思科网络词典—A（续3）
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2008-2-1 12:17:36
Advanced Research Projects Agency. Research and development organization that is part of DoD. ARPA is responsible for numerous technological advances in communications and networking. ARPA evolved into DARPA, and then back into ARPA again (in 1994). See also DARPA.
ARPANET
Advanced Research Projects Agency Network. Landmark packet-switching network established in 1969. ARPANET was developed in the 1970s by BBN and funded by ARPA (and later DARPA). It eventually evolved into the Internet. The term ARPANET was officially retired in 1990. See also ARPA, BBN, DARPA, and Internet.
ARQ
automatic repeat request. Communication technique in which the receiving device detects errors and requests retransmissions.
ARU
alarm relay unit.
AS
See autonomous system.
ASAM
ATMsubscriber access multiplexer. A telephone central office multiplexer that supports SDL ports over a wide range of network interfaces. An ASAM sends and receives subscriber data (often Internet services) over existing copper telephone lines, concentrating all traffic onto a single high-speed trunk for transport to the Internet or the enterprise intranet. This device is similar to a DSLAM (different manufacturers use different terms for similar devices).
ASBR
autonomous system boundary router. ABR located between an OSPF autonomous system and a non-OSPF network. ASBRs run both OSPF and another routing protocol, such as RIP. ASBRs must reside in a nonstub OSPF area. See also ABR, non-stub area, and OSPF.
ASCII
American Standard Code for Information Interchange. 8-bit code for character representation (7 bits plus parity).
ASCU
agent-set control unit.
ASI
ATM Service Interface.
ASN
auxiliary signal network.
ASN.1
Abstract Syntax Notation One. OSI language for describing data types independent of particular computer structures and representation techniques. Described by ISO International Standard 8824. See also BER, basic encoding rules.
ASP
1. AppleTalk Session Protocol. Protocol that uses ATP to provide session establishment, maintenance, and teardown, as well as request sequencing. See also ATP.
2. Telecommunications: Auxiliary signal path. Link between TransPaths that allows them to exchange signaling information that is incompatible with the PSTN backbone network; used to provide feature transparency.
assigned numbers
RFC [STD2] documents the currently assigned values from several series of numbers used in network protocol implementations. This RFC is updated periodically, and current information can be obtained from the IANA. If you are developing a protocol or application that will require the use of a link, socket, port, protocol, and so forth, contact the IANA to receive a number assignment. See IANA and STD.
association control service element
See ACSE.
associative memory
Memory that is accessed based on its contents, not on its memory address. Sometimes called content addressable memory (CAM).
AST
automatic spanning tree. Function that supports the automatic resolution of spanning trees in SRB networks, providing a single path for spanning explorer frames to traverse from a given node in the network to another. AST is based on the IEEE 802.1 standard. See IEEE 802.1 and SRB.
ASTA
Advanced Software Technology and Algorithms. Component of the HPCC program intended to develop software and algorithms for implementation on high-performance computer and communications systems. See also HPCC.
async
Subset of tty.
Asynchronous Balanced Mode
See ABM.
asynchronous response mode
See ARM.
asynchronous time-division multiplexing
See ATDM.
Asynchronous Transfer Mode
See ATM.
asynchronous transmission
Term describing digital signals that are transmitted without precise clocking. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and end of each character. Compare with isochronous transmission, plesiochronous transmission, and synchronous transmission.
ATCP
AppleTalk Control Protocol. Protocol that establishes and configures AppleTalk over PPP, as defined in RFC 1378. See also PPP.
ATDM
asynchronous time-division multiplexing. Method of sending information that resembles normal TDM, except that time slots are allocated as needed rather than preassigned to specific transmitters. Compare with FDM, statistical multiplexing, and TDM.
ATG
See ATG (address translation gateway) in the “Cisco Systems Terms and Acronyms” section.
ATH
attention hangup.
at-least-once transaction
See ALO transaction.
ATM
Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
ATM adaptation layer
See AAL.
ATM adaptation layer 1
See AAL1.
ATM adaptation layer 2
See AAL2.
ATM adaptation layer 3/4
See AAL3/4.
ATM adaptation layer 5
See AAL5.
ATM ARP server
Device that provides address-resolution services to LISs when running classical IP over ATM. See also LIS.
ATM data service unit
See ADSU.
ATM endpoint
Point in an ATM network where an ATM connection is initiated or terminated. ATM endpoints include ATM-attached workstations, ATM-attached servers, ATM-to-LAN switches, and ATM routers.
