diff --git a/net.c b/net.c
index d9854ec2..1e9bed3a 100644
--- a/net.c
+++ b/net.c
@@ -1,6 +1,6 @@
 /* net.c -- CoAP network interface
  *
- * Copyright (C) 2010--2012 Olaf Bergmann <bergmann@tzi.org>
+ * Copyright (C) 2010--2013 Olaf Bergmann <bergmann@tzi.org>
  *
  * This file is part of the CoAP library libcoap. Please see
  * README for terms of use. 
@@ -87,6 +87,43 @@ int print_wellknown(coap_context_t *, unsigned char *, size_t *, coap_opt_t *);
 void coap_handle_failed_notify(coap_context_t *, const coap_address_t *, 
 			       const str *);
 
+unsigned int
+coap_adjust_basetime(coap_context_t *ctx, coap_tick_t now) {
+  unsigned int result = 0;
+  coap_tick_diff_t delta = now - ctx->sendqueue_basetime;
+
+  if (ctx->sendqueue) {
+    /* delta < 0 means that the new time stamp is before the old. */
+    if (delta <= 0) {
+      ctx->sendqueue->t -= delta;
+    } else {
+      /* This case is more complex: The time must be advanced forward,
+       * thus possibly leading to timed out elements at the queue's
+       * start. For every element that has timed out, its relative
+       * time is set to zero and the result counter is increased. */
+
+      coap_queue_t *q = ctx->sendqueue;
+      coap_tick_t t = 0;
+      while (q && (t + q->t < (coap_tick_t)delta)) {
+	t += q->t;
+	q->t = 0;
+	result++;
+	q = q->next;
+      }
+
+      /* finally adjust the first element that has not expired */
+      if (q) {
+	q->t = (coap_tick_t)delta - t;
+      }
+    }
+  }
+
+  /* adjust basetime */
+  ctx->sendqueue_basetime += delta;
+
+  return result;
+}
+
 int
 coap_insert_node(coap_queue_t **queue, coap_queue_t *node) {
   coap_queue_t *p, *q;
diff --git a/net.h b/net.h
index c0b17899..63290002 100644
--- a/net.h
+++ b/net.h
@@ -1,6 +1,6 @@
 /* net.h -- CoAP network interface
  *
- * Copyright (C) 2010,2011 Olaf Bergmann <bergmann@tzi.org>
+ * Copyright (C) 2010--2013 Olaf Bergmann <bergmann@tzi.org>
  *
  * This file is part of the CoAP library libcoap. Please see
  * README for terms of use. 
@@ -43,9 +43,9 @@ struct coap_queue_t;
 typedef struct coap_queue_t {
   struct coap_queue_t *next;
 
-  coap_tick_t t;	        /* when to send PDU for the next time */
-  unsigned char retransmit_cnt;	/* retransmission counter, will be removed when zero */
-  unsigned int timeout;		/* the randomized timeout value */
+  coap_tick_t t;	        /**< when to send PDU for the next time */
+  unsigned char retransmit_cnt;	/**< retransmission counter, will be removed when zero */
+  unsigned int timeout;		/**< the randomized timeout value */
 
   coap_address_t local;		/**< local address */
   coap_address_t remote;	/**< remote address */
@@ -54,16 +54,16 @@ typedef struct coap_queue_t {
   coap_pdu_t *pdu;		/**< the CoAP PDU to send */
 } coap_queue_t;
 
-/* adds node to given queue, ordered by node->t */
+/** Adds node to given queue, ordered by node->t. */
 int coap_insert_node(coap_queue_t **queue, coap_queue_t *node);
 
-/* destroys specified node */
+/** Destroys specified node. */
 int coap_delete_node(coap_queue_t *node);
 
-/* removes all items from given queue and frees the allocated storage */
+/** Removes all items from given queue and frees the allocated storage. */
 void coap_delete_all(coap_queue_t *queue);
 
-/* creates a new node suitable for adding to the CoAP sendqueue */
+/** Creates a new node suitable for adding to the CoAP sendqueue. */
 coap_queue_t *coap_new_node();
 
 struct coap_resource_t;
@@ -151,13 +151,21 @@ coap_register_option(coap_context_t *ctx, unsigned char type) {
   coap_option_setb(ctx->known_options, type);
 }
 
-/* Returns the next pdu to send without removing from sendqeue. */
+
+/**
+ * Set sendqueue_basetime in the given context object @p ctx to @p
+ * now. This function returns the number of elements in the queue
+ * head that have timed out.
+ */
+unsigned int coap_adjust_basetime(coap_context_t *ctx, coap_tick_t now);
+
+/** Returns the next pdu to send without removing from sendqeue. */
 coap_queue_t *coap_peek_next( coap_context_t *context );
 
-/* Returns the next pdu to send and removes it from the sendqeue. */
+/** Returns the next pdu to send and removes it from the sendqeue. */
 coap_queue_t *coap_pop_next( coap_context_t *context );
 
-/* Creates a new coap_context_t object that will hold the CoAP stack status.  */
+/** Creates a new coap_context_t object that will hold the CoAP stack status.  */
 coap_context_t *coap_new_context(const coap_address_t *listen_addr);
 
 /**