Traditional DNS resolution randomly selects an IP address to return to the visitor without distinguishing the visitor source. In contrast, intelligent DNS resolution returns IP addresses to visitors by sources. This lets visitors obtain specified IP addresses when accessing websites, reducing resolution latency and improving website access speed.
Function overview
For example, the domain name www.cloud-example.com can be resolved to three IP addresses: China Unicom IP, China Mobile IP, and China Telecom IP, with the goal of implementing nearby resolution.
Intelligent DNS resolution | Traditional DNS resolution | |
Configuration |
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Effect | Cloud DNS determines the source of visitors:
| Traditional DNS resolution does not determine the source of visitors: It returns all three addresses (192.x.x.1, 192.x.x.2, and 192.x.x.3) to the visitor's LocalDNS. The visitor's LocalDNS then returns one of the IP addresses to the visitor through random selection or optimization. Traditional DNS resolution may cause visitors to access across networks. |
How it works
Alibaba Cloud DNS determines the source of visitors by identifying the egress IP address of the LocalDNS (local domain name server's egress IP, not the IP address of the access terminal). There are three specific scenarios:
LocalDNS supports EDNS
Because Alibaba Cloud DNS supports edns-client-subnet, when obtaining the visitor's source IP address, it prioritizes obtaining the IP address carried in the edns-client-subnet extension. If an IP address exists in the edns-client-subnet extension, Alibaba Cloud DNS uses this IP address to determine the visitor's geographic location. If no IP address exists, Alibaba Cloud DNS uses the LocalDNS egress IP address to determine the visitor's geographic location.
LocalDNS does not support EDNS
LocalDNS iteratively queries to Alibaba Cloud DNS, and Alibaba Cloud DNS determines the visitor's location based on the visitor's LocalDNS egress IP address to implement intelligent DNS resolution.
LocalDNS indirectly supports EDNS
When a user enters example.com in a browser, the user sends a query request to the local domain name server. At this point, the LocalDNS sends the request to a secondary node, which then sends a request to Alibaba Cloud DNS. Alibaba Cloud DNS returns specific line resolution results based on the geographic location of the LocalDNS secondary node.
Supported ISPs
Lines have multiple classification levels. You can configure intelligent resolution rules based on major categories or child class line sources.
Line | Primary classification | Secondary classification | Tertiary classification |
Region | China Region, Overseas | Northeast, North China, Asia, Europe, etc. | Beijing |
ISPs | China Mobile, China Unicom, etc. | Northeast, North China, etc. | Beijing |
Providers | Alibaba Cloud | China Region, Overseas | Northeast, North China, etc. |
Search engine | Google, Bing | China Region, Overseas | - |
Custom | Custom classification | - | - |
For more information, see Resolution line enumeration.
Priority
Line priority: Custom line > Search engine > Cloud provider > ISPs > Region > Default.
Within each major category line, more specific lines have higher priority. For example: Beijing > North China > China Region.
The Default line has low priority and is used as a fallback resolution. It is recommended to set a resolution record with the resolution request source as Default to avoid resolution failure when some resolution requests do not match any corresponding "resolution request source" resolution records.
Pricing
The intelligent DNS resolution feature itself does not incur fees, but the services available to each Paid Edition vary.
Enterprise Standard Edition, Enterprise Ultimate Edition: All lines are available. For purchase information, see Instance purchase and domain name binding.
Free Edition: Some primary categories of lines are available, such as the primary classification of Region Lines. Other classifications have usage restrictions.
Configuration by use case
Use case 1: ISP lines
If your domain name www.cloud-example.com is resolved to three IP addresses located in China Telecom, China Unicom, and China Mobile networks, and you want to achieve the following effect:
For visitors from sources other than China Telecom and China Mobile ISPs,
192.168.0.1is returned.For visitors from China Mobile ISP,
192.168.0.2is returned.For visitors from China Telecom ISP,
192.168.0.3is returned.
Procedure
Alibaba Cloud DNS - Public Zone page, click the target domain name to go to Settings.
In Settings, click the Add Record button.
According to the following table, add three resolution records:
Host Record
Record Type
Resolution Request Source
Record Value
www
A
China Mobile
192.168.0.2
www
A
China Telecom
192.168.0.3
www
A
Default
192.168.0.1
Use case 2: Regional lines
If the domain name test.cloud-example.com is resolved to three IP addresses located in Zhejiang, Guangdong, and Beijing, and you want to achieve the following effect:
For visitors from regions other than South China and North China,
192.168.0.7is returned.For visitors from South China region,
192.168.0.8is returned.For visitors from North China region,
192.168.0.9is returned.
Procedure
Alibaba Cloud DNS - Public Zone page, click the target domain name to go to Settings.
In Settings, click the Add Record button.
According to the following table, add three resolution records.
Host Record
Record Type
Resolution Request Source
Record Value
www
A
China Region_South China
192.168.0.8
www
A
China Region_North China
192.168.0.9
www
A
Default
192.168.0.7