What is Global Traffic Manager 3.0? - Alibaba Cloud DNS - Alibaba Cloud Documentation Center

Global Traffic Manager (GTM) 3.0 is an upgraded version of the GTM service. It provides a graphical interface for configuration orchestration, a rich set of health check templates, and multiple load balancing policies, such as proximity-based, weighted, sequential, and round-robin. GTM 3.0 also lets you combine multiple types of request lines. This service provides enterprises with a flexible and efficient disaster recovery scheduling mechanism for fine-grained and intelligent management of inbound traffic.

Product overview

Global Traffic Manager (GTM) supports proximity-based access, high-concurrency load balancing, health checks, and failover to help enterprises quickly build active zone-redundancy and geo-disaster recovery architectures. GTM also supports the management of both Alibaba Cloud and non-Alibaba Cloud IP addresses. This allows enterprise customers to quickly build disaster recovery architectures for hybrid cloud applications.

GTM is a DNS-level service. It uses DNS to return specific service endpoints to users. Clients then connect to these endpoints directly. Therefore, GTM is not a proxy, a gateway device, or an application access service. GTM does not process or view the network traffic between clients and application services. Click the link to purchase Global Traffic Manager.

After you activate a GTM instance, you must set a CNAME access domain name and then create a CNAME record to map your business domain name to the GTM access domain name. This enables disaster recovery switchovers and intelligent resolution for your application services.

Features

This topic describes the features of Global Traffic Manager.

Feature	Description	References
GTM access domain name	The access domain name of Global Traffic Manager (GTM) is the domain name through which GTM provides services. You typically add a CNAME record that maps your business domain name to the GTM access domain name to integrate your business with GTM. To configure a GTM access domain name, you must have at least one independently hosted root domain or subdomain under your account. For example, `example.com` is a root domain under your account. The GTM access domain name format is `Host Record`.`Root Domain`. Example: `gtm.example.com`. If your domain name is hosted on Alibaba Cloud DNS, you can enter the host record of your business domain name as the host record of the access domain name. In this case, your GTM access domain name is your business domain name.	1. Access domain name configuration
Address pool	An address pool is a GTM feature that manages application service addresses, which can be IP addresses or domain names. An address pool represents a group of IP addresses or domain names that provide the same application service and have the same ISP or regional properties. You can configure multiple address pools for a GTM instance. This allows users in different regions to access different address pools to implement proximity-based access. If an entire address pool becomes unavailable, GTM can perform a switchover to a backup address pool.	2. Address pool configuration
Address	An address is the service endpoint of an application. It is also the response that GTM returns after its parsing and decision-making processes. An address can be an IP address or a domain name. The service port is an important parameter for health checks to detect service availability.	3. Address configuration
Load balancing policy	A load balancing policy is a dynamic resource scheduling mechanism that selects an appropriate address pool for an access domain name and an appropriate address within the address pool based on specific algorithms and policies. The following load balancing methods are supported: Proximity-based: This intelligent resolution feature accurately identifies the source of a request based on the client's geographic location or network ISP. It directs traffic to the service endpoint that is geographically closest to the user or in the same ISP environment to optimize network latency and improve service response speed. Sequential: Address pools or addresses are selected one by one based on a preset sequence to ensure orderly access to available servers. Round-robin: All address pools and addresses are allocated in a round-robin manner to ensure that all available servers receive a relatively even number of access requests, which achieves a balanced load distribution. Specifically, a single address pool is selected from multiple address pools based on the round-robin mechanism, and all addresses in that address pool are returned in a round-robin manner. Weighted: Weight values are set based on the processing capabilities or performance of different servers. Addresses are allocated based on these weight ratios. This allows servers with higher weights to handle more requests, which ensures the efficient utilization of system resources. These flexible load balancing policies enable the efficient distribution and optimal management of inbound network traffic.	To meet the complex scheduling scenarios of enterprises, GTM 3.0 supports two-level access policy scheduling. The logic is as follows: First-level scheduling: An appropriate address pool is selected for the domain name based on a load balancing policy. For more information, see Get started. Second-level scheduling: An appropriate address is selected from the address pool. The address pool selects an available address based on a load balancing policy and returns the address to the client. For more information, see 2. Address pool configuration.
Health check template	The health check mechanism performs real-time probes on the addresses in an address pool to evaluate the operational status and availability of application services. Supported monitoring methods include ICMP ping monitoring, TCP connectivity monitoring, and HTTP or HTTPS endpoint response monitoring. GTM 3.0 provides health check templates that allow you to configure multi-dimensional protocol detection templates to comprehensively assess the availability of application service addresses.	4. Probing templates

