Introduction to CDN [backup]

Problem statement

Let’s start by asking a question: If millions of users worldwide use our data-intensive applications, and our service is deployed in a single data center to serve the users’ requests, what possible problems can arise?

Following problems can arise.

1. Latency: The user-perceived latency will be high due to the physical distance from the serving data center. User-perceived latency has many components, such as transmission delays (a function of available bandwidth), propagation delays (a function of distance), queuing delays (a function of network congestion), and nodal processing delays. Thus, data transmission over a large distance results in higher latency. Real-time applications require a latency below 200 milliseconds in general. For VoIP (Voice over Internet Protocol), latency should not be more than 150 ms whereas video streaming applications cannot tolerate a latency above a few seconds.

According to one of the readings on 21-12-2021, the average latency from US East (N. Virginia) to US West (N. California) was 62.9 milliseconds, and across continents, for example, from the US East (N. Virginia) to Africa (Cape Town) was 225.63 milliseconds. Here, latency is two-way, known as round-trip latency.

2. Data-intensive applications: Data-intensive applications require transferring large traffic. Over a longer distance, this could be a problem due to network path stretching through different kinds of ISPs. Because of some smaller Path Message Transmission UnitA path MTU refers to the smallest data unit that can traverse from source to destination without the need for splitting. (MTU) links, the throughput of applications on