CachePilot Glossary A-Z

Automatic content mirroring (data pull)
The ability of a caching appliance to automatically check its content against a remote server containing the source content data, and copying any new or modified files and directories.

Boundary Caching
A unique Equiinet method of caching at the boundary or 'gateway' to a local area network, i.e. inside the Equiinet appliance.

Cache Hit Ratios
When a Cache finds a requested object of a web page in its memory, this is known as a 'Cache Hit'. When it finds it has to refer to the origin server to obtain the content, this is known as a 'Cache Miss'. To be effective the caching device should have a high ratio of hits to misses.

Central content distribution (data push)
Involves the Smart Cache being capable of receiving updates and modifications pro-actively sent to it from the remote server holding the source content data. This is a useful function where many local caching appliances under the control of a single authority are remotely updated by that authority.

Content Acceleration
Content acceleration involves smart caching to regulate the flow of this information without impacting the core network and without necessitating new bandwidth infrastructure.

Content Filtering
A facility to block or allow Internet sites and content from being accessed and viewed by an individual, a group of individuals, or all the connected users.

Domain Name Server (DNS)
A server that contains a database of host names and their corresponding IP addresses.

Dynamic web page content
Frequently changing objects within a web page that are flagged as always having to come from the origin server, i.e. objects that must not be cached - opposite to static content. Example - latest information from a constantly changing database.

File Transfer Protocol (FTP)
A service that supports the transfer of objects using TCP/IP between local and remote computers over the Internet.

Firewall
A firewall typically guards an internal network against malicious access from the outside. May also be configured to limit access to the outside from internal users.

Freshness
The length of time that an object can be cached and used without an up-to-date or revalidation check.

Gateway Device
An inter-networking device that joins two networks together. Specifically, a device that acts as the intermediary between the Local Area Network (LAN) and the WAN connection to the Internet. The Gateway may be physically be a Smart Cache, or is often a router unit with extra functionality.

Gateway Functionality
The Gateway device as a minimum will provide simple routing functionality, but often has much higher-level knowledge and capabilities with the applications being utilised. May also incorporate a firewall, access controls and content filtering.

Hierarchical Proxy Caching
The process of configuring Web servers to communicate with each other to determine whether documents missing from one cache might be present in another. In this environment an unlimited number of caches and users can cooperate using industry-standard Internet Cache Protocol (ICP) to speed access to shared content and eliminate redundant Web server requests.

HTML (Hypertext Markup Language)
The coding language used to create Hypertext documents. A set of markup symbols or codes is inserted in a file that tells a Web browser how to display a Web page's words and images for the user. The "hyper" in Hypertext comes from facility of HTML to additionally specify that a block of text, or an image, is linked to another file on the Internet.

HTTP -- (HyperText Transfer Protocol)
The protocol for moving hypertext files across the Internet.

HTTP headers
A newer version of HTTP - version 1.1 - has headers that provide more control for caching content more efficiently.

HTTPS (Hypertext Transfer Protocol over Secure Socket Layer, or HTTP over SSL)
Web protocol built into browsers that encrypts and decrypts user page requests as well as the pages that are returned by the Web server.

Internet Cache Protocol (ICP)
The protocol used for querying proxy servers for cached objects.

ISP (Internet service provider)
A company that provides individuals and other organisations access to the Internet and other related services such as Web site building and virtual hosting.

LAN (Local Area Network)
A LAN spans a limited local geographical area such as a school campus. LANs typically use Ethernet technology and are usually an order of magnitude faster and more capable than the WANs that are used to connect then to services such as the Internet.

Origin Server
The web server that hosts a particular resource, such as a web page.

Overlay Networking
The creation of an additional network to carry bandwidth-intensive applications and relieve the burden on a network. Overlay networks can be achieved using a number of different transmission media, from ISDN and ADSL to cable and satellite

Pre-Caching
Loading the cache storage area with content prior to when it is needed. Typically this is loading activity conducted out of prime time e.g. overnight when free bandwidth capacity is available.

Pre-Loading (of WebShare)
Also known as Web Mirroring see below.

Proxy
A device whose IP address is specified as a configuration option to the browser or other protocol program in order to handle Internet service requests between web clients and servers.

Proxy Auto-configuration (PAC) file
A file used to configure the IP address and port of the proxy server in a browser.

Proxy server
An intermediary server that accepts requests from clients and forwards them to other proxy servers, the origin server, or services.

Ready Video
Video-on-demand, stored within the Video Server.

Router
A device that physically joins multiple networks - maybe a combination of LANs and WANs. Also acts as a traffic forwarder - as it understands the where network traffic has come from and where it is destined.

Secure Shell (SSH)
A program to log into another computer over a network. SSH provides authentication and secure communications over insecure channels.

Secure Sockets Layer (SSL)
A security protocol used for sending encrypted information for Internet transactions and communications between client web browsers and web servers.

Smart Caching
Equiinet terminology to encapsulate all its caching techniques built into a modern caching solution for content delivery in educational environments. This also includes a range of Internet Gateway functions as well as sophisticated pre-caching.

Smart Caching Protocol (SCP)
SCP a proprietary Equiinet protocol based on the draft RFC BTFTP, enabling Predictive and Reactive cashing and re-transmission techniques.

Static web page content
Objects within a web page that are flagged as rarely changing, i.e. objects that can be cached - opposite to dynamic content. Examples include logos and graphics.

Structured data store
The ability to faithfully replicate the directory and file structure of the source content, which will enable the speedy retrieval and delivery of the content without unnecessary searching.

Traditional Caching
Functionality provided by a first generation caching device. Will have the ability to automatically cache HTML and FTP. It may have some ability to preload but only into cache, and has none of the content control and storage, and additional access control and gateway features of a Smart Cache.

Uniform Resource Locator (URL)
The address of a file or resource accessible on the Internet, which contains the name of the protocol required access the resource, a domain name that identifies a specific computer on the Internet, and a description of a file location on the computer.

WAN (Wide Area Network)
A WAN spans a large geographic area, and is typically used to interconnect multiple LANs. WANs typically use communications media such as leased lines, ADSL, ISDN etc., which are all relatively slow compared to LAN technology.

Web Mirroring
The ability to replicate entire web pages from an origin server and place them into a local WebShare area on the Smart Cache. Issues such as creating a localised relative web page addressing structure, rather than an absolute or relative addressing structure relating to the origin server are also resolved.

Web Server
A server that retrieves and delivers requested web pages to users who enter the URL in a web browser.

WebShare
An area reserved on the Smart Cache reserved for storage of local content. This may be pre-loaded web pages from a specialist content provider, or it may be content created as a result of Web Mirroring.

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