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Archived Manual Chapter: 3-DNS Administrator Guide v3.0: Glossary
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Glossary



3-DNS Maintenance menu
A command line utility that you can use to manually configure the 3-DNS Controller.

3-DNS web server
A standard web server that runs on the 3-DNS Controller and hosts the Configuration utility, and also provides access to useful downloads.

A record
The A record is the ADDRESS resource record that a 3-DNS Controller returns to a local DNS server in response to a name resolution request. The A record contains a variety of information, including one or more IP addresses that resolve to the requested domain name.

access control list (ACL)
A list of local DNS server IP addresses that are excluded from path probing, hops, or port discovery queries.

active unit
In a redundant system, the controller that currently load balances connections. If the active unit in the redundant system fails, the standby unit assumes control and begins to load balance connections.

alternate method
Specifies the load balancing mode to use if the preferred method fails.

authoritative DNS
A DNS server that is considered authoritative for one or more DNS zones. Any DNS server that contains a complete copy of the zone file for a given domain is said to be authoritative for that zone. A complete zone file will contain a start of authority resource record (SOA record). See also zones.

big3d agent
A monitoring agent that collects metrics information about server performance and network paths between a data center and a specific local DNS server. The 3-DNS Controller uses the information collected by the big3d agent for dynamic load balancing.

BIND (Berkeley Internet Name Domain)
The most common implementation of DNS, which provides a system for matching domain names to IP addresses.

completion rate
The percentage of packets that a server successfully processes during a given conversation.

Configuration utility
The browser-based application that you use to configure the 3-DNS Controller. The 3-DNS web server hosts the Configuration utility.

content delivery network (CDN)
A content delivery network (CDN) is an architecture of Web-based network components that helps dramatically reduce the wide-area network latency between a client and the content they wish to access. A CDN includes some or all of the following network components: wide-area traffic managers, Internet service providers, content server clusters, caches, and origin content providers.

data center
A physical location that houses one or more 3-DNS Controllers, BIG-IP Controllers, EDGE-FX Caches, or host machines.

discovery factory
A tool managed by the big3d agent that checks for alternate ports to ping when trying to collect path data for a local DNS.

dynamic load balancing modes
Dynamic load balancing modes base connection distribution on live data, such as current server performance and current connection load.

dynamic ratio
An option for the Quality of Service load balancing mode. The dynamic ratio feature uses QOS scores as ratios for virtual servers and distributes connections according to the ratio weight for each virtual server. See also QOS coefficient.

ECV (Extended Content Verification)
A service monitor that checks the availability of actual content, (such as a file or an image) on a server, rather than just checking the availability of a port or service, such as HTTP on port 80.

fail-over
The process in which a standby unit in a redundant system takes over due to a software or hardware failure detected on the active unit.

fail-over cable
The cable that directly connects the two controller units in a redundant system.

FDDI (Fiber Distributed Data Interface)
A multi-mode protocol for transmitting data at up to 100 Mbps on optical-fiber cables.

First-Time Boot utility
A utility that walks you through the initial system configuration process on the 3-DNS Controller. The First-Time Boot utility runs automatically when you turn on a controller for the first time.

fallback method
Specifies the last load balancing mode that the 3-DNS Controller tries to use if both the preferred and the alternate methods fail.

hardware-based fail-over
A redundant system in which the two units are connected directly by a cable.

hops
One point-to-point transmission in a network path between a host and a client server. A network path that included a stop at a network router would have two hops: the first from the client to the router, and the second from the router to the host server.

hops factory
A type of factory run by the big3d agent that collects hops data for network paths.

host
A network server which manages one or more virtual servers that the 3-DNS Controller uses for load balancing.

ICMP (Internet Control Message Protocol)
An Internet communications protocol used to determine information about routes to destination addresses, such as virtual servers managed by BIG-IP Controllers, EDGE-FX Caches, or hosts.

iQuery
A UDP-based protocol used to exchange information between big3d agents and 3-DNS Controllers. The iQuery protocol is officially registered for port 4353.

LDNS probe state
The status of an local DNS server with respect to metrics collection.

LDNS Round Robin
A standard DNS feature that allows a DNS server, or a 3-DNS Controller, to return multiple IP addresses in the A record. The local DNS, or even the browser, can cache the IP addresses and use them for future name resolutions.

local DNS (LDNS)
A local DNS server is typically found at a client's Internet service provider. The 3-DNS Controller calculates path information for the path between the local DNS and the virtual servers that the 3-DNS Controller is load balancing, and also uses the local DNS IP address for topology load balancing.

metrics
Performance data, including server performance and network path integrity, collected by big3d agents and used by the 3-DNS Controller for dynamic load balancing.

named
The name server daemon, which manages domain name service software.

