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A content delivery network or content distribution networks (CDNs) is a system of computers networked together across the Internet that cooperate transparently to deliver content (especially large media content) to end users. The first web content based CDN's were Sandpiper, Mirror Image and Skycache followed by Akamai and Digital Island. The first video based CDN was iBEAM Broadcasting [citation needed]. This article is about the machine. ...
A computer network is an interconnection of a group of computers. ...
Akamai Technologies, Inc. ...
Digital ISLAND Limited is a full service business to business telecommunications provider based in Auckland New Zealand. ...
CDN nodes are deployed in multiple locations, often over multiple backbones. These nodes cooperate with each other to satisfy requests for content by end users, transparently moving content behind the scenes to optimize the delivery process. Optimization can take the form of reducing bandwidth costs, improving end-user performance, or both. Each line is drawn between two nodes, representing two IP addresses. ...
Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. ...
The number of nodes and servers making up a CDN varies, depending on the architecture, some reaching thousands of nodes with tens of thousands of servers.
Requests for content are intelligently directed to nodes that are optimal in some way. When optimizing for performance, locations that can serve content quickly to the user may be chosen. This may be measured by choosing locations that are the fewest hops or fewest number of network seconds away from the requestor, so as to optimize delivery across local networks. When optimizing for cost, locations that are less expensive to serve from may be chosen instead. Often these two goals tend to align, as servers that are close to the end user sometimes have an advantage in serving costs, perhaps because they are located within the same network as the end user.
Content networking techniques
The Internet was designed according to the end-to-end principle [1]. This principle keeps the core network relatively simple and moves the intelligence as much as possible to the network end-points: the hosts and clients. As a result the core network is specialized, simplified, and optimized to only forward data packets. Content Delivery Networks augment the end-to end transport network by distributing on it a variety of intelligent applications employing techniques designed to optimize content delivery. The resulting tightly integrated overlay uses web caching, server-load balancing, request routing, and content services[2]. These techniques are briefly described below.
Because closer is better, web caches store popular content closer to the user. These shared network appliances reduce bandwidth requirements, reduce server load, and improve the client response times for content stored in the cache. Web caching is the caching of web documents (HTML pages, images, etc. ...
Server-load balancing uses one or more layer 4–7 switches, also known as a web switch, content switch, or multilayer switch to share traffic among a number of servers or web caches. Here the switch is assigned a single virtual IP address. Traffic arriving at the switch is then directed to one of the real web servers attached to the switch. This has the advantages of balancing load, increasing total capacity, improving scalability, and providing increased reliability by redistributing the load of a failed web server and providing server health checks. It has been suggested that layer 4 router be merged into this article or section. ...
An IP address (Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address. ...
The term web server can mean one of two things: a computer responsible for serving web pages, mostly HTML documents, via the HTTP protocol to clients, mostly web browsers; a software program that is working as a daemon serving web documents. ...
A content cluster or service node can be formed using a layer 4–7 switch to balance load across a number of servers or a number of web caches within the network.
Request routing directs client requests to the content source best able to serve the request. This may involve directing a client request to the service node that is closest to the client, or to the one with the most capacity. A variety of algorithms are used to route the request. These include Global Server Load Balancing, DNS-based request routing, HTML rewriting[3], and anycasting[4]. Proximity—choosing the closest service node—is estimated using a variety of techniques including reactive probing, proactive probing, and connection monitoring. Routing Schemes anycast broadcast multicast unicast Anycast is a network addressing and routing scheme whereby data is routed to the nearest or best destination as viewed by the routing topology. ...
Service providers increasingly provide value-added services beyond basic data transport. Features such as virus scanning and parental control are being offered, hoping to increase service attractiveness, user loyalty, revenue, and profit. Web caches and service nodes distributed throughout the content delivery network provide convenient dispatch points for connecting to enhanced services. This handing messages off for further processing is sometimes called vectoring of messages.
content service protocols Two protocols suites are designed to provide access to a wide variety of content services distributed throughout a content network. The Internet Content Adaptation Protocol (ICAP) was developed in the late 1990’s[5] [6] to provide an open standard for connecting application servers. A more recently defined and robust solution is provided by the Open Pluggable Edge Services (OPES) protocol[7]. This architecture defines OPES service applications that can reside on the OPES processor itself or be executed remotely on a Callout Server. See ICAP/4 for the computer program. ...
See also
Commercial CDNs Akamai Technologies, Inc. ...
Amazon S3 (Simple Storage Service) is an online storage web service offered by Amazon Web Services. ...
CacheFly is a CDN provider based in Chicago, IL. Unlike the traditional hosting method of holding all files in one centralized server location CacheFly uses a decentralized model with servers placed around the globe. ...
Streaming media is multimedia that is continuously received by, and normally displayed to, the end-user while it is being delivered by the provider. ...
Flumotion, SA is a Spanish company based in Barcelona, which has developped a multiformat streaming platform to publish audio and video content via internet. ...
Level 3 is an international communications and information services company and is headquartered in Broomfield, Colorado. ...
LocalMirror is a U.S.-based privately held corporation that offers Content Delivery Network service incorporated in 2005. ...
NACEVI (NAtional CEnter for VIdeo) is Czech content delivery Network operated by Visual Connection. ...
NTT Europe Online provides managed hosting and related services such as application management and security management for many types of business connected to the Internet. ...
Panther Express is a content delivery network or CDN based in New York City. ...
Streaming media is multimedia that is continuously received by, and normally displayed to, the end-user while it is being delivered by the provider. ...
VeriSign, Inc. ...
This article or section does not cite its references or sources. ...
Internap Network Services Corporation, commonly referred to as Internap, provides computer network routing services and operates several data colocation centers throughout the world. ...
Academic CDNs Coral is an open source, peer-to-peer content distribution network designed to mirror web content. ...
Codeen is a proxy server system created at Princeton and deployed for general use on PlanetLab. ...
Globule is an open-source collaborative content delivery network developed at the Vrije Universiteit in Amsterdam. ...
FCAN (Flash Crowds Alleviation Network) is an adaptive CDN network that dynamically optimizes the system structure between peer-to-peer (P2P) and client-server(C/S) configurations as a possible way to alleviate flash crowds effect. ...
Notes - ^ Saltzer, J. H., Reed, D. P., Clark, D. D.: “End-to-End Arguments in System Design,” ACM Transactions on Communications, 2(4), 1984
- ^ Hofmann, Markus; Leland R. Beaumont (2005). Content Networking: Architecture, Protocols, and Practice. Morgan Kaufmann Publisher. ISBN 1-55860-834-6
- ^ RFC 3568 Barbir, A., Cain, B., Nair, R., Spatscheck, O.: "Known Content Network (CN) Request-Routing Mechanisms," July 2003
- ^ RFC 1546 Partridge, C., Mendez, T., Milliken, W.: "Host Anycasting Services," November 1993.
- ^ RFC 3507 Elson, J., Cerpa, A.: "Internet Content Adaptation Protocol (ICAP)," April 2003.
- ^ ICAP Forum
- ^ RFC 3835 Barbir, A., Penno, R., Chen, R., Hofmann, M., and Orman, H.: "An Architecture for Open Pluggable Edge Services (OPES)," August 2004.
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