diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 00e1c6c..2569f59 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -970,6 +970,76 @@
                   void  *p_dbg );
 
 /**
+ * \brief          Callback type: send data on the network.
+ *
+ * \note           That callback may be either blocking or non-blocking.
+ *
+ * \param ctx      Context for the send callback (typically a file descriptor)
+ * \param buf      Buffer holding the date to send
+ * \param len      Length of the data to send
+ *
+ * \return         The callback must return the number of bytes sent if any,
+ *                 or a non-zero error code.
+ *                 If performing non-blocking I/O, \c MBEDTLS_ERR_SSL_WANT_WRITE
+ *                 must be returned when the operation would block.
+ *
+ * \note           The callback is allowed to send less bytes than requested.
+ *                 It must always return the number of bytes actually sent.
+ */
+typedef int mbedtls_ssl_send_t( void *ctx,
+                                const unsigned char *buf,
+                                size_t len );
+
+/**
+ * \brief          Callback type: receive data from the network.
+ *
+ * \note           That callback may be either blocking or non-blocking.
+ *
+ * \param ctx      Context for the send callback (typically a file descriptor)
+ * \param buf      Buffer to write the received data to
+ * \param len      Length of the receive buffer
+ *
+ * \return         The callback must return the number of bytes received,
+ *                 or a non-zero error code.
+ *                 If performing non-blocking I/O, \c MBEDTLS_ERR_SSL_WANT_READ
+ *                 must be returned when the operation would block.
+ *
+ * \note           The callback may receive less bytes than the length of the
+ *                 buffer. It must always return the number of bytes actually
+ *                 received and written to the buffer.
+ */
+typedef int mbedtls_ssl_recv_t( void *ctx,
+                                unsigned char *buf,
+                                size_t len );
+
+/**
+ * \brief          Callback type: receive data from the network, with timeout
+ *
+ * \note           That callback must block until data is received, or the
+ *                 timeout delay expires, or the operation is interrupted by a
+ *                 signal.
+ *
+ * \param ctx      Context for the send callback (typically a file descriptor)
+ * \param buf      Buffer to write the received data to
+ * \param len      Length of the receive buffer
+ * \param timeout  Maximum nomber of millisecondes to wait for data
+ *                 0 means no timeout (potentially wait forever)
+ *
+ * \return         The callback must return the number of bytes received,
+ *                 or a non-zero error code:
+ *                 \c MBEDTLS_ERR_SSL_TIMEOUT if the operation timed out,
+ *                 \c MBEDTLS_ERR_SSL_WANT_READ if interrupted by a signal.
+ *
+ * \note           The callback may receive less bytes than the length of the
+ *                 buffer. It must always return the number of bytes actually
+ *                 received and written to the buffer.
+ */
+typedef int mbedtls_ssl_recv_timeout_t( void *ctx,
+                                        unsigned char *buf,
+                                        size_t len,
+                                        uint32_t timeout );
+
+/**
  * \brief          Set the underlying BIO callbacks for write, read and
  *                 read-with-timeout.
  *
@@ -978,8 +1048,6 @@
  * \param f_send   write callback
  * \param f_recv   read callback
  * \param f_recv_timeout blocking read callback with timeout.
- *                 The last argument is the timeout in milliseconds,
- *                 0 means no timeout (block forever until a message comes)
  *
  * \note           One of f_recv or f_recv_timeout can be NULL, in which case
  *                 the other is used. If both are non-NULL, f_recv_timeout is
@@ -991,12 +1059,20 @@
  *
  * \note           For DTLS, you need to provide either a non-NULL
  *                 f_recv_timeout callback, or a f_recv that doesn't block.
+ *
+ * \note           See the documentations of \c mbedtls_ssl_sent_t,
+ *                 \c mbedtls_ssl_recv_t and \c mbedtls_ssl_recv_timeout_t for
+ *                 the convetions those callbacks must follow.
+ *
+ * \note           On some platforms, net.c provides \c mbedtls_net_send(),
+ *                 \c mbedtls_net_recv() and \c mbedtls_net_recv_timeout()
+ *                 that are suitable to be used here.
  */
 void mbedtls_ssl_set_bio( mbedtls_ssl_context *ssl,
-        void *p_bio,
-        int (*f_send)(void *, const unsigned char *, size_t),
-        int (*f_recv)(void *, unsigned char *, size_t),
-        int (*f_recv_timeout)(void *, unsigned char *, size_t, uint32_t) );
+                          void *p_bio,
+                          mbedtls_ssl_send_t *f_send,
+                          mbedtls_ssl_recv_t *f_recv,
+                          mbedtls_ssl_recv_timeout_t *f_recv_timeout );
 
