diff --git a/ompi/mca/btl/usnic/btl_usnic.h b/ompi/mca/btl/usnic/btl_usnic.h
index 58ae77656f..84f463e5d6 100644
--- a/ompi/mca/btl/usnic/btl_usnic.h
+++ b/ompi/mca/btl/usnic/btl_usnic.h
@@ -190,8 +190,18 @@ typedef mca_btl_base_recv_reg_t ompi_btl_usnic_recv_reg_t;
  * Size for sequence numbers (just to ensure we use the same size
  * everywhere)
  */
-typedef uint64_t ompi_btl_usnic_seq_t;
-#define UDSEQ PRIu64
+typedef uint16_t ompi_btl_usnic_seq_t;
+#define UDSEQ PRIu16
+
+/* sequence number comparison macros that allow for rollover.
+ * Relies on the fact that sequence numbers should be relatively close
+ * together as compared to (1<<31)
+ */
+#define SEQ_DIFF(A,B) ((int16_t)((A)-(B)))
+#define SEQ_LT(A,B) (SEQ_DIFF(A,B) < 0)
+#define SEQ_LE(A,B) (SEQ_DIFF(A,B) <= 0)
+#define SEQ_GT(A,B) (SEQ_DIFF(A,B) > 0)
+#define SEQ_GE(A,B) (SEQ_DIFF(A,B) >= 0)
 
 /**
  * Register the usnic BTL MCA params
diff --git a/ompi/mca/btl/usnic/btl_usnic_ack.c b/ompi/mca/btl/usnic/btl_usnic_ack.c
index 6131609193..6a0624ff4a 100644
--- a/ompi/mca/btl/usnic/btl_usnic_ack.c
+++ b/ompi/mca/btl/usnic/btl_usnic_ack.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -71,7 +71,7 @@ ompi_btl_usnic_handle_ack(
     module = endpoint->endpoint_module;
 
     /* ignore if this is an old ACK */
-    if (ack_seq < endpoint->endpoint_ack_seq_rcvd) {
+    if (SEQ_LT(ack_seq, endpoint->endpoint_ack_seq_rcvd)) {
 #if MSGDEBUG1
         opal_output(0, "Got OLD DUP ACK seq %"UDSEQ" < %"UDSEQ"\n",
                 ack_seq, endpoint->endpoint_ack_seq_rcvd);
@@ -89,7 +89,7 @@ ompi_btl_usnic_handle_ack(
 
     /* Does this ACK have a new sequence number that we haven't
        seen before? */
-    for (is = endpoint->endpoint_ack_seq_rcvd + 1; is <= ack_seq; ++is) {
+    for (is = endpoint->endpoint_ack_seq_rcvd + 1; SEQ_LE(is, ack_seq); ++is) {
         sseg = endpoint->endpoint_sent_segs[WINDOW_SIZE_MOD(is)];
 
 #if MSGDEBUG1
@@ -99,7 +99,7 @@ ompi_btl_usnic_handle_ack(
 #endif
 
         assert(sseg != NULL);
-        assert(sseg->ss_base.us_btl_header->seq == is);
+        assert(sseg->ss_base.us_btl_header->pkt_seq == is);
 #if MSGDEBUG1
         if (sseg->ss_hotel_room == -1) {
             opal_output(0, "=== ACKed frag in sent_frags array is not in hotel/enqueued, module %p, endpoint %p, seg %p, seq %" UDSEQ ", slot %lu",
@@ -264,7 +264,7 @@ ompi_btl_usnic_ack_timeout(
     {
         opal_output(0, "Send timeout!  seg %p, room %d, seq %" UDSEQ "\n",
                     (void*)seg, seg->ss_hotel_room,
-                    seg->ss_base.us_btl_header->seq);
+                    seg->ss_base.us_btl_header->pkt_seq);
     }
 #endif
 
