X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Fconsensus%2Fgnunet-service-consensus.c;h=cb7ab2c6835f8477f0fa7aef88b91e80df6b6b0c;hb=d88cf34549d5aa0d8367ace1d5482289d4925525;hp=d223360dcbc9f89355e59af5e65f4c7869481f93;hpb=4dc3faf5e88b8ca602602aa28a6ff76c02d34848;p=oweals%2Fgnunet.git

diff --git a/src/consensus/gnunet-service-consensus.c b/src/consensus/gnunet-service-consensus.c
index d223360dc..cb7ab2c68 100644
--- a/src/consensus/gnunet-service-consensus.c
+++ b/src/consensus/gnunet-service-consensus.c
@@ -1,6 +1,6 @@
 /*
       This file is part of GNUnet
-      (C) 2012 Christian Grothoff (and other contributing authors)
+      (C) 2012, 2013 Christian Grothoff (and other contributing authors)
 
       GNUnet is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
@@ -20,7 +20,7 @@
 
 /**
  * @file consensus/gnunet-service-consensus.c
- * @brief 
+ * @brief multi-peer set reconciliation
  * @author Florian Dold
  */
 
@@ -29,213 +29,90 @@
 #include "gnunet_protocols.h"
 #include "gnunet_applications.h"
 #include "gnunet_util_lib.h"
+#include "gnunet_set_service.h"
 #include "gnunet_consensus_service.h"
-#include "gnunet_core_service.h"
-#include "gnunet_stream_lib.h"
 #include "consensus_protocol.h"
-#include "ibf.h"
 #include "consensus.h"
 
 
 /**
- * Number of IBFs in a strata estimator.
+ * Log macro that prefixes the local peer and the peer we are in contact with.
  */
-#define STRATA_COUNT 32
-/**
- * Number of buckets per IBF.
- */
-#define STRATA_IBF_BUCKETS 80
-/**
- * hash num parameter for the difference digests and strata estimators
- */
-#define STRATA_HASH_NUM 3
+#define LOG_PP(kind, cpi, m,...) GNUNET_log (kind, "P%d for P%d: " m, \
+   cpi->session->local_peer_idx, (int) (cpi - cpi->session->info),##__VA_ARGS__)
 
-/**
- * Number of buckets that can be transmitted in one message.
- */
-#define BUCKETS_PER_MESSAGE ((1<<15) / IBF_BUCKET_SIZE)
 
 /**
- * The maximum size of an ibf we use is 2^(MAX_IBF_ORDER).
- * Choose this value so that computing the IBF is still cheaper
- * than transmitting all values.
+ * Number of exponential rounds, used in the exp and completion round.
  */
-#define MAX_IBF_ORDER (32)
-
+#define NUM_EXP_ROUNDS 4
 
 /* forward declarations */
 
-struct ConsensusSession;
-struct IncomingSocket;
+/* mutual recursion with struct ConsensusSession */
 struct ConsensusPeerInformation;
 
+/* mutual recursion with round_over */
 static void
-send_next (struct ConsensusSession *session);
-
-static void 
-write_strata (void *cls, enum GNUNET_STREAM_Status status, size_t size);
-
-static void 
-write_ibf (void *cls, enum GNUNET_STREAM_Status status, size_t size);
-
-static void 
-write_requests_and_elements (void *cls, enum GNUNET_STREAM_Status status, size_t size);
-
-static int
-get_peer_idx (const struct GNUNET_PeerIdentity *peer, const struct ConsensusSession *session);
-
+subround_over (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);
 
-/**
- * An element that is waiting to be transmitted.
- */
-struct PendingElement
-{
-  /**
-   * Pending elements are kept in a DLL.
-   */
-  struct PendingElement *next;
-
-  /**
-   * Pending elements are kept in a DLL.
-   */
-  struct PendingElement *prev;
-
-  /**
-   * The actual element
-   */
-  struct GNUNET_CONSENSUS_Element *element;
-
-  /* peer this element is coming from */
-  struct ConsensusPeerInformation *cpi;
-};
 
 /**
- * Information about a peer that is in a consensus session.
+ * Describes the current round a consensus session is in.
  */
-struct ConsensusPeerInformation
+enum ConsensusRound
 {
-  struct GNUNET_STREAM_Socket *socket;
-
-  /**
-   * Is socket's connection established, i.e. can we write to it?
-   * Only relevent on outgoing cpi.
-   */
-  int is_connected;
-
-  /**
-   * Type of the peer in the all-to-all rounds,
-   * GNUNET_YES if we initiate reconciliation.
-   */
-  int is_outgoing;
-
-  /**
-   * if the peer did something wrong, and was disconnected,
-   * never interact with this peer again.
-   */
-  int is_bad;
-
-  /**
-   * Did we receive/send a consensus hello?
-   */
-  int hello;
-
-  /**
-   * Handle for currently active read
-   */
-  struct GNUNET_STREAM_ReadHandle *rh;
-
-  /**
-   * Handle for currently active read
-   */
-  struct GNUNET_STREAM_WriteHandle *wh;
-
-  enum {
-    IBF_STATE_NONE,
-    IBF_STATE_RECEIVING,
-    IBF_STATE_TRANSMITTING,
-    IBF_STATE_DECODING
-  } ibf_state ;
-
-  /**
-   * What is the order (=log2 size) of the ibf
-   * we're currently dealing with?
-   */
-  int ibf_order;
-
   /**
-   * The current IBF for this peer,
-   * purpose dependent on ibf_state
+   * Not started the protocol yet.
    */
-  struct InvertibleBloomFilter *ibf;
-
+  CONSENSUS_ROUND_BEGIN=0,
   /**
-   * How many buckets have we transmitted/received (depending on state)?
+   * Distribution of elements with the exponential scheme.
    */
-  int ibf_bucket_counter;
-
+  CONSENSUS_ROUND_EXCHANGE,
   /**
-   * Strata estimator of the peer, NULL if our peer
-   * initiated the reconciliation.
+   * Exchange which elements each peer has, but don't
+   * transmit the element's data, only their SHA-512 hashes.
+   * This round uses the all-to-all scheme.
    */
-  struct InvertibleBloomFilter **strata;
-
+  CONSENSUS_ROUND_INVENTORY,
   /**
-   * difference estimated with the current strata estimator
+   * Collect and distribute missing values with the exponential scheme.
    */
-  unsigned int diff;
-
-  struct GNUNET_SERVER_MessageStreamTokenizer *mst;
-
+  CONSENSUS_ROUND_COMPLETION,
   /**
-   * Back-reference to the consensus session,
-   * to that ConsensusPeerInformation can be used as a closure
+   * Consensus concluded. After timeout and finished communication with client,
+   * consensus session will be destroyed.
    */
-  struct ConsensusSession *session;
-
-  struct PendingElement *send_pending_head;
-  struct PendingElement *send_pending_tail;
+  CONSENSUS_ROUND_FINISH
 };
 
-struct QueuedMessage
-{
-  struct GNUNET_MessageHeader *msg;
-
-  /**
-   * Queued messages are stored in a doubly linked list.
-   */
-  struct QueuedMessage *next;
-
-  /**
-   * Queued messages are stored in a doubly linked list.
-   */
-  struct QueuedMessage *prev;
-};
 
-enum ConsensusRound
+/**
+ * Complete information about the current round and all
+ * subrounds.
+ */
+struct RoundInfo
 {
   /**
-   * distribution of information with the exponential scheme
+   * The current main round.
    */
-  CONSENSUS_ROUND_EXP_EXCHANGE,
+  enum ConsensusRound round;
   /**
-   * All-to-all, exchange missing values
+   * The current exp round, valid if
+   * the main round is an exp round.
    */
-  CONSENSUS_ROUND_A2A_EXCHANGE,
+  uint32_t exp_round;
   /**
-   * All-to-all, check what values are missing, don't exchange anything
+   * The current exp subround, valid if
+   * the main round is an exp round.
    */
-  CONSENSUS_ROUND_A2A_INVENTORY
-
-  /*
-  a round to exchange the information for fraud-detection
-  CONSENSUS_ROUNT_A2_INVENTORY_AGREEMENT
-  */
+  uint32_t exp_subround;
 };
 
