Structure representing the DHCP configuration for the network manager.

This structure holds the DHCP configuration parameters for the network manager. It includes the minimum and maximum retry intervals for discovery and request, as well as the maximum number of retries for discovery and request.

Theory Behind the Retry Interval and Total Time Calculation#

When retrying a request (such as DHCP discovery or request), the retry interval increases exponentially, starting from the minimum retry interval (e.g., min_discover_retry_interval or min_request_retry_interval). Each successive retry interval doubles, but it is capped by the maximum retry interval (e.g., max_discover_retry_interval or max_request_retry_interval).

• Retry Interval Formula:

  R_n = min(max_retry_interval, min_retry_interval × 2^(n-1))
  

  Where:

  • R_n: Retry interval for the nth attempt.

  • min_retry_interval: Starting retry interval (e.g., min_discover_retry_interval).

  • max_retry_interval: Upper limit for the retry interval (e.g., max_discover_retry_interval).

  • n: Retry attempt number (1-based index).

As retries progress, the interval continues to double until it reaches the max_retry_interval, after which it remains constant.

• Total Retry Time Formula:

  T_total = sum(R_n) for n = 1 to N_max
  

  Where:

  • T_total: Total retry time.

  • N_max: Maximum number of retries (e.g., max_discover_retries or max_request_retries).

Example#

Given the following configuration:

• min_discover_retry_interval = 5 seconds

• max_discover_retry_interval = 100 seconds

• max_discover_retries = 10

The retry intervals will be: R = [5, 10, 20, 40, 80, 100, 100, 100, 100, 100] Total retry time: T_total = 655 seconds

Reference Implementation#

Below is an example implementation to calculate the total retry time based on the retry parameters:

uint16_t calculateTotalRetryTime(uint16_t min_interval, uint16_t max_interval, uint8_t max_retries) {
    uint16_t total_time = 0, interval = min_interval;
    for (uint8_t i = 1; i <= max_retries; i++) {
        total_time += interval;  // Add the current retry interval to the total time
        interval = (interval * 2 > max_interval) ? max_interval : interval * 2;  // Cap interval at max_interval
    }
    return total_time;
}

// Example usage:
uint16_t total_time = calculateTotalRetryTime(5, 100, 10);
printf("Total Retry Time: %d seconds\n", total_time); // Output: 655 seconds

Note

• • This configuration is not supported for IPv6 in SI91X_INTERNAL_STACK.

  • The retry interval formula and total retry time formula apply to both discovery (min_discover_retry_interval, max_discover_retry_interval, max_discover_retries) and request (min_request_retry_interval, max_request_retry_interval, max_request_retries).

  • The total wait time is the sum of the total discovery retry time and the total request retry time.

  • Moving forward, 'min_discover_retries' member variable will be deprecated. Instead, use the max_discover_retries. This is retained for backward compatibility.