diff --git a/ompi/mca/btl/usnic/btl_usnic_ack.h b/ompi/mca/btl/usnic/btl_usnic_ack.h
index 5dbb06a73c..5af81748ed 100644
--- a/ompi/mca/btl/usnic/btl_usnic_ack.h
+++ b/ompi/mca/btl/usnic/btl_usnic_ack.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -70,12 +70,13 @@ ompi_btl_usnic_piggyback_ack(
         ompi_btl_usnic_remove_from_endpoints_needing_ack(endpoint);
         sseg->ss_base.us_btl_header->ack_seq = 
             endpoint->endpoint_next_contig_seq_to_recv - 1;
+        sseg->ss_base.us_btl_header->ack_present = 1;
 #if MSGDEBUG1
         opal_output(0, "Piggy-backing ACK for sequence %"UDSEQ"\n",
                 sseg->ss_base.us_btl_header->ack_seq);
 #endif
     } else {
-        sseg->ss_base.us_btl_header->ack_seq = 0;
+        sseg->ss_base.us_btl_header->ack_present = 0;
     }
 }
 
diff --git a/ompi/mca/btl/usnic/btl_usnic_endpoint.h b/ompi/mca/btl/usnic/btl_usnic_endpoint.h
index 76d87d5ed6..8654744f94 100644
--- a/ompi/mca/btl/usnic/btl_usnic_endpoint.h
+++ b/ompi/mca/btl/usnic/btl_usnic_endpoint.h
@@ -11,7 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2006      Sandia National Laboratories. All rights
  *                         reserved.
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -44,8 +44,8 @@ struct ompi_btl_usnic_send_segment_t;
  */
 #define WINDOW_SIZE 4096
 #define WINDOW_SIZE_MOD(a) (((a) & (WINDOW_SIZE - 1)))
-#define WINDOW_OPEN(E) ((E)->endpoint_next_seq_to_send < \
-        ((E)->endpoint_ack_seq_rcvd + WINDOW_SIZE))
+#define WINDOW_OPEN(E) (SEQ_LT((E)->endpoint_next_seq_to_send, \
+        ((E)->endpoint_ack_seq_rcvd + WINDOW_SIZE)))
 #define WINDOW_EMPTY(E) ((E)->endpoint_ack_seq_rcvd == \
         ((E)->endpoint_next_seq_to_send-1))
 
diff --git a/ompi/mca/btl/usnic/btl_usnic_frag.c b/ompi/mca/btl/usnic/btl_usnic_frag.c
index 297d8d26ef..62bb0e18f9 100644
--- a/ompi/mca/btl/usnic/btl_usnic_frag.c
+++ b/ompi/mca/btl/usnic/btl_usnic_frag.c
@@ -11,7 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2006      Sandia National Laboratories. All rights
  *                         reserved.
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -109,6 +109,7 @@ ack_seg_constructor(
     /* ACK value embedded in BTL header */
     bseg->us_btl_header->payload_type = OMPI_BTL_USNIC_PAYLOAD_TYPE_ACK;
     bseg->us_btl_header->payload_len = 0;
+    bseg->us_btl_header->ack_present = 1;
 
     bseg->us_sg_entry[0].length = sizeof(bseg->us_btl_header);
 }
diff --git a/ompi/mca/btl/usnic/btl_usnic_frag.h b/ompi/mca/btl/usnic/btl_usnic_frag.h
index 1a9a70250f..94d3a1d37e 100644
--- a/ompi/mca/btl/usnic/btl_usnic_frag.h
+++ b/ompi/mca/btl/usnic/btl_usnic_frag.h
@@ -11,7 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2006      Sandia National Laboratories. All rights
  *                         reserved.
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -121,9 +121,8 @@ typedef struct {
     /* Hashed RTE process name of the sender */
     uint64_t sender;
 
-    /* Sliding window sequence number (echoed back in an ACK).  This
-       is 64 bits. */
-    ompi_btl_usnic_seq_t seq;
+    /* Sliding window sequence number (echoed back in an ACK). */
+    ompi_btl_usnic_seq_t pkt_seq;
     ompi_btl_usnic_seq_t ack_seq;       /* for piggy-backing ACKs */
 
     /* payload legnth (in bytes).  We unfortunately have to include
@@ -137,6 +136,9 @@ typedef struct {
     /* Type of BTL header (see enum, above) */
     uint8_t payload_type;
 
