diff --git a/ospf6d/ospf6_ism.c b/ospf6d/ospf6_ism.c
new file mode 100644
index 0000000..d13be12
--- /dev/null
+++ b/ospf6d/ospf6_ism.c
@@ -0,0 +1,519 @@
+/*
+ * Copyright (C) 1999 Yasuhiro Ohara
+ *
+ * This file is part of GNU Zebra.
+ *
+ * GNU Zebra is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * GNU Zebra is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Zebra; see the file COPYING.  If not, write to the 
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330, 
+ * Boston, MA 02111-1307, USA.  
+ */
+
+/* Interface State Machine */
+
+#include "ospf6d.h"
+
+int
+ifs_change (state_t ifs_next, char *reason, struct ospf6_interface *o6i)
+{
+  state_t ifs_prev;
+
+  ifs_prev = o6i->state;
+
+  if (ifs_prev == ifs_next)
+    return 0;
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: %s -> %s (%s)",
+               o6i->interface->name,
+               ospf6_interface_state_string[ifs_prev],
+               ospf6_interface_state_string[ifs_next], reason);
+
+  if ((ifs_prev == IFS_DR || ifs_prev == IFS_BDR) &&
+      (ifs_next != IFS_DR && ifs_next != IFS_BDR))
+    ospf6_leave_alldrouters (o6i->interface->ifindex);
+  else if ((ifs_prev != IFS_DR && ifs_prev != IFS_BDR) &&
+           (ifs_next == IFS_DR || ifs_next == IFS_BDR))
+    ospf6_join_alldrouters (o6i->interface->ifindex);
+
+  o6i->state = ifs_next;
+
+  if (o6i->prevdr != o6i->dr || o6i->prevbdr != o6i->bdr)
+    {
+      if (IS_OSPF6_DUMP_INTERFACE)
+        {
+          char dr[16], bdr[16], prevdr[16], prevbdr[16];
+          inet_ntop (AF_INET, &o6i->prevdr, prevdr, sizeof (prevdr));
+          inet_ntop (AF_INET, &o6i->prevbdr, prevbdr, sizeof (prevbdr));
+          inet_ntop (AF_INET, &o6i->dr, dr, sizeof (dr));
+          inet_ntop (AF_INET, &o6i->bdr, bdr, sizeof (bdr));
+          zlog_info ("I/F: %s: DR: %s -> %s", o6i->interface->name,
+                     prevdr, dr);
+          zlog_info ("I/F: %s: BDR: %s -> %s", o6i->interface->name,
+                     prevbdr, bdr);
+        }
+    }
+
+  CALL_CHANGE_HOOK (&interface_hook, o6i);
+  return 0;
+}
+
+
+/* Interface State Machine */
+int
+interface_up (struct thread *thread)
+{
+  struct ospf6_interface *ospf6_interface;
+
+  ospf6_interface = (struct ospf6_interface *)THREAD_ARG (thread);
+
+  assert (ospf6_interface);
+  assert (ospf6_interface->interface);
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: InterfaceUp",
+               ospf6_interface->interface->name);
+
+  /* check physical interface is up */
+  if (!if_is_up (ospf6_interface->interface))
+    {
+      if (IS_OSPF6_DUMP_INTERFACE)
+        zlog_warn ("  interface %s down, can't execute InterfaceUp",
+                   ospf6_interface->interface->name);
+      return -1;
+    }
+
+  /* if already enabled, do nothing */
+  if (ospf6_interface->state > IFS_DOWN)
+    {
+      zlog_warn ("Interface %s already up",
+                 ospf6_interface->interface->name);
+      return 0;
+    }
+
+  /* ifid of this interface */
+  ospf6_interface->if_id = ospf6_interface->interface->ifindex;
+
+  /* Join AllSPFRouters */
+  ospf6_join_allspfrouters (ospf6_interface->interface->ifindex);
+
+  /* set socket options */
+  ospf6_set_reuseaddr ();
+  ospf6_reset_mcastloop ();
+  ospf6_set_pktinfo ();
+  ospf6_set_checksum ();
+
+  /* Schedule Hello */
+  if (! CHECK_FLAG (ospf6_interface->flag, OSPF6_INTERFACE_FLAG_PASSIVE))
+    thread_add_event (master, ospf6_send_hello, ospf6_interface, 0);
+
+  /* decide next interface state */
+  if (if_is_pointopoint (ospf6_interface->interface))
