CDN stands for Content Delivery Network or Content Distribution Network which is a system of computers which hold copies of data at various point in a network to expand the bandwidth for access to the data from the users or clients through the network.
A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, so as to avoid bottlenecks near that server.
Benefits of CDN
The capacity sum of strategically placed servers can be higher than the network backbone capacity. This can result in an impressive increase in the number of concurrent users. For instance, when there is a 10 Gbit/s network backbone and 200 Gbit/s central server capacity, only 10 Gbit/s can be delivered. But when 10 servers are moved to 10 edge locations, total capacity can be 10×10 Gbit/s.
Strategically placed edge servers decrease the load on interconnects, public peers, private peers and backbones, freeing up capacity and lowering delivery costs. It uses the same principle as above. Instead of loading all traffic on a backbone or peer link, a CDN can offload these by redirecting traffic to edge servers.
CDNs generally deliver content over TCP and UDP connections. TCP throughput over a network is impacted by both latency and packet loss. In order to reduce both of these parameters, CDNs traditionally place servers as close to the edge networks that users are on as possible. Theoretically the closer the content the faster the delivery, although network distance may not be the factor that leads to best performance.
CDNs can have automatic server availability sensing with instant user redirection. A CDN can offer 100% availability, even with large power, network or hardware outages.
CDN technologies give more control of asset delivery and network load. They can optimize capacity per customer, provide views of real-time load and statistics, reveal which assets are popular, show active regions and report exact viewing details to the customers. These usage details are an important feature that a CDN provider must provide, since the usage logs are no longer available at the content source server after it has been plugged into the CDN, because the connections of end-users are now served by the CDN edges instead of the content source.
Content Delivery Service Providers
- Coral Content Distribution Network
- coBlitz (a subproject of CoDeeN)
- Akamai Technologies
- Amazon CloudFront
- CDNetworks (PantherExpress)
- EdgeCast Networks
- Highwinds Network Group
- Level 3 Communications
- Limelight Networks
- Mirror Image Internet
- PEER 1
Source – Wikipedia