An attribute is a variable that the cache statement uses to direct requests. Attributes can be either required or optional.
BIG-IP active unit
In a redundant system, the controller which currently load balances connections. If the active unit in the redundant system fails, the standby unit assumes control and begins to load balance connections.
BIG-IP web server
The web server that runs on a BIG-IP Controller and hosts the Configuration utility.
A utility that provides command line access to the BIG-IP Controller.
A statistical monitoring utility that ships on the BIG-IP Controller. This utility provides a snap-shot of statistical information.
A statistical monitoring utility that ships on the BIG-IP Controller. This utility provides real-time information.
A monitoring utility that collects metrics information about paths between a BIG-IP Controller and a specific local DNS server. The big3d utility runs on BIG-IP Controllers and it forwards metrics information to a 3-DNS Controller.
BIND (Berkeley Internet Name Domain)
The most common implementation of DNS, which provides a system for matching domain names to IP addresses.
cacheable content determination
Determines the type of content you cache on the basis of any combination of elements in the HTTP header.
cacheable content expression
An expression that determines, based on evaluating variables in the HTTP header of the request, whether or not a BIG-IP Cache Controller directs a given request to a cache server or to an origin server. Any content that does not meet the criteria in the cacheable content expression is deemed non-cacheable.
Specifies a pool of cache servers to which requests are directed in a manner that optimizes cache performance. The BIG-IP Cache Controller directs all requests bound for your origin server to this pool, unless you have configured the hot content load balancing feature and the request is for hot (frequently requested) content. See also hot and origin server.
A series of filtering criteria used to restrict access to an IP address. The order of the criteria in the chain determines how the filter is applied, from the general criteria first, to the more detailed criteria at the end of the chain.
Ensures that a given subset of content remains associated with a given cache server to the maximum extent possible, even when cache servers become unavailable, or are added or removed. This feature also maximizes efficient use of cache memory.
content demand status
A measure of the frequency with which content in a given hot content subset is requested over a given hit_period. Content demand status is either hot, in which case the number of requests for content in the hot content subset during the most recent hit_period has exceeded the hot_threshold, or cool, in which case the number of requests during the most recent hit period is less than the cool_threshold. See also cool, cool_threshold, hit_period, hot, hot content subset, and hot_threshold.
Specifies the number of units, or hot content subsets, into which the content is divided when determining whether content is hot or cool. The requests for all content in a given subset are summed, and a state (hot or cool) is assigned to each subset. The content_hash_size should be within the same order of magnitude as the actual number of requests possible. For example, if the entire site is composed of 500,000 pieces of content, a content_hash_size of 100,000 is typical.
If you specify a value for hot_pool, but do not specify a value for this variable, the cache statement uses a default hash size of 10 subsets. See also cool, hot, and hot content subset.
Cookie persistence is a mode of persistence you can configure on the BIG-IP Controller where the controller stores persistent connection information in a cookie.
A term used to describe content demand status when using hot content load balancing. See also content demand status, hot, and hot content load balancing.
Specifies the maximum number of requests for given content that will cause that content to change from hot to cool at the end of the hit period.
If you specify a variable for hot_pool, but do not specify a value for this variable, the cache statement uses a default cool threshold of 10 requests. See also cool, hit_period, and hot.
default wildcard virtual server
A virtual server that has an IP address and port number of 0.0.0.0:0. This virtual server accepts all traffic which does not match any other virtual server defined in the configuration.
Destination processing means that the interface rewrites the destination address of an incoming packet.
Included in destination processing, destination translation means that the interface rewrites the destination address of an incoming packet. See also destination processing.
dynamic load balancing
Dynamic load balancing modes use current performance information from each node to determine which node should receive each new connection. The different dynamic load balancing modes incorporate different performance factors.
dynamic load balancing modes
Dynamic load balancing modes base connection distribution on live data, such as current server performance and current connection load.
dynamic site content
A type of site content that is automatically generated each time a user accesses the site. Examples are current stock quotes or weather satellite images.
EAV service check
A service check feature that uses an external program to determine if a node is up or down based on whether the node returns specific content. EAV service check is only one of the three types of service checks available on a BIG-IP Controller. See also service check, and external service checker program.
ECV service check
A service check feature that allows you to determine if a node is up or down based on whether the node returns specific content. ECV service check is only one of the three types of service checks available on a BIG-IP Controller. See also service check.
Extended Application Verification (EAV)
A service check feature that uses an external program to determine if a node is up or down based on whether the node returns specific content.
Extended Content Verification (ECV)
A service check feature that allows you to determine if a node is up or down based on whether the node returns specific content.
A network interface on the BIG-IP Controller configured to process destination requests. In a basic configuration, this interface has the administration ports locked down. In a normal configuration, this is typically a network interface on which external clients request connections to internal servers.
external service checker program
A custom program that performs a service check on behalf of the BIG-IP Controller. See also, EAV service check.
An encryption utility that allows secure shell connections to a remote system.
