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Definitions of Important CDN Terms


A network addressing and routing methodology in which a single destination address has multiple routing paths to two or multiple endpoint destinations. Routers will select the desired path on the basis of the number of hops, distance, lowest cost, latency measurements or based on the least congested route.

Application Delivery

A computer network device in a datacenter, usually included in an application delivery network that helps perform common tasks, like those executed by web accelerators to remove load from the web servers themselves.

Application Acceleration

Application that improves application performance utilizing methods such as compression, caching and transmission control protocol (TCP) optimization. It is a common feature in an application delivery controller (ADC) to improve response time over network connections.

Application Delivery Controller

A computer network device in a datacenter, often part of an application delivery network (ADN), that contributes in tasks performance, like those done by web accelerators to remove load from the web servers themselves.

Application Performance Monitoring

The monitoring and management of performance and availability of software applications. APM aims to detect and diagnose complex application performance problems to maintain a sustainable level of service.


Application Program Interface, a range of routines, protocols, and tools for building software applications. APIs specify how software components should interact and are used for programming graphical user interface (GUI) components.

Big Data

A field that treats ways to analyze, systematically extract information from, or otherwise deal with data sets that are too large or complex to be dealt with by traditional data-processing application software.

Brotli Compression

A compression algorithm developed by Google. It is open-sourced and it aims to reduce the size of files.


The process of storing data in a cache. A cache is a temporary storage space. For instance, the files one automatically requests from a user by looking at a Web page are stored on their hard disk in a cache subdirectory under the directory for their browser.


An HTTP header used to specify browser caching policies in both client requests and server responses. Policies include how and where a resource is cached, and its maximum age before expiring.

Cloud Computing

Storing and accessing data and programs over the Internet instead of one’s computer's hard drive. In this context, the cloud is the Internet itself.

Cloud Computing Architecture

The components and subcomponents required for cloud computing. These components typically consist of a front end platform, back end platforms, a cloud-based delivery, and a network. Combined, these components make up cloud computing architecture.

Cloud Services

Any service made available to users on-demand via the Internet from a cloud computing provider's servers, contrarily to being provided from a company's own on-premises


A Canonical Name Record or Alias Record. A type of resource record in the Domain Name System (DNS), that underlines that one domain name is an alias of another canonical domain name.

Content Delivery Network (CDN)

A system of distributed servers-network- that deliver web content to an end-user, based on their geographic locations, the origin of the webpage and the content delivery server.


Dynamic Adaptive Streaming over HTTP (DASH), also known as MPEG-DASH, is an adaptive bitrate streaming technique that enables high quality streaming of media content over the Internet delivered from conventional HTTP web servers.

Data Center

Also known as datacenter, is a repository that includes computing facilities such as servers, routers, switches, and firewalls, as well as supporting components like backup equipment, fire suppression facilities, and air conditioning.

Edge Server

A type of edge device that provides an entry point into a network. Other edges devices include routers and routing switches. Edge devices are often placed inside Internet exchange points (IxPs) to allow different networks to connect and share transit.


Or entity tag is part of HTTP. It is one of the mechanisms that HTTP provides for Web cache validation, which enables a user to make conditional requests. This allows caches to be more efficient and saves bandwidth, as a Web server does not need to send a full response if the content has remained the same.


Global server load balancing (GSLB) refers to the smart distribution of traffic across server resources located in different geographic locations. The servers can be on-premises in a company's own data centers or hosted in a private cloud or the public cloud.

HLS (HTTP Live Streaming)

An HTTP-based adaptive bitrate streaming communications protocol implemented by Apple Inc. as part of its QuickTime, Safari, OS X, and iOS software.


A major update to the HTTP protocol that makes more efficient use of network resources. HTTP/2 added compression of the HTTP headers and interleaves multiple data streams on a single TCP connection.

Hybrid Cloud

A cloud computing environment that utilizes a mix of on-premises, private cloud and third-party, public cloud services with coordination between the two platforms.

Hybrid CDN

A CDN Service that offers Multi-CDNs together with Private CDN service for the specific purposes of your company. With this service, you get both your own Private CDN network and a high-performance CDN service at the same time. Hybrid takes its name from these parallel services.
Cloud + Private = Hybrid

Image Resolutions

The number of pixels in an image. Usually identified by the width and height of the image as well as the total number of pixels in the image.

Infrastructure as a Service (IaaS)

Online services that provide high-level APIs used to dereference various low-level details of underlying network infrastructure like physical computing resources, location, data partitioning, scaling, security, backup, etc.

Internet Exchange Point

A physical network access point through which major network providers connect their networks and exchange traffic. IXPs provide a common place for ISPs to exchange their Internet traffic between autonomous network systems.


The Last-Modified response HTTP header contains information about the date and time during which the origin server considers the resource was last modified. It is used as a validator to determine if a resource received or stored is the same. Less accurate than an ETag header, it is a fallback mechanism. Conditional requests containing If-Modified-Since or If-Unmodified-Since headers make use of this field.