NameSurfer
The third-party application that automatically manages DNS zone files on 3-DNS Controllers.

network-based redundant system
A redundant system in which two units communicate over a network connection, rather than a hard-wired connection.

path
The network route between two specific IP addresses. For dynamic load balancing, the 3-DNS Controller uses information about the path between a client LDNS and a specific virtual server that it is load balancing.

packet rate
The number of packets per second going in or coming out of a given server.

pool
A group of virtual servers to which the 3-DNS Controller distributes connections when load balancing a specific domain.

port
A number that is associated with a specific service supported by a host.

preferred method
Specifies the primary load balancing mode used to load balance a wide IP. See also alternate method and fallback method.

principal 3-DNS Controller
A 3-DNS Controller that initiates metrics collection by the big3d agents and distributes the metrics to other members of the sync group. Note that a sync group can have only one principal. See also receiver 3-DNS Controller.

prober factory
A tool managed by the big3d agent that queries virtual servers to determine whether they are up or down, and also to determine path metrics such as round trip time and hops.

production rule
A tool on the 3-DNS Controller that can change system behavior under specific operating conditions. For example, a production rule can switch load balancing modes or can reroute network traffic to a specific set of servers, based on triggers such as time of day, or current network traffic load.

QOS coefficient
The ratio weight for a specific factor used in a QOS equation, such as Hops, Round Trip Time, Packet Rate, Completion Rate, KBPS, or Topology scores. Each factor has a default coefficient of 1, but you can change the QOS coefficients to put more weight on a specific factor, and to put less weight on other factors.

QOS equation
A calculation based on various path statistics used for dynamic load balancing including Hops, Round Trip Time, Packet Rate, Completion Rate, KBPS, and Topology scores.

QOS score
The result of a QOS calculation. When using dynamic load balancing modes, the 3-DNS Controller uses the QOS score to determine which virtual server has the best performance and should receive new connections.

ratio
A parameter that assigns a weight to a virtual server for load balancing purposes.

Ratio mode
The Ratio load balancing mode distributes connections across an array of virtual servers in proportion to the ratio weights assigned to each individual virtual server.

receiver 3-DNS Controller
A 3-DNS Controller in a sync group that receives metrics data that are broadcast from big3d agents, but does not initiate metrics collection. See also principal 3-DNS Controller.

redundant system
A pair of controllers that are configured for fail-over. In a redundant system, there are two controller units that share an IP address, one running as the active unit and one running as the standby unit. If the active unit fails, the standby unit takes over and manages connection requests. See also shared IP alias.

remote administrative IP address
An IP address from which a controller allows shell connections, such as Telnet or SSH.

rsetup
The script that configures the remote login tools, rsh and rcp, on a controller.

slave DNS server
A DNS server that updates its records by querying a master DNS server.

shared IP alias
The IP address that represents a redundant system.

SNMP (Simple Network Management Protocol)
A standard Internet standard protocol developed to manage nodes on an IP network.

SNMP agent
The agent that controls SNMP communications on a server.

SNMP factory
A type of factory run by big3d agents that uses the SNMP protocol to collect metrics data for host servers.

SNMP MIB (Management Information Base)
A text file in standard SNMP format that defines the individual objects you can manage with common SNMP tools, such as HP OpenView.

sod (switch-over daemon)
A daemon that controls the fail-over process in a redundant system.

standby unit
A controller in a redundant system that is always prepared to become the active unit if the active unit fails.

static load balancing mode
A static load balancing mode bases connection distribution on a pre-defined list of criteria; it does not take current server performance or current connection load into account.

sync group
A group of 3-DNS Controllers that share configuration information. Each sync group has one principal 3-DNS Controller, and can also have one or more receiver 3-DNS Controllers.

time tolerance value
The number of seconds that one 3-DNS Controller's clock is allowed to differ in comparison to another 3-DNS Controller's clock, without the two clocks being considered out of sync.

topology record
A record that specifies a score for a local DNS location endpoint and virtual server location endpoint. Topology records are used by the topology load balancing mode to redirect DNS queries to the geographically-closest virtual server based on location information derived from the DNS query message.

topology score
The weight assigned to a topology record when the 3-DNS Controller is filtering the topology records to find the best match for a DNS query.

topology statement
A collection of topology records.

traceroute
The utility that the hops factory uses to calculate total number of network hops between an LDNS and a specific data center.

TTL (time-to-live)
The number of seconds for which a specific DNS record or metric is considered to be valid. When a TTL expires, the server usually must refresh the information before using it.

virtual server
A specific combination of a virtual address and virtual port, associated with a content site that is managed by a BIG-IP Controller, EDGE-FX Cache, or other type of host server.

watchdog timer card
A hardware device that monitors the 3-DNS Controller for hardware failure.

well known services (WKS)
A type of resource record that describes the services usually provided by a particular protocol on a particular port.

wide IP
A mapping of a fully-qualified domain name to a set of virtual servers that host the domain content, such as a web site or an e-commerce site. See also pool.

zone
A subset of DNS records for one or more domains.

zone file
A set of DNS records that contain domains with one or many domain names, designated mail servers, a list of other name servers that can answer resolution requests, and a set of zone attributes called SOA (Start Of Authority).

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