diff --git a/src/modules/async/README b/src/modules/async/README
index 2e8357b52d3..079b77e694c 100644
--- a/src/modules/async/README
+++ b/src/modules/async/README
@@ -26,20 +26,26 @@ Daniel-Constantin Mierla
         3. Parameters
 
               3.1. workers (int)
+              3.2. ms_timer (int)
 
         4. Functions
 
               4.1. async_route(routename, seconds)
-              4.2. async_sleep(seconds)
-              4.3. async_task_route(routename)
+              4.2. async_ms_route(routename, milliseconds)
+              4.3. async_sleep(seconds)
+              4.4. async_ms_sleep(milliseconds)
+              4.5. async_task_route(routename)
 
    List of Examples
 
    1.1. Set workers parameter
-   1.2. async_route usage
-   1.3. async_sleep usage
-   1.4. async_workers usage
-   1.5. async_task_route usage
+   1.2. Set ms_timer parameter
+   1.3. async_route usage
+   1.4. async_ms_route usage
+   1.5. async_sleep usage
+   1.6. async_ms_sleep usage
+   1.7. async_workers usage
+   1.8. async_task_route usage
 
 Chapter 1. Admin Guide
 
@@ -54,12 +60,15 @@ Chapter 1. Admin Guide
    3. Parameters
 
         3.1. workers (int)
+        3.2. ms_timer (int)
 
    4. Functions
 
         4.1. async_route(routename, seconds)
-        4.2. async_sleep(seconds)
-        4.3. async_task_route(routename)
+        4.2. async_ms_route(routename, milliseconds)
+        4.3. async_sleep(seconds)
+        4.4. async_ms_sleep(milliseconds)
+        4.5. async_task_route(routename)
 
 1. Overview
 
@@ -94,6 +103,7 @@ Chapter 1. Admin Guide
 3. Parameters
 
    3.1. workers (int)
+   3.2. ms_timer (int)
 
 3.1. workers (int)
 
@@ -107,11 +117,27 @@ Chapter 1. Admin Guide
 modparam("async", "workers", 2)
 ...
 
+3.2. ms_timer (int)
+
+   Enables millisecond timer for async_ms_sleep() and async_ms_route()
+   functions. The integer value is the timer resolution in milliseconds.
+   ms_timer = 1 enables 1 millisecond timer but generates higher load on
+   the system. ms_timer = 20 enables 20 ms timer.
+
+   Default value is 0.
+
+   Example 1.2. Set ms_timer parameter
+...
+modparam("async", "ms_timer", 1)
+...
+
 4. Functions
 
    4.1. async_route(routename, seconds)
-   4.2. async_sleep(seconds)
-   4.3. async_task_route(routename)
+   4.2. async_ms_route(routename, milliseconds)
+   4.3. async_sleep(seconds)
+   4.4. async_ms_sleep(milliseconds)
+   4.5. async_task_route(routename)
 
 4.1.  async_route(routename, seconds)
 
@@ -134,7 +160,7 @@ modparam("async", "workers", 2)
 
    This function can be used from REQUEST_ROUTE.
 
-   Example 1.2. async_route usage
+   Example 1.3. async_route usage
 ...
 request_route {
     ...
@@ -147,7 +173,42 @@ route[RESUME] {
 }
 ...
 
-4.2.  async_sleep(seconds)
+4.2.  async_ms_route(routename, milliseconds)
+
+   Simulate a sleep of 'milliseconds' and then continue the processing of
+   the SIP request with the route[routename]. In case of internal errors,
+   the function returns false, otherwise the function exits the execution
+   of the script at that moment (return 0 behaviour). This function works
+   only if the ms_timer parameter has a value greater then 0.
+
+   The routename parameter can be a static string or a dynamic string
+   value with config variables.
+
+   The sleep parameter represent the number of milliseconds to suspend the
+   processing of a SIP request. Maximum value is 30000 (30 sec). The
+   parameter can be a static integer or a variable holding an integer.
+
+   Since the SIP request handling is resumed in another process, the
+   config file execution state is practically lost. Therefore beware that
+   the execution of config after resume will end once the route[routename]
+   is finished.
+
+   This function can be used from REQUEST_ROUTE.
+
+   Example 1.4. async_ms_route usage
+...
+request_route {
+    ...
+    async_ms_route("RESUME", "250");
+    ...
+}
+route[RESUME] {
+   send_reply("404", "Not found");
+   exit;
+}
+...
+
+4.3.  async_sleep(seconds)
 
    Simulate a sleep of 'seconds' and then continue the processing of SIP
    request with the next action. In case of internal errors, the function
@@ -159,14 +220,49 @@ route[RESUME] {
 
    This function can be used from REQUEST_ROUTE.
 
-   Example 1.3. async_sleep usage
+   Example 1.5. async_sleep usage
 ...
 async_sleep("4");
 send_reply("404", "Not found");
 exit;
 ...
 
-4.3.  async_task_route(routename)
+4.4.  async_ms_sleep(milliseconds)
+
+   Simulate a sleep of 'milliseconds' and then continue the processing of
+   SIP request with the next action. In case of internal errors, the
+   function returns false. This function works only if the ms_timer
+   parameter has a value greater then 0.
+
+   The sleep parameter represent the number of milliseconds to suspend the
+   processing of SIP request. Maximum value is 30000 (30 sec). The
+   parameter can be a static integer or a variable holding an integer.
+
+   This function can be used from REQUEST_ROUTE.
+
+   Example 1.6. async_ms_sleep usage
+...
+route[REQUESTSHAPER] {
+        $var(res) = http_connect("leakybucket",
+                                 "/add?key=$fd", $null, $null,"$avp(delay)");
+        $var(d) = $(avp(delay){s.int});
+        if ($var(d) > 0) {
+                # Delay the request by $avp(delay) ms
+                async_ms_sleep("$var(d)");
+                if (!t_relay()) {
+                        sl_reply_error();
+                }
+                exit;
+        }
+        # No delay
+        if (!t_relay()) {
+                sl_reply_error();
+        }
+        exit;
+}
+...
+
+4.5.  async_task_route(routename)
 
    Continue the processing of the SIP request with the route[routename] in
    one of the processes from core asynchronous framework. The core
@@ -178,7 +274,7 @@ exit;
    async_workers core parameter in the configuration file. See the core
    cookbook for more information.
 
-   Example 1.4. async_workers usage
+   Example 1.7. async_workers usage
 ...
 # Enable 8 worker processes used by async and other modules
 async_workers=8
@@ -198,7 +294,7 @@ async_workers=8
 
    This function can be used from REQUEST_ROUTE.
 
-   Example 1.5. async_task_route usage
+   Example 1.8. async_task_route usage
 ...
 request_route {
     ...