# Ensure service reliability (/en/api-reference/api-ref/rtc/ensure-service-reliability)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

To ensure high availability of REST services, Agora enables you to switch domain names when you experience service outage due to regional network failures.

## Switch the domain name [#switch-the-domain-name]

1. Set the primary domain name based on the location of your service server:

   * If the DNS address of the service server is located outside mainland China, set the primary domain name to `api.agora.io`.
   * If the DNS address of the service server is in mainland China, set the primary domain name to `api.sd-rtn.com`.

2. If your attempt to initiate a REST API request using the primary domain fails, use the following retry strategy:

   * **Primary domain retry**: Retry using the same primary domain name.
   * **Alternate domain retry**: If the current primary domain name is `api.sd-rtn.com`, use `api.agora.io` as the alternate domain name. If the current primary domain name is `api.agora.io`, use `api.sd-rtn.com` as the alternate domain name.
   * **Adjacent domain retry**: If alternate domain retry fails, retry using a regional domain name adjacent to the current region.

For example, suppose your business server is located in Europe. You set the primary domain name to `api.agora.io`, and the business server resolves the primary domain to Germany. Germany is in Central Europe, corresponding to `api-eu-central-1.agora.io`. The adjacent region is Western Europe, so you can retry using `api-eu-west-1.agora.io` or `api-eu-west-1.sd-rtn.com`.

## Precautions [#precautions]

* To avoid exceeding the QPS limit with retry requests, use a backoff strategy. For example, wait 1 second before the first retry, 3 seconds before the second retry, and 6 seconds before the third retry.
* If the request fails because of a network problem rather than DNS resolution, skip alternate domain retry and proceed to adjacent domain retry.
* Before switching to a regional domain name, make sure the REST service you call, such as Channel Management, is deployed in that region.

## Domain name table [#domain-name-table]

| Primary domain name | Region domain name              | Region                 |
| ------------------- | ------------------------------- | ---------------------- |
| `api.sd-rtn.com`    | `api-us-west-1.sd-rtn.com`      | Western United States  |
| `api.sd-rtn.com`    | `api-us-east-1.sd-rtn.com`      | Eastern United States  |
| `api.sd-rtn.com`    | `api-ap-southeast-1.sd-rtn.com` | Southeast Asia Pacific |
| `api.sd-rtn.com`    | `api-ap-northeast-1.sd-rtn.com` | Northeast Asia Pacific |
| `api.sd-rtn.com`    | `api-eu-west-1.sd-rtn.com`      | Western Europe         |
| `api.sd-rtn.com`    | `api-eu-central-1.sd-rtn.com`   | Central Europe         |
| `api.sd-rtn.com`    | `api-cn-east-1.sd-rtn.com`      | East China             |
| `api.sd-rtn.com`    | `api-cn-north-1.sd-rtn.com`     | North China            |
| `api.agora.io`      | `api-us-west-1.agora.io`        | Western United States  |
| `api.agora.io`      | `api-us-east-1.agora.io`        | Eastern United States  |
| `api.agora.io`      | `api-ap-southeast-1.agora.io`   | Southeast Asia Pacific |
| `api.agora.io`      | `api-ap-northeast-1.agora.io`   | Northeast Asia Pacific |
| `api.agora.io`      | `api-eu-west-1.agora.io`        | Western Europe         |
| `api.agora.io`      | `api-eu-central-1.agora.io`     | Central Europe         |
| `api.agora.io`      | `api-cn-east-1.agora.io`        | East China             |
| `api.agora.io`      | `api-cn-north-1.agora.io`       | North China            |