+    ifs_change (IFS_PTOP, "IF Type PointToPoint", ospf6_interface);
+  else if (ospf6_interface->priority == 0)
+    ifs_change (IFS_DROTHER, "Router Priority = 0", ospf6_interface);
+  else
+    {
+      ifs_change (IFS_WAITING, "Priority > 0", ospf6_interface);
+      thread_add_timer (master, wait_timer, ospf6_interface,
+                        ospf6_interface->dead_interval);
+    }
+
+  CALL_FOREACH_LSA_HOOK (hook_interface, hook_change, ospf6_interface);
+
+  return 0;
+}
+
+int
+wait_timer (struct thread *thread)
+{
+  struct ospf6_interface *ospf6_interface;
+
+  ospf6_interface = (struct ospf6_interface *)THREAD_ARG  (thread);
+  assert (ospf6_interface);
+
+  if (ospf6_interface->state != IFS_WAITING)
+    return 0;
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: WaitTimer", ospf6_interface->interface->name);
+
+  ifs_change (dr_election (ospf6_interface),
+              "WaitTimer:DR Election", ospf6_interface);
+  return 0;
+}
+
+int backup_seen (struct thread *thread)
+{
+  struct ospf6_interface *ospf6_interface;
+
+  ospf6_interface = (struct ospf6_interface *)THREAD_ARG  (thread);
+  assert (ospf6_interface);
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: BackupSeen", ospf6_interface->interface->name);
+
+  if (ospf6_interface->state == IFS_WAITING)
+    ifs_change (dr_election (ospf6_interface),
+                "BackupSeen:DR Election", ospf6_interface);
+
+  return 0;
+}
+
+int neighbor_change (struct thread *thread)
+{
+  struct ospf6_interface *ospf6_interface;
+
+  ospf6_interface = (struct ospf6_interface *)THREAD_ARG  (thread);
+  assert (ospf6_interface);
+
+  if (ospf6_interface->state != IFS_DROTHER &&
+      ospf6_interface->state != IFS_BDR &&
+      ospf6_interface->state != IFS_DR)
+    return 0;
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: NeighborChange", ospf6_interface->interface->name);
+
+  ifs_change (dr_election (ospf6_interface),
+              "NeighborChange:DR Election", ospf6_interface);
+
+  return 0;
+}
+
+int
+loopind (struct thread *thread)
+{
+  struct ospf6_interface *ospf6_interface;
+
+  ospf6_interface = (struct ospf6_interface *)THREAD_ARG (thread);
+  assert (ospf6_interface);
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: LoopInd", ospf6_interface->interface->name);
+
+  /* XXX not yet */
+
+  return 0;
+}
+
+int
+interface_down (struct thread *thread)
+{
+  struct ospf6_interface *ospf6_interface;
+
+  ospf6_interface = (struct ospf6_interface *) THREAD_ARG (thread);
+  assert (ospf6_interface);
+
+  if (IS_OSPF6_DUMP_INTERFACE)
+    zlog_info ("I/F: %s: InterfaceDown", ospf6_interface->interface->name);
+
+  if (ospf6_interface->state == IFS_NONE)
+    return 1;
+
+  /* Leave AllSPFRouters */
+  if (ospf6_interface_is_enabled (ospf6_interface->interface->ifindex))
+    ospf6_leave_allspfrouters (ospf6_interface->interface->ifindex);
+
+  ifs_change (IFS_DOWN, "Configured", ospf6_interface);
+
+  return 0;
+}
+
+
+/* 9.4 of RFC2328 */
+int
+dr_election (struct ospf6_interface *ospf6_interface)
+{
+  list candidate_list = list_new ();
+  listnode i, j, n;
+  ifid_t prevdr, prevbdr, dr = 0, bdr;
+  struct ospf6_neighbor *nbpi, *nbpj, myself, *nbr;
+  int declare = 0;
+  int gofive = 0;
+
+  /* statistics */
+  ospf6_interface->ospf6_stat_dr_election++;
+
+  /* pseudo neighbor "myself" */
+  memset (&myself, 0, sizeof (myself));
+  myself.state = NBS_TWOWAY;
+  myself.dr = ospf6_interface->dr;
+  myself.bdr = ospf6_interface->bdr;
+  myself.priority = ospf6_interface->priority;