ATM Forum
International organization jointly founded in 1991 by Cisco Systems, NET/ADAPTIVE, Northern Telecom, and Sprint that develops and promotes standards-based implementation agreements for ATM technology. The ATM Forum expands on official standards developed by ANSI and ITU-T, and develops implementation agreements in advance of official standards.
ATM interface processor
See AIS.
ATM layer
Service-independent sublayer of the data link layer in an ATMnetwork. The ATMlayer receives the 48-byte payload segments from the AAL and attaches a 5-byte header to each, producing standard 53-byteATMcells. These cells are passed to the physical layer for transmission across the physical medium. See also AAL.
ATMM
ATM management. Process that runs on an ATM switch that controls VCI translation and rate enforcement. See also ATM and VCD.
ATM management
See ATMM.
ATM network
See ATM network in the “Cisco Systems Terms and Acronyms” section.
ATM NIC
See ATM network interface card in the “Cisco Systems Terms and Acronyms” section.
ATM service interface.
See ASCU.
ATM UNI
See UNI.
ATM user-user connection
Connection created by the ATM layer to provide communication between two or more ATM service users, such as ATMM processes. Such communication can be unidirectional, using one VCC, or bidirectional, using two VCCs. See also ATM layer, ATMM, and VCC.
ATP
AppleTalk Transaction Protocol. Transport-level protocol that provides a loss-free transaction service between sockets. The service allows exchanges between two socket clients in which one client requests the other to perform a particular task and to report the results. ATP binds the request and response together to ensure the reliable exchange of request-response pairs.
Attached Resource Computer Network
See ARCnet.
attachment unit interface
See AUI.
attenuation
Loss of communication signal energy.
attribute
Form of information items provided by the X.500 Directory Service. The directory information base consists of entries, each containing one or more attributes. Each attribute consists of a type identifier together with one or more values.
AU
access unit. Device that provides ISDN access to PSNs. See also PSN.
AUI
attachment unit interface. IEEE 802.3 interface between an MAU and a NIC. The term AUI can also refer to the rear panel port to which an AUI cable might attach. Also called transceiver cable. See also IEEE 802.3, MAU, and NIC.
AUP
acceptable use policy. Many transit networks have policies that restrict the use to which the network can be put. Enforcement of AUPs varies with the network.
AURP
AppleTalk Update-Based Routing Protocol. Method of encapsulating AppleTalk traffic in the header of a foreign protocol, allowing the connection of two or more discontiguous AppleTalk internetworks through a foreign network (such as TCP/IP) to form an AppleTalk WAN. This connection is called an AURP tunnel. In addition to its encapsulation function, AURP maintains routing tables for the entire AppleTalk WAN by exchanging routing information between exterior routers. See also AURP tunnel and exterior router.
AURP tunnel
Connection created in an AURP WAN that functions as a single, virtual data link between AppleTalk internetworks physically separated by a foreign network (a TCP/IP network, for example). See also AURP.
AUSM
ATM user service module.
authentication
In security, the verification of the identity of a person or process.
authority zone
Associated with DNS, an authority zone is a section of the domain-name tree for which one name server is the authority. See also DNS.
Automated Packet Recognition/Translation
See APaRT in the “Cisco Systems Terms and Acronyms” section.
automatic call distribution
See ACD.
automatic call reconnect
Feature permitting automatic call rerouting away from a failed trunk line.
automatic protection switching
See APS.
automatic repeat request
See ARQ.
Automatic Routing Management
Formerly AutoRoute. Connection-oriented mechanism used in CiscoWAN switches to provide connectivity across the network. Switches perform a connection admission control (CAC) function on all types of connections in the network. Distributed network intelligence enables the CAC function to automatically route and reroute connections over optimal paths, while guaranteeing the required QoS.
automatic spanning tree
See AST.
autonomous confederation
Group of autonomous systems that rely on their own network reachability and routing information more than they rely on that received from other autonomous systems or confederations.
autonomous switching
See autonomous switching in the “Cisco Systems Terms and Acronyms” section.
autonomous system
Collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the IANA. Sometimes abbreviated as AS. See also area and IANA.
autonomous system boundary router
See ASAM.
autoreconfiguration
Process performed by nodes within the failure domain of a Token Ring network. Nodes automatically perform diagnostics in an attempt to reconfigure the network around the failed areas. See also failure domain.
available bit rate
See ABR.
average rate
Average rate, in kilobits per second (kbps), at which a given virtual circuit will transmit
AVM
ATM voice multiplexer.
