This topic describes Alibaba Cloud Network Time Protocol (NTP) servers. Alibaba Cloud provides internal and public NTP servers to synchronize the local time of Elastic Compute Service (ECS) instances in networks.
Internal and public NTP servers
NTP is used to synchronize computer time in a network.
The consistency of time and time zones in ECS is crucial because it can affect task execution results. For example, when you update a database or analyze logs, the time sequence significantly impacts the results. When you run business on ECS instances, you must standardize the time zones of all involved instances to prevent issues such as logical confusions and network request errors. You can use NTP servers to synchronize the local time of all your ECS instances in a network.
ECS provides high-precision NTP servers for your use. The ntp.cloud.aliyuncs.com server offers a distributed NTP service that uses Stratum 1 servers. Stratum 1 servers are suitable for industries that require precise timing, such as finance, communication, scientific research, and astronomy. The NTP service is also used to synchronize the local time between ECS instances and other cloud services. The following table describes the domain names of Alibaba Cloud NTP servers in various networks. These domain names support only IPv4.
| Classic network (internal network) | Virtual private cloud (VPC) (internal network) | Internet |
|---|---|---|
| - | ntp.cloud.aliyuncs.com | ntp.aliyun.com |
| ntp1.cloud.aliyuncs.com | ntp7.cloud.aliyuncs.com | ntp1.aliyun.com |
| ntp2.cloud.aliyuncs.com | ntp8.cloud.aliyuncs.com | ntp2.aliyun.com |
| ntp3.cloud.aliyuncs.com | ntp9.cloud.aliyuncs.com | ntp3.aliyun.com |
| ntp4.cloud.aliyuncs.com | ntp10.cloud.aliyuncs.com | ntp4.aliyun.com |
| ntp5.cloud.aliyuncs.com | ntp11.cloud.aliyuncs.com | ntp5.aliyun.com |
| ntp6.cloud.aliyuncs.com | ntp12.cloud.aliyuncs.com | ntp6.aliyun.com |
| - | - | ntp7.aliyun.com |
Other public services
The following table describes other public services provided by Alibaba Cloud.
| Public service | Description |
|---|---|
| Public Domain Name System (DNS): 223.5.5.5/223.6.6.6 | Alibaba Cloud Public DNS Free Edition: https://www.alidns.com |
Website of public images: https://developer.aliyun.com/mirror | Update frequency: Images are updated from 02:00 to 04:00 every day (UTC+8). The images contain a wide collection of Linux distributions and open source software. |