diff --git a/configs/samv71-xult/netnsh/defconfig b/configs/samv71-xult/netnsh/defconfig
index b6512741955..395fe4df825 100644
--- a/configs/samv71-xult/netnsh/defconfig
+++ b/configs/samv71-xult/netnsh/defconfig
@@ -96,6 +96,7 @@ CONFIG_ARCH="arm"
 # CONFIG_ARCH_CHIP_LPC2378 is not set
 # CONFIG_ARCH_CHIP_LPC31XX is not set
 # CONFIG_ARCH_CHIP_LPC43XX is not set
+# CONFIG_ARCH_CHIP_MOXART is not set
 # CONFIG_ARCH_CHIP_NUC1XX is not set
 # CONFIG_ARCH_CHIP_SAMA5 is not set
 # CONFIG_ARCH_CHIP_SAMD is not set
@@ -107,7 +108,7 @@ CONFIG_ARCH_CHIP_SAMV7=y
 # CONFIG_ARCH_CHIP_STM32L4 is not set
 # CONFIG_ARCH_CHIP_STR71X is not set
 # CONFIG_ARCH_CHIP_TMS570 is not set
-# CONFIG_ARCH_CHIP_MOXART is not set
+# CONFIG_ARCH_CHIP_XMC4 is not set
 # CONFIG_ARCH_ARM7TDMI is not set
 # CONFIG_ARCH_ARM926EJS is not set
 # CONFIG_ARCH_ARM920T is not set
@@ -457,6 +458,8 @@ CONFIG_SCHED_WAITPID=y
 #
 # CONFIG_PTHREAD_MUTEX_TYPES is not set
 CONFIG_PTHREAD_MUTEX_ROBUST=y
+# CONFIG_PTHREAD_MUTEX_UNSAFE is not set
+# CONFIG_PTHREAD_MUTEX_BOTH is not set
 CONFIG_NPTHREAD_KEYS=4
 # CONFIG_PTHREAD_CLEANUP is not set
 # CONFIG_CANCELLATION_POINTS is not set
@@ -1160,6 +1163,7 @@ CONFIG_EXAMPLES_NSH=y
 # CONFIG_EXAMPLES_USBSERIAL is not set
 # CONFIG_EXAMPLES_WATCHDOG is not set
 # CONFIG_EXAMPLES_WEBSERVER is not set
+# CONFIG_EXAMPLES_XBC_TEST is not set
 
 #
 # File System Utilities
diff --git a/include/nuttx/net/sixlowpan.h b/include/nuttx/net/sixlowpan.h
index 4887d255f0a..be7f9f1e366 100644
--- a/include/nuttx/net/sixlowpan.h
+++ b/include/nuttx/net/sixlowpan.h
@@ -50,8 +50,11 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <stdint.h>
 
+#include <nuttx/net/netdev.h>
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -223,51 +226,66 @@
    (((a)->u16[6]) == 0) && \
    (((a)->u8[14]) == 0))
 
-/* Maximum size of an IEEE802.15.4 frame */
+/* This maximum size of an IEEE802.15.4 frame.  Certain, non-standard
+ * devices may exceed this value, however.
+ */
 
-#define SIXLOWPAN_MAC_MAXFRAME 127
+#define SIXLOWPAN_MAC_STDFRAME 127
 
 /****************************************************************************
  * Public Types
  ****************************************************************************/
 
-/* The header for fragments
+/* The device structure for IEEE802.15.4 MAC network device differs from the
+ * standard Ethernet MAC device structure.  The main reason for this
+ * difference is that fragmentation must be supported.
  *
- * NOTE: We do not define different structures for FRAG1 and FRAGN headers,
- * which are different. For FRAG1, the offset field is just not used
+ * The IEEE802.15.4 MAC does not use the d_buf packet buffer directly.
+ * Rather, it uses a smaller frame buffer.  The packet data is provided to
+ * the frame buffer each time that the IEEE802.15.4 MAC needs to send
+ * more data.
+ *
+ * This is accomplished by "inheriting" the standard 'struct net_driver_s'
+ * and appending the frame buffer as well as other metadata needed to
+ * manage the fragmentation.  'struct ieee802154_driver_s' is cast
+ * compatible with 'struct net_driver_s' when CONFIG_NET_MULTINIC is not
+ * defined or when dev->d_lltype == NET_LL_IEEE802154.
  */
 