 
 /**
  * A consensus session consists of one local client and the remote authorities.
- *
  */
 struct ConsensusSession
 {
@@ -249,167 +126,139 @@ struct ConsensusSession
    */
   struct ConsensusSession *prev;
 
-  /**
-   * Join message. Used to initialize the session later,
-   * if the identity of the local peer is not yet known.
-   * NULL if the session has been fully initialized.
-   */
-  struct GNUNET_CONSENSUS_JoinMessage *join_msg;
-
   /**
   * Global consensus identification, computed
-  * from the local id and participating authorities.
+  * from the session id and participating authorities.
   */
   struct GNUNET_HashCode global_id;
 
   /**
-   * Local client in this consensus session.
-   * There is only one client per consensus session.
+   * Client that inhabits the session
    */
   struct GNUNET_SERVER_Client *client;
 
   /**
-   * Values in the consensus set of this session,
-   * all of them either have been sent by or approved by the client.
-   * Contains GNUNET_CONSENSUS_Element.
-   */
-  struct GNUNET_CONTAINER_MultiHashMap *values;
-
-  /**
-   * Elements that have not been approved (or rejected) by the client yet.
+   * Queued messages to the client.
    */
-  struct PendingElement *approval_pending_head;
+  struct GNUNET_MQ_Handle *client_mq;
 
   /**
-   * Elements that have not been approved (or rejected) by the client yet.
+   * Timeout for all rounds together, single rounds will schedule a timeout task
+   * with a fraction of the conclude timeout.
+   * Only valid once the current round is not CONSENSUS_ROUND_BEGIN.
    */
-  struct PendingElement *approval_pending_tail;
-
+  struct GNUNET_TIME_Relative conclude_timeout;
+  
   /**
-   * Messages to be sent to the local client that owns this session
+   * Timeout task identifier for the current round.
    */
-  struct QueuedMessage *client_messages_head;
+  GNUNET_SCHEDULER_TaskIdentifier round_timeout_tid;
 
   /**
-   * Messages to be sent to the local client that owns this session
+   * Number of other peers in the consensus.
    */
-  struct QueuedMessage *client_messages_tail;
+  unsigned int num_peers;
 
   /**
-   * Currently active transmit handle for sending to the client
+   * Information about the other peers,
+   * their state, etc.
    */
-  struct GNUNET_SERVER_TransmitHandle *th;
+  struct ConsensusPeerInformation *info;
 
   /**
-   * Once conclude_requested is GNUNET_YES, the client may not
-   * insert any more values.
+   * Index of the local peer in the peers array
    */
-  int conclude_requested;
+  unsigned int local_peer_idx;
 
   /**
-   * Minimum number of peers to form a consensus group
+   * Current round
    */
-  int conclude_group_min;
+  enum ConsensusRound current_round;
 
   /**
-   * Number of other peers in the consensus
+   * Permutation of peers for the current round,
+   * maps logical index (for current round) to physical index (location in info array)
    */
-  unsigned int num_peers;
+  uint32_t *shuffle;
 
   /**
-   * Information about the other peers,
-   * their state, etc.
+   * Current round of the exponential scheme.
    */
-  struct ConsensusPeerInformation *info;
+  uint32_t exp_round;
 
   /**
-   * Sorted array of peer identities in this consensus session,
-   * includes the local peer.
+   * Current sub-round of the exponential scheme.
    */
-  struct GNUNET_PeerIdentity *peers;
+  uint32_t exp_subround;
 
   /**
-   * Index of the local peer in the peers array
+   * The partner for the current exp-round
    */
-  int local_peer_idx;
+  struct ConsensusPeerInformation *partner_outgoing;
 
   /**
-   * Strata estimator, computed online
+   * The partner for the current exp-round
    */
-  struct InvertibleBloomFilter **strata;
+  struct ConsensusPeerInformation *partner_incoming;
 
   /**
-   * Pre-computed IBFs
+   * The consensus set of this session.
    */
-  struct InvertibleBloomFilter **ibfs;
+  struct GNUNET_SET_Handle *element_set;
 
   /**
-   * Current round
+   * Listener for requests from other peers.
+   * Uses the session's global id as app id.
    */
-  enum ConsensusRound current_round;
+  struct GNUNET_SET_ListenHandle *set_listener;
 };
 
 
 /**
- * Sockets from other peers who want to communicate with us.
- * It may not be known yet which consensus session they belong to.
+ * Information about a peer that is in a consensus session.
  */
-struct IncomingSocket
+struct ConsensusPeerInformation
 {
   /**
-   * Incoming sockets are kept in a double linked list.
+   * Peer identitty of the peer in the consensus session
    */
-  struct IncomingSocket *next;
+  struct GNUNET_PeerIdentity peer_id;
 
   /**
-   * Incoming sockets are kept in a double linked list.
-   */
-  struct IncomingSocket *prev;
-
-  /**
-   * The actual socket.
-   */
-  struct GNUNET_STREAM_Socket *socket;
-
-  /**
-   * Handle for currently active read
+   * Back-reference to the consensus session,
+   * to that ConsensusPeerInformation can be used as a closure
    */
-  struct GNUNET_STREAM_ReadHandle *rh;
+  struct ConsensusSession *session;
 
   /**
-   * Peer that connected to us with the socket.
+   * We have finishes the exp-subround with the peer.
    */
-  struct GNUNET_PeerIdentity *peer;
+  int exp_subround_finished;
 
   /**
-   * Message stream tokenizer for this socket.
+   * Set operation we are currently executing with this peer.
    */
-  struct GNUNET_SERVER_MessageStreamTokenizer *mst;
+  struct GNUNET_SET_OperationHandle *set_op;
 
   /**
-   * Peer-in-session this socket belongs to, once known, otherwise NULL.
+   * Set operation we are planning on executing with this peer.
    */
-  struct ConsensusPeerInformation *cpi;
+  struct GNUNET_SET_OperationHandle *delayed_set_op;
 
   /**
-   * Set to the global session id, if the peer sent us a hello-message,
-   * but the session does not exist yet.
-   *
-   * FIXME: not implemented yet
+   * Info about the round of the delayed set operation.
    */
-  struct GNUNET_HashCode *requested_gid;
+  struct RoundInfo delayed_round_info;
 };
 
-static struct IncomingSocket *incoming_sockets_head;
-static struct IncomingSocket *incoming_sockets_tail;
 
 /**
- * Linked list of sesstions this peer participates in.
+ * Linked list of sessions this peer participates in.
  */
 static struct ConsensusSession *sessions_head;
 
 /**
- * Linked list of sesstions this peer participates in.
+ * Linked list of sessions this peer participates in.
  */
 static struct ConsensusSession *sessions_tail;
 
@@ -426,559 +275,507 @@ static struct GNUNET_SERVER_Handle *srv;
 /**
  * Peer that runs this service.
  */
-static struct GNUNET_PeerIdentity *my_peer;
+static struct GNUNET_PeerIdentity my_peer;
 
-/**
- * Handle to the core service. Only used during service startup, will be NULL after that.
- */
-static struct GNUNET_CORE_Handle *core;
 