+    /* true if there is piggy-backed ACK */
+    uint8_t ack_present;
+
     /* tag for upper layer */
     mca_btl_base_tag_t tag;
 } ompi_btl_usnic_btl_header_t; 
diff --git a/ompi/mca/btl/usnic/btl_usnic_module.c b/ompi/mca/btl/usnic/btl_usnic_module.c
index 7cc4379c3f..51404fad20 100644
--- a/ompi/mca/btl/usnic/btl_usnic_module.c
+++ b/ompi/mca/btl/usnic/btl_usnic_module.c
@@ -969,7 +969,7 @@ usnic_do_resends(
         endpoint = sseg->ss_parent_frag->sf_endpoint;
 
         /* clobber any stale piggy-backed ACK */
-        sseg->ss_base.us_btl_header->ack_seq = 0;
+        sseg->ss_base.us_btl_header->ack_present = 0;
 
         /* Only post this segment if not already posted */
         if (sseg->ss_send_posted == 0) {
@@ -1816,10 +1816,8 @@ static ompi_btl_usnic_seq_t
 get_initial_seq_no(void)
 {
     ompi_btl_usnic_seq_t isn;
-    /* only utilize the bottom 62 bits to avoid hitting seq # overflow */
-    isn = (((uint64_t)opal_rand(&ompi_btl_usnic_rand_buff) & ((1LL<<30)-1)) << 32) |
-        ((uint64_t)opal_rand(&ompi_btl_usnic_rand_buff) & ((1LL<<32)-1));
-    isn += 2;      /* guarantee > 1 */
+
+    isn = (ompi_btl_usnic_seq_t)opal_rand(&ompi_btl_usnic_rand_buff);
 
     return isn;
 }
diff --git a/ompi/mca/btl/usnic/btl_usnic_recv.c b/ompi/mca/btl/usnic/btl_usnic_recv.c
index 7c5b252265..5a585e530d 100644
--- a/ompi/mca/btl/usnic/btl_usnic_recv.c
+++ b/ompi/mca/btl/usnic/btl_usnic_recv.c
@@ -11,7 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2006      Sandia National Laboratories. All rights
  *                         reserved.
- * Copyright (c) 2008-2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2008-2014 Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2012      Los Alamos National Security, LLC.  All rights
  *                         reserved. 
  * $COPYRIGHT$
@@ -93,7 +93,7 @@ void ompi_btl_usnic_recv_call(ompi_btl_usnic_module_t *module,
         opal_output(0, "=== Unknown sender; dropped: from MAC %s to MAC %s, seq %" UDSEQ, 
                     src_mac, 
                     dest_mac, 
-                    bseg->us_btl_header->seq);
+                    bseg->us_btl_header->pkt_seq);
 #endif
         ++module->stats.num_unk_recvs;
         goto repost_no_endpoint;
@@ -113,12 +113,12 @@ void ompi_btl_usnic_recv_call(ompi_btl_usnic_module_t *module,
 
 #if MSGDEBUG1
         opal_output(0, "<-- Received FRAG ep %p, seq %" UDSEQ ", len=%d\n",
-                    (void*) endpoint, hdr->seq, hdr->payload_len);
+                    (void*) endpoint, hdr->pkt_seq, hdr->payload_len);
 #if 0
 
         opal_output(0, "<-- Received FRAG ep %p, seq %" UDSEQ " from %s to %s: GOOD! (rel seq %d, lowest seq %" UDSEQ ", highest seq: %" UDSEQ ", rwstart %d) seg %p, module %p\n",
                     (void*) endpoint,
-                    seg->rs_base.us_btl_header->seq, 
+                    seg->rs_base.us_btl_header->pkt_seq,
                     src_mac, dest_mac,
                     window_index,
                     endpoint->endpoint_next_contig_seq_to_recv,
@@ -182,7 +182,7 @@ void ompi_btl_usnic_recv_call(ompi_btl_usnic_module_t *module,
         opal_output(0, "<-- Received CHUNK fid %d ep %p, seq %" UDSEQ " from %s to %s: GOOD! (rel seq %d, lowest seq %" UDSEQ ", highest seq: %" UDSEQ ", rwstart %d) seg %p, module %p\n",
                     seg->rs_base.us_btl_chunk_header->ch_frag_id,
                     (void*) endpoint,
-                    seg->rs_base.us_btl_chunk_header->ch_hdr.seq, 
+                    seg->rs_base.us_btl_chunk_header->ch_hdr.pkt_seq,
                     src_mac, dest_mac,
                     window_index,
                     endpoint->endpoint_next_contig_seq_to_recv,
diff --git a/ompi/mca/btl/usnic/btl_usnic_recv.h b/ompi/mca/btl/usnic/btl_usnic_recv.h
index c591b718e2..ca02dc3138 100644
--- a/ompi/mca/btl/usnic/btl_usnic_recv.h
+++ b/ompi/mca/btl/usnic/btl_usnic_recv.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -116,11 +116,12 @@ ompi_btl_usnic_check_rx_seq(
 {
     uint32_t i;
     ompi_btl_usnic_seq_t seq;
+    int delta;
 