The process whereby a standby unit in a redundant system takes over when a software failure or a hardware failure is detected on the active unit.
The cable that directly connects the two controller units together in a redundant system.
A dynamic load balancing mode that bases connection distribution on which server currently exhibits the fastest response time to node pings.
FDDI (Fiber Distributed Data Interface)
A multi-mode protocol for transmitting data on optical-fiber cables up to 100 Mbps.
First-Time Boot utility
A utility that walks you through the initial system configuration process. The First-Time Boot utility runs automatically when you turn on a controller for the first time.
forward proxy caching
A configuration, in which a BIG-IP Cache Controller redundant system uses content-aware traffic direction to enhance the efficiency of an array of cache servers storing Internet content for internal users.
In products that support BIG-IP Cache, the hit_period specifies the period in seconds over which to count requests for particular content before determining whether to change the state (hot or cool) of the content.
If you specify a value for hot_pool, but do not specify a value for this variable, the cache statement uses a default hit period of 10 seconds. See also cool, hot, and hot_pool.
A network server which manages one or more virtual servers that the 3-DNS Controller uses for load balancing.
In products that support BIG-IP Cache, hot is a term used to define frequently requested content based on the number of requests in a given time period for a given hot content subset. See also hot content subset.
A designated group of cache servers to which requests are load balanced when the requested content is hot. If a request is for hot content, the BIG-IP Cache Controller redundant system directs the request to this pool.
hot content load balancing
Identifies hot, or frequently requested, content on the basis of number of requests in a given time period for a given hot content subset. A hot content subset is different from, and typically smaller than, the content subsets used for content striping. Requests for hot content are redirected to a cache server in the hot pool, a designated group of cache servers. This feature maximizes the use of cache server processing power without significantly affecting the memory efficiency gained by cacheable content determination. See also hot, hot content subset, and hot_pool.
hot content subset
A hot content subset is different from, and typically smaller than, the content subsets used for cacheable content determination. This is created once content has been determined to be hot and is taken or created from the content subset. See also cacheable content determination.
Specifies the minimum number of requests for content in a given hot content subset that will cause that content to change from cool to hot at the end of the period.
If you specify a value for hot_pool, but do not specify a value for this variable, the cache statement uses a default hot threshold of 100 requests. See also cool, hot, hot content subset, and hot_pool.
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 and 3-DNS Controllers.
intelligent cache population
Allows caches to retrieve content from other caches in addition to the origin web server. This feature is useful only when working with non-transparent cache servers, which can receive requests that are destined for the cache servers themselves, as opposed to transparent cache servers, which can intercept requests destined for a web server but cannot themselves receive requests. Intelligent cache population minimizes the load on the origin web server and speeds cache population. See also non-transparent cache server and transparent cache server.
A network interface on the BIG-IP Controller configured to process source requests. In a basic configuration, this interface has the administration ports open. In a normal configuration, this is typically a network interface which handles connections from internal servers.
A UDP based protocol used to exchange information between BIG-IP Controllers and 3-DNS Controllers. The iQuery protocol is officially registered for port 4353.
A last hop is the previous hop a connection took to get to the BIG-IP Controller. You can configure the BIG-IP Controller to send packets back to the device from which they originated when that device is part of a last hop pool.
Least Connections mode
A dynamic load balancing mode that bases connection distribution on which server currently manages the fewest open connections.
load balancing mode
A particular method of determining how to distribute connections across an array.
A loopback adapter is a software interface that is not associated with an actual network card. The nPath routing configuration requires you to configure loopback adapters on servers.
MAC (Media Access Control)
A protocol that defines the way workstations gain access to transmission media, most widely used in reference to LANs. For IEEE LANs, the MAC layer is the lower sublayer of the data link layer protocol.
An address used to represent hardware devices on an Ethernet network.
A reference to a node when it is included in a particular virtual server mapping. Virtual server mappings typically include multiple member nodes.
A feature on the BIG-IP Controller that preserves connection and persistence information in a BIG-IP Controller redundant system.
A miss request results from a request for content a cache does not have.
The name server daemon, which manages domain name server software.
NAT (Network Address Translation)
An alias IP address that identifies a specific node managed by the BIG-IP Controller to the external network.
A specific combination of an IP address and port number associated with a server in the array managed by the BIG-IP Controller.
The IP address associated with one or more nodes. This IP address can be the real IP address of a network server, or it can be an alias IP address on a network server.
A node address that the BIG-IP Controller uses to verify the status of multiple nodes. When the BIG-IP Controller uses a node alias to check node status, it pings the node alias. If the BIG-IP Controller receives a response to the ping, it marks all nodes associated with the node alias as up, and if it does not receive a response to the ping, the BIG-IP Controller marks all nodes associated with the node alias as down.
A feature that the BIG-IP Controller uses to determine whether nodes are up or down. Node ping sends standard echo pings to servers and transparent devices. If the server or device responds to the ping, it marks the related nodes up. If the server or device does not respond to the ping, it marks the related nodes down.
The port number or service name hosted by a specific node.