+  myself.ifid = ospf6_interface->if_id;
+  myself.router_id = ospf6_interface->area->ospf6->router_id;
+
+/* step_one: */
+
+  ospf6_interface->prevdr = prevdr = ospf6_interface->dr;
+  ospf6_interface->prevbdr = prevbdr = ospf6_interface->bdr;
+
+step_two:
+
+  /* Calculate Backup Designated Router. */
+  /* Make Candidate list */
+  if (!list_isempty (candidate_list))
+    list_delete_all_node (candidate_list);
+  declare = 0;
+  for (i = listhead (ospf6_interface->neighbor_list); i; nextnode (i))
+    {
+      nbpi = (struct ospf6_neighbor *)getdata (i);
+      if (nbpi->priority == 0)
+        continue;
+      if (nbpi->state < NBS_TWOWAY)
+        continue;
+      if (nbpi->dr == nbpi->router_id)
+        continue;
+      if (nbpi->bdr == nbpi->router_id)
+        declare++;
+      listnode_add (candidate_list, nbpi);
+    }
+
+  if (myself.priority)
+    {
+      if (myself.dr != myself.router_id)
+        {
+          if (myself.bdr == myself.router_id)
+            declare++;
+          listnode_add (candidate_list, &myself);
+        }
+    }
+
+  /* Elect BDR */
+  for (i = listhead (candidate_list);
+       candidate_list->count > 1;
+       i = listhead (candidate_list))
+    {
+      j = i;
+      nextnode(j);
+      assert (j);
+      nbpi = (struct ospf6_neighbor *)getdata (i);
+      nbpj = (struct ospf6_neighbor *)getdata (j);
+      if (declare)
+        {
+          int deleted = 0;
+          if (nbpi->bdr != nbpi->router_id)
+            {
+              listnode_delete (candidate_list, nbpi);
+              deleted++;
+            }
+          if (nbpj->bdr != nbpj->router_id)
+            {
+              listnode_delete (candidate_list, nbpj);
+              deleted++;
+            }
+          if (deleted)
+            continue;
+        }
+      if (nbpi->priority > nbpj->priority)
+        {
+          listnode_delete (candidate_list, nbpj);
+          continue;
+        }
+      else if (nbpi->priority < nbpj->priority)
+        {
+          listnode_delete (candidate_list, nbpi);
+          continue;
+        }
+      else /* equal, case of tie */
+        {
+          if (ntohl (nbpi->router_id) > ntohl (nbpj->router_id))
+            {
+              listnode_delete (candidate_list, nbpj);
+              continue;
+            }
+          else if (ntohl (nbpi->router_id) < ntohl (nbpj->router_id))
+            {
+              listnode_delete (candidate_list, nbpi);
+              continue;
+            }
+          else
+            assert (0);
+        }
+    }
+
+  if (!list_isempty (candidate_list))
+    {
+      assert (candidate_list->count == 1);
+      n = listhead (candidate_list);
+      nbr = (struct ospf6_neighbor *)getdata (n);
+      bdr = nbr->router_id;
+    }
+  else
+    bdr = 0;
+
+/* step_three: */
+
+  /* Calculate Designated Router. */
+  /* Make Candidate list */
+  if (!list_isempty (candidate_list))
+    list_delete_all_node (candidate_list);
+  declare = 0;
+  for (i = listhead (ospf6_interface->neighbor_list); i; nextnode (i))
+    {
+      nbpi = (struct ospf6_neighbor *)getdata (i);
+      if (nbpi->priority == 0)
+        continue;
+      if (nbpi->state < NBS_TWOWAY)
+        continue;
+      if (nbpi->dr == nbpi->router_id)
+        {
+          declare++;
+          listnode_add (candidate_list, nbpi);
+        }
+    }
+  if (myself.priority)
+    {
+      if (myself.dr == myself.router_id)
+        {
+          declare++;
+          listnode_add (candidate_list, &myself);
+        }
+    }
+
+  /* Elect DR */
+  if (declare == 0)