     /*
      * Handle piggy-backed ACK if present
      */
-    if (seg->rs_base.us_btl_header->ack_seq != 0) {
+    if (seg->rs_base.us_btl_header->ack_present) {
 #if MSGDEBUG1
         opal_output(0, "Handle piggy-packed ACK seq %"UDSEQ"\n", seg->rs_base.us_btl_header->ack_seq);
 #endif
@@ -151,12 +152,12 @@ ompi_btl_usnic_check_rx_seq(
            or
          seq >= next_contig_seg_to_recv + WINDOW_SIZE
     */
-    seq = seg->rs_base.us_btl_header->seq;
-    if (seq < endpoint->endpoint_next_contig_seq_to_recv ||
-        seq >= endpoint->endpoint_next_contig_seq_to_recv + WINDOW_SIZE) {
+    seq = seg->rs_base.us_btl_header->pkt_seq;
+    delta = SEQ_DIFF(seq, endpoint->endpoint_next_contig_seq_to_recv);
+    if (delta < 0 || delta >= WINDOW_SIZE) {
 #if MSGDEBUG1
             opal_output(0, "<-- Received FRAG/CHUNK ep %p, seq %" UDSEQ " outside of window (%" UDSEQ " - %" UDSEQ "), %p, module %p -- DROPPED\n",
-                        (void*)endpoint, seg->rs_base.us_btl_header->seq, 
+                        (void*)endpoint, seg->rs_base.us_btl_header->pkt_seq, 
                         endpoint->endpoint_next_contig_seq_to_recv,
                         (endpoint->endpoint_next_contig_seq_to_recv + 
                          WINDOW_SIZE - 1),
@@ -165,7 +166,7 @@ ompi_btl_usnic_check_rx_seq(
 #endif
 
         /* Stats */
-        if (seq < endpoint->endpoint_next_contig_seq_to_recv) {
+        if (delta < 0) {
             ++endpoint->endpoint_module->stats.num_oow_low_recvs;
         } else {
             ++endpoint->endpoint_module->stats.num_oow_high_recvs;
@@ -196,19 +197,19 @@ ompi_btl_usnic_check_rx_seq(
 
            rfstart = (rfstart + num_acks_sent) % WINDOW_SIZE
     */
-    i = seq - endpoint->endpoint_next_contig_seq_to_recv;
+    i = SEQ_DIFF(seq, endpoint->endpoint_next_contig_seq_to_recv);
     i = WINDOW_SIZE_MOD(i + endpoint->endpoint_rfstart);
     if (endpoint->endpoint_rcvd_segs[i]) {
 #if MSGDEBUG1
         opal_output(0, "<-- Received FRAG/CHUNK ep %p, seq %" UDSEQ ", seg %p: duplicate -- DROPPED\n",
-            (void*) endpoint, seg->rs_base.us_btl_header->seq, (void*) seg);
+            (void*) endpoint, seg->rs_base.us_btl_header->pkt_seq, (void*) seg);
 #endif
         /* highest_seq_rcvd is for debug stats only; it's not used
            in any window calculations */
-        assert(seq <= endpoint->endpoint_highest_seq_rcvd);
+        assert(SEQ_LE(seq, endpoint->endpoint_highest_seq_rcvd));
         /* next_contig_seq_to_recv-1 is the ack number we'll
            send */
-        assert (seq > endpoint->endpoint_next_contig_seq_to_recv - 1);
+        assert (SEQ_GT(seq, endpoint->endpoint_next_contig_seq_to_recv - 1));
 
