Dynamic Route for CDN (DCDN) charges the basic services by using the pay-by-traffic or pay-by-bandwidth billing method. This topic describes how to select a billing method based on your actual business needs.
When you activate Alibaba Cloud DCDN, you can select the pay-by-bandwidth or pay-by-traffic billing method for the basic services. For more information about pricing, see DCDN Pricing.
|Pay-by-bandwidth||The basic services of DCDN are billed based on the daily peak bandwidth. A bandwidth value is calculated at intervals of 5 minutes. A total of 288 values can be obtained each day. The maximum value is the daily peak bandwidth.||The DCDN traffic curve is relatively flat, and the daily bandwidth usage exceeds 30%.|
|Pay-by-traffic||The basic services of DCDN are billed based on the amount of daily outbound data from DCDN nodes.||Large fluctuations and bandwidth spikes exist in the DCDN traffic curve. The daily bandwidth usage is less than 30%.|
- Consumption of TCP and IP packet headers
HTTP requests are transmitted based on the TCP/IP protocol stack. The maximum transmission unit (MTU) over the Internet is 1,500 bytes, of which the TCP and IP headers occupy 40 bytes. The headers are inserted into each packet by the system kernel based on the underlying protocols in the TCP/IP protocol stack. The data transfer for the headers is not captured at the application layer, and is not reflected in the logs. This leads to an estimated 3% of outbound data that is untracked. This estimate is based on the following calculation: 40/(1,500 - 40) = 2.74%
- TCP retransmission
Depending on the physical network conditions of the Internet, about 3% to 10% of packets may be lost during transmission. These discarded packets will be retransmitted by the system kernel based on the underlying protocols in the TCP/IP protocol stack. The data transfer for packet retransmission is not captured at the application layer. The proportion that the data used for retransmission is of the data recorded in the logs varies, depending on the network conditions. For example, the proportion is lower at off-peak hours in the morning than that at peak hours in the evening. In most cases, the proportion is from 3% to 7%.
Therefore, as an industry standard practice, an excess of 7% to 15% of data usage is added to the total billable data. An average of 10% is used for DCDN.