AW
administrative weight.Value set by the network administrator to indicate the desirability of a network link. One of four link metrics exchanged by PTSPs to determine the available resources of an ATM network.
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ARPANET
Advanced Research Projects Agency Network. Landmark packet-switching network established in 1969. ARPANET was developed in the 1970s by BBN and funded by ARPA (and later DARPA). It eventually evolved into the Internet. The term ARPANET was officially retired in 1990. See also ARPA, BBN, DARPA, and Internet.
ARQ
automatic repeat request. Communication technique in which the receiving device detects errors and requests retransmissions.
ARU
alarm relay unit.
AS
See autonomous system.
ASAM
ATMsubscriber access multiplexer. A telephone central office multiplexer that supports SDL ports over a wide range of network interfaces. An ASAM sends and receives subscriber data (often Internet services) over existing copper telephone lines, concentrating all traffic onto a single high-speed trunk for transport to the Internet or the enterprise intranet. This device is similar to a DSLAM (different manufacturers use different terms for similar devices).
ASBR
autonomous system boundary router. ABR located between an OSPF autonomous system and a non-OSPF network. ASBRs run both OSPF and another routing protocol, such as RIP. ASBRs must reside in a nonstub OSPF area. See also ABR, non-stub area, and OSPF.
ASCII
American Standard Code for Information Interchange. 8-bit code for character representation (7 bits plus parity).
ASCU
agent-set control unit.
ASI
ATM Service Interface.
ASN
auxiliary signal network.
ASN.1
Abstract Syntax Notation One. OSI language for describing data types independent of particular computer structures and representation techniques. Described by ISO International Standard 8824. See also BER, basic encoding rules.
ASP
1. AppleTalk Session Protocol. Protocol that uses ATP to provide session establishment, maintenance, and teardown, as well as request sequencing. See also ATP.
2. Telecommunications: Auxiliary signal path. Link between TransPaths that allows them to exchange signaling information that is incompatible with the PSTN backbone network; used to provide feature transparency.
assigned numbers
RFC [STD2] documents the currently assigned values from several series of numbers used in network protocol implementations. This RFC is updated periodically, and current information can be obtained from the IANA. If you are developing a protocol or application that will require the use of a link, socket, port, protocol, and so forth, contact the IANA to receive a number assignment. See IANA and STD.
association control service element
See ACSE.
associative memory
Memory that is accessed based on its contents, not on its memory address. Sometimes called content addressable memory (CAM).
AST
automatic spanning tree. Function that supports the automatic resolution of spanning trees in SRB networks, providing a single path for spanning explorer frames to traverse from a given node in the network to another. AST is based on the IEEE 802.1 standard. See IEEE 802.1 and SRB.
ASTA
Advanced Software Technology and Algorithms. Component of the HPCC program intended to develop software and algorithms for implementation on high-performance computer and communications systems. See also HPCC.
async
Subset of tty.
Asynchronous Balanced Mode
See ABM.
asynchronous response mode
See ARM.
asynchronous time-division multiplexing
See ATDM.
Asynchronous Transfer Mode
See ATM.
asynchronous transmission
Term describing digital signals that are transmitted without precise clocking. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and end of each character. Compare with isochronous transmission, plesiochronous transmission, and synchronous transmission.
ATCP
AppleTalk Control Protocol. Protocol that establishes and configures AppleTalk over PPP, as defined in RFC 1378. See also PPP.
ATDM
asynchronous time-division multiplexing. Method of sending information that resembles normal TDM, except that time slots are allocated as needed rather than preassigned to specific transmitters. Compare with FDM, statistical multiplexing, and TDM.
ATG
See ATG (address translation gateway) in the “Cisco Systems Terms and Acronyms” section.
ATH
attention hangup.
at-least-once transaction
See ALO transaction.
ATM
Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
ATM adaptation layer
See AAL.
ATM adaptation layer 1
See AAL1.
ATM adaptation layer 2
See AAL2.
ATM adaptation layer 3/4
See AAL3/4.
ATM adaptation layer 5
See AAL5.
ATM ARP server
Device that provides address-resolution services to LISs when running classical IP over ATM. See also LIS.
ATM data service unit
See ADSU.
ATM endpoint
Point in an ATM network where an ATM connection is initiated or terminated. ATM endpoints include ATM-attached workstations, ATM-attached servers, ATM-to-LAN switches, and ATM routers.
