diff --git a/ChangeLog b/ChangeLog
index 2d26a4f..fbc24cf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,11 @@
    * Fix unused variable/function compilation warnings in pem.c, x509_crt.c and
      x509_csr.c that are reported when building mbed TLS with a config.h that
      does not define MBEDTLS_PEM_PARSE_C. Found by omnium21. #562
+   * Fix incorrect renegotiation condition in ssl_check_ctr_renegotiate() that
+     would compare 64 bits of the record counter instead of 48 bits as indicated
+     in RFC 6347 Section 4.3.1. This could cause the execution of the
+     renegotiation routines at unexpected times when the protocol is DTLS. Found
+     by wariua. #687
 
 = mbed TLS 2.4.1 branch released 2016-12-13
 
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 1a6c9cc..8042693 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2183,7 +2183,7 @@
 
 /**
  * \brief          Set record counter threshold for periodic renegotiation.
- *                 (Default: 2^64 - 256.)
+ *                 (Default: 2^48 - 1)
  *
  *                 Renegotiation is automatically triggered when a record
  *                 counter (outgoing or ingoing) crosses the defined
@@ -2194,9 +2194,11 @@
  *                 Lower values can be used to enforce policies such as "keys
  *                 must be refreshed every N packets with cipher X".
  *
+ * \note           When the transport is set to MBEDTLS_SSL_TRANSPORT_DATAGRAM,
+ *                 the maximum renegotiation period is 2^48 - 1.
+ *
  * \param conf     SSL configuration
  * \param period   The threshold value: a big-endian 64-bit number.
- *                 Set to 2^64 - 1 to disable periodic renegotiation
  */
 void mbedtls_ssl_conf_renegotiation_period( mbedtls_ssl_config *conf,
                                    const unsigned char period[8] );
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 121c135..abad0b3 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -6482,6 +6482,10 @@
  */
 static int ssl_check_ctr_renegotiate( mbedtls_ssl_context *ssl )
 {
+    size_t ep_len = ssl_ep_len( ssl );
+    int in_ctr_cmp;
+    int out_ctr_cmp;
+
     if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER ||
         ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING ||
         ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED )
@@ -6489,8 +6493,12 @@
         return( 0 );
     }
 
-    if( memcmp( ssl->in_ctr,  ssl->conf->renego_period, 8 ) <= 0 &&
-        memcmp( ssl->out_ctr, ssl->conf->renego_period, 8 ) <= 0 )
+    in_ctr_cmp = memcmp( ssl->in_ctr + ep_len,
+                        ssl->conf->renego_period + ep_len, 8 - ep_len );
+    out_ctr_cmp = memcmp( ssl->out_ctr + ep_len,
+                          ssl->conf->renego_period + ep_len, 8 - ep_len );
+
+    if( in_ctr_cmp <= 0 && out_ctr_cmp <= 0 )
     {
         return( 0 );
     }
@@ -7231,8 +7239,8 @@
 
 #if defined(MBEDTLS_SSL_RENEGOTIATION)
     conf->renego_max_records = MBEDTLS_SSL_RENEGO_MAX_RECORDS_DEFAULT;
-    memset( conf->renego_period, 0xFF, 7 );
-    conf->renego_period[7] = 0x00;
+    memset( conf->renego_period,     0x00, 2 );
+    memset( conf->renego_period + 2, 0xFF, 6 );
 #endif
 
 #if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_SRV_C)
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 18bda59..d98b669 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -63,6 +63,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdint.h>
+#include <inttypes.h>
 