 /**
  * \brief          Set the timeout period for mbedtls_ssl_read()
@@ -1017,24 +1093,67 @@
 void mbedtls_ssl_conf_read_timeout( mbedtls_ssl_config *conf, uint32_t timeout );
 
 /**
- * \brief          Set the timer callbacks
- *                 (Mandatory for DTLS.)
+ * \brief          Callback type: set a pair of timers/delays to watch
+ *
+ * \param ctx      Context pointer
+ * \param int_ms   Intermediate delay in milliseconds
+ * \param fin_ms   Final delay in milliseconds
+ *                 0 cancels the current timer.
+ *
+ * \note           This callback must at least store the necessary information
+ *                 for the associated \c mbedtls_ssl_get_timer_t callback to
+ *                 return correct information.
+ *
+ * \note           If using a event-driven style of programming, an event must
+ *                 be generated when the final delay is passed. The event must
+ *                 cause a call to \c mbedtls_ssl_handshake() with the proper
+ *                 SSL context to be scheduled. Care must be taken to ensure
+ *                 that at most one such call happens at a time.
+ *
+ * \note           Only one timer at a time must be running. Calling this
+ *                 function while a timer is running must cancel it. Cancelled
+ *                 timers must not generate any event.
+ */
+typedef void mbedtls_ssl_set_timer_t( void * ctx,
+                                      uint32_t int_ms,
+                                      uint32_t fin_ms );
+
+/**
+ * \brief          Callback type: get status of timers/delays
+ *
+ * \param ctx      Context pointer
+ *
+ * \return         This callback must return:
+ *                 -1 if cancelled (fin_ms == 0),
+ *                  0 if none of the delays is passed,
+ *                  1 if only the intermediate delay is passed,
+ *                  2 if the final delay is passed.
+ */
+typedef int mbedtls_ssl_get_timer_t( void * ctx );
+
+/**
+ * \brief          Set the timer callbacks (Mandatory for DTLS.)
  *
  * \param ssl      SSL context
- * \param p_timer  parameter (context) shared by timer callback
+ * \param p_timer  parameter (context) shared by timer callbacks
  * \param f_set_timer   set timer callback
- *                 Accepts an intermediate and a final delay in milliseconcs
- *                 If the final delay is 0, cancels the running timer.
  * \param f_get_timer   get timer callback. Must return:
- *                 -1 if cancelled
- *                 0 if none of the delays is expired
- *                 1 if the intermediate delay only is expired
- *                 2 if the final delay is expired
+ *
+ * \note           See the documentation of \c mbedtls_ssl_set_timer_t and
+ *                 \c mbedtls_ssl_get_timer_t for the conventions this pair of
+ *                 callbacks must fallow.
+ *
+ * \note           On some platforms, timing.c provides
+ *                 \c mbedtls_timing_set_delay() and
+ *                 \c mbedtls_timing_get_delay() that are suitable for using
+ *                 here, except if using an event-driven style.
+ *
+ * \note           See also the "DTLS tutorial" article in our knowledge base.
  */
 void mbedtls_ssl_set_timer_cb( mbedtls_ssl_context *ssl,
                                void *p_timer,
-                               void (*f_set_timer)(void *, uint32_t int_ms, uint32_t fin_ms),
-                               int (*f_get_timer)(void *) );
+                               mbedtls_ssl_set_timer_t *f_set_timer,
+                               mbedtls_ssl_get_timer_t *f_get_timer );
 
 /**
  * \brief           Callback type: generate and write session ticket