How it works

For example, the business domain name of a website is www.example.com.

Add three server IP addresses, 1.1.XX.XX, 2.2.XX.XX, and 3.3.XX.XX, to the GTM address pool and enable health checks.
Configure an access policy as needed.
Activate a GTM instance and complete the basic configuration. A CNAME access domain name is generated based on your configuration. For example: gtm.example.com.
Create a CNAME record to map the business domain name www.example.com to gtm.example.com.

Flowchart

Working principle and flow

An end user's client queries the local recursive DNS system for the application service domain name www.example.com.
If the local recursive DNS system has no cache for www.example.com, it sends a DNS query for this domain name to a root DNS server. The root DNS server responds to the local recursive DNS server with the address of the DNS server for .com based on the domain name's suffix.
After receiving the address of the .com DNS server from the root server, the local recursive DNS server queries the .com DNS server for www.example.com. The .com DNS server then responds with the address of the DNS server for example.com. If the domain name uses Alibaba Cloud DNS, this address points to an Alibaba Cloud DNS server.
After receiving the address of the Alibaba Cloud DNS server from the authoritative DNS server for the .com TLD, the local recursive DNS server queries the Alibaba Cloud DNS server for www.example.com. In response, Alibaba Cloud DNS finds a CNAME record that maps www.example.com to the GTM endpoint gtm.example.com and returns gtm.example.com to the local recursive DNS server.
The local recursive DNS server receives gtm.example.com from Alibaba Cloud DNS and then queries the GTM DNS server for gtm.example.com. GTM receives the request and, based on its preconfigured policies, returns the final IP address of the application service to the local recursive DNS server.
The local recursive DNS server uses the IP address from the last query as the final address for www.example.com. It returns the IP address to the end user and caches it. This allows the local recursive DNS server to directly return the cached result for subsequent queries.
The end user's client receives the IP address from the local recursive DNS server and initiates a direct network connection to the application service.

Service architecture

Description of the service architecture diagram:

The DNS module in the GTM system resolves access requests from end users to the addresses in the application service address pools. For example, users in the Chinese mainland access application services in address pool A, and users outside the Chinese mainland access application services in address pool B. The load balancing policy for both address pools is set to Sequential.
The HealthCheck module in the GTM system performs health checks from multiple regions on the application service addresses in the address pools. These health checks use the ping, TCP, or HTTP/HTTPS method.
If an application service address in address pool A fails a health check, the HealthCheck module detects the failure and notifies the DNS module. The DNS module then temporarily removes the faulty address from the list of available application service addresses. If the HealthCheck module detects that the application service address has become available again, the DNS module restores the address to the list of available application service addresses.

This process ensures that end users are automatically routed to the optimal application service by the GTM system, providing uninterrupted user access.

System architecture

Global Traffic Manager consists of a control layer and a resolution layer:

Control layer: The control layer provides services through the console and OpenAPI. It is used to perform create, retrieve, update, and delete (CRUD) operations and store data, such as DNS records, configurations, monitoring data, and logs. The control layer is located in the China (Zhangjiakou) and China (Hangzhou) regions.
Resolution layer: The resolution layer provides services through globally deployed resolution server clusters. The resolution layer receives DNS record data from the control layer and responds to DNS queries. The resolution layer has nodes deployed on major continents and in key regions across the globe.

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