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What Is Smart DNS?

Smart DNS is an intelligent domain name resolution technology that dynamically returns an IP address corresponding to the visitor's information such as the carrier and geographical location, so as to increase the website access speed and improve user experience. For example, when a China Unicom (CU) user and a China Telecom (CT) user access the same domain name, the CU IP address is returned to the CU user, while the CT IP address is returned to the CT user. In this way, inter-carrier network access is avoided.
In addition, the smart DNS technology can be used in scenarios such as load balancing, quality of service (QoS) guarantee, anti-DDoS, and content delivery network (CDN) acceleration to provide customer sites with stable, secure, and fast domain name resolution services.

Why Do We Need Smart DNS?

The external application server of an enterprise generally has IP addresses of multiple carriers. When a user accesses an enterprise application website, traditional DNS resolution returns a random IP address to the user. If a CU user obtains the CT IP address, which is referred to as inter-carrier network access, access latency increases and user access experience is affected.

In addition, enterprises deploy application servers in different regions around the world to carry out global business. They expect users in different regions to access their nearest application servers, so as to reduce access latency.

This is where smart DNS comes in. The most basic function of smart DNS is to identify users based on their sources and geographical locations, resolve a domain name into different IP addresses, and return the IP addresses to corresponding users. CT users obtain the CT IP address, CU users obtain the CU IP address, and users outside China obtain the IP addresses of their local servers. In this case, every user can quickly access enterprise application websites regardless of their sources, which improves user access experience.

Advantages of Smart DNS

Smart DNS can intelligently resolve domain names to improve network access experience. The advantages are as follows:

Unified domain name management

Enterprise application websites provide users with a unified domain name, so that enterprises do not need to apply for different domain names even if users in different regions need to access different servers. Smart DNS enables users in different regions to access servers in the corresponding regions with different IP addresses.

Load balancing

Through smart DNS resolution, flow distribution can be performed by establishing multiple mirror websites or deploying the website content on several servers, thus reducing the load on servers and shortening website response time.

CDN acceleration

As one of the core technologies of CDN, smart DNS can direct users' access requests to the nearest website content cache servers based on user sources to shorten website response time.

Attack defense

Smart DNS integrates a host of security functions such as DDoS attack mitigation and malicious domain name filtering to enhance the security of domain name resolution.

Health check and line scheduling

Smart DNS periodically performs health check on lines and servers. Once an exception is detected, user traffic is automatically switched to a low-latency line or a healthy server.

How Does Smart DNS Work?

Simply put, the smart DNS system sets different domain name records for different user groups. When users access a website, the system identifies their sources and returns the corresponding IP address to them.

The following uses the website for which a dual-carrier line is available as an example to illustrate the working mechanism of smart DNS.

  1. When CU users attempt to access the website, they send domain name resolution requests to the locally-configured DNS server first.
  2. The DNS server forwards the domain name resolution requests to the smart DNS system, which is also called the DNS delegation.
  3. The smart DNS system detects that the DNS domain name resolution requests are from CU users. It then queries domain name records, and returns the CU IP address 198.51.100.12 to CU users.
  4. CU users access the website using this IP address, which avoids inter-carrier network access.
Working mechanism of smart DNS
Working mechanism of smart DNS

Smart DNS of Huawei Firewalls

Huawei firewalls provide smart DNS services for enterprises. Specifically, the firewall modifies the Answers field in a domain name resolution response packet, and returns the public IP address of the carrier to the corresponding users.

A web server is deployed on the enterprise intranet to provide services for Internet users. The web server has obtained two public IP addresses 198.51.100.12 and 192.0.2.11 from CU and CT, respectively. These two public IP addresses are added in the domain name records of the DNS server on the enterprise intranet, and the DNS delegation is complete on the DNS server on the public network. Without smart DNS, however, Internet users will obtain a random public IP address from a domain name resolution response packet. The obtained IP address may not be that of the carrier to which these users belong.

On a firewall, smart DNS first establishes a smart DNS mapping table based on the interfaces and the public IP addresses of the servers on the lines connected to the interfaces. When a domain name resolution response packet from the DNS server on the intranet passes through the firewall, the firewall matches the outbound interface of the packet against the smart DNS mapping table to find the IP address that matches the outbound interface, and replaces the IP address in the Answers field of the packet with the IP address in the mapping table.

An example is as follows: Interface 1 is the outbound interface of a domain name resolution response packet from the DNS server on the intranet. When CU users access the web server, the IP address in the Answers field of the packet may be the randomly returned CT IP address 192.0.2.11. However, through smart DNS, the firewall matches the packet against the interface 1 entry in the smart DNS mapping table, and modifies the IP address in the Answers field to the CU IP address 198.51.100.12. This ensures that no inter-carrier network access occurs.

Smart DNS of Huawei firewalls
Smart DNS of Huawei firewalls

For more information about products, visit Huawei AI firewalls. For details about smart DNS configuration and maintenance, see Smart DNS (Inbound Link Selection).

About This Topic
  • Author: Liu Shui, Chen Xiaoyun
  • Updated on: 2024-09-11
  • Views: 953
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