-/**
- * Listener for sockets from peers that want to reconcile with us.
- */
-static struct GNUNET_STREAM_ListenSocket *listener;
+static int
+have_exp_subround_finished (const struct ConsensusSession *session)
+{
+  int not_finished;
+  not_finished = 0;
+  if ( (NULL != session->partner_outgoing) && 
+       (GNUNET_NO == session->partner_outgoing->exp_subround_finished) )
+    not_finished++;
+  if ( (NULL != session->partner_incoming) &&
+       (GNUNET_NO == session->partner_incoming->exp_subround_finished) )
+    not_finished++;
+  if (0 == not_finished)
+    return GNUNET_YES;
+  return GNUNET_NO;
+}
 
 
 /**
- * Queue a message to be sent to the inhabiting client of a sessino
- *
- * @param session session
- * @param msg message we want to queue
+ * Destroy a session, free all resources associated with it.
+ * 
+ * @param session the session to destroy
  */
 static void
-queue_client_message (struct ConsensusSession *session, struct GNUNET_MessageHeader *msg)
+destroy_session (struct ConsensusSession *session)
 {
-  struct QueuedMessage *qm;
-  qm = GNUNET_malloc (sizeof *qm);
-  qm->msg = msg;
-  GNUNET_CONTAINER_DLL_insert_tail (session->client_messages_head, session->client_messages_tail, qm);
+  int i;
+
+  GNUNET_CONTAINER_DLL_remove (sessions_head, sessions_tail, session);
+  if (NULL != session->element_set)
+  {
+    GNUNET_SET_destroy (session->element_set);
+    session->element_set = NULL;
+  }
+  if (NULL != session->set_listener)
+  {
+    GNUNET_SET_listen_cancel (session->set_listener);
+    session->set_listener = NULL;
+  }
+  if (NULL != session->client_mq)
+  {
+    GNUNET_MQ_destroy (session->client_mq);
+    session->client_mq = NULL;
+  }
+  if (NULL != session->client)
+  {
+    GNUNET_SERVER_client_disconnect (session->client);
+    session->client = NULL;
+  }
+  if (NULL != session->shuffle)
+  {
+    GNUNET_free (session->shuffle);
+    session->shuffle = NULL;
+  }
+  if (NULL != session->info)
+  {
+    for (i = 0; i < session->num_peers; i++)
+    {
+      struct ConsensusPeerInformation *cpi;
+      cpi = &session->info[i];
+      if (NULL != cpi->set_op)
+      {
+        GNUNET_SET_operation_cancel (cpi->set_op);
+        cpi->set_op = NULL;
+      }
+    }
+    GNUNET_free (session->info);
+    session->info = NULL;
+  }
+  GNUNET_free (session);
 }
 
+
 /**
- * Get peer index associated with the peer information,
- * unique for every session among all peers.
+ * Iterator for set elements.
+ *
+ * @param cls closure
+ * @param element the current element, NULL if all elements have been
+ *        iterated over
+ * @return GNUNET_YES to continue iterating, GNUNET_NO to stop.
  */
 static int
-get_cpi_index (struct ConsensusPeerInformation *cpi)
+send_to_client_iter (void *cls,
+                     const struct GNUNET_SET_Element *element)
 {
-  return cpi - cpi->session->info;
+  struct ConsensusSession *session = cls;
+  struct GNUNET_MQ_Envelope *ev;
+
+  if (NULL != element)
+  {
+    struct GNUNET_CONSENSUS_ElementMessage *m;
+
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d: got element for client\n",
+                session->local_peer_idx);
+
+    ev = GNUNET_MQ_msg_extra (m, element->size, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_RECEIVED_ELEMENT);
+    m->element_type = htons (element->type);
+    memcpy (&m[1], element->data, element->size);
+    GNUNET_MQ_send (session->client_mq, ev);
+  }
+  else
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d: finished iterating elements for client\n",
+                session->local_peer_idx);
+    ev = GNUNET_MQ_msg_header (GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_CONCLUDE_DONE);
+    GNUNET_MQ_send (session->client_mq, ev);
+  }
+  return GNUNET_YES;
 }
 
+
 /**
- * Mark the peer as bad, free as state we don't need anymore.
+ * Start the next round.
+ * This function can be invoked as a timeout task, or called manually (tc will be NULL then).
+ *
+ * @param cls the session
+ * @param tc task context, for when this task is invoked by the scheduler,
+ *           NULL if invoked for another reason
  */
-static void
-mark_peer_bad (struct ConsensusPeerInformation *cpi)
+static void 
+round_over (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "peer #%u marked as bad\n", get_cpi_index (cpi));
-  cpi->is_bad = GNUNET_YES;
-  /* FIXME: free ibfs etc. */
+  struct ConsensusSession *session;
+
+  /* don't kick off next round if we're shutting down */
+  if ((NULL != tc) && (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+    return;
+
+  session = cls;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d: round over\n", session->local_peer_idx);
+
+  if (session->round_timeout_tid != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (session->round_timeout_tid);
+    session->round_timeout_tid = GNUNET_SCHEDULER_NO_TASK;
+  }
+
+  switch (session->current_round)
+  {
+    case CONSENSUS_ROUND_BEGIN:
+      session->current_round = CONSENSUS_ROUND_EXCHANGE;
+      session->exp_round = 0;
+      subround_over (session, NULL);
+      break;
+    case CONSENSUS_ROUND_EXCHANGE:
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d: finished, sending elements to client\n",
+                  session->local_peer_idx);
+      session->current_round = CONSENSUS_ROUND_FINISH;
+      GNUNET_SET_iterate (session->element_set, send_to_client_iter, session);
+      break;
+    default:
+      GNUNET_assert (0);
+  }
 }
 
 
 /**
- * Estimate set difference with two strata estimators,
- * i.e. arrays of IBFs.
+ * Create a new permutation for the session's peers in session->shuffle.
+ * Uses a Fisher-Yates shuffle with pseudo-randomness coming from
+ * both the global session id and the current round index.
+ *
+ * @param session the session to create the new permutation for
  */
-static int
-estimate_difference (struct InvertibleBloomFilter** strata1,
-                     struct InvertibleBloomFilter** strata2)
+static void
+shuffle (struct ConsensusSession *session)
 {
-  int i;
-  int count;
-  count = 0;
-  for (i = STRATA_COUNT - 1; i >= 0; i--)
+  uint32_t i;
+  uint32_t randomness[session->num_peers-1];
+
+  if (NULL == session->shuffle)
+    session->shuffle = GNUNET_malloc (session->num_peers * sizeof (*session->shuffle));
+
+  GNUNET_CRYPTO_kdf (randomness, sizeof (randomness), 
+		     &session->exp_round, sizeof (uint32_t),
+                     &session->global_id, sizeof (struct GNUNET_HashCode),
+		     NULL);
+
+  for (i = 0; i < session->num_peers; i++)
+    session->shuffle[i] = i;
+
+  for (i = session->num_peers - 1; i > 0; i--)
   {
-    struct InvertibleBloomFilter *diff;
-    int ibf_count;
-    int more;
-    ibf_count = 0;
-    diff = ibf_dup (strata1[i]);
-    ibf_subtract (diff, strata2[i]);
-    for (;;)
-    {
-      more = ibf_decode (diff, NULL, NULL);
-      if (GNUNET_NO == more)
-      {
-        count += ibf_count;
-        break;
-      }
-      if (GNUNET_SYSERR == more)
-      {
-        ibf_destroy (diff);
-        return count * (1 << (i + 1));
-      }
-      ibf_count++;
-    }
-    ibf_destroy (diff);
+    uint32_t x;
+    uint32_t tmp;
+    x = randomness[i-1] % session->num_peers;
+    tmp = session->shuffle[x];
+    session->shuffle[x] = session->shuffle[i];
+    session->shuffle[i] = tmp;
   }
-  return count;
 }
 
