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ADPCM
ADPCM-32 is a 32-bit voice compression method that converts analog signals to digital data, thus allowing voice transmission over digital lines.
AAL
AAL converges packets from upper layers into ATM cells as defined by ITU-T, ETSI and the ATM Forum. AAL has several service types and classes of operation to accommodate different types of classes.
AAL-2
A connection oriented, VBR (Variable Bit Rate) protocol for real-time applications. It is similar to T1 or T3 and provides a variety of data rates. See AAL.
AAL-5
A UBR (Unspecified Bit Rate) protocol that provides spare bandwidth to non-critical services such as file transfers. See AAL.
ADSL
This is an asymmetrical technology which means that the downstream data rate of the line is much higher than the upstream data rate. ADSL operates in a frequency range that is above the frequency range of voice services, so both can operate over the same cable.
A-Law
A-Law and Mu-Law are Pulse Code Modulation (PCM) techniques that dictate forms of compression for audio signals. They are widely-used standard methods of coding voice as they improve signal-to-noise ratio without increasing the amount of data. Mu-Law is a standard in North America; A-Law in Europe.
Analog
An electrical circuit that is represented by means of continuous, variable physical quantities (such as voltages and frequencies), as opposed to discrete representations (like the 0/1, off/on representation of digital circuits).
ANSI
ANSI is the primary organization for fostering the development of technology standards (defining coding standards and signaling schemes) in the United States.
ANSI Mode
This is a VDSL mode that operates in a specific frequency band allocation with associated upstream and downstream speeds.
ARP
Address Resolution Protocol is a protocol for mapping an Internet Protocol address (IP address) to a physical computer address that is recognized in the local network.
AT&T 5ESS
A digital central office switching system made by AT&T.
ATM
ATM is a LAN and WAN networking technology that provides high-speed data transfer. ATM uses fixed-size packets of information called cells. With ATM, a high QoS (Quality of Service) can be guaranteed.
Authenticity
Proof that the information came from the person or location that reportedly sent it. One example of authenticating software is through digital signatures.
ALG
An Application Layer Gateway (ALG) is a device that manages a specific protocol (such as SIP, H.323 or FTP) at the application layer.
Alarm Profile
An alarm profile is a set of thresholds that trigger an alarm when one is reached.
AH
Authentication Header (RFC 2402) is a protocol that IPSec uses to verify integrity of a data packet (including the header) and the identity of it’s sender.
Authentication Algorithm
This is an established, step-by-step procedure for verifying the identity of a packet’s sender.
Aggressive Mode
Aggressive mode is an IPSec phase 1 negotiation mode (see Negotiation Mode). Aggressive mode is quicker than Main Mode because it eliminates several steps. However the faster speed limits its negotiating power and it also does not provide identity protection. See also Main Mode.
Ad-Hoc
An Ad-Hoc wireless LAN is a group of computers that uses wireless LAN cards, to connect as an independent wireless LAN. An Ad-Hoc wireless LAN is sometimes referred to as a Basic Service Set (BSS).
Access Point
An Access Point (AP) is a network device that acts as a bridge between a wired and a wireless network.
Access Line
This is the physical telecommunications circuit (line) in the local network that connects the CO (Central Office) with the customer’s residence. See also Local Loop.
ATU-C
This is the hardware at the CO (Central Office) that terminates an ADSL connection.
ATU-R
This is the hardware at a customer’s location that provides termination for an ADSL connection.
Always-on
Always-on refers to broadband services that are connected all the time, eliminating the need to dial-up to connect.
ASIC
This is a chip engineered for a particular use or function.
ATM25
ATM25 is a 25.6 Mbps cell-based user interface defined by the ATM Forum.
Auxiliary Port
This port can be used as a traditional dial-up connection in reserve if ever the broadband connection to the WAN port fails. See also Dial Backup.
Antenna
An antenna acts as a radiator that propagates a radio frequency signal from a wireless device through the air. An antenna also works in reverse by capturing signals from the air.
Acknowledged Alarms
This means that an administrator has decided to handle the cause of this alarm. Other administrators see that person’s name in their alarm screen, thus avoiding duplicate effort to solve the same problem.
Active Alarms
“Active” is the initial state of an alarm, which means the alarm is new and an administrator is yet to assume responsibility for handling it.