-struct sixlowpan_frag_hdr
+struct ieee802154_driver_s
 {
-  uint16_t dispatch_size;
-  uint16_t tag;
-  uint8_t offset;
-};
+  /* This definitiona must appear first in the structure definition to
+   * assure cast compatibility.
+   */
 
-/* The HC1 header when HC_UDP is not used
- *
- * When all fields are compressed and HC_UDP is not used, we use this
- * structure. If HC_UDP is used, the ttl is in another spot, and we use the
- * sixlowpan_hc1_hc_udp structure
- */
+  struct net_driver_s i_dev;
 
-struct sixlowpan_hc1hdr_s
-{
-  uint8_t dispatch;
-  uint8_t encoding;
-  uint8_t ttl;
-};
+  /* IEEE802.15.4 MAC-specific definitions follow. */
 
-/* HC1 followed by HC_UDP */
+  /* The i_frame array is used to hold outgoing frame.   When the
+   * IEEE802.15.4 device polls for new data, the outgoing frame containing
+   * the next fragment is placed in i_frame.
+   *
+   * The network will handle only a single outgong frame at a time.  The
+   * IEEE802.15.4 MAC driver design may be concurrently sending and
+   * requesting new framesusing break-off fram buffers.  That frame buffer
+   * management must be controlled by the IEEE802.15.4 MAC driver.
+   *
+   * Driver provied frame buffers should be 16-bit aligned.
+   */
 
-struct sixlowpan_hc1_hcudp_hdr_s
-{
-  uint8_t dispatch;
-  uint8_t hc1_encoding;
-  uint8_t hc_udp_encoding;
-  uint8_t ttl;
-  uint8_t ports;
-  uint16_t udpchksum;
+  FAR uint8_t *i_frame;
+
+  /* The length of valid data in the i_frame buffer.
+   *
+   * When the network device driver calls the network input function,
+   * i_framelen should be set to zero.  If there is frame to be sent
+   * by the network, i_framelen will be set to indicate the size of
+   * frame to be sent.  The value zero means that there is no frame
+   * to be sent.
+   */
+
+  uint16_t i_framelen;
 };
 
 /* The structure of a next header compressor.  This compressor is provided
diff --git a/net/netdev/netdev_register.c b/net/netdev/netdev_register.c
index 9a3a01c66d2..4dda608c1ac 100644
--- a/net/netdev/netdev_register.c
+++ b/net/netdev/netdev_register.c
@@ -230,7 +230,7 @@ int netdev_register(FAR struct net_driver_s *dev, enum net_lltype_e lltype)
 #ifdef CONFIG_NET_6LOWPAN
           case NET_LL_IEEE802154: /* IEEE 802.15.4 MAC */
             dev->d_llhdrlen = 0;  /* REVISIT */
-            dev->d_mtu      = SIXLOWPAN_MAC_MAXFRAME;
+            dev->d_mtu      = CONFIG_NET_6LOWPAN_FRAMELEN;
 #ifdef CONFIG_NET_TCP
             dev->d_recvwndo = CONFIG_NET_6LOWPAN_TCP_RECVWNDO;
 #endif
diff --git a/net/sixlowpan/Kconfig b/net/sixlowpan/Kconfig
index 1a3882d1ad3..84cb1c6652e 100644
--- a/net/sixlowpan/Kconfig
+++ b/net/sixlowpan/Kconfig
@@ -20,6 +20,14 @@ config NET_6LOWPAN_FRAG
 		CONFIG_NET_6LOWPAN_FRAG specifies if 6lowpan fragmentation should be
 		used or not. Fragmentation is on by default.
 