 #if !defined(_WIN32)
 #include <signal.h>
@@ -113,7 +115,7 @@
 #define DFL_ALLOW_LEGACY        -2
 #define DFL_RENEGOTIATE         0
 #define DFL_RENEGO_DELAY        -2
-#define DFL_RENEGO_PERIOD       -1
+#define DFL_RENEGO_PERIOD       ( (uint64_t)-1 )
 #define DFL_EXCHANGES           1
 #define DFL_MIN_VERSION         -1
 #define DFL_MAX_VERSION         -1
@@ -292,7 +294,7 @@
     "    renegotiation=%%d    default: 0 (disabled)\n"      \
     "    renegotiate=%%d      default: 0 (disabled)\n"      \
     "    renego_delay=%%d     default: -2 (library default)\n" \
-    "    renego_period=%%d    default: (library default)\n"
+    "    renego_period=%%d    default: (2^64 - 1 for TLS, 2^48 - 1 for DTLS)\n"
 #else
 #define USAGE_RENEGO ""
 #endif
@@ -351,6 +353,19 @@
     "    force_ciphersuite=<name>    default: all enabled\n"            \
     " acceptable ciphersuite names:\n"
 
+
+#define PUT_UINT64_BE(out_be,in_le,i)                                   \
+{                                                                       \
+    (out_be)[(i) + 0] = (unsigned char)( ( (in_le) >> 56 ) & 0xFF );    \
+    (out_be)[(i) + 1] = (unsigned char)( ( (in_le) >> 48 ) & 0xFF );    \
+    (out_be)[(i) + 2] = (unsigned char)( ( (in_le) >> 40 ) & 0xFF );    \
+    (out_be)[(i) + 3] = (unsigned char)( ( (in_le) >> 32 ) & 0xFF );    \
+    (out_be)[(i) + 4] = (unsigned char)( ( (in_le) >> 24 ) & 0xFF );    \
+    (out_be)[(i) + 5] = (unsigned char)( ( (in_le) >> 16 ) & 0xFF );    \
+    (out_be)[(i) + 6] = (unsigned char)( ( (in_le) >> 8  ) & 0xFF );    \
+    (out_be)[(i) + 7] = (unsigned char)( ( (in_le) >> 0  ) & 0xFF );    \
+}
+
 /*
  * global options
  */
@@ -377,7 +392,7 @@
     int allow_legacy;           /* allow legacy renegotiation               */
     int renegotiate;            /* attempt renegotiation?                   */
     int renego_delay;           /* delay before enforcing renegotiation     */
-    int renego_period;          /* period for automatic renegotiation       */
+    uint64_t renego_period;     /* period for automatic renegotiation       */
     int exchanges;              /* number of data exchanges                 */
     int min_version;            /* minimum protocol version accepted        */
     int max_version;            /* maximum protocol version accepted        */
@@ -1041,8 +1056,8 @@
         }
         else if( strcmp( p, "renego_period" ) == 0 )
         {
-            opt.renego_period = atoi( q );
-            if( opt.renego_period < 2 || opt.renego_period > 255 )
+            if( sscanf( q, "%" SCNu64, &opt.renego_period ) != 1 ||
+                opt.renego_period < 2 )
                 goto usage;
         }
         else if( strcmp( p, "exchanges" ) == 0 )
@@ -1757,7 +1772,7 @@
 
     if( opt.renego_period != DFL_RENEGO_PERIOD )
     {
-        renego_period[7] = opt.renego_period;
+        PUT_UINT64_BE( renego_period, opt.renego_period, 0 );
         mbedtls_ssl_conf_renegotiation_period( &conf, renego_period );
     }
 #endif
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 57155b8..41fbc3d 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1601,6 +1601,19 @@
             -s "=> renegotiate" \
             -s "write hello request"
 
+run_test    "Renegotiation: DTLS, renego_period overflow" \
+            "$P_SRV debug_level=3 dtls=1 exchanges=4 renegotiation=1 renego_period=18446462598732840962 auth_mode=optional" \
+            "$P_CLI debug_level=3 dtls=1 exchanges=4 renegotiation=1" \
+            0 \
+            -c "client hello, adding renegotiation extension" \
+            -s "received TLS_EMPTY_RENEGOTIATION_INFO" \
+            -s "found renegotiation extension" \
+            -s "server hello, secure renegotiation extension" \
+            -s "record counter limit reached: renegotiate" \
+            -c "=> renegotiate" \
+            -s "=> renegotiate" \
+            -s "write hello request" \
+
 requires_gnutls
 run_test    "Renegotiation: DTLS, gnutls server, client-initiated" \
             "$G_SRV -u --mtu 4096" \