 
 /**
- * Called when receiving data from a peer that is member of
- * an inhabited consensus session.
+ * Find and set the partner_incoming and partner_outgoing of our peer,
+ * one of them may not exist (and thus set to NULL) if the number of peers
+ * in the session is not a power of two.
  *
- * @param cls the closure from GNUNET_STREAM_read
- * @param status the status of the stream at the time this function is called
- * @param data traffic from the other side
- * @param size the number of bytes available in data read; will be 0 on timeout 
- * @return number of bytes of processed from 'data' (any data remaining should be
- *         given to the next time the read processor is called).
+ * @param session the consensus session
  */
-static size_t
-session_stream_data_processor (void *cls,
-                       enum GNUNET_STREAM_Status status,
-                       const void *data,
-                       size_t size)
+static void
+find_partners (struct ConsensusSession *session)
 {
-  struct ConsensusPeerInformation *cpi;
-  int ret;
+  unsigned int arc;
+  unsigned int num_ghosts;
+  unsigned int largest_arc;
+  int partner_idx;
 
-  GNUNET_assert (GNUNET_STREAM_OK == status);
+  /* shuffled local index */
+  int my_idx = session->shuffle[session->local_peer_idx];
 
-  cpi = cls;
+  /* distance to neighboring peer in current subround */
+  arc = 1 << session->exp_subround;
+  largest_arc = 1;
+  while (largest_arc < session->num_peers)
+    largest_arc <<= 1;
+  num_ghosts = largest_arc - session->num_peers;
 
-  GNUNET_assert (NULL != cpi->mst);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "num ghosts: %d\n", num_ghosts);
 
-  ret = GNUNET_SERVER_mst_receive (cpi->mst, cpi, data, size, GNUNET_NO, GNUNET_YES);
-  if (GNUNET_SYSERR == ret)
+  if (0 == (my_idx & arc))
   {
-    /* FIXME: handle this correctly */
-    GNUNET_assert (0);
+    /* we are outgoing */
+    partner_idx = (my_idx + arc) % session->num_peers;
+    session->partner_outgoing = &session->info[session->shuffle[partner_idx]];
+    session->partner_outgoing->exp_subround_finished = GNUNET_NO;
+    /* are we a 'ghost' of a peer that would exist if
+     * the number of peers was a power of two, and thus have to partner
+     * with an additional peer?
+     */
+    if (my_idx < num_ghosts)
+    {
+      int ghost_partner_idx;
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "my index %d, arc %d, peers %u\n", my_idx, arc, session->num_peers);
+      ghost_partner_idx = (my_idx - (int) arc) % (int) session->num_peers;
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "ghost partner is before %d\n", ghost_partner_idx);
+      /* platform dependent; modulo sometimes returns negative values */
+      if (ghost_partner_idx < 0)
+        ghost_partner_idx += session->num_peers;
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "ghost partner is after %d\n", ghost_partner_idx);
+      session->partner_incoming = &session->info[session->shuffle[ghost_partner_idx]];
+      session->partner_incoming->exp_subround_finished = GNUNET_NO;
+      return;
+    }
+    session->partner_incoming = NULL;
+    return;
   }
-
-  /* read again */
-  cpi->rh = GNUNET_STREAM_read (cpi->socket, GNUNET_TIME_UNIT_FOREVER_REL,
-                                &session_stream_data_processor, cpi);
-
-  /* we always read all data */
-  return size;
+  partner_idx = (my_idx - (int) arc) % (int) session->num_peers;
+  if (partner_idx < 0)
+    partner_idx += session->num_peers;
+  session->partner_outgoing = NULL;
+  session->partner_incoming = &session->info[session->shuffle[partner_idx]];
+  session->partner_incoming->exp_subround_finished = GNUNET_NO;
 }
 
+
 /**
- * Called when we receive data from a peer that is not member of
- * a session yet, or the session is not yet inhabited.
+ * Callback for set operation results. Called for each element
+ * in the result set.
  *
- * @param cls the closure from GNUNET_STREAM_read
- * @param status the status of the stream at the time this function is called
- * @param data traffic from the other side
- * @param size the number of bytes available in data read; will be 0 on timeout 
- * @return number of bytes of processed from 'data' (any data remaining should be
- *         given to the next time the read processor is called).
+ * @param cls closure
+ * @param element a result element, only valid if status is GNUNET_SET_STATUS_OK
+ * @param status see enum GNUNET_SET_Status
  */
-static size_t
-incoming_stream_data_processor (void *cls,
-                       enum GNUNET_STREAM_Status status,
-                       const void *data,
-                       size_t size)
+static void 
+set_result_cb (void *cls,
+               const struct GNUNET_SET_Element *element,
+               enum GNUNET_SET_Status status)
 {
-  struct IncomingSocket *incoming;
-  int ret;
+  struct ConsensusPeerInformation *cpi = cls;
+  unsigned int remote_idx = cpi - cpi->session->info;
+  unsigned int local_idx = cpi->session->local_peer_idx;
 
-  GNUNET_assert (GNUNET_STREAM_OK == status);
+  GNUNET_assert ((cpi == cpi->session->partner_outgoing) ||
+                 (cpi == cpi->session->partner_incoming));
 
-  incoming = cls;
-
-  ret = GNUNET_SERVER_mst_receive (incoming->mst, incoming, data, size, GNUNET_NO, GNUNET_YES);
-  if (GNUNET_SYSERR == ret)
+  switch (status)
   {
-    /* FIXME: handle this correctly */
-    GNUNET_assert (0);
+    case GNUNET_SET_STATUS_OK:
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: set result from P%u: element\n",
+                  local_idx, remote_idx);
+      break;
+    case GNUNET_SET_STATUS_FAILURE:
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: set result from P%u: failure\n",
+                  local_idx, remote_idx);
+      cpi->set_op = NULL;
+      return;
+    case GNUNET_SET_STATUS_HALF_DONE:
+    case GNUNET_SET_STATUS_DONE:
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: set result from P%u: done\n",
+                  local_idx, remote_idx);
+      cpi->exp_subround_finished = GNUNET_YES;
+      cpi->set_op = NULL;
+      if (have_exp_subround_finished (cpi->session) == GNUNET_YES)
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: all reconciliations of subround done\n",
+                    local_idx);
+        subround_over (cpi->session, NULL);
+      }
+      else
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: waiting for further set results\n",
+                    local_idx);
+      }
+      return;
+    default:
+      GNUNET_break (0);
+      return;
   }
 
-  /* read again */
-  incoming->rh = GNUNET_STREAM_read (incoming->socket, GNUNET_TIME_UNIT_FOREVER_REL,
-                                     &incoming_stream_data_processor, incoming);
-
-  /* we always read all data */
-  return size;
+  switch (cpi->session->current_round)
+  {
+    case CONSENSUS_ROUND_EXCHANGE:
+      GNUNET_SET_add_element (cpi->session->element_set, element, NULL, NULL);
+      break;
+    default:
+      GNUNET_break (0);
+      return;
+  }
 }
 
 
 /**
- * Iterator to insert values into an ibf.
+ * Compare the round the session is in with the round of the given context message.
  *
- * @param cls closure
- * @param key current key code
- * @param value value in the hash map
- * @return GNUNET_YES if we should continue to
- *         iterate,
- *         GNUNET_NO if not.
+ * @param session a consensus session
+ * @param round a round context message
+ * @return 0 if it's the same round, -1 if the session is in an earlier round,
+ *         1 if the session is in a later round
  */
 static int
-ibf_values_iterator (void *cls,
-                     const struct GNUNET_HashCode *key,
-                     void *value)
-{
-  struct ConsensusPeerInformation *cpi;
-  cpi = cls;
-  ibf_insert (cpi->session->ibfs[cpi->ibf_order], ibf_key_from_hashcode (key));
-  return GNUNET_YES;
-}
-
-static void
-prepare_ibf (struct ConsensusPeerInformation *cpi)
+rounds_compare (struct ConsensusSession *session,
+                struct RoundInfo* ri)
 {
-  if (NULL == cpi->session->ibfs[cpi->ibf_order])
+  if (session->current_round < ri->round)
+    return -1;
+  if (session->current_round > ri->round)
+    return 1;
+  if (session->current_round == CONSENSUS_ROUND_EXCHANGE)
   {
-    cpi->session->ibfs[cpi->ibf_order] = ibf_create (1 << cpi->ibf_order, STRATA_HASH_NUM, 0);
-    GNUNET_CONTAINER_multihashmap_iterate (cpi->session->values, ibf_values_iterator, cpi);
+    if (session->exp_round < ri->exp_round)
+      return -1;
+    if (session->exp_round > ri->exp_round)
+      return 1;
+    if (session->exp_subround < ri->exp_subround)
+      return -1;
+    if (session->exp_subround < ri->exp_subround)
+      return 1;
+    return 0;
   }
+  /* comparing rounds when we are not in a exp round */
+  GNUNET_assert (0);
 }
 
