/** Asserts that the expected retransmission requests match the actual ones */
 protected void assertXmitRequests(long... expected_seqnos) {
   List<Long> actual_xmit_reqs = transport.getXmitRequests();
   assert actual_xmit_reqs.size() == expected_seqnos.length
       : "size mismatch: expected="
           + Arrays.toString(expected_seqnos)
           + ", received="
           + actual_xmit_reqs;
   for (int i = 0; i < expected_seqnos.length; i++) {
     assert expected_seqnos[i] == actual_xmit_reqs.get(i)
         : "expected=" + Arrays.toString(expected_seqnos) + ", received=" + actual_xmit_reqs;
   }
   actual_xmit_reqs.clear();
 }