Node status indicates whether a node is up and available to receive connections, or down and unavailable. The BIG-IP Controller uses the node ping and service check features to determine node status.
Content that is not identified in the cacheable content condition part of a cache rule statement. See also cacheable content condition.
non-transparent cache server
Cache servers that can receive requests that are destined for the cache servers themselves.
The web server on which all original copies of your content reside.
Specifies a pool of servers that contain original copies of all content. Requests are load balanced to this pool when any of the following are true: the requested content is not cacheable, no cache server is available, or the BIG-IP Cache Controller redundant system is redirecting a request from a cache server that did not have the requested content.
A dynamic load balancing mode that bases connection distribution on a combination of two factors: the server that currently hosts the fewest connections, and also has the fastest response time.
A series of related connections received from the same client, having the same session ID. When persistence is turned on, a controller sends all connections having the same session ID to the same node instead of load balancing the connections.
A pool is a group of devices that you want the BIG-IP Controller to load balance.
A number that is associated with a specific service supported by a host. Refer to the Services and Port Index for a list of port numbers and corresponding services.
port-specific wildcard virtual server
A wildcard virtual server address that uses a port number other than 0.
A dynamic load balancing mode that bases connection distribution on a combination of two factors: the server that currently hosts the fewest connections, but also has the fastest response time. Predictive mode also ranks server performance over time, and passes connections to servers which exhibit an improvement in performance rather than a decline.
A static load balancing mode that bases connection distribution on server priority levels. The BIG-IP Controller distributes connections in a round robin fashion to all nodes in the highest priority group. If all the nodes in the highest priority group become unavailable, the BIG-IP Controller begins to pass connections to nodes in the next lower priority group.
A rate class determines the volume of traffic allowed through a rate filter.
A parameter that assigns a weight to a virtual server for load balancing purposes.
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.
A receive expression is the text string that the BIG-IP Controller looks for in the web page returned by a web server during an extended content verification (ECV) service check.
A pair of controllers that are configured for fail-over. In a redundant system, there are two controller units, 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.
remote administrative IP address
An IP address from which a controller allows shell connections, such as Telnet or SSH.
remote server acceleration
A configuration in which a BIG-IP Cache Controller redundant system uses content-aware traffic direction to enhance the efficiency of an array of cache servers that cache content for a remote web server.
Round Robin mode
A static load balancing mode that bases connection distribution on a set server order. Round Robin mode sends a connection request to the next available server in the order.
A send string is the request that the BIG-IP Controller sends to the web server during an extended content verification (ECV) service check.
A BIG-IP Controller feature that determines whether a node is up or down. When a BIG-IP Controller issues a service check, it attempts to connect to the service hosted by the node. If the connection is successful, the node is up. If the connection fails, the node is down. See also ECV service check, and EAV service check.
SNAT (Secure Network Address Translation)
A SNAT is a feature you can configure on the BIG-IP Controller. A SNAT defines a routable alias IP address that one or more nodes can use as a source IP address when making connections to hosts on the external network.
SNMP (Simple Network Management Protocol)
The Internet standard protocol, defined in STD 15, RFC 1157, developed to manage nodes on an IP network.
sod (switch over daemon)
A daemon that controls the fail-over process in a redundant system.
Source processing means that the interface rewrites the source of an incoming packet.
A controller in a redundant system that is always prepared to become the active unit if the active unit fails.
stateful site content
Content that maintains dynamic information for clients on an individual basis and is commonly found on e-commerce sites. For example, a site that allows a user to fill a shopping cart, leave the site, and then return and purchase the items in the shopping cart at a later time has stateful site content which retains the information for that client's particular shopping cart.
static load balancing modes
Static load balancing modes base connection distribution on a pre-defined list of criteria; it does not take current server performance or current connection load into account.
static site content
A type of site content that is stored in HTML pages, and changes only when an administrator edits the HTML document itself.
A sticky mask is a special IP mask that you can configure on the BIG-IP Controller. This mask optimizes sticky persistence entries by grouping more of them together.
In products that support caching, stripes are cacheable content subsets distributed among your cache servers.
transparent cache server
A cache server that can intercept requests destined for a web server, but are incapable of receiving requests.
A node that appears as a router to other network devices, including the BIG-IP Controller.
An IP address associated with one or more virtual servers managed by the BIG-IP Controller.
The port number or service name associated with one or more virtual servers managed by the BIG-IP Controller. A virtual port number should be the same TCP or UDP port number to which client programs expect to connect.
A specific combination of a virtual address and virtual port, associated with a content site that is managed by a BIG-IP Controller or other type of host server.
virtual server mapping
The group of nodes across which a virtual server load balances connections for a given site.
watchdog timer card
A hardware device that monitors the BIG-IP Controller for hardware failure.
wildcard virtual server
A virtual server that uses an IP address of 0.0.0.0. A wildcard virtual server accepts connection requests for destinations outside of the local network. Wildcard virtual servers are included only in Transparent Node Mode configurations.