. WPA2 supports encryption in accordance with the AES (Advanced Encryption Standard) standard, which has several advantages over the one used in WEP RC4, for example, a much more robust crypto algorithm.
A wireless network, a computer network that does not use wire as a transmission medium.
Algorithm of data compression. Before the broadcast, the data on the hardware level is compressed, and on the receiving side, they are decompressed and restored. The whole process is absolutely transparent in real time on the hardware level and does not affect the channel protocol. The effectiveness of this technique directly depends on the nature of the data transmitted.
see Access Point
A point antenna that emits energy equally in all directions. The radiation pattern of such an antenna is a sphere whose center coincides with the position of the point antenna.
Equipment designed to work with the base station.
A server that supports several network services.
A special mode, transition to which is carried out automatically when the signal level at reception decreases below the threshold -90dBm. In this mode, the device is capable of operating at 3Mbps; 2 Mbit / s; 1 Mbit / s; 0.5 Mbps; 0.25Mbit / s, which allows you to keep communication at the cost of reducing the speed.
Limiting the bandwidth of the channel. A finer tuning of the bandwidth of the radio channel, taking into account the needs of each client device, can be done by setting up polling .