Performance

Delivering from CDN nodes inside mainland China is a separate product and compliance decision, not just a checkbox on a global network map. Confirm current requirements with qualified local counsel and the selected service provider before launch; this page is technical guidance, not legal advice. Start with the delivery region Decide whether the requirement is: edge delivery from nodes inside mainland China; delivery from nearby locations outside the mainland, such as Hong Kong, Japan, or Singapore; or one global configuration that includes the mainland. These designs have different onboarding, performance, feature, contract, and regulatory consequences. For example, Alibaba Cloud’s current CDN documentation distinguishes mainland-only, global, and global-excluding-mainland acceleration regions. It requires an ICP filing for the first two and not for the third. See Alibaba Cloud’s acceleration-region documentation . ...

Multi-CDN and Dynamic Site Acceleration (DSA) are both strategies to make content delivery faster and more reliable. They are often mentioned together, but they tackle different parts of the problem. Multi-CDN chooses between providers, while DSA focuses on optimizing the transport path between the CDN edge and the origin. What DSA Does Dynamic Site Acceleration was introduced in the 2000s as a premium CDN feature. It targets dynamic content that cannot be cached. Instead of improving speed through storage at the edge, DSA makes the path between the edge and the origin faster. ...

Dynamic Site Acceleration, or DSA, is a group of techniques for requests that still need to reach the origin . A CDN edge accepts the client connection, reuses optimized connections toward the origin, and may choose a better measured route. DSA can reduce network and connection delay, but it cannot remove slow application processing. DSA is not an HTTP standard or one uniform product. Providers use different names and combine different controls. Evaluate the documented behavior and measured result, not the label. ...

Using multiple CDNs at once is now a common strategy for large platforms. Known as Multi-CDN , it provides resilience, global reach, and performance tuning beyond what any single provider can guarantee. This article traces the history of Multi-CDN, from early experiments with failover to modern platforms that automate real-time traffic steering across many networks. Early beginnings: redundancy and failover The first Multi-CDN setups in the early 2000s were crude but effective. Enterprises with global audiences, especially in media and finance, sometimes contracted with more than one provider. Typically, they designated a “primary” CDN and configured a “backup” to handle traffic if the main service failed. ...

Content Delivery Networks, or CDNs , are now invisible yet essential infrastructure. They accelerate websites, deliver video, block attacks, and connect billions of users to online services. Their story stretches from the late 1990s, when a few pioneering companies sold premium acceleration to media giants, to today, when free CDN tiers are available to anyone running a blog. This article traces that history, highlighting the technical and commercial shifts that shaped the CDN industry. ...

Multi-CDN is a strategy that uses more than one CDN at the same time. Instead of relying on a single provider, traffic flows through multiple networks and is steered to whichever one works best at that moment. This approach improves reach, resilience, and sometimes cost efficiency. If you are unfamiliar with the basics of CDNs, see the Top 10 Questions About CDNs first. 1. What is a Multi-CDN and how does it differ from a single CDN? A single CDN depends on one provider’s network of points of presence . A Multi-CDN combines the reach of several providers, switching between them based on performance, location, or availability. The result is fewer single points of failure and a smoother experience for global audiences. ...

Content Delivery Networks , or CDNs, keep much of the modern web running smoothly. They are behind faster page loads, fewer outages, and safer browsing experiences. If you have wondered how they work or whether you should use one, here are the ten questions people ask most - with answers in plain language. For more advanced strategies that combine multiple providers, see the Top 10 Questions About Multi-CDN . 1. What is a CDN and how does it work? A CDN is a network of servers in many locations. It stores copies of website content on those servers so they can be delivered from a place closer to the visitor. Instead of every request going back to the main origin server, a CDN routes the visitor to the nearest edge server. The shorter the journey, the faster the response. ...

Caching is one of the simplest ways to improve delivery. A cache saves a copy of a response so it can be served without a round trip to the origin . The core control surface is the Cache-Control header and the time-to-live (TTL ). Freshness and validation determine when a cache can reuse a stored response and when it must contact the origin. Quick answers max-age sets freshness for private and shared caches. s-maxage overrides max-age in a shared cache such as a CDN. It does not change the browser’s freshness lifetime. Vary tells a cache which request headers selected the response. Each meaningful value can create a separate representation. Vary: * prevents normal reuse because the cache cannot prove that a later request is equivalent. no-cache allows storage but requires validation before reuse. no-store prohibits storage. Freshness vs validation A cache serves a response when it is fresh. Freshness comes from an explicit lifetime such as max-age or from an older Expires date. After freshness ends, a cache either revalidates or fetches again. ...

Synopsis Multi-CDN architectures commonly use DNS steering, a layer 7 proxy or aggregator, client-side selection, or a hybrid. Each pattern changes failure behavior, latency, and operational complexity, so the selection must follow the workload and its recovery requirements. DNS-based steering Authoritative DNS answers with records that point to different CDNs based on geography, network, or other criteria. This pattern has low per-request overhead because the routing decision happens before HTTP, but it reacts on the scale of DNS caching. Time to live and resolver behavior affect how quickly changes take effect. Geo and ASN databases must be maintained. Health-driven routing requires either short TTLs or resolver-aware mechanisms that may not be consistent across networks. DNS steering is simple to deploy and scales well, but it is limited in how fast it can respond to sudden failures and it has coarse visibility into per-request signals. ...

Synopsis Traffic steering converts health, performance, policy, and cost signals into routing decisions. Safe operation depends on input quality, explicit precedence, stable failover behavior, and controlled rollout. Inputs and data Effective policies need inputs that reflect user experience and provider health. Synthetic measurements provide controlled and repeatable data but can miss last mile conditions. Real user measurements capture actual paths and networks but require sampling, privacy controls, and careful aggregation. Health signals from providers are useful but should not be trusted without verification. Logs and metrics from the service stack provide the ground truth for outcomes. ...