Content delivery network

The goal is to provide high availability and performance ("speed") by distributing the service spatially relative to end users.

In turn, a CDN pays Internet service providers (ISPs), carriers, and network operators for hosting its servers in their data centers.

CDN vendors may cross over into other industries like security, DDoS protection and web application firewalls (WAF), and WAN optimization.

Notable content delivery service providers include Akamai Technologies, Edgio, Cloudflare, Amazon CloudFront, Fastly, and Google Cloud CDN.

Benefits include reducing bandwidth costs, improving page load times, and increasing the global availability of content.

As such these services are being pointed out as potential privacy intrusions for the purpose of behavioral targeting[6] and solutions are being created to restore single-origin serving and caching of resources.

Subresource Integrity mechanism was created in response to ensure that the page loads a script whose content is known and constrained to a hash referenced by the website author.

The resulting tightly integrated overlay uses web caching, server-load balancing, request routing, and content services.

These include Global Server Load Balancing, DNS-based request routing, Dynamic metafile generation, HTML rewriting,[13] and anycasting.

[11] CDNs use a variety of methods of content delivery including, but not limited to, manual asset copying, active web caches, and global hardware load balancers.

The Internet Content Adaptation Protocol (ICAP) was developed in the late 1990s[15][16] to provide an open standard for connecting application servers.

Edge Side Includes or ESI is a small markup language for edge-level dynamic web content assembly.

This property is one of the major advantages of using P2P networks because it makes the setup and running costs very small for the original content distributor.

[25][26] The rapid growth of streaming video traffic[27] uses large capital expenditures by broadband providers[28] in order to meet this demand and retain subscribers by delivering a sufficiently good quality of experience.

This deep caching minimizes the distance that video data travels over the general Internet and delivers it more quickly and reliably.

Content management operations performed by CDNs are usually applied without (or with very limited) information about the network (e.g., topology, utilization etc.)

These pose a number of challenges for the telco-operators who have a limited sphere of action in face of the impact of these operations on the utilization of their resources.

They will grow by enrollment of new telcos joining the federation and bringing network presence and their Internet subscriber bases to the existing ones.

This approach, called end-user mapping,[32] has been adopted by CDNs and it has been shown to drastically reduce the round-trip latencies and improve performance for clients who use public DNS or other non-local resolvers.

As the virtual cache placement is based on both the content type and server or end-user geographic location, the vCDNs have a significant impact on service delivery and network congestion.