See Twisted Pair Cable.
An ATM function which determines whether a virtual circuit (VC) connection request should be accepted or rejected. Two mechanisms used to control the set up of virtual circuits. Overbooking, which allows one connection to exceed permissible traffic limits, assumes that other active connections are not using the maximum available resources. Full booking limits network access once maximum resources are committed and only adds connections that specify acceptable traffic parameters.
(source: foldoc)
A small fast memory holding recently accessed data, designed to speed up
subsequent access to the same data. Most often applied to processor-memory
access but also used for a local copy of data accessible over a network
etc.
When data is read from, or written to, {main memory} a copy is also saved
in the cache, along with the associated main memory address. The cache monitors
addresses of subsequent reads to see if the required data is already in
the cache. If it is (a {cache hit}) then it is returned immediately and
the main memory read is aborted (or not started). If the data is not cached
(a {cache miss}) then it is fetched from main memory and also saved in the
cache.
The cache is built from faster memory chips than main memory so a cache
hit takes much less time to complete than a normal memory access. The cache
may be located on the same {integrated circuit} as the {CPU}, in order to
further reduce the access time. In this case it is often known as {primary
cache} since there may be a larger, slower {secondary cache} outside the
CPU chip.
The most important characteristic of a cache is its {hit rate} - the fraction
of all memory accesses which are satisfied from the cache. This in turn
depends on the cache design but mostly on its size relative to the main
memory. The size is limited by the cost of fast memory chips.
The hit rate also depends on the access pattern of the particular program
being run (the sequence of addresses being read and written). Caches rely
on two properties of the access patterns of most programs: temporal locality
- if something is accessed once, it is likely to be accessed again soon,
and spatial locality - if one memory location is accessed then nearby memory
locations are also likely to be accessed. In order to exploit spatial locality,
caches often operate on several words at a time, a "{cache line}" or "cache
block". Main memory reads and writes are whole {cache lines}.
When the processor wants to write to main memory, the data is first written
to the cache on the assumption that the processor will probably read it
again soon. Various different policies are used. In a {write-through} cache,
data is written to main memory at the same time as it is cached. In a {write-back}
cache it is only written to main memory when it is forced out of the cache.
If all accesses were writes then, with a write-through policy, every write
to the cache would necessitate a main memory write, thus slowing the system
down to main memory speed. However, statistically, most accesses are reads
and most of these will be satisfied from the cache. Write-through is simpler
than write-back because an entry that is to be replaced can just be overwritten
in the cache as it will already have been copied to main memory whereas
write-back requires the cache to initiate a main memory write of the flushed
entry followed (for a processor read) by a main memory read. However, write-back
is more efficient because an entry may be written many times in the cache
without a main memory access.
When the cache is full and it is desired to cache another line of data then
a cache entry is selected to be written back to main memory or "flushed".
The new line is then put in its place. Which entry is chosen to be flushed
is determined by a "{replacement algorithm}".
Some processors have separate instruction and data caches. Both can be active
at the same time, allowing an instruction fetch to overlap with a data read
or write. This separation also avoids the possibility of bad {cache conflict}
between say the instructions in a loop and some data in an array which is
accessed by that loop.
See also {direct mapped cache}, {fully associative cache}, {sector mapping},
{set associative cache}. (1997-06-25)
Le mécanisme de cache peut-être aussi mis en oeuvre sur un serveur pour stocker temporairement des données fréquemment utilisées et se trouvant sur un site distant(proxy server). C'est aussi un mécanisme utilisé par certains protocoles comme le DNS, ou ARP.
Term given to applications which support these functions.
A network which encompasses interconnectivity between floors of a building and/or buildings in a confined geographic area such as a campus or industrial park. Such networks would not require public rights-of-way and operate over fairly short distances. (see LAN, MAN, WAN).
Réseau qui fourni une connectivité entre les étages d'un immeuble, ou entre immeuble dans une zone géographique se limitant à un campus ou à un site industriel. De tels réseaux opérent sur un domaine privé et sur de courtes distances,et ne nécessittent pas d'autorisations ou de demandes de services liés à la traversée ou à l'utilisation d'un domaine public(route).
Two-wire serial bus used in automobile electronics.
Bus composé de deux câbles série utilisé dans l'électronique automobile.
A modulation technique developed by Bell Labs. It was the first ADSL transceiver to be commercially deployed. CAP technology is a variation of Quadrature Amplitude Modulation (QAM), which is the technology used by the vast majority of existing modems. With CAP, the three channels (POTS, downstream data and upstream data) are supported by splitting the frequency spectrum. Voice occupies the standard 0-4 Khz frequency, followed by the upstream channel and the high-speed downstream channel.
