User access rate limiting among content delivery nodes

1. One or more non-transitory computer readable media having stored thereon program instructions executable by a first content delivery node (CDN) of a content delivery system comprising a plurality of CDNs that caches content for delivery to end users, when executed by the first CDN, direct the first CDN to:

monitor content requests received from at least a first end user for the content cached by the first CDN to detect when the content requests comprise an attack on the first CDN;

responsive to detecting the attack on the first CDN, establish a rate limit in the first CDN on at least the content requests received by the first CDN for the content;

transfer an indication of the attack comprising the rate limit for delivery to at least a second CDN of the content delivery system that caches the content for delivery to the end users, wherein the indication of the attack prompts the second CDN to preemptively apply the rate limit to further content requests received for the content at the second CDN before the further content requests are received at the second CDN;

receive a further indication of the attack comprising a modified rate limit from at least another CDN of the content delivery system that caches the content for delivery to the end users; and

modify the rate limit in the first CDN based at least on the modified rate limit in the further indication of the attack.

2. The one or more non-transitory computer readable media of claim 1 , wherein the attack comprises a denial of service (DoS) attack.

3. The one or more non-transitory computer readable media of claim 1 , having further instructions stored thereon, that when executed by the first CDN, direct the first CDN to:

establish a content request response rate slower than a rate of the content requests for the content to establish the rate limit.

4. The one or more non-transitory computer readable media of claim 1 , having further instructions stored thereon, that when executed by the first CDN, direct the first CDN to:

establish a content request response rate slower than a rate of the content requests only received from the first end user to establish the rate limit.

5. The one or more non-transitory computer readable media of claim 1 , having further instructions stored thereon, that when executed by the first CDN, direct the first CDN to:

withhold response to the content requests received from the first end user to establish the rate limit.

6. The one or more non-transitory computer readable media of claim 1 , having further instructions stored thereon, that when executed by the first CDN, direct the first CDN to:

compare a network address associated with the first end user against a network address included in the further indication of the attack to modify the rate limit in the first CDN.

7. A method of operating a content delivery system comprising a plurality of content delivery nodes that caches content for delivery to end users, the method comprising:

in at least one processing device of a first CDN that caches the content for delivery to the end users, monitoring content requests received from at least a first end user for the content at the first CDN to determine when the content requests comprise an attack on the first CDN;

responsive to the attack on the first CDN, in the at least one processing device of the first CDN, establishing a rate limit in the first CDN on at least the content requests for the content received by the first CDN and transferring an indication of the attack comprising the rate limit for delivery to at least a second CDN that caches the content for delivery to the end users;

responsive to the indication of the attack received by the second CDN, in at least one processing device of the second CDN, preemptively applying the rate limit for further content requests received for the content at the second CDN before the further content requests are received at the second CDN, and transferring the indication of the attack for delivery to at least one further CDN that caches the content for delivery to the end users.

8. The method of claim 7 , wherein the attack comprises a denial of service (DoS) attack.

9. The method of claim 7 , wherein establishing the rate limit comprises establishing a content request response rate slower than a rate of the content requests for the content.

10. The method of claim 7 , wherein establishing the rate limit comprises establishing a content request response rate slower than a rate of the content requests only received from the first end user.

11. The method of claim 7 , wherein establishing the rate limit comprises withholding response to the content requests received from the first end user.

12. The method of claim 7 , further comprising:

in the first CDN, receiving a further indication of the attack transferred by the second CDN which includes a second network address of the end user different than a first network address of the end user included in the indication of the attack, and modifying the rate limit in the first CDN based at least on the second network address of the end user.

13. A content delivery system with one or more content delivery nodes (CDN) that caches content for delivery to end users, the content delivery system comprising:

at least one processing device of a first CDN that caches the content for delivery to the end users configured to monitor content requests received from at least a first end user for the content to determine when the content requests comprise an attack on the first CDN;

responsive to the attack on the first CDN, the at least one processing device of the first CDN configured to establish a rate limit on at least the content requests received for the content by the first CDN and transfer an indication of the attack comprising the rate limit for delivery to at least a second CDN that caches the content for delivery to the end users;

responsive to the indication of the attack received by the second CDN, at least one processing device of the second CDN configured to preemptively apply in the second CDN the rate limit for further content requests received for the content at the second CDN before the further content requests are received at the second CDN, and transfer the indication of the attack for delivery to at least one further CDN that caches the content for delivery to the end users.

14. The content delivery system of claim 13 , comprising:

the first CDN configured to establish a content request response rate slower than a rate of the content requests for the content to establish the rate limit.

15. The content delivery system of claim 13 , comprising:

the first CDN configured to establish a content request response rate slower than a rate of the content requests only received from the first end user to establish the rate limit.

16. The content delivery system of claim 13 , comprising:

the first CDN configured to withhold response to the content requests received from the first end user to establish the rate limit.

17. The content delivery system of claim 13 , comprising:

the first CDN configured to receive a further indication of the attack transferred by the second CDN which includes a second network address of the end user different than a first network address of the end user included in the indication of the attack, and modify the rate limit in the first CDN based at least on the second network address of the end user.