         /* Stats */
         ++endpoint->endpoint_module->stats.num_dup_recvs;
@@ -216,7 +217,7 @@ ompi_btl_usnic_check_rx_seq(
     }
 
     /* Stats: is this the highest sequence number we've received? */
-    if (seq > endpoint->endpoint_highest_seq_rcvd) {
+    if (SEQ_GT(seq, endpoint->endpoint_highest_seq_rcvd)) {
         endpoint->endpoint_highest_seq_rcvd = seq;
     }
 
@@ -246,6 +247,7 @@ ompi_btl_usnic_recv_fast(ompi_btl_usnic_module_t *module,
     mca_btl_active_message_callback_t* reg;
     ompi_btl_usnic_seq_t seq;
     ompi_btl_usnic_endpoint_t *endpoint;
+    int delta;
     int i;
 
     bseg = &seg->rs_base;
@@ -264,9 +266,9 @@ ompi_btl_usnic_recv_fast(ompi_btl_usnic_module_t *module,
                 (void*)(seg->rs_recv_desc.sg_list[0].addr),
                 seg->rs_recv_desc.sg_list[0].length);
 
-        seq = seg->rs_base.us_btl_header->seq;
-        if (seq < endpoint->endpoint_next_contig_seq_to_recv ||
-            seq >= endpoint->endpoint_next_contig_seq_to_recv + WINDOW_SIZE)  {
+        seq = seg->rs_base.us_btl_header->pkt_seq;
+        delta = SEQ_DIFF(seq, endpoint->endpoint_next_contig_seq_to_recv);
+        if (delta < 0 || delta >= WINDOW_SIZE) {
             goto drop;
         }
 
diff --git a/ompi/mca/btl/usnic/btl_usnic_send.h b/ompi/mca/btl/usnic/btl_usnic_send.h
index 3eda92d647..8ef4ffecc6 100644
--- a/ompi/mca/btl/usnic/btl_usnic_send.h
+++ b/ompi/mca/btl/usnic/btl_usnic_send.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2013-2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -157,12 +157,13 @@ ompi_btl_usnic_endpoint_send_segment(
 
             next_seq_to_send > ack_seq_rcvd + WINDOW_SIZE
     */
-    assert(endpoint->endpoint_next_seq_to_send > 
-           endpoint->endpoint_ack_seq_rcvd);
+    assert(SEQ_GT(endpoint->endpoint_next_seq_to_send,
+                  endpoint->endpoint_ack_seq_rcvd));
     assert(WINDOW_OPEN(endpoint));
 
     /* Assign sequence number and increment */
-    sseg->ss_base.us_btl_header->seq = endpoint->endpoint_next_seq_to_send++;
+    sseg->ss_base.us_btl_header->pkt_seq =
+        endpoint->endpoint_next_seq_to_send++;
 
     /* Fill in remote address to indicate PUT or not */
     sseg->ss_base.us_btl_header->put_addr =
@@ -183,7 +184,7 @@ ompi_btl_usnic_endpoint_send_segment(
         opal_output(0, "--> Sending %s: seq: %" UDSEQ ", sender: 0x%016lx from device %s MAC %s, qp %u, seg %p, room %d, wc len %u, remote MAC %s, qp %u",
             (sseg->ss_parent_frag->sf_base.uf_type == OMPI_BTL_USNIC_FRAG_LARGE_SEND)?
                 "CHUNK" : "FRAG",
-            sseg->ss_base.us_btl_header->seq, 
+            sseg->ss_base.us_btl_header->pkt_seq,
             sseg->ss_base.us_btl_header->sender, 
             endpoint->endpoint_module->device->name,
             mac_str1, module->local_addr.qp_num[sseg->ss_channel],
@@ -200,7 +201,7 @@ ompi_btl_usnic_endpoint_send_segment(
        is the same length as the sender's window (i.e., WINDOW_SIZE).
        To find a unique slot in this array, use (seq % WINDOW_SIZE).
      */
-    sfi = WINDOW_SIZE_MOD(sseg->ss_base.us_btl_header->seq);
+    sfi = WINDOW_SIZE_MOD(sseg->ss_base.us_btl_header->pkt_seq);
     endpoint->endpoint_sent_segs[sfi] = sseg;
     sseg->ss_ack_pending = true;