+    {
+      assert (list_isempty (candidate_list));
+      /* No one declare but candidate_list not empty */
+      dr = bdr;
+    }
+  else
+    {
+      assert (!list_isempty (candidate_list));
+      for (i = listhead (candidate_list);
+           candidate_list->count > 1;
+           i = listhead (candidate_list))
+        {
+          j = i;
+          nextnode (j);
+          assert (j);
+          nbpi = (struct ospf6_neighbor *)getdata (i);
+          nbpj = (struct ospf6_neighbor *)getdata (j);
+
+          if (nbpi->dr != nbpi->router_id)
+            {
+              list_delete_node (candidate_list, i);
+              continue;
+            }
+          if (nbpj->dr != nbpj->router_id)
+            {
+              list_delete_node (candidate_list, j);
+              continue;
+            }
+
+          if (nbpi->priority > nbpj->priority)
+            {
+              list_delete_node (candidate_list, j);
+              continue;
+            }
+          else if (nbpi->priority < nbpj->priority)
+            {
+              list_delete_node (candidate_list, i);
+              continue;
+            }
+          else /* equal, case of tie */
+            {
+              if (nbpi->router_id > nbpj->router_id)
+                {
+                  list_delete_node (candidate_list, j);
+                  continue;
+                }
+              else if (nbpi->router_id < nbpj->router_id)
+                {
+                  list_delete_node (candidate_list, i);
+                  continue;
+                }
+              else
+                {
+                  zlog_warn ("!!!THE SAME ROUTER ID FOR DIFFERENT NEIGHBOR");
+                  zlog_warn ("!!!MISCONFIGURATION?");
+                  list_delete_node (candidate_list, i);
+                  continue;
+                }
+            }
+        }
+      if (!list_isempty (candidate_list))
+        {
+          assert (candidate_list->count == 1);
+          n = listhead (candidate_list);
+          nbr = (struct ospf6_neighbor *)getdata (n);
+          dr = nbr->router_id;
+        }
+      else
+        assert (0);
+    }
+
+/* step_four: */
+
+  if (gofive)
+    goto step_five;
+
+  if (dr != prevdr)
+    {
+      if ((dr == myself.router_id || prevdr == myself.router_id)
+          && !(dr == myself.router_id && prevdr == myself.router_id))
+        {
+          myself.dr = dr;
+          myself.bdr = bdr;
+          gofive++;
+          goto step_two;
+        }
+    }
+  if (bdr != prevbdr)
+    {
+      if ((bdr == myself.router_id || prevbdr == myself.router_id)
+          && !(bdr == myself.router_id && prevbdr == myself.router_id))
+        {
+          myself.dr = dr;
+          myself.bdr = bdr;
+          gofive++;
+          goto step_two;
+        }
+    }
+
+step_five:
+
+  ospf6_interface->dr = dr;
+  ospf6_interface->bdr = bdr;
+
+  if (prevdr != dr || prevbdr != bdr)
+    {
+      for (i = listhead (ospf6_interface->neighbor_list); i; nextnode (i))
+        {
+          nbpi = getdata (i);
+          if (nbpi->state < NBS_TWOWAY)
+            continue;
+          /* Schedule or Execute AdjOK. which does "invoke" mean? */
+          thread_add_event (master, adj_ok, nbpi, 0);
+        }
+    }
+
+  list_delete (candidate_list);
+
+  if (dr == myself.router_id)
+    {
+      assert (bdr != myself.router_id);
+      return IFS_DR;
+    }
+  else if (bdr == myself.router_id)
+    {
+      assert (dr != myself.router_id);
+      return IFS_BDR;
+    }
+  else
+    return IFS_DROTHER;
+}
+
+