A-end (IPSec)
This is the end of a VPN tunnel opposite the Z-end (see also Z-end).
Auto-crossover
An auto-crossover Ethernet port enables you to use either a crossover Ethernet cable or a straight-through Ethernet cable to connect your device to either a computer or external hub. In other words these ports automatically adjust according to the type of cable so that either straight-through Ethernet cable or crossover Ethernet cable may be used.
ADSL2
ADSL2 (ITU G.992.3 and G.992.4) offers improved performance and interoperability over ADSL. Key improvements are enhanced data rates, loop reach, diagnostics, rate adaptation and power management.
Auto-MDI/MDIX
Auto-MDI (Medium Dependent Interface)/MDIX (MDI crossover) is an Ethernet port feature that automatically adjusts to crossover or straight-through Ethernet cable so you can use either to connect your device to a computer or a switch/external hub. See also auto-crossover.
Account Generator Printer
When connected to an Internet service gateway device, an account generator printer allows you to create and print out subscriber accounts automatically. The account generator printer is also known as the statement printer.
AES
Advanced Encryption Standard is method of data encryption that uses a secret key. AES may use a 128-bit, 192-bit or 256-bit key. AES is faster than 3DES.
ABR
Available Bit Rate is an ATM traffic class that provides a minimum amount of bandwidth and allows the use of more if it is available. ABR is used for bursty data traffic. End devices using ABR get feedback from the network and can use flow-control to dynamically adjust transmission rates. See also RM.
Advertising Interval
In VRRP, this is the time interval between sending the Hello messages.
AS
An autonomous system (AS) is a collection of networks using a common routing protocol to exchange routing information.
Area
In OSPF, an area is a logical grouping of adjacent networks. All areas are connected to a backbone (also known as area 0).
ABR
In OSPF, an Area Border Router connects two or more areas.
AS Boundary Router
In OSPF, an AS boundary router exchanges routing information with routers in other ASes.
Any IP
The Any IP feature allows a computer to access the Internet or a device without changing the network settings (such as IP address and subnet mask) of the computer, even when the IP addresses of the computer and the device are not in the same subnet.
ADSL2+
ADSL2+ (ITU G.992.5) offers improved performance over ADSL2.
Authentication Code
For hardware products this is the LAN MAC address of the device. For software products, it is a generated number that is displayed after you install the software. You need this number to register your product.
Activation Key
An activation key is a number generated at myZyXEL.com from the license key that represents a specific service.
Alarms
Alarms are time-critical information that a device automatically sends out at the time of occurrence.
Available Bandwidth
In load balancing, available bandwidth is the actual bandwidth provided by the ISP.
Active/Passive (Fail Over) Mode
When a router with multiple WAN ports is in Active/Passive (fail over) operation mode, the router uses the second highest priority WAN port as a back up. The router will normally use the primary WAN and only uses the second highest priority WAN port when the primary WAN port's connection fails.
Active/Active Mode
When a router with multiple WAN ports is in Active/Active mode, the router uses both of the WAN ports at the same time and allows you to enable load balancing. See also Load Balancing.
Address Record
An address record contains the mapping of a fully qualified domain name (FQDN) to an IP address.
Access Control
Access control refers to procedures and controls that limit or detect access. Access control is used typically to control user access to network resources such as servers, directories, and files.
Anomaly Analysis
This detection system identifies “normal” traffic on a network, and then classifies anything “non-normal” to be an “intrusion”. Anomaly detection can recognize previously unseen attacks, since it is not reliant on knowing what an attack looks like. See also Heuristic Analysis, Protocol Decode, Protocol Anomaly Detection and Traffic Flow Anomaly.
API
An API is the specific method an application program uses to make requests of an operating system or another application program.
Anti-virus
Anti-virus features or software scan files and help stop viruses from infecting computer(s) on a network. See also host-based anti-virus and network-based anti-virus.
Annex L
Annex L is an addendum to the ADSL2+ standard (ITU G.992.5). Also known as Reach-Extended ADSL2 it allows increased ADSL2 connection distances.
Adware
Adware is either software that collects information about the user's web browsing patterns in order to display related advertisements or application software that has advertisements already embedded. See also Spyware.
Anti-Spam
Anti-spam is a feature that marks or discards unsolicited commercial or junk e-mail (spam).