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Archived Manual Chapter: BIG-IP Solutions Guide v4.1: Glossary
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Glossary



Any IP Traffic

Any IP Traffic is a feature that allows the BIG-IP to load balance protocols other than TCP and UDP.

ARL (Akamai Resource Locator)

An ARL is a URL that is modified to point to content on the Akamai Freeflow NetworkTM. In content conversion (akamaization), the URL is converted to an ARL, which retrieves the resource from a geographically nearby server on the Akamai Freeflow Network for faster content delivery.

BIG-IP active unit

In a redundant system, the BIG-IP active unit is 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.

BIG-IP web server

The BIG-IP web server runs on a BIG-IP and hosts the Configuration utility.

bigpipe

The bigpipe utility provides command line access to the BIG-IP.

BIG/stat

BIG/stat is a statistical monitoring utility that ships on the BIG-IP. This utility provides a snap-shot of statistical information.

BIG/top

BIG/top is a statistical monitoring utility that ships on the BIG-IP. This utility provides real-time statistical information.

big3d

The big3d utility is a monitoring utility that collects metrics information about paths between a BIG-IP and a specific local DNS server. The big3d utility runs on BIG-IP units and it forwards metrics information to 3-DNS Controllers.

BIND (Berkeley Internet Name Domain)

BIND is the most common implementation of DNS, which provides a system for matching domain names to IP addresses.

cacheable content determination

Cacheable content determination is a process that determines the type of content you cache on the basis of any combination of elements in the HTTP header.

cacheable content expression

The cacheable content expression determines, based on evaluating variables in the HTTP header of the request, whether 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.

cache pool

The cache pool 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.

chain

A chain is 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.

content affinity

Content affinity 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 converter gateway

A content converter gateway is a gateway for converting URLs to ARLs. See also ARL.

content demand status

The content demand status is 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.

content hash size

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.

content stripes

In products that support caching, content stripes are cacheable content subsets distributed among your cache servers.

cookie persistence

Cookie persistence is a mode of persistence you can configure on the BIG-IP where the controller stores persistent connection information in a cookie.

cool

Cool describes content demand status when you are using hot content load balancing. See also content demand status, hot, and hot content load balancing.

cool threshold

The cool threshold 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 VLANs

The BIG-IP is configured with two default VLANs, one for each interface. One default VLAN is named internal and one is named external. See also VLAN.

default wildcard virtual server

A default wildcard virtual server has an IP address and port number of 0.0.0.0:0. or *:* or "any":"any". This virtual server accepts all traffic that does not match any other virtual server defined in the configuration.

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 such as current server performance and current connection load.

Dynamic Ratio load balancing mode

Dynamic Ratio mode is like Ratio mode (see Ratio mode), except that ratio weights are based on continuous monitoring of the servers and are therefore continually changing. Dynamic Ratio load balancing may currently be implemented on RealNetworks RealServer platforms, on Windows platforms equipped with Windows Management Instrumentation (WMI), or on a server equipped with either the UC Davis SNMP agent or Windows 2000 Server SNMP agent.

dynamic site content

Dynamic site content is site content that is automatically generated each time a user accesses the site. Examples are current stock quotes or weather satellite images.

EAV (Extended Application Verification)

EAV is a health check that verifies an application on a node by running that application remotely. EAV health check is only one of the three types of health checks available on a BIG-IP. See also health check, health monitor and external monitor.

ECV (Extended Content Verification)

ECV is a health check that allows you to determine if a node is up or down based on whether the node returns specific content. ECV health check is only one of the three types of health checks available on a BIG-IP. See also health check.

external monitor

An external monitor is a user-supplied health monitor. See also, health check, health monitor.

external VLAN

The external VLAN is a default VLAN on the BIG-IP. In a basic configuration, this VLAN has the administration ports locked down. In a normal configuration, this is typically a VLAN on which external clients request connections to internal servers.

F-Secure SSH

F-Secure SSH is an encryption utility that allows secure shell connections to a remote system.

fail-over

Fail-over is 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.

fail-over cable

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

Fastest mode

Fastest mode is 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)

FDDI is a multi-mode protocol used for transmitting data on optical-fiber cables at speeds up to 100 Mbps.

First-Time Boot utility

The First-Time Boot utility walks you through the initial system configuration process. You can run the First-Time Boot utility from either the command line or the Configuration utility start page.

floating self IP address

A floating self IP address is an additional self IP address for a VLAN that serves as a shared address by both units of a BIG-IP redundant system.

forward proxy caching

Forward proxy caching is 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.

health check

A health check is a BIG-IP feature that determines whether a node is up or down. Health checks are implemented through health monitors. See also health monitor, ECV, EAV, and external monitor.

health monitor

A health monitor checks a node to see if it is up and functioning for a given service. If the node fails the check, it is marked down. Different monitors exist for checking different services. See also health check, EAV, ECV, and external monitor.

hit period

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.

host

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

hot

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.

hot content load balancing

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.

hot pool

A hot pool is 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 threshold

The hot threshold 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.

