This topic describes the major performance indicators that are used to evaluate the performance of content delivery before and after a website is connected to Alibaba Cloud Content Delivery Network (CDN). This topic also describes the benefits of Alibaba Cloud CDN.

Alibaba Cloud CDN can reduce workloads on origin servers and accelerate content delivery. You can use common and scenario-specific performance indicators to evaluate the content delivery performance. You can learn how Alibaba Cloud CDN accelerates content delivery and how it is applied to your services by referencing these indicators. This helps you make adjustments and business decisions.

Common performance indicators

You can use the following indicators to measure the performance of your website before and after the website is connected to Alibaba Cloud CDN. The indicators include but are not limited to:
  • Latency: the total amount of time it takes for a server to receive a request from a client and then return a response to the client. Lower latency indicates higher performance.
  • Download speed: the data transfer rate when users download data from the Internet or web servers. A faster download speed indicates higher performance.
  • Website content loading speed: the time it takes to load a web page. A faster loading speed indicates higher performance.
  • Packet loss rate: the ratio of lost packets to total packets during data transmission.
  • Back-to-origin rate: includes the back-to-origin request rate and back-to-origin data transfer ratio.
    • Back-to-origin request rate: the ratio of requests redirected back to the origin server to total requests. Edge nodes redirect requests back to the origin server when the requested content is not found, has expired, or cannot be cached. A lower rate indicates higher performance.
    • Back-to-origin data transfer ratio: the ratio of the amount of back-to-origin data (the amount of requested data and the amount of data generated by the request redirected back to the origin server) to the total amount of request data. The following formula is used to calculate this ratio: Back-to-origin data transfer ratio = Amount of back-to-origin data/(Amount of back-to-origin data + Amount of data generated by the request initiated from the client). The lower the rate, the higher the performance.
  • Cache hit ratio: the ratio of cache hits to total requests. A cache hit occurs if a user requests data from an edge node and the edge node has cached the requested data. A higher cache hit ratio indicates higher performance.
Note The back-to-origin rate and cache hit ratio are indicators used to measure the performance of your website after the website is connected to Alibaba Cloud CDN. If your website is not connected to Alibaba Cloud CDN, the back-to-origin request rate is 100% and the cache hit ratio is 0.
Typically, after your website is connected to Alibaba Cloud CDN, the network latency, packet loss rate, and back-to-origin data transfer ratio are reduced. The download speed, website content loading speed, and cache hit ratio are increased. The actual performance of the content delivery acceleration service provided by Alibaba Cloud CDN may vary based on the scenario and workload type. Therefore, we provide these common indicators for you to measure the performance of your website.
Alibaba Cloud CDN also provides multiple scenario-specific performance indicators. You can use the following indicators to measure the performance of your website in a specific scenario:

Scenario-specific performance metrics: Small files acceleration

Small files refer to HTML, JavaScript, JPG, and CSS web content. The delivery of these types of content requires extremely low latency. High latency causes websites to load slowly and makes it difficult to retain users. This may cause losses in sales.

The indicators that are used to measure the content loading latency include connection time, time to first byte (TTFB), and download time. Among these indicators, TTFB is the core indicator.
  • Connection time: the amount of time that it takes to establish a TCP connection to the resolved IP address. The connection time can help you check the number of available CDN nodes and their capabilities for content delivery.
  • TTFB: the total amount of time that it takes for a server to receive the first request sent from a client and then return a response to the client. This indicator is used to measure the overall performance of the CDN nodes.
    • For content uploading, TTFB includes the DNS resolution time, TCP connection time, SSL handshake time, request delivery time, and response reception time.Upload content
    • For content downloading, TTFB includes DNS resolution time, TCP connection time, SSL handshake time, request delivery time, response reception time, and download time.Download content
    Note A newly purchased domain may require a longer time than other domains in DNS resolution. This is irrelevant to the cache retrieval time.

Alibaba Cloud CDN provides a configuration guide for accelerating the delivery of small files. For more information, see Image and small file distribution.

Large file acceleration

A large file is a file that is larger than 20 MB. The download speed and total download time are the core indicators used to measure the performance of large file downloading.

Alibaba Cloud CDN provides a configuration guide for accelerating large file downloading. For more information, see Downloads of large files.

VOD services

The types of media file used in video on-demand (VOD) services include FLV, MP4, WMV, and MKV files. The initial loading time and stalling rate are the core indicators used to measure the performance of VOD services.
  • Initial loading time: the total amount of time that it takes to complete loading the first frame of a stream. The DNS resolution time, connection time, and TTFB all have impacts on the initial loading time.
  • Stalling rate: stalling events may occur when a video or audio stream is played or a resource is loaded. The stalling rate refers to the rate of viewers that have stalling events among every 100 viewers. A lower stalling rate indicates higher performance.

Alibaba Cloud CDN provides a configuration guide for accelerating VOD services. For more information, see ApsaraVideo for VOD.

Live streaming services

Same as VOD services, the core indicators used to measure the performance of live streaming services are the initial loading time and stalling rate. For more information, see What is ApsaraVideo Live.

Benefits of Alibaba Cloud CDN

Alibaba Cloud CDN has more than 2,800 nodes deployed across the world. The throughput of the entire content delivery network is up to 130 Tbit/s. Alibaba Cloud CDN is fast, stable, cost-effective, and easy-to-use. For more information, see Benefits.