Load Balancing

An efficiently distributing incoming network traffic across a group of backend servers, also called “server farm” or “server pool”.

Multi CDN

A technology that combines several existing CDN providers into one large global network. This technology dynamically optimizes and unifies leading cloud and network infrastructure providers across the globe to rapidly, securely and reliably accelerate web content to users regardless of their location in the world.

Network Optimization

A technology used for improving network performance for a given environment. Network optimization is important as information technology is growing faster with business users producing large volumes of data and thus consuming larger network bandwidths.

NoSQL (not only SQL)

An alternative to traditional relational databases in which data is placed in tables and data schema is carefully designed before the database is built.

Origin Server

A Web server which contains the original Web page. The term is used to differentiate the Web server from the cache server. Because physically, there is no difference between a digital original and a digital copy, the origin server is considered to be the one that is maintained and updated by the enterprise.

Origin Shield

An extra caching layer between the CDN edge servers and the user’s origin. When a CDN edge server gets a request from a user and can't satisfy the request from cache, the edge server will fetch the object from the shield POP rather than pulling from the customer origin directly.

OTT (Over The Top)

A streaming media service offered directly to viewers over the Internet. OTT bypasses cable, broadcast and satellite television platforms that traditionally act as a controller or distributor of such content.The term is most synonymous with subscription-based video on demand services that offer access to film and television content.

Platform as a Service (PaaS)

A cloud computing model where a third-party provider delivers hardware and software tools to users over the internet. A PaaS provider hosts the hardware and software on its own infrastructure.

PoP (Point of Presence)

An access point from one place to the rest of the Internet that necessarily has a unique Internet Protocol (IP) address.

Private Cloud

A cloud computing model where IT services are provisioned over private IT infrastructure for the use of one and only one organization. A private cloud is usually managed via internal resources.

Private CDN

A technology that consists of POPs that are only serving content for their owner. These POPs can be caching servers, reverse proxies or application delivery controllers. It can be as simple as two caching servers, or large enough to serve petabytes of content.

Public Cloud

Computing services offered by third-party providers over the public Internet, making them available for use and purchase by anyone. They can either be free or sold on-demand, giving customers the right to pay only per usage for consumed CPU cycles, storage, or bandwidth.


A command to the CDN to start serving a file from the origin server instead of the cache. The response from the origin server delivers the newer file versions which edge server will cache and serve to visitors.

Query String

The part of a uniform resource locator which assigns values to specified parameters. The query string commonly includes fields added to a base URL by a Web browser or other client application, for example as part of an HTML form.

Reverse Proxy

A server that sits in front of web servers and forwards client requests to those web servers. Reverse proxies are typically implemented to help increase security, performance, and reliability.

Round-trip Time (RTT)

The duration in milliseconds needed for a network request to go from a starting point to a destination and back again to the starting point.

SDN (Software Defined Network)

An approach to network management that enables dynamic, programmatically efficient network configuration in order to improve network performance and monitoring making it similar to cloud computing than traditional network management.

SDS (Software Defined Storage)

A storage architecture that separates storage software from its hardware. SDS is generally conceived to perform on any industry-standard or x86 system, removing the software’s dependence on proprietary hardware.


A hybrid media delivery method. It operates like streaming, but is actually based on HTTP progressive download. The HTTP downloads are performed in a series of small chunks, allowing the media to be easily and cheaply cached along the edge of the network, closer to end-users.

Software as a Service (SaaS)

A software model where customers and users access applications via the Internet, and where the software applications are hosted in a multi-tenant cloud infrastructure.

SSL Acceleration

Also called TLS acceleration, is a method of offloading processor-intensive public-key encryption for Transport Layer Security (TLS) and its predecessor Secure Sockets Layer (SSL) to a hardware accelerator.

Time-to-first-byte (TTFB):

The name given to the time between the first request of the end-user to a web server and the response back of that request from the web server to the end-user

Time-to-live (TTL)

The time that an object is stored in a caching system before it’s deleted or refreshed.

Transport Layer Security (TLS)

A security protocol by the IETF (Internet Engineering Task Force) that relies on and supersedes SSL 3.0 (Secure Sockets Layer 3.0). Just like SSL, TLS uses digital certificates to authenticate both the user and the network.

Transmission Control Protocol

One of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol. Therefore, the entire suite is commonly referred to as TCP/IP.

Virtual Machine

A software computer that, like a physical computer, runs an operating system and applications. The virtual machine is comprised of a set of specification and configuration files and is backed by the physical resources of a host.

Virtual Private Server (VPS)

A virtual machine sold as a service by an Internet hosting service. The virtual dedicated server (VDS) has also a similar meaning

Web Services

A software service used to communicate between two devices on a network. More specifically, a Web service is a software application with a standardized way of providing interoperability between disparate applications. It does so over HTTP using technologies such as XML, SOAP, WSDL, and UDDI.

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