HTTP redirect

An HTTP redirect sends an HTTP 302 Object Found message to clients. You can configure a pool with an HTTP redirect to send clients to another node or virtual server if the members of the pool are marked down.

ICMP (Internet Control Message Protocol)

ICMP is an Internet communications protocol used to determine information about routes to destination addresses, such as virtual servers managed by BIG-IP units and 3-DNS Controllers.

intelligent cache population

Intelligent cache population allows caches to retrieve content from other caches in addition to the origin web server. Use this feature when working with non-transparent cache servers that can receive requests destined for the cache servers themselves. 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.

interface

The physical port on a BIG-IP is called an interface. See also link.

IPSEC

IPSEC (Internet Security Protocol) is a communications protocol that provides security for the network layer of the Internet without imposing requirements on applications running above it.

iQuery

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

internal VLAN

The internal VLAN is a default VLAN on the BIG-IP. In a basic configuration, this VLAN has the administration ports open. In a normal configuration, this is a network interface that handles connections from internal servers.

last hop

A last hop is the final hop a connection took to get to the BIG-IP. You can allow the BIG-IP to determine the last hop automatically to send packets back to the device from which they originated. You can also specify the last hop manually by making it a member of a last hop pool.

Least Connections mode

Least Connections mode is a dynamic load balancing mode that bases connection distribution on which server currently manages the fewest open connections.

link

A link is a physical interface on the BIG-IP connected to another physical interface in a network.

link aggregation

The link aggregation feature allows you to combine a number of links together to act as one interface.

load balancing mode

A particular method of determining how to distribute connections across an array.

loopback adapter

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)

MAC is a protocol that defines the way workstations gain access to transmission media, and is most widely used in reference to LANs. For IEEE LANs, the MAC layer is the lower sublayer of the data link layer protocol.

MAC address

A MAC address is used to represent hardware devices on an Ethernet network.

member

Member is a reference to a node when it is included in a particular pool. Pools typically include multiple member nodes.

minimum active members

The minimum active members is the number of members that must be active in a priority group in order for the BIG-IP to send its requests to that group. If the number of active members falls below this number, requests are sent to the next highest priority group (the priority group with the next lowest priority number).

miss request

When a cache does not have requested content and cannot respond to the request, it is called a miss request.

monitor

The BIG-IP uses monitors to determine whether nodes are up or down. There are several different types of monitors and they use various methods to determine the status of a server or service.

monitor destination IP address or IP address:port

The monitor destination IP address or address:port for a user defined monitor is used mainly for setting up a node alias for the monitor to check. All nodes associated with that monitor will be marked down if the alias node (destination IP address:port) is marked down. See also node alias.

monitor instance

You create a monitor instance when a health monitor is associated with a node, node address, or port. It is the monitor instance that actually performs the health check, not the monitor.

monitor template

A monitor template is a system-supplied health monitor that is used primarily as a template to create user-defined monitors, but in some cases can be used as is. The BIG-IP includes a number of monitor templates, each specific to a service type, for example, HTTP and FTP. The template has a template type that corresponds to the service type and is usually the name of the template.

named

Named is the name server utility, which manages domain name server software.

NAT (Network Address Translation)

A NAT is an alias IP address that identifies a specific node managed by the BIG-IP to the external network.

node

A node is a specific combination of an IP address and port (service) number associated with a server in the array that is managed by the BIG-IP.

node address

A node address is 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.

node alias

A node alias is a node address that the BIG-IP uses to verify the status of multiple nodes. When the BIG-IP uses a node alias to check node status, it pings the node alias. If the BIG-IP receives a response to the ping, it marks all nodes associated with the node alias as up. If the controller does not receive a response to the ping, the it marks all nodes associated with the node alias as down.

node port

A node port is the port number or service name that is hosted by a specific node.

node status

Node status indicates whether a node is up and available to receive connections, or down and unavailable. The BIG-IP uses the node ping and health check features to determine node status.

non-cacheable content

Non-cacheable content is content that is not identified in the cacheable content condition part of a cache rule statement.

non-transparent cache server

Cache servers that can receive requests that are destined for the cache servers themselves are called non-transparent cache servers.

origin server

An origin server is the web server on which all original copies of your content reside.

origin pool

The origin pool specifies a pool of servers that contain original copies of all content. Requests are load balanced to this pool when any of the following is 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.

