Static Rules

This section defines security ruleset parameters that apply to your entire Reblaze planet. They are "static" because they are simple settings, and do not vary according to context or circumstance.

The main page for this section has three tabs:

• Timeouts

• Sizing

• Speed & Rate

Each tab is discussed in-depth below.

At the upper right corner of this screen, there is a choice of two different sets of settings: Default and DDoS. Please ignore the DDoS settings: this mode has been deprecated, and will be removed from a future version of the interface. You should only work with the Default settings, since only these settings will be used by Reblaze.

Timeouts

The Timeout settings allow the system to monitor the time required to serve resources to each client. Any connection that exceeds the specific limits will be dropped.

The Timeout settings allow Reblaze to block unresponsive requestors, whether their unresponsiveness is malicious or not. For most Reblaze deployments, the default timeout settings work very well. They are sufficient to filter out hostile traffic, while still accommodating even those users with low bandwidth.

All times are specified in seconds, as shown in the example below.

Sizing

This tab allows you to place limits on the amount of data that users can upload to the system. The defaults usually work well; however, if your application accepts user-generated content or other large files, then changes to these settings might be necessary.

Speed & Rate

This tab allows you to limit the amount of resources consumed by an IP or individual user.

Reblaze can limit consumption by the average number of requests per second (the "IP Requests" and "User Requests" settings), while also allowing temporary bursts at a higher rate ("IP Maximum Burst" and "User Maximum Burst").

Note that this rate limiting is a global metric across all sites. For example, if one IP address is submitting requests to multiple web applications within a Reblaze planet, all the requests are combined when determining if rate limits have been violated.

Here's an example screenshot:

When a requestor exceeds any of these thresholds, subsequent requests will be answered with error code 503 (Service Unavailable).

Average and Burst Rate Limiting

In the Speed & Rate section, the rate limiting settings can be nonintuitive. Here is an explanation of how they work.

IP/User Requests sets the allowable per-second average of incoming requests, enforced on an incremental basis (where "increment" refers to the number of milliseconds allowed for one request). IP/User Maximum Burst sets a higher per-increment ceiling.

Example: IP Requests is set to 100 r/s. Thus, 100 requests are allowed per second. However, the system does not enforce rate limits on a per-second basis; it used a granularity of milliseconds. Therefore, it will allow one request every 10 milliseconds. (100 r/s, divided by 1000 ms/s, equals 1r/10ms.)

Without burst limits—i.e., if IP Maximum Burst is set to zero—the system will reject every request that was received less than 10ms after the previous one.

Now the Reblaze admin sets IP Maximum Burst to 20. This means that Reblaze will accept 21 requests (1 original plus 20 additional) per 10 milliseconds. In other words, when a request is received, up to 20 more can be received and accepted within the following 10 ms. If instead 25 total requests are received during that time, the last four requests will be denied with a 503 error.