 
 /**
- * Called when a peer sends us its strata estimator.
- * In response, we sent out IBF of appropriate size back.
+ * Do the next subround in the exp-scheme.
+ * This function can be invoked as a timeout task, or called manually (tc will be NULL then).
  *
- * @param cpi session
- * @param strata_msg message
+ * @param cls the session
+ * @param tc task context, for when this task is invoked by the scheduler,
+ *           NULL if invoked for another reason
  */
-static int
-handle_p2p_strata (struct ConsensusPeerInformation *cpi, const struct StrataMessage *strata_msg)
+static void
+subround_over (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
+  struct ConsensusSession *session;
   int i;
-  uint64_t *key_src;
-  uint32_t *hash_src;
-  uint8_t *count_src;
 
-  GNUNET_assert (GNUNET_NO == cpi->is_outgoing);
-
-  if (NULL == cpi->strata)
+  /* don't kick off next subround if we're shutting down */
+  if ((NULL != tc) && (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+    return;
+  session = cls;
+  /* cancel timeout */
+  if (session->round_timeout_tid != GNUNET_SCHEDULER_NO_TASK)
   {
-    cpi->strata = GNUNET_malloc (STRATA_COUNT * sizeof (struct InvertibleBloomFilter *));
-    for (i = 0; i < STRATA_COUNT; i++)
-      cpi->strata[i] = ibf_create (STRATA_IBF_BUCKETS, STRATA_HASH_NUM, 0);
+    GNUNET_SCHEDULER_cancel (session->round_timeout_tid);
+    session->round_timeout_tid = GNUNET_SCHEDULER_NO_TASK;
   }
-
-  /* for correct message alignment, copy bucket types seperately */
-  key_src = (uint64_t *) &strata_msg[1];
-
-  for (i = 0; i < STRATA_COUNT; i++)
+  
+  if (session->exp_round >= NUM_EXP_ROUNDS)
   {
-    memcpy (cpi->strata[i]->id_sum, key_src, STRATA_IBF_BUCKETS * sizeof *key_src);
-    key_src += STRATA_IBF_BUCKETS;
+    round_over (session, NULL);
+    return;
   }
 
-  hash_src = (uint32_t *) key_src;
-
-  for (i = 0; i < STRATA_COUNT; i++)
+  if (session->exp_round == 0)
   {
-    memcpy (cpi->strata[i]->hash_sum, hash_src, STRATA_IBF_BUCKETS * sizeof *hash_src);
-    hash_src += STRATA_IBF_BUCKETS;
+    /* initialize everything for the log-rounds */
+    session->exp_round = 1;
+    session->exp_subround = 0;
+    if (NULL == session->shuffle)
+      session->shuffle = GNUNET_malloc ((sizeof (int)) * session->num_peers);
+    for (i = 0; i < session->num_peers; i++)
+      session->shuffle[i] = i;
   }
-
-  count_src = (uint8_t *) hash_src;
-
-  for (i = 0; i < STRATA_COUNT; i++)
+  else if (session->exp_subround + 1 >= (int) ceil (log2 (session->num_peers)))
   {
-    memcpy (cpi->strata[i]->count, count_src, STRATA_IBF_BUCKETS);
-    count_src += STRATA_IBF_BUCKETS;
+    /* subrounds done, start new log-round */
+    session->exp_round++;
+    session->exp_subround = 0;
+    //shuffle (session);
+  }
+  else 
+  {
+    session->exp_subround++;
   }
 
-  cpi->diff = estimate_difference (cpi->session->strata, cpi->strata);
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "received strata, diff=%d\n", cpi->diff);
-
-  /* send IBF of the right size */
-  cpi->ibf_order = 0;
-  while ((1 << cpi->ibf_order) < cpi->diff)
-    cpi->ibf_order++;
-  if (cpi->ibf_order > MAX_IBF_ORDER)
-    cpi->ibf_order = MAX_IBF_ORDER;
-  cpi->ibf_order += 2;
-  /* create ibf if not already pre-computed */
-  prepare_ibf (cpi);
-  cpi->ibf = ibf_dup (cpi->session->ibfs[cpi->ibf_order]);
-  cpi->ibf_state = IBF_STATE_TRANSMITTING;
-  write_ibf (cpi, GNUNET_STREAM_OK, 0);
-
-  return GNUNET_YES;
-}
-
-
-static int
-handle_p2p_ibf (struct ConsensusPeerInformation *cpi, const struct DifferenceDigest *digest)
-{
-  int num_buckets;
-  uint64_t *key_src;
-  uint32_t *hash_src;
-  uint8_t *count_src;
+  /* determine the incoming and outgoing partner */
+  find_partners (session);
 
-  num_buckets = (ntohs (digest->header.size) - (sizeof *digest)) / IBF_BUCKET_SIZE;
+  GNUNET_assert (session->partner_outgoing != &session->info[session->local_peer_idx]);
+  GNUNET_assert (session->partner_incoming != &session->info[session->local_peer_idx]);
 
-  if (IBF_STATE_NONE == cpi->ibf_state)
+  /* initiate set operation with the outgoing partner */
+  if (NULL != session->partner_outgoing)
   {
-    cpi->ibf_state = IBF_STATE_RECEIVING;
-    cpi->ibf_order = digest->order;
-    cpi->ibf_bucket_counter = 0;
+    struct GNUNET_CONSENSUS_RoundContextMessage *msg;
+    msg = GNUNET_new (struct GNUNET_CONSENSUS_RoundContextMessage);
+    msg->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_ROUND_CONTEXT);
+    msg->header.size = htons (sizeof *msg);
+    msg->round = htonl (session->current_round);
+    msg->exp_round = htonl (session->exp_round);
+    msg->exp_subround = htonl (session->exp_subround);
+
+    if (NULL != session->partner_outgoing->set_op)
+    {
+      GNUNET_SET_operation_cancel (session->partner_outgoing->set_op);
+    }
+    session->partner_outgoing->set_op =
+        GNUNET_SET_prepare (&session->partner_outgoing->peer_id,
+                            &session->global_id,
+                            (struct GNUNET_MessageHeader *) msg,
+                            0, /* FIXME: salt */
+                            GNUNET_SET_RESULT_ADDED,
+                            set_result_cb, session->partner_outgoing);
+    GNUNET_free (msg);
+    GNUNET_SET_commit (session->partner_outgoing->set_op, session->element_set);
   }
 
-  if ( (IBF_STATE_RECEIVING != cpi->ibf_state) ||
-       (cpi->ibf_bucket_counter + num_buckets > (1 << cpi->ibf_order)) )
+  /* commit to the delayed set operation */
+  if ((NULL != session->partner_incoming) && (NULL != session->partner_incoming->delayed_set_op))
   {
-    mark_peer_bad (cpi);
-    return GNUNET_NO;
-  }
+    int cmp = rounds_compare (session, &session->partner_incoming->delayed_round_info);
 