Observed mode

Observed mode is 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.

performance monitor

A performance monitor gathers statistics and checks the state of a target device.

persistence

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.

pool

A pool is composed of a group of network devices (called members). The BIG-IP load balances requests to the nodes within a pool based on the load balancing method and persistence method you choose when you create the pool or edit its properties.

port

A port is can be represented by 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 port-specific wildcard virtual server is a wildcard virtual server that uses a port number other than 0. See wildcard virtual server.

port mirroring

Port mirroring is a feature that allows you to copy traffic from any port or set of ports to a single, separate port where a sniffing device is attached.

Predictive mode

Predictive mode is 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. Predictive mode also ranks server performance over time, and passes connections to servers which exhibit an improvement in performance rather than a decline.

rate class

You create a rate filter from the Configuration utility or command line utility. When you assign a rate class to a rate filter, a rate class determines the volume of traffic allowed through a rate filter. See also rate filter.

rate filter
Rate filters consist of a basic filter with a rate class. Rate filters are a type of extended IP filter. They use the same IP filter method, but they apply a rate class, which determines the volume of network traffic allowed through the filter. See also rate class.

ratio

A ratio is 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.

receive expression

A receive expression is the text string that the BIG-IP looks for in the web page returned by a web server during an extended content verification (ECV) health check.

redundant system

Redundant system refers to 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.

RFC 1918 addresses

An RFC 1918 address is an address that is within the range of non-routable addresses described in the IETF RFC 1918.

remote administrative IP address

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

remote server acceleration

A remote server acceleration configuration is 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

Round Robin mode is 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.

self IP address

Self IP addresses are the IP addresses owned by the BIG-IP that you use to access the internal and external VLANs.

send string

A send string is the request that the BIG-IP sends to the web server during an extended content verification (ECV) health check.

service

Service refers to services such as TCP, UDP, HTTP, and FTP.

SNAT (Secure Network Address Translation)

A SNAT is a feature you can configure on the BIG-IP. 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.

SNAT automap

This feature allows the BIG-IP to perform a SNAT automatically on any connection that is coming from the controller's internal VLAN. It is easier to use than traditional SNATs and solves certain problems associated with the latter.

SNMP (Simple Network Management Protocol)

SNMP is the Internet standard protocol, defined in STD 15, RFC 1157, developed to manage nodes on an IP network.

source processing

Source processing means that the interface rewrites the source of an incoming packet.

spanning tree protocol (STP)

Spanning tree protocol is a protocol that provides loop resolution in configurations where one or more external switches is connected in parallel with the BIG-IP.

SSL gateway

An SSL gateway is a gateway for decrypting HTTP requests to an HTTP server and encrypting the reply.

standby unit

A standby unit in a redundant system is a unit 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 is called stateful site content. 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.

state mirroring

State mirroring is a feature on the BIG-IP that preserves connection and persistence information in a BIG-IP redundant system.

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

Static site content is a type of site content that is stored in HTML pages, and changes only when an administrator edits the HTML document itself.

sticky mask

A sticky mask is a special IP mask that you can configure on the BIG-IP. This mask optimizes sticky persistence entries by grouping more of them together.

tagged VLAN

You can define any interface as a member of a tagged VLAN. You can create a list of VLAN tags or names for each tagged interface.

transparent cache server

A transparent cache server can intercept requests destined for a web server, but cannot receive requests.

transparent node

A transparent node appears as a router to other network devices, including the BIG-IP.

trunk

A trunk is a combination of two or more interfaces and cables configured as one link. See also link aggregation.

user-defined monitor

A user-defined monitor is a custom monitor configured by a user, based on a system-supplied monitor template. For some monitor types, you must create a user-defined monitor in order to use them. For all monitor types, you must create a user-defined monitor to change system supplied monitor default values.

virtual address

A virtual address is an IP address associated with one or more virtual servers managed by the BIG-IP.

virtual port

A virtual port is the port number or service name associated with one or more virtual servers managed by the BIG-IP. A virtual port number should be the same TCP or UDP port number to which client programs expect to connect.

virtual server

Virtual servers are a specific combination of virtual address and virtual port, associated with a content site that is managed by a BIG-IP or other type of host server.

VLAN

VLAN stands for virtual local area network. A VLAN is a logical grouping of network devices. You can use a VLAN to logically group devices that are on different network segments.

VLAN name

A VLAN name is the symbolic name used to identify a VLAN. For example, you might configure a VLAN named marketing, or a VLAN named development. See also VLAN.

watchdog timer card

A watchdog timer card is a hardware device that monitors the BIG-IP for hardware failure.

wildcard virtual server

A wildcard virtual server is a virtual server that uses an IP address of 0.0.0.0, * or "any". 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.

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