CDN (Content Delivery Network)
Introduction

Content Delivery Network (CDN) is a network, which consists of huge number of distribution points (called nodes). This network is running over the Internet network and can defectively deliver huge amount of content to huge amount of recipients.

The most popular usage of these networks is distribution of software updates.

CDN is owned by a CDN provider, which is responsible for content distribution, which is ingested by a CDN customer.

The advantage of CDN is in resource sharing, because if every software developer wants to distribute updates over his customers in Internet, he must build system of servers, maintain and operate its. Then there will be numbers of parallel systems to the same point. This overlap and low utilization of nodes will increase the price/usability ratio. Distribution from one central point will use huge amount of capacity for transferring the same thing many times.

CDN network is organized in two layers:

CDN distribution is split in two methods:

1. on-line – is the same as multicast, all recipients get the same data at same time.

Good example is sport match, when every customer wants to see the match with minimal delay (acceptable value is tens of seconds).

2. off-line – information which generation has started and ended in the past. Off-line distribution can be split in two types of delivery methods: download, streaming.

Example can be well known video stream (YouTube) or distribution of updates.

CDN Architecture