Which is the best DDoS protection solution for a big ISP for monitoring and mitigating?

For L3 /4, I'd look to Akamai Prolexic or Equinix.For L7, I'd need more information to give a proper recommendation.

While there are many DDOS protection solutions available, some of them clearly take the industry lead. In my opinion, some of the best DDOS protection products include the following: Arbor DDoS: Arbor’s suite of visibility, DDoS protection, and advanced threat solutions provide customers with a micro view of their network enhanced by a macro view of global internet traffic and emerging threats through their ATLAS infrastructure. Arbor DDoS is easy to use, provides effective blocking of DDoS attacks, and can be used for DNS, web, and main servers. Additionally, this solution is far easier to operate than other solutions, such as Fortinet DDoS. Arbor DDoS can also be used for traffic analysis and capacity planning as well. I think the biggest advantage that this solution offers is that you can automatically identify and stop all types of DDoS attacks and other cyber threats before they impact the availability of business-critical services, which is crucial for any organization. Imperva Incapsula: I think Imperva Incapsula is a close second to Arbor DDoS. For starters, it protects websites and safeguards web applications and their data from attacks and improves their performance by enhancing user experience. What makes it powerful is that it includes a security platform with a web application firewall, DDoS mitigation, content delivery network, and global load balancer to maximize performance. Some of its most useful features are that it protects against broken authentication and it has remote execution of code. In addition, there is no need to have an appliance in house for the services because it is on the cloud. It also has a unique interface for managing security performance. Furthermore, It is stable, scalable, quick, and easy to use. CloudFlare: CloudFlare is also a really good DDoS protection option. It is different from the alternatives listed above because it protects and accelerates any Internet application online without adding hardware, installing software, or changing a line of code. Internet properties powered by Cloudflare have all web traffic routed through its intelligent global network, which gets smarter with each new site added. As a result, performance improves and the number of spam and other attacks rapidly decreases. CloudFlare is robust, secure, and innovative. It is also easy to manage, with a good web application firewall. In my opinion, CloudFlare is an intuitive solution that's great for small businesses. Another thing I like about CloudFlare is that you can choose to activate the 'I'm under attack' mode, which can protect against even the most sophisticated of DDoS attacks by presenting a Javascript challenge. Radware DefensePro: Last but not least, I would say Radware DefensePro is also a good choice. Specifically, it defends against IoT-based, Burst, DNS and TLS/SSL attacks to secure organizations against emerging network multivector attacks, ransom DDoS campaigns, IoT botnets, phantom floods, and other types of cyberattacks. It does so by leveraging patented behavior-based detection technology that enables organizations to detect attacks in real-time, and also helps minimize false positives. Moreover, the solution has attack signatures that can be generated automatically to accurately protect from zero-day and unknown attacks. Some of the best features it offers include verbose and descriptive reporting, good scalability, and great reliability. In addition, Radware DefensePro offers granular control, and also has a hybrid model approach for those that prefer it.