Many enterprises and individual users will deploy their own servers overseas to meet the diversified needs of cross-border business, global content distribution, international website access, email system construction, scientific research and so on. However, in recent years, frequent disconnection, abnormal delay, high packet loss rate and instability occurred when mainland users visited overseas servers. How to solve this situation has become an important issue that technicians and business managers have to face.
One of the most common reasons for mainland users to access overseas servers is that international export bandwidth resources are limited. China's international export network is mainly managed by several major operators (such as China Telecom, China Unicom, China Mobile), and its international bandwidth resources are not unlimited, especially in the peak period due to the surge in user visits and bottlenecks. When a large number of users access overseas video, cloud services, social media, or do a lot of data synchronization, bandwidth congestion can lead to a decline in access quality, manifested by unstable connections, frequent disconnections, or slow response, and even "no access" in severe cases.
Secondly, the network routing policy between different regions will also affect the stability of the connection. If there is a problem with one of the hop routing nodes, or if the operator adjusts the BGP policy, the connection interruption can occur. In addition, due to the monitoring and content filtering mechanism of some international network communications in the mainland, some abnormal packets may be actively discarded or limited, further aggravating the situation of poor access.
Another factor that cannot be ignored is DNS contamination or resolution failure. There is DNS hijacking or contamination of some domain names in the mainland, especially those involving foreign social platforms, cloud services or content platforms. When a user tries to access an overseas server through a contaminated DNS, they may be redirected to the wrong IP or fail to resolve at all, resulting in a failed connection. Even if the server itself is running properly, users cannot establish a stable connection.
Firewall policy is also an important cause of disconnection. For security reasons, some overseas servers deploy strict firewall rules, such as limiting frequent connection requests from the mainland IP segment, or blocking some common ports (such as SSH, 3389, etc.). Especially in the event of an attack, the server may temporarily shut down certain ports or block large segments of IP to protect itself, resulting in an otherwise normal connection being interrupted.
Some of the disconnections may also come from the domestic network environment itself. If the quality of the network where the client is located is poor, such as the use of shared bandwidth, inferior broadband equipment, ARP attacks, LAN congestion, or unstable WiFi at home, it will also affect the stability of overseas access. At the same time, broadband operators in some regions may impose speed limits or restrictions on international traffic, especially during night peaks or when P2P software is used frequently.
In response to the problem of disconnection of mainland access to overseas servers, users are first advised to choose high-quality international lines. Examples include CN2 GIA (China Telecom International Premium Network), CU VIP (China Unicom Preferred Line), and Mobile CMI (International Export), which typically have lower latency, less packet loss, and higher stability. When purchasing a server, you should preferentially select a room or vendor with these lines. Although the price is slightly higher than that of ordinary lines, this stability investment is well worth it for important business.
Second, the network path can be optimized by deploying intelligent transit nodes. Setting up a transit node between the mainland and overseas servers (such as Hong Kong, Taiwan, Japan or Singapore) to quickly forward data to the target server through Intranet transmission or encrypted channels can not only shorten the connection path, but also effectively avoid some intermediate routing bottlenecks and improve the overall access experience. With acceleration protocols (such as BBR, QUIC, and UDP Relay), you can further enhance the anti-jitter capability of the connection.
If DNS pollution exists, you are advised to use a trusted overseas DNS resolution service, such as Google DNS (8.8.8.8) and Cloudflare DNS (1.1.1.1), and configure the router, VPN, or modify the hosts file to avoid the pollution. If necessary, DoH (DNS over HTTPS) or DoT (DNS over TLS) encryption protocols can also be used to ensure the security and accuracy of DNS requests.
From the server side, you are advised to periodically check the port availability, firewall policies, and blacklist Settings of the server to ensure that normal IP connections are not blocked by mistake. At the same time, you are advised to use multi-line access, load balancing, or CDN reverse to reduce the impact of a single node failure on the overall service availability. In addition, in response to attacks or abnormal access, servers should deploy security components with automatic defense and recovery capabilities, such as Fail2Ban, iptables, Cloudflare firewall, etc.
A dedicated line or SD-WAN is also a solution for users with heavy services or extensive impact. By negotiating with operators to rent a stable international export dedicated line, bypass public network congestion, so as to achieve high-quality, high-availability network connections. This mode is mostly used for enterprise-level applications, such as ERP system interconnection, real-time synchronization of overseas databases, and remote working.
Finally, it is recommended that users establish a daily network monitoring mechanism and use tools such as Ping, Traceroute, MTR, Smokeping to regularly detect network status. In case of disconnection or abnormal delay, the source of the problem can be quickly located and emergency measures can be taken. For critical services, it can also be paired with email alerts, SMS notifications or self-recovery scripts to reduce downtime.
It is recommended that you choose stable lines, optimize your network architecture, improve security protection, properly configure clients and servers, and cooperate with scientific monitoring and scheduling strategies, which can ensure the continuity and reliability of cross-border network communication to a large extent.