Technique de modulation developpée par "Bell Labs". Première technologie de transmetteur ADSL à être déployée commerciallement, CAP est une variation de la modulation d'amplitude en quadrature (MAQ).
An implementation of Apple Computer's AppleTalk protocols for Unix 4.2BSD and its derivatives, from Columbia University. There are two different LAP delivery mechanisms for: IPTalk and Ethertalk (possibly using UAB).
CAP supports the following AppleTalk protocols: AppleTalk Transaction
Protocol (ATP), Name Binding Protocol (NBP), Printer Access Protocol (PAP),
AppleTalk Session Protocol (ASP), AppleTalk Filing Protocol (AFP) client
side. In addition, the Datagram Delivery Protocol (DDP) and Zone Information
Protocol (ZIP) are partially available. The structure of the Internet Appletalk
Bridge software makes it impossible to provide full DDP service. Only the
Get Zone List ATP ZIP command is implemented for ZIP.
Reference site: http://www.cs.mu.oz.au/appletalk/.
CAP implante les protocoles AppleTalk: AppleTalk Transaction Protocol (ATP), Name Binding Protocol (NBP), Printer Access Protocol (PAP), AppleTalk Session Protocol (ASP), AppleTalk Filing Protocol (AFP) partie cliente, et partiellement Datagram Delivery Protocol (DDP) et Zone Information Protocol (ZIP). Il utilise deux mécanismes de communication réseau : IPTalk et EtherTalk phase 1 et 2. Le choix d'Ethertalk s'impose pour pouvoir exploiter les dispositifs connectés directement sur Ethernet. CAP a été porté sur plusieurs plateformes (à la différence de Netatalk).
CAP offre trois services principaux :
- l'impression à partir d'une machine UNIX sur une LaserWriter connectée sur un réseau AppleTalk: papif.
- serveur AppleShare sur UNIX : AUFS.
- l'impression à partir d'un Mac sur une imprimante connectée sur Ethernet ou directement sur une machine UNIX via le démon lpd : lwsrv.
[Common] Carrier (Or "phone company")
(network, communications, company)
A private company that offers telecommunications services to the public.(see
also IXC, Local
Exchange Carrier, BICI, Public
Network, Telco).
Terme désignant les opérateurs en télécommunication ou "transporteurs", tous privés aux Etats-Unis.
A type of UTPcommonly used with ATM interfaces for cell transmission at low speeds, 25-50 Mbps and at distances up to 100 meters.
Type d'UTP communement utilisée comme interface ATM pour la transmission de cellules à des basses vitesses, entre 25 et 50 Mbps sur des distances inférieures à 100 mètres.
A type of UTP commonly used with ATM interfaces for higher-speed cell transmission (more than 50 Mbps).
Type d'UTP communement utilisée comme interface ATM pour la transmission de cellules à des hautes vitesses, supérieures à 50 Mbps.
Service d'interconnexion de réseaux locaux défini par l'ETSI d'après le service de SMDS de bellcore. CBDS reprend toutes les options de SMDS en y adjoignant la définition du service à une interface nommé USI(User Service Interface) permettant de raccorder directement un réseau local.
Traffic service category used to carry digital information, such as video and digitized voice, that must be represented by a continuous stream of bits. CBR traffic requires guaranteed throughput rates and services levels. CBR is also called class A service.
Catégorie de trafic utilisée pour le transport d'information numériques comme la vidéo ou la voix, qui peut être représenté par un flux continu de bits. Le trafic CBR nécessite une bande passante et un niveau de service garanti. CBR est aussi appelé service de classe A.
A cell used periodically to check whether a connection is idle or has failed (i.e. at the cross-connect nodes), in order to guarantee a continuation in the flow of the information cells. Continuity checking is one of the OAM function types for fault management (see also AIS, RDI).
Cellule utilisée périodiquement pour tester si la connexion est inactive(idle) ou en faute (i.e. à un noeud d'interconnexion??), de façon à garantir la continuité du flux des cellules d'information. Le test de continuité est une des fonctions de gestion des fautes de l'OAM (voir aussi AIS, RDI).
Call Control (network)
Centre
commun d'études de télédiffusion et télécommunications
(norme) Organisme français de recherche et développement, implanté à Rennes, dépendant à la fois de TDF (Télévision et télédiffusion de France) et du Cnet (Centre national d'études des télécoms).
Comité
consultatif international des radiocommunications (norme) Organisme international de normalisation, chargé d'émettre des avis sur la technique et la réglementation des radio communications, notamment l'attribution des fréquences radio.
Part of the ITU. Now called ITU-T.