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "receiving %d buckets at %d of %d\n", num_buckets, cpi->ibf_bucket_counter, (1 << cpi->ibf_order));
-
-  if (NULL == cpi->ibf)
-    cpi->ibf = ibf_create (1 << cpi->ibf_order, STRATA_HASH_NUM, 0);
-
-  key_src = (uint64_t *) &digest[1];
-
-  memcpy (cpi->ibf->hash_sum, key_src, num_buckets * sizeof *key_src);
-  hash_src += num_buckets;
-
-  hash_src = (uint32_t *) key_src;
-
-  memcpy (cpi->ibf->id_sum, hash_src, num_buckets * sizeof *hash_src);
-  hash_src += num_buckets;
-
-  count_src = (uint8_t *) hash_src;
-
-  memcpy (cpi->ibf->count, count_src, num_buckets * sizeof *count_src);
-
-  cpi->ibf_bucket_counter += num_buckets;
-
-  if (cpi->ibf_bucket_counter == (1 << cpi->ibf_order))
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "received full ibf\n");
-    GNUNET_assert (NULL != cpi->wh);
-    cpi->ibf_state = IBF_STATE_DECODING;
-    prepare_ibf (cpi);
-    ibf_subtract (cpi->ibf, cpi->session->ibfs[cpi->ibf_order]);
-    write_requests_and_elements (cpi, GNUNET_STREAM_OK, 0);
-  }
-  return GNUNET_YES;
-}
-
-
-static int
-handle_p2p_element (struct ConsensusPeerInformation *cpi, const struct GNUNET_MessageHeader *element_msg)
-{
-  struct PendingElement *pending_element;
-  struct GNUNET_CONSENSUS_Element *element;
-  struct GNUNET_CONSENSUS_ElementMessage *client_element_msg;
-  size_t size;
-
-  size = ntohs (element_msg->size) - sizeof *element_msg;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "receiving element, size=%d\n", size);
-
-  element = GNUNET_malloc (size + sizeof *element);
-  element->size = size;
-  memcpy (&element[1], &element_msg[1], size);
-  element->data = &element[1];
-
-  pending_element = GNUNET_malloc (sizeof *pending_element);
-  pending_element->element = element;
-  GNUNET_CONTAINER_DLL_insert_tail (cpi->session->approval_pending_head, cpi->session->approval_pending_tail, pending_element);
-
-  client_element_msg = GNUNET_malloc (size + sizeof *client_element_msg);
-  client_element_msg->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_RECEIVED_ELEMENT);
-  client_element_msg->header.size = htons (size + sizeof *client_element_msg);
-  memcpy (&client_element_msg[1], &element[1], size);
-
-  queue_client_message (cpi->session, (struct GNUNET_MessageHeader *) client_element_msg);
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "received element\n");
-
-  send_next (cpi->session);
-  
-  return GNUNET_YES;
-}
-
-
-/**
- * Handle a request for elements.
- * Only allowed in exchange-rounds.
- *
- * FIXME: implement
- */
-static int
-handle_p2p_element_request (struct ConsensusPeerInformation *cpi, const struct ElementRequest *msg)
-{
-  /* FIXME: implement */
-  return GNUNET_YES;
-}
-
-
-/**
- * Handle a HELLO-message, send when another peer wants to join a session where
- * our peer is a member. The session may or may not be inhabited yet.
- */
-static int
-handle_p2p_hello (struct IncomingSocket *inc, const struct ConsensusHello *hello)
-{
-  /* FIXME: session might not exist yet. create an uninhabited session and wait for a client */
-  struct ConsensusSession *session;
-  session = sessions_head;
-  while (NULL != session)
-  {
-    if (0 == GNUNET_CRYPTO_hash_cmp (&session->global_id, &hello->global_id))
+    if (NULL != session->partner_incoming->set_op)
     {
-      int idx;
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "peer helloed session\n");
-      idx = get_peer_idx (inc->peer, session);
-      GNUNET_assert (-1 != idx);
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "idx is %d\n", idx);
-      inc->cpi = &session->info[idx];
-      GNUNET_assert (GNUNET_NO == inc->cpi->is_outgoing);
-      inc->cpi->mst = inc->mst;
-      inc->cpi->hello = GNUNET_YES;
-      inc->cpi->socket = inc->socket;
-      return GNUNET_YES;
+      GNUNET_SET_operation_cancel (session->partner_incoming->set_op);
+      session->partner_incoming->set_op = NULL;
+    }
+    if (cmp == 0)
+    {
+      GNUNET_SET_commit (session->partner_incoming->delayed_set_op, session->element_set);
+      session->partner_incoming->set_op = session->partner_incoming->delayed_set_op;
+      session->partner_incoming->delayed_set_op = NULL;
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d resumed delayed round with P%d\n",
+                  session->local_peer_idx, (int) (session->partner_incoming - session->info));
+    }
+    else
+    {
+      /* this should not happen -- a round has been skipped! */
+      GNUNET_break_op (0);
     }
-    session = session->next;
   }
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "peer tried to HELLO uninhabited session\n");
-  GNUNET_break (0);
-  return GNUNET_NO;
-}
 
-
-/**
- * Functions with this signature are called whenever a
- * complete message is received by the tokenizer.
- *
- * Do not call GNUNET_SERVER_mst_destroy in callback
- *
- * @param cls closure
- * @param client identification of the client
- * @param message the actual message
- *
- * @return GNUNET_OK on success, GNUNET_SYSERR to stop further processing
- */
-static int
-mst_session_callback (void *cls, void *client, const struct GNUNET_MessageHeader *message)
-{
-  struct ConsensusPeerInformation *cpi;
-  cpi =  cls;
-  switch (ntohs (message->type))
+#ifdef GNUNET_EXTRA_LOGGING
   {
-    case GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_DELTA_ESTIMATE:
-      return handle_p2p_strata (cpi, (struct StrataMessage *) message);
-    case GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_DIFFERENCE_DIGEST:
-      return handle_p2p_ibf (cpi, (struct DifferenceDigest *) message);
-    case GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_ELEMENTS:
-      return handle_p2p_element (cpi, message);
-    case GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_ELEMENTS_REQUEST:
-      return handle_p2p_element_request (cpi, (struct ElementRequest *) message);
-    default:
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "unexpected message type from peer: %u\n", ntohs (message->type));
-      /* FIXME: handle correctly */
-      GNUNET_assert (0);
+    int in;
+    int out;
+    if (session->partner_outgoing == NULL)
+      out = -1;
+    else
+      out = (int) (session->partner_outgoing - session->info);
+    if (session->partner_incoming == NULL)
+      in = -1;
+    else
+      in = (int) (session->partner_incoming - session->info);
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: doing exp-round, r=%d, sub=%d, in: %d, out: %d\n", session->local_peer_idx,
+                session->exp_round, session->exp_subround, in, out);
   }
-  return GNUNET_OK;
-}
+#endif /* GNUNET_EXTRA_LOGGING */
 
-
-/**
- * Handle tokenized messages from stream sockets.
- * Delegate them if the socket belongs to a session,
- * handle hello messages otherwise.
- *
- * Do not call GNUNET_SERVER_mst_destroy in callback
- *
- * @param cls closure, unused
- * @param client incoming socket this message comes from
- * @param message the actual message
- *
- * @return GNUNET_OK on success, GNUNET_SYSERR to stop further processing
- */
-static int
-mst_incoming_callback (void *cls, void *client, const struct GNUNET_MessageHeader *message)
-{
-  struct IncomingSocket *inc;
-  inc = (struct IncomingSocket *) client;
-  switch (ntohs( message->type))
-  {
-    case GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_HELLO:
-      return handle_p2p_hello (inc, (struct ConsensusHello *) message);
-    default:
-      if (NULL != inc->cpi)
-        return mst_session_callback (inc->cpi, client, message);
-      /* FIXME: disconnect peer properly */
-      GNUNET_assert (0);
-  }
-  return GNUNET_OK;
 }
 
