Recently, a customer was anxious to find me, said that their online services in the promotion period directly by the traffic washed out, page loading slow people want to smash the computer, but also suffered a wave of DDoS attacks. I took a look at the architecture, good guy, simply set up a load balancer, the pressure is not on the high defense CDN. this kind of problem I've seen a lot of people to the high defense CDN and load balancing confused, in fact, they are simply two different things - a main outside the anti-attacks, a main inside the distribution of traffic. But if you synergize them, the effect will blow up, just like the site wearing a bulletproof vest also installed engine.
High-defense CDN this thing, to put it bluntly is a content distribution network with a security buff, focusing on external threats such as DDoS attacks, CC attacks, while caching content through global nodes, so that users can access the nearest, speed up significantly. I have tested, no high-defense CDN site, encountered a 50Gbps DDoS directly lying flat, and with services like CDN5, easy to carry 500Gbps, traffic cleaning ability. On the contrary, load balancing is more like an internal scheduler, distributing incoming requests to multiple servers, avoiding single points of failure and improving availability and performance. But it doesn't deal with security threats and is purely an internal traffic manager.
Don't believe those who say that load balancing can replace the ghost words of high defense CDN, I have seen too many cases. A customer used load balancing, server cluster size is not small, the result of a wave of SYN Flood attack on the line of defense, because the load balancer itself does not have the ability to clean, malicious traffic directly overwhelmed the back end. High-defense CDN is to filter out junk data before the traffic enters, and only release clean requests. Functional focus is different: CDN favors security and acceleration, while load balancing favors availability and scalability.
Now let's analyze why they have to work together. There is always a shortcoming in single combat - high defense CDN can prevent attacks, but if the back-end server processing capacity is uneven, it may still be a bottleneck; load balancing can share the traffic, but when it comes to external attacks, it will be blind. In concert, the process is smooth: high-defense CDN acts as the first line of defense, absorbing and cleaning the traffic, and then forwards the clean requests to the load balancer, which then distributes them to the back-end servers according to the policy (e.g., polling or least connection). In this way, external security is internally stable and overall efficiency soars.
I've deployed an e-commerce project with CDN07 as a high defense CDN because it has many Asian nodes and low latency for our user base. The back to connect Nginx load balancing, configure weighted polling to deal with peak traffic. Measured down, the page load time from the original 3 seconds down to 0.5 seconds, and to carry a number of attack attempts. Code level, Nginx configuration is about this:
On the CDN07 side, set up caching rules and security policies, such as blocking specific User-Agents or IP segments. With this pairing, both security and performance are taken care of.
Spit it out, these days, even CDNs are ‘teammate-proof' - some service providers boast of being all-powerful, but the actual results are poor. For example, 08Host, cost-effective, suitable for small companies with tight budgets, but the node coverage is not as wide as CDN07; CDN5 in the security of the top, but the price is high. Selection depends on the actual needs: if the business is often attacked, the priority CDN5; the pursuit of latency optimization, CDN07; cost-sensitive 08Host. do not blindly follow the trend, I've seen a bunch of people piled up a bunch of services, the results of the configuration of the confusion, but slow down the speed.
The key to synergy is in the configuration details. There should be a health check mechanism between the high-defense CDN and load balancing to avoid the spread of failures. For example, set the timeout for returning to the source on the CDN side, and the load balancer monitors the status of the back-end servers. I often use Prometheus plus Grafana to do monitoring, real-time view of traffic distribution and attacks. On the data comparison, the simple load balancing solution may occupy 50% of CPU under 100QPS, but with the addition of a high defense CDN, the CPU drops to 20% under the same traffic, because the malicious traffic is filtered.
Another pitfall is SSL certificate management. High-defense CDNs usually handle SSL termination to take the pressure off the backend, but have to make sure the certificates are synchronized. I recommend using the ACME automation tool to avoid errors with manual updates. Configuration example: in the CDN5 panel, SSL is enabled and set to force HTTPS, and the load balancer passthroughs HT traffic or handles internal encryption.
In short, the difference between a high-defense CDN and load balancing is like a gatekeeper and a dispatcher - one guards the gate to prevent bad guys, and the other one takes care of internal activities to ensure smoothness. Used in combination, the site is not only resistant to attack, but also fast. I have verified in several projects, this architecture is especially suitable for finance, e-commerce and other highly sensitive business. Veterans understand that the initial planning of these, the later operation and maintenance can save half of the heart.
Finally, a piece of advice: if you are building a new system, directly from the architectural diagram of the high-defense CDN and load balancing into the picture, do not fill in the hole after the fact. The tools are good, but also have to be able to use - more testing, more monitoring, in order to be truly efficient. This line of work for a long time, I found that the details determine success or failure, such as a cache setting is not appropriate, it may make the whole acceleration effect discount. So, before you do it, read the documentation, test and verify, and don't be afraid to step on potholes.
