This topic describes the major performance indicators that are used to evaluate the performance of content delivery before and after a website is accelerated by Alibaba Cloud CDN.
You can make informed business decisions based on the performance indicators. Performance indicators include:
Common performance indicators
You can monitor the following performance indicators to evaluate the performance of content delivery before and after your website is accelerated by Alibaba Cloud CDN. Common performance indicators include but are not limited to the ones described in this topic.
After a website is accelerated by Alibaba Cloud CDN, the network latency, packet loss rate, and back-to-origin rate are typically reduced, and the cache hit ratio is increased. However, the actual performance may vary based on the business scenario and workload type. The performance indicators that are described in this topic are based on pure statistics.
The back-to-origin rate and cache hit ratio that are described in the following table are used to evaluate the performance of content delivery for a website after it is accelerated by Alibaba Cloud CDN. If your website is not accelerated by Alibaba Cloud CDN, the back-to-origin rate is 100%, and the cache hit ratio is 0.
How content is delivered to a client
How content is downloaded by a client
Performance indicator | Description |
DNS time | The amount of time required for a client to initiate a request and receive the IP address of the destination host. |
TCP time | The amount of time required for a client to establish a TCP connection to the destination server. |
SSL time | The amount of time required for a client to establish an SSL connection to a web server. |
Delivery time | The amount of time required for a client to complete sending a request after SSL handshakes are completed. |
Connection time | If a POP uses HTTP to accelerate content delivery, the connection time consists of the DNS time and TCP time. If a POP uses HTTPS to accelerate content delivery, the connection time consists of the DNS time, TCP time, and SSL time. The connection time shows the coverage of POPs and the capabilities of the POPs to deliver content. |
Response Time | The amount of time required for a web server to process an HTTP request and return a response to a client. |
Download time | The amount of time required for a client to receive and download the first packet returned from a web server. |
Time to first packet | The amount of time required for a client to send a request and receive the first HTTP packet from a server. The time to first packet shows the overall performance of POPs. For content uploading and downloading, the time to first packet consists of the DNS time, TCP time, SSL time, request time, and response time. Note A new domain name may require a longer period of time for DNS resolution than other domain names. However, this does not affect the cache retrieval time. |
Overall performance | The amount of time required to upload or download an entire file. |
Packet loss rate | The rate of lost packets to total packets during transmission. |
Back-to-origin rate | The back-to-origin rate is classified into two: back-to-origin request rate and back-to-origin data transfer rate.
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Cache hit ratio | The cache hit ratio of Alibaba Cloud CDN is classified into the byte cache hit ratio and request cache hit ratio. The cache hit ratio of Alibaba Cloud CDN is represented by the byte cache hit ratio. A higher cache hit ratio indicates a higher performance.
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Performance indicators for small file distribution
Small files refer to HTML, JavaScript, JPG, and CSS files. The delivery of these types of files is latency-sensitive. Lower latency indicates higher performance. The latency is determined by the following factors:
Time to first packet (most critical factor)
Connection time
Download time
Alibaba Cloud CDN provides common scenarios that small file distribution is suitable for. For more information, see Image and small file distribution.
Performance indicators for large file distribution
Large files refer to files that are larger than 20 MB. The key indicators for large file distribution include:
Download rate
Download time
Alibaba Cloud CDN provides common scenarios that large file distribution is suitable for. For more information, see Large file distribution.
Performance indicators for on-demand video and audio streaming
On-demand audio and video streaming uses FLV, MP4, WMV, and MKV files. The key indicators for on-demand video and audio streaming include:
Initial load time
The amount of time required to complete loading the first frame of a stream. The initial load time is determined by the DNS time, connection time, and time to first packet. A shorter initial load time indicates higher performance.
Stalling rate
Stalling events may occur when a video or audio stream is played or a resource is loaded. The stalling rate is calculated by using the following formula: Number of viewers that have stalling events/100. A lower stalling rate indicates better performance.
Alibaba Cloud CDN provides common scenarios that on-demand video and audio streaming is suitable for. For more information, see On-demand audio and video streaming.