 
 /**
- * Functions of this type are called upon new stream connection from other peers
- * or upon binding error which happen when the app_port given in
- * GNUNET_STREAM_listen() is already taken.
+ * Search peer in the list of peers in session.
  *
- * @param cls the closure from GNUNET_STREAM_listen
- * @param socket the socket representing the stream; NULL on binding error
- * @param initiator the identity of the peer who wants to establish a stream
- *            with us; NULL on binding error
- * @return GNUNET_OK to keep the socket open, GNUNET_SYSERR to close the
- *             stream (the socket will be invalid after the call)
+ * @param peer peer to find
+ * @param session session with peer
+ * @return index of peer, -1 if peer is not in session
  */
 static int
-listen_cb (void *cls,
-           struct GNUNET_STREAM_Socket *socket,
-           const struct GNUNET_PeerIdentity *initiator)
-{
-  struct IncomingSocket *incoming;
-
-  GNUNET_assert (NULL != socket);
-
-  incoming = GNUNET_malloc (sizeof *incoming);
-
-  incoming->socket = socket;
-  incoming->peer = GNUNET_memdup (initiator, sizeof *initiator);
-
-  incoming->rh = GNUNET_STREAM_read (socket, GNUNET_TIME_UNIT_FOREVER_REL,
-                                     &incoming_stream_data_processor, incoming);
-
-
-  incoming->mst = GNUNET_SERVER_mst_create (mst_incoming_callback, incoming);
-
-  GNUNET_CONTAINER_DLL_insert_tail (incoming_sockets_head, incoming_sockets_tail, incoming);
-
-  return GNUNET_OK;
-}
-
-
-static void
-destroy_session (struct ConsensusSession *session)
-{
-  /* FIXME: more stuff to free! */
-  GNUNET_CONTAINER_DLL_remove (sessions_head, sessions_tail, session);
-  GNUNET_SERVER_client_drop (session->client);
-  GNUNET_free (session);
-}
-
-
-/**
- * Disconnect a client, and destroy all sessions associated with it.
- *
- * @param client the client to disconnect
- */
-static void
-disconnect_client (struct GNUNET_SERVER_Client *client)
+get_peer_idx (const struct GNUNET_PeerIdentity *peer, const struct ConsensusSession *session)
 {
-  struct ConsensusSession *session;
-  GNUNET_SERVER_client_disconnect (client);
-  
-  /* if the client owns a session, remove it */
-  session = sessions_head;
-  while (NULL != session)
-  {
-    if (client == session->client)
-    {
-      destroy_session (session);
-      break;
-    }
-    session = session->next;
-  }
+  int i;
+  for (i = 0; i < session->num_peers; i++)
+    if (0 == memcmp (peer, &session->info[i].peer_id, sizeof *peer))
+      return i;
+  return -1;
 }
 
 
@@ -988,98 +785,24 @@ disconnect_client (struct GNUNET_SERVER_Client *client)
  * Thus, if the local id of two consensus sessions coincide, but are not comprised of
  * exactly the same peers, the global id will be different.
  *
- * @param local_id local id of the consensus session
- * @param peers array of all peers participating in the consensus session
- * @param num_peers number of elements in the peers array
- * @param dst where the result is stored, may not be NULL
+ * @param session session to generate the global id for
+ * @param session_id local id of the consensus session
  */
 static void
-compute_global_id (const struct GNUNET_HashCode *local_id,
-                   const struct GNUNET_PeerIdentity *peers, int num_peers, 
-                   struct GNUNET_HashCode *dst)
+compute_global_id (struct ConsensusSession *session, const struct GNUNET_HashCode *session_id)
 {
   int i;
   struct GNUNET_HashCode tmp;
 
-  *dst = *local_id;
-  for (i = 0; i < num_peers; ++i)
-  {
-    GNUNET_CRYPTO_hash_xor (dst, &peers[0].hashPubKey, &tmp);
-    *dst = tmp;
-    GNUNET_CRYPTO_hash (dst, sizeof (struct GNUNET_PeerIdentity), &tmp);
-    *dst = tmp;
-  }
-}
-
-
-/**
- * Function called to notify a client about the connection
- * begin ready to queue more data.  "buf" will be
- * NULL and "size" zero if the connection was closed for
- * writing in the meantime.
- *
- * @param cls consensus session
- * @param size number of bytes available in buf
- * @param buf where the callee should write the message
- * @return number of bytes written to buf
- */
-static size_t
-transmit_queued (void *cls, size_t size,
-                 void *buf)
-{
-  struct ConsensusSession *session;
-  struct QueuedMessage *qmsg;
-  size_t msg_size;
-
-  session = cls;
-  session->th = NULL;
+  /* FIXME: use kdf? */
 
-
-  qmsg = session->client_messages_head;
-  GNUNET_CONTAINER_DLL_remove (session->client_messages_head, session->client_messages_tail, qmsg);
-  GNUNET_assert (qmsg);
-
-  if (NULL == buf)
-  {
-    destroy_session (session);
-    return 0;
-  }
-
-  msg_size = ntohs (qmsg->msg->size);
-
-  GNUNET_assert (size >= msg_size);
-
-  memcpy (buf, qmsg->msg, msg_size);
-  GNUNET_free (qmsg->msg);
-  GNUNET_free (qmsg);
-
-  send_next (session);
-
-  return msg_size;
-}
-
-
-/**
- * Schedule sending the next message (if there is any) to a client.
- *
- * @param cli the client to send the next message to
- */
-static void
-send_next (struct ConsensusSession *session)
-{
-
-  GNUNET_assert (NULL != session);
-
-  if (NULL != session->th)
-    return;
-
-  if (NULL != session->client_messages_head)
+  session->global_id = *session_id;
+  for (i = 0; i < session->num_peers; ++i)
   {
-    int msize;
-    msize = ntohs (session->client_messages_head->msg->size);
-    session->th = GNUNET_SERVER_notify_transmit_ready (session->client, msize, 
-                                                       GNUNET_TIME_UNIT_FOREVER_REL,
-                                                       &transmit_queued, session);
+    GNUNET_CRYPTO_hash_xor (&session->global_id, &session->info[i].peer_id.hashPubKey, &tmp);
+    session->global_id = tmp;
+    GNUNET_CRYPTO_hash (&session->global_id, sizeof (struct GNUNET_PeerIdentity), &tmp);
+    session->global_id = tmp;
   }
 }
 