A list of CCITT standards.
ITU site: http://www.itu.ch/
Organisme international de normalisation en télécommunications, dépendant de l'Union Internationale des Télécommunications (UIT), siégeant à Genève. Le CCITT est devenu l'UIT-T.
Une liste des normes CCITT.
Le site de l'UIT: http://www.itu.ch/.
A field in the RM cell header that indicates the current complying cell rate a user can transmit over a virtual connection (VC).
Champ dans l'entête de cellule RM qui indique le débit courant auquel l'utilisateur peut transmettre des cellules à travers une connexion virtuelle(VC).
International standard protocol defined for open signaling in the digital public switched network. It is based on a 64 kbps channel and allows for information transfer for call control, database and billing management, and for maintenance functions.
Temporary name for an emerging variation of FDDI capable of operating at 100 Mbps over twisted wire pair instead of fiber optic cable.
A form of multiplexing where the transmitter encodes the signal using a pseudo-random sequence which the reciever also knows and can use to decode the received signal. Each different random sequence corresponds to a different communication channel.
Motorola uses CDMA for digital cellular phones.
(15 Feb 1995)
Forme de multiplexage oû l'émetteur encode le signal en utilisant une séquence pseudo-aléatoire, que le récepteur connaît et utilise pour décoder le signal reçu. Chaque séquence aléatoire correspond à un canal de communication différent.
The service will allow users to run applications such as e-mail, two-way messaging and dispatch and database inquiry over existing voice-oriented cellular networks at 19.2 Kbps. The technology sends data in packets during idle time on cellular voice channels.
Measures the allowable variance in delay between one cell and the next, expressed in fractions of a second. A QoS parameter that measures the difference between a single cell's transfer delay (CTD) and the expected transfer delay. It gives a measure of how closely cells are spaced in a Virtual Circuit (VC). When emulating a circuit, CDV measurements allow the network to determine if cells are arriving too fast or too slow. CDV can be introduced by ATM multiplexers (MUXs) or switches.
Mesure la variance en retard permise entre une cellule et la suivante, exprimées en fraction de seconde. CDV est un paramètre de QoS qui mesure la différence entre le temps de retard dans le transfert d'une cellule (CTD) et le retard de transfert attendu. Il donne une mesure de la façon sont espacées dans un circuit virtuel (VC). Dans le cas d'émulation de circuit, les mesures de CDV permettent au réseau de déterminer si les cellules arrivent trop vite ou pas assez. CDV peut être introduit par les multiplexeurs ATM (MUX) ou les commutateurs ATM.
A measure of the cell clumping phenomenon by which cells are delayed in the network and are clumped together and arrive at a system at a faster rate than negociated. Used in CBR traffic it specifies the acceptable tolerance of the CDV (jitter).
Utilisé dans le trafic de type CBR pour spécifier la tolérance acceptable en matière de variation du retard des cellules(CDV).
A terminator at one end of a layer connection within a SAP.
Identifier of a CE that can be used to identify the connection at a SAP.
Commission chargée des normes en matière d'électricité et d'électronique.
An ATM cell consists of 53 bytes or "octets." Of these, 5 constitute the header; the remaining 48 carry the data payload.
La cellule ATM a 53 octets divisé en 5 octets constituant l'entête (ou header) et 48 octets contenant les données(champ d'information ou payload).
Entête de 5 octets de la cellule ATM qui contient l'information conçernant la destination et le contrôle de flux. Plus spécifiquement elle contient les champs suivants: GFC, VPI, VCI,PT, CLP et HEC.
Identique à la couche ATM.
Comité
Européen de Normalisation (norme) Organisme de normalisation officiel dans la Communauté Economique européenne.
Comité
européen de normalisation électrotechnique (norme)
Joue un rôle similaire au CEN dans le domaine de l'électrotechnique. Le CEN et le Cenelec harmonisent leurs décisions au sein d'une structure commune, le CEN-Cenelec.
European Conference on post and telecommunicationsEuropean organisation of 26 European Post and Telecommunication governing services to support European advices by the CCITT.
European standard for digital physical interface at 2.048 Mbps. European acronym. The US equivalent acronym is E-1
European standard for digital physical interface at 34.368 Mbps. It can simultaneously support 16 E-1/CEPT-1 circuits. European acronym. The US equivalent acronym is E-3
European standard for digital physical interface at 139.264 Mbps. European acronym. The US equivalent acronym is E-4.
A QoS parameter that measures the fraction of transmitted cells that are erroneous (they have errors when they arrive at the destination).
Paramètre de QoS qui mesure la fraction des cellules transmises qui sont erronées(elles comportent des erreurs quand elles arrivent à destination).