+config NET_6LOWPAN_FRAMELEN
+	int "IEEE802.15.4 MAC Frame Length"
+	default 127
+	range 127 999999
+	---help---
+		Some wireless devices may use non-standard frame lengths.  This
+		setting should never be smaller than 127.
+
 choice
 	prompt "6loWPAN Compression"
 	default NET_6LOWPAN_COMPRESSION_HC06
diff --git a/net/sixlowpan/sixlowpan_send.c b/net/sixlowpan/sixlowpan_send.c
index de338945975..b85c685f420 100644
--- a/net/sixlowpan/sixlowpan_send.c
+++ b/net/sixlowpan/sixlowpan_send.c
@@ -54,6 +54,7 @@
 
 #ifdef CONFIG_NET_6LOWPAN
 
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -62,11 +63,20 @@
  * Name: sixlowpan_send
  *
  * Description:
- *   Process an outgoing UDP or TCP packet.  Called from UDP/TCP logic to
- *   determine if the the packet should be formatted for 6loWPAN output.
+ *   Process an outgoing UDP or TCP packet.  Takes an IP packet and formats
+ *   it to be sent on an 802.15.4 network using 6lowpan.  Called from common
+ *   UDP/TCP send logic.
+ *
+ *  The payload data is in the caller 'buf' and is of length 'len'.
+ *  Compressed headers will be added and if necessary the packet is
+ *  fragmented. The resulting packet/fragments are put in dev->d_buf and
+ *  the first frame will be delivered to the 802.15.4 MAC. via ieee->i_frame.
+ *
+ * Input Parmeters:
  *
  * Input Parameters:
- *   dev - The IEEE802.15.4 MAC network driver interface.
+ *   dev   - The IEEE802.15.4 MAC network driver interface.
+ *   raddr - The MAC address of the destination
  *
  * Returned Value:
  *   Ok is returned on success; Othewise a negated errno value is returned.
@@ -79,8 +89,10 @@
  *
  ****************************************************************************/
 
-int sixlowpan_send(FAR struct net_driver_s *dev)
+int sixlowpan_send(FAR struct net_driver_s *dev, net_ipv6addr_t raddr)
 {
+  FAR struct ieee802154_driver_s *ieee = (FAR struct ieee802154_driver_s *)dev;
+
   net_lock();
   /* REVISIT: To be provided */
   net_unlock();
@@ -143,6 +155,7 @@ ssize_t psock_6lowpan_tcp_send(FAR struct socket *psock, FAR const void *buf,
   conn = (FAR struct tcp_conn_s *)psock->s_conn;
   DEBUGASSERT(conn != NULL);
 
+#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
   /* Ignore if not IPv6 domain */
 
   if (conn->domain != PF_INET6)
@@ -150,6 +163,7 @@ ssize_t psock_6lowpan_tcp_send(FAR struct socket *psock, FAR const void *buf,
       nwarn("WARNING: Not IPv6\n");
       return (ssize_t)-EPROTOTYPE;
     }
+#endif
 
   /* Route outgoing message to the correct device */
 
@@ -188,7 +202,7 @@ ssize_t psock_6lowpan_tcp_send(FAR struct socket *psock, FAR const void *buf,
    * packet.
    */
 
-  ret = sixlowpan_send(dev);
+  ret = sixlowpan_send(dev, conn->u.ipv6.raddr);
   if (ret < 0)
     {
       nerr("ERROR: sixlowpan_send() failed: %d\n", ret);
@@ -251,6 +265,7 @@ ssize_t psock_6lowpan_udp_send(FAR struct socket *psock, FAR const void *buf,
   conn = (FAR struct udp_conn_s *)psock->s_conn;
   DEBUGASSERT(conn != NULL);
 
+#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
   /* Ignore if not IPv6 domain */
 
   if (conn->domain != PF_INET6)
@@ -258,6 +273,7 @@ ssize_t psock_6lowpan_udp_send(FAR struct socket *psock, FAR const void *buf,
       nwarn("WARNING: Not IPv6\n");
       return (ssize_t)-EPROTOTYPE;
     }
+#endif
 
   /* Route outgoing message to the correct device */
 
@@ -296,7 +312,7 @@ ssize_t psock_6lowpan_udp_send(FAR struct socket *psock, FAR const void *buf,
    * packet.
    */
 
-  ret = sixlowpan_send(dev);
+  ret = sixlowpan_send(dev, conn->u.ipv6.raddr);
   if (ret < 0)
     {
       nerr("ERROR: sixlowpan_send() failed: %d\n", ret);