Cross-border CDN scheduling systems are intelligent mechanisms that optimize content delivery by efficiently routing user requests to the most appropriate edge servers. These systems use advanced algorithms to determine the best server for each request based on multiple factors:
- Geographical proximity to the user (especially considering national/regional borders in cross-border scenarios)
- Current server load and health status
- Cross-border network conditions and performance (including international bandwidth quality)
- Available server resources
- Compliance requirements (data regulation policies in different countries)
The scheduling system acts as the "brain" of the CDN, performing two key functions:
- Intelligent Request Routing: Automatically directs cross-border user requests to the optimal edge server to minimize international latency and ensure fast content delivery.
- Load Distribution: Balances cross-border traffic across multiple servers, preventing international link overloads, maintaining high availability, and providing seamless failover in case of issues.
This intelligent routing and load balancing ensure reliable cross-border content delivery while maximizing network efficiency and maintaining consistent performance for global users.
1. Application of DNS Scheduling in Cross-Border Scenarios
How it works:
DNS scheduling makes cross-border routing decisions based on the egress IP attribution and carrier properties of the client's local DNS. The cross-border scheduling process:
- The client's DNS TTL expires without a first visit, initiating a DNS query to the local DNS.
- During the recursive resolution process, the local DNS initiates a resolution request to the CDN scheduling server.
- The CDN scheduling server can see the local DNS's egress IP (sometimes also the client IP based on EDNS).
- Through the IP library, the geographical and carrier attributes of the previous step's IP are obtained, matching the policy rules of the current scheduling domain. Combined with factors like cross-border quality monitoring and international bandwidth costs, the optimal IP set is determined.
2. Special Value of 302 Scheduling in Cross-Border Scenarios
How it works:
302 scheduling performs redirection based on the client's real IP, making it particularly suitable for scenarios requiring precise cross-border routing. The cross-border scheduling process:
- The user accesses the original URL.
- A 302 response is received, with the Location header containing the precisely assigned cross-border node.
- The browser initiates a request to the specified cross-border node to retrieve content.
3. Unique Advantages of Anycast Routing Scheduling in Cross-Border Scenarios
How it works:
Anycast advertises the same IP address in multiple geographical locations via BGP routing, and the routing system automatically directs users to the closest cross-border node. Characteristics of cross-border Anycast scheduling:
- Uses the same IP globally or regionally (simplifies DNS configuration).
- Automatically selects the optimal cross-border path at the routing layer.
- DNS TTL is usually longer (2 hours+).
Advantages in cross-border scenarios:
- Automatically avoids international link congestion.
- Natural DDoS resistance (attack traffic is dispersed to global nodes).
- Fast failover (routing convergence is usually faster than DNS updates).
For outbound traffic from mainland China, 302 scheduling provides the most precise routing control; for global businesses, Anycast should be prioritized; small and medium-sized enterprises with limited budgets can use DNS scheduling as a foundation. In actual deployment, a hybrid approach combining multiple scheduling methods often yields the best results. For example, Anycast can ensure baseline performance, critical paths can be supplemented with precise 302 scheduling, and DNS can serve as a general fallback option.
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