The CERT was formed by ARPA in November 1988 in response to the needs exhibited during the Internet worm incident. The CERT charter is to work with the Internet community to facilitate its response to computer security events involving Internet hosts, to take proactive steps to raise the community's awareness of computer security issues, and to conduct research targeted at improving the security of existing systems.
CERT products and services include 24-hour technical assistance for responding to computer security incidents, product vulnerability assistance,technical documents, and tutorials.
In addition, the team maintains a number of mailing lists (including one for CERTAdvisories), and provides an anonymous FTP server, at "cert.org",where security-related documents and tools are archived. The CERT may be reached by email at "cert@cert.org" and by telephone at+1-412-268-7090 (24-hour hotline).
See also: Advanced Research Projects Agency, worm.
Le "CERT" a été fondé en novembre 1988 par "DARPA" en réponse aux incidents de sécurité sur Internet. Pour mentionner un incident de sécurité sur Internet, vous pouvez communiquer par courrier électronique à l'adresse cert@cert.org ou par téléphone au (412) 268-7090.
ATM Forum-defined class of service which provides a virtual circuit connection which emulates the characteristics of a real, constant-bit-rate, dedicated-bandwidth circuit. TDM-type, constant-bit-rate (CBR)circuits are emulated by the AAL1.
Classe de services definie par l'ATM Forum qui fournie une connexion de circuit virtuel émulant les caractéristiques d'un circuit dédié à bande passante et à débit binaire constant. Les circuits TDM à débit constant(CBR) sont émulés par AAL1.
One of IBM's earliest hardware video display standards for use in IBM PCs. CGA can display 80*25 or 40*25 text in 16 colors, 640*200 pixels graphics in 2 colors or 320*200 in 4 colors (PC video modes 0-6). It is now obsolete.
A bit in the RM cell to indicate congestion (it is set by the destination if the last cell received was marked).
Bit dans la cellule RM qui indique la congestion(est positionné par le destinataire si la dernière cellule reçue était marquée).
Champ de 8 bits de l'entête AAL2 de la
cellule ATM. CID identifie la connexion à laquelle appartient la mini-cellule.
Le numéro 0 est interdit, le numéro 1 est utilisé pour
la signalisation, les numéros 2 à 7 sont réservés.
Il est donc possible distinguer 248 connexions.
The payload (48bytes) of an ATM cell.
Champ d'Information (payload) de la cellule ATM.
A standard scheme for describing management data, whether the source is CMIP(Common Management Information Protocol), DMI or SNMP. Cim is being defined by the DMTF. See also HMMS, WBEM, HMON
Standard développé par le DMTF(Desktop Management Task Force) qui décrit les données d'administration, quelle que soit leur provenance: CMIP(Common Management Information Protocol), DMI, SNMP...
CMI est basé sur HMMS (HyperMedia Management Schema), qui lui est spécifié par WBEM (Web-Based Enterprise Management). Voir aussi HMON
Pour plus d'informations, consulter les sites suivants:
- Desktop Management task Force: http://www.dmtf.org,
- WBEM: http://wbem.freerange.com/,
- Evolution de la normalisation: http://www.apogee-com.fr/.
CODEC utilisé pour la digitalisation vidéo.
An adaptation of TCP/IP and its address resolution protocol (ARP) for ATM defined by the IETF (Internet Engineering Task Force) in RFCs (Requests for Comment) 1483 and 1577(i.e. IP support for the QoS classes,ARP over SVC and PVCnetworks). It places IP packets and ARP requests directly into PDUs (protocol data units) and converts them into ATM cells. The main issues in the transport of IP over ATM are the packet encapsulation and the address resolution. Classical IP does not recognize conventional MAC layer protocols like Ethernet or token ring.(see also LANE).
Adaptation de TCP/IP et du protocole ARP (Adress Resolution Protocol) au dessus de ATM. Cette adaptation a été faite par par l'IETF (Internet Engineering Task Force) dans les RFCs (Requests for Comment) 1483 et 1577. CIP place les paquets IP et ARP directement dans des PDU et les converti en cellules ATM. CIP ne reconnait pas les protocoles conventionnels de la couche MAC comme Ethernet ou token Ring.
A term used in Frame Relay, which defines the Average transmission rate over time the network is committed to provide the user with, under any network conditions (for a given virtual circuit).
Cell Insertion Ratio (ATM)
(atm)
Service de circuit virtuel offert aux utilisateurs terminaux où les caractéristiques d'une ligne numérique actuelle orientée bit (i.e. trafic vidéo) est émulée (i.e. 2 ou 45 Mbps).