ATM Forum
International organization jointly founded in 1991 by Cisco Systems, NET/ADAPTIVE, Northern Telecom, and Sprint that develops and promotes standards-based implementation agreements for ATM technology. The ATM Forum expands on official standards developed by ANSI and ITU-T, and develops implementation agreements in advance of official standards.
ATM interface processor
See AIS.
ATM layer
Service-independent sublayer of the data link layer in an ATMnetwork. The ATMlayer receives the 48-byte payload segments from the AAL and attaches a 5-byte header to each, producing standard 53-byteATMcells. These cells are passed to the physical layer for transmission across the physical medium. See also AAL.
ATMM
ATM management. Process that runs on an ATM switch that controls VCI translation and rate enforcement. See also ATM and VCD.
ATM management
See ATMM.
ATM network
See ATM network in the “Cisco Systems Terms and Acronyms” section.
ATM NIC
See ATM network interface card in the “Cisco Systems Terms and Acronyms” section.
ATM service interface.
See ASCU.
ATM UNI
See UNI.
ATM user-user connection
Connection created by the ATM layer to provide communication between two or more ATM service users, such as ATMM processes. Such communication can be unidirectional, using one VCC, or bidirectional, using two VCCs. See also ATM layer, ATMM, and VCC.
ATP
AppleTalk Transaction Protocol. Transport-level protocol that provides a loss-free transaction service between sockets. The service allows exchanges between two socket clients in which one client requests the other to perform a particular task and to report the results. ATP binds the request and response together to ensure the reliable exchange of request-response pairs.
Attached Resource Computer Network
See ARCnet.
attachment unit interface
See AUI.
attenuation
Loss of communication signal energy.
attribute
Form of information items provided by the X.500 Directory Service. The directory information base consists of entries, each containing one or more attributes. Each attribute consists of a type identifier together with one or more values.
AU
access unit. Device that provides ISDN access to PSNs. See also PSN.
AUI
attachment unit interface. IEEE 802.3 interface between an MAU and a NIC. The term AUI can also refer to the rear panel port to which an AUI cable might attach. Also called transceiver cable. See also IEEE 802.3, MAU, and NIC.
AUP
acceptable use policy. Many transit networks have policies that restrict the use to which the network can be put. Enforcement of AUPs varies with the network.
AURP
AppleTalk Update-Based Routing Protocol. Method of encapsulating AppleTalk traffic in the header of a foreign protocol, allowing the connection of two or more discontiguous AppleTalk internetworks through a foreign network (such as TCP/IP) to form an AppleTalk WAN. This connection is called an AURP tunnel. In addition to its encapsulation function, AURP maintains routing tables for the entire AppleTalk WAN by exchanging routing information between exterior routers. See also AURP tunnel and exterior router.
AURP tunnel
Connection created in an AURP WAN that functions as a single, virtual data link between AppleTalk internetworks physically separated by a foreign network (a TCP/IP network, for example). See also AURP.
AUSM
ATM user service module.
authentication
In security, the verification of the identity of a person or process.
authority zone
Associated with DNS, an authority zone is a section of the domain-name tree for which one name server is the authority. See also DNS.
Automated Packet Recognition/Translation
See APaRT in the “Cisco Systems Terms and Acronyms” section.
automatic call distribution
See ACD.
automatic call reconnect
Feature permitting automatic call rerouting away from a failed trunk line.
automatic protection switching
See APS.
automatic repeat request
See ARQ.
Automatic Routing Management
Formerly AutoRoute. Connection-oriented mechanism used in CiscoWAN switches to provide connectivity across the network. Switches perform a connection admission control (CAC) function on all types of connections in the network. Distributed network intelligence enables the CAC function to automatically route and reroute connections over optimal paths, while guaranteeing the required QoS.
automatic spanning tree
See AST.
autonomous confederation
Group of autonomous systems that rely on their own network reachability and routing information more than they rely on that received from other autonomous systems or confederations.
autonomous switching
See autonomous switching in the “Cisco Systems Terms and Acronyms” section.
autonomous system
Collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the IANA. Sometimes abbreviated as AS. See also area and IANA.
autonomous system boundary router
See ASAM.
autoreconfiguration
Process performed by nodes within the failure domain of a Token Ring network. Nodes automatically perform diagnostics in an attempt to reconfigure the network around the failed areas. See also failure domain.
available bit rate
See ABR.
average rate
Average rate, in kilobits per second (kbps), at which a given virtual circuit will transmit
AVM
ATM voice multiplexer.
AW
administrative weight.Value set by the network administrator to indicate the desirability of a network link. One of four link metrics exchanged by PTSPs to determine the available resources of an ATM network.
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