This document explains the features of Alibaba Cloud DNS to help you familiarize yourself with this service.
A Distributed Denial of Service (DDoS) attack occurs when servers are maliciously used to send large volumes of domain name resolution requests to targeted DNS servers, thereby flooding the domain with queries that result in the DNS servers crawling, or crashing completely.
Alibaba Cloud DNS uses built-in anti-DDoS protection to defend over 10 million domain names against DDoS attacks. For specific protection capabilities and prices, see the DNS product details page.
TTL (Time to Live) is the time that a record is cached on a local DNS server.
When a local DNS server receives a resolution request, it sends a request to the authoritative DNS server to obtain a resolution record, and caches the record for a period of time. During this period, if more resolution requests are received for the same domain name, the local DNS server directly returns the record instead of sending the requests to the authoritative DNS server.
The minimum TTL, that is, the minimum cached time, is 1 second.
The minimum TTL handles situations where records are frequently modified, or record addresses need to be urgently switched. It helps achieve fast resolution speed and accelerate DNS change propagation, so that you do not have to wait for the TTL to expire.
Subdomains are extensions of your domain name that you can forward to URLs or point to IP addresses instead of purchasing additional domains. Generally, they are used for segmentation or verification of different services associated with a domain name. For example,
a.example.com is a subdomain for
a is the second subdomain name. Alibaba Cloud DNS allows you to set a subdomain to 10 levels deep.
A record limit indicates the maximum number of A records that you can add for the same host and resolution line.
China ISP lines indicate carrier lines in a China-based network environment. To accelerate access speed for China-based Internet carrier users, Alibaba Cloud’s authoritative DNS servers allow you to set different carrier lines (such as default line, China Unicom, China Telecom, China Mobile, or CERNET) based on access sources.
An ISP line is required when you add a record. If you are targeting the China-based market, you can set this line based on your actual needs. The following China-based ISP lines are available:
- China Telecom
- China Unicom
- China Mobile
World lines indicate the subdivided lines used for international business. You can set resolution record based on different access source regions (either by continent or by country).
The following world lines are available:
- Asia, Australia, North America, South America, Europe, and Africa
- Australia, New Zealand, Malaysia, UAE, Thailand, Singapore, Vietnam, Japan, Hong Kong, Taiwan, Macau, Myanmar, Maldives, Nepal, India, Saudi Arabia, South Korea, Philippines, Indonesia, Laos, Cambodia, Mexico, Argentina, Canada, United States, Brazil, Switzerland, Spain, France, Russia, and Sweden.
If your business has international availability requirements, we recommend that you use a world line. If your business only uses one server, you can set a single default line instead of line subdivisions.
Adding a line allows search engine robots to:
- Index, even if your website shuts down.
- Provide an exclusive resolution address for web crawlers (web crawlers may have a certain impact on website access performance).
- Increase the speed and probability of crawlers indexing your website.
After buying an Alibaba Cloud advanced DNS instance, you must associate the instance with a domain name to enable the service. One instance can only be associated with one domain name. However, you can change the domain names for a few times, that is, the number of domain name changes.
Internationally certified BGP data centers serve the advanced DNS service. Nodes are deployed in the following regions: US East, US West, Singapore, Hong Kong, Australia, China Zhangbei, and China Hangzhou.
Note: The Alibaba Cloud advanced DNS and basic DNS belong to different DNS clusters. The advanced DNS uses global data centers, while the data centers for basic DNS are located predominantly in China Shanghai, China Zhangbei, China Shenzhen, and China Hangzhou.