@@ -1093,762 +816,362 @@ send_next (struct ConsensusSession *session)
  * @param h2 some hash code
  * @return 1 if h1 > h2, -1 if h1 < h2 and 0 if h1 == h2.
  */
-static int
-hash_cmp (const void *a, const void *b)
-{
-  return GNUNET_CRYPTO_hash_cmp ((struct GNUNET_HashCode *) a, (struct GNUNET_HashCode *) b);
-}
-
-
-/**
- * Search peer in the list of peers in session.
- *
- * @param peer peer to find
- * @param session session with peer
- * @return index of peer, -1 if peer is not in session
- */
-static int
-get_peer_idx (const struct GNUNET_PeerIdentity *peer, const struct ConsensusSession *session)
-{
-  const struct GNUNET_PeerIdentity *needle;
-  needle = bsearch (peer, session->peers, session->num_peers, sizeof (struct GNUNET_PeerIdentity), &hash_cmp);
-  if (NULL == needle)
-    return -1;
-  return needle - session->peers;
-}
-
-
-
-/**
- * Called when stream has finishes writing the hello message
- */
-static void
-hello_cont (void *cls, enum GNUNET_STREAM_Status status, size_t size)
-{
-  struct ConsensusPeerInformation *cpi;
-
-  cpi = cls;
-  cpi->hello = GNUNET_YES;
-  
-  GNUNET_assert (GNUNET_STREAM_OK == status);
-
-  if (cpi->session->conclude_requested)
-  {
-    write_strata (cpi, GNUNET_STREAM_OK, 0);  
-  }
-}
-
-
-/**
- * Functions of this type will be called when a stream is established
- *
- * @param cls the closure from GNUNET_STREAM_open
- * @param socket socket to use to communicate with the other side (read/write)
- */
-static void
-open_cb (void *cls, struct GNUNET_STREAM_Socket *socket)
-{
-  struct ConsensusPeerInformation *cpi;
-  struct ConsensusHello *hello;
-
-
-  cpi = cls;
-  cpi->is_connected = GNUNET_YES;
-
-  hello = GNUNET_malloc (sizeof *hello);
-  hello->header.size = htons (sizeof *hello);
-  hello->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_HELLO);
-  memcpy (&hello->global_id, &cpi->session->global_id, sizeof (struct GNUNET_HashCode));
-
-  cpi->wh =
-      GNUNET_STREAM_write (socket, hello, sizeof *hello, GNUNET_TIME_UNIT_FOREVER_REL, hello_cont, cpi);
-
-  cpi->rh = GNUNET_STREAM_read (socket, GNUNET_TIME_UNIT_FOREVER_REL,
-                                &session_stream_data_processor, cpi);
-
-}
-
-
-static void
-initialize_session_info (struct ConsensusSession *session)
-{
-  int i;
-  int last;
-
-  for (i = 0; i < session->num_peers; ++i)
-  {
-    /* initialize back-references, so consensus peer information can
-     * be used as closure */
-    session->info[i].session = session;
-  }
-
-  session->current_round = CONSENSUS_ROUND_A2A_EXCHANGE;
-
-  last = (session->local_peer_idx + ((session->num_peers - 1) / 2) + 1) % session->num_peers;
-  i = (session->local_peer_idx + 1) % session->num_peers;
-  while (i != last)
-  {
-    session->info[i].is_outgoing = GNUNET_YES;
-    session->info[i].socket = GNUNET_STREAM_open (cfg, &session->peers[i], GNUNET_APPLICATION_TYPE_CONSENSUS,
-                                                  open_cb, &session->info[i], GNUNET_STREAM_OPTION_END);
-    session->info[i].mst = GNUNET_SERVER_mst_create (mst_session_callback, &session->info[i]);
-    i = (i + 1) % session->num_peers;
-
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "peer %d contacts peer %d\n", session->local_peer_idx, i);
-  }
-  // tie-breaker for even number of peers
-  if (((session->num_peers % 2) == 0) && (session->local_peer_idx < last))
-  {
-    session->info[last].is_outgoing = GNUNET_YES;
-    session->info[last].socket = GNUNET_STREAM_open (cfg, &session->peers[last], GNUNET_APPLICATION_TYPE_CONSENSUS,
-                                                     open_cb, &session->info[last], GNUNET_STREAM_OPTION_END);
-    session->info[last].mst = GNUNET_SERVER_mst_create (mst_session_callback, &session->info[last]);
-
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "peer %d contacts peer %d (tiebreaker)\n", session->local_peer_idx, last);
-  }
-}
-
-
-/**
- * Create the sorted list of peers for the session,
- * add the local peer if not in the join message.
- */
-static void
-initialize_session_peer_list (struct ConsensusSession *session)
-{
-  int local_peer_in_list;
-  int listed_peers;
-  const struct GNUNET_PeerIdentity *msg_peers;
-  unsigned int i;
-
-  GNUNET_assert (NULL != session->join_msg);
-
-  /* peers in the join message, may or may not include the local peer */
-  listed_peers = ntohs (session->join_msg->num_peers);
-  
-  session->num_peers = listed_peers;
-
-  msg_peers = (struct GNUNET_PeerIdentity *) &session->join_msg[1];
-
-  local_peer_in_list = GNUNET_NO;
-  for (i = 0; i < listed_peers; i++)
-  {
-    if (0 == memcmp (&msg_peers[i], my_peer, sizeof (struct GNUNET_PeerIdentity)))
-    {
-      local_peer_in_list = GNUNET_YES;
-      break;
-    }
-  }
-
-  if (GNUNET_NO == local_peer_in_list)
-    session->num_peers++;
-
-  session->peers = GNUNET_malloc (session->num_peers * sizeof (struct GNUNET_PeerIdentity));
-
-  if (GNUNET_NO == local_peer_in_list)
-    session->peers[session->num_peers - 1] = *my_peer;
-
-  memcpy (session->peers, msg_peers, listed_peers * sizeof (struct GNUNET_PeerIdentity));
-  qsort (session->peers, session->num_peers, sizeof (struct GNUNET_PeerIdentity), &hash_cmp);
-}
-
-
-static void
-strata_insert (struct InvertibleBloomFilter **strata, struct GNUNET_HashCode *key)
-{
-  uint32_t v;
-  int i;
-  v = key->bits[0];
-  /* count trailing '1'-bits of v */
-  for (i = 0; v & 1; v>>=1, i++)
-    /* empty */;
-  ibf_insert (strata[i], ibf_key_from_hashcode (key));
-}
-
-
-/**
- * Initialize the session, continue receiving messages from the owning client
- *
- * @param session the session to initialize
- */
-static void
-initialize_session (struct ConsensusSession *session)
-{
-  const struct ConsensusSession *other_session;
-  int i;
-
-  GNUNET_assert (NULL != session->join_msg);
-
-  initialize_session_peer_list (session);
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "session with %u peers\n", session->num_peers);
-
-  compute_global_id (&session->join_msg->session_id, session->peers, session->num_peers, &session->global_id);
-
-  /* Check if some local client already owns the session. */
-  other_session = sessions_head;
-  while (NULL != other_session)
-  {
-    if ((other_session != session) && 
-        (0 == GNUNET_CRYPTO_hash_cmp (&session->global_id, &other_session->global_id)))
-    {
-      /* session already owned by another client */
-      GNUNET_break (0);
-      disconnect_client (session->client);
-      return;
-    }
-    other_session = other_session->next;
-  }
-
-  session->values = GNUNET_CONTAINER_multihashmap_create (256, GNUNET_NO);
-
-  session->local_peer_idx = get_peer_idx (my_peer, session);
-  GNUNET_assert (-1 != session->local_peer_idx);
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "%d is the local peer\n", session->local_peer_idx);
-
-  session->strata = GNUNET_malloc (STRATA_COUNT * sizeof (struct InvertibleBloomFilter *));
-  for (i = 0; i < STRATA_COUNT; i++)
-    session->strata[i] = ibf_create (STRATA_IBF_BUCKETS, STRATA_HASH_NUM, 0);
-
-  session->ibfs = GNUNET_malloc (MAX_IBF_ORDER * sizeof (struct InvertibleBloomFilter *));
-
-  session->info = GNUNET_malloc (session->num_peers * sizeof (struct ConsensusPeerInformation));
-  initialize_session_info (session);
-
-  GNUNET_free (session->join_msg);
-  session->join_msg = NULL;
-
-  GNUNET_SERVER_receive_done (session->client, GNUNET_OK);
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "session %s initialized\n", GNUNET_h2s (&session->global_id));
-}
-
-
-/**
- * Called when a client wants to join a consensus session.
- *
- * @param cls unused
- * @param client client that sent the message
- * @param m message sent by the client
- */
-static void
-client_join (void *cls,
-             struct GNUNET_SERVER_Client *client,
-             const struct GNUNET_MessageHeader *m)
-{
-  struct ConsensusSession *session;
-
-  // make sure the client has not already joined a session
-  session = sessions_head;
-  while (NULL != session)
-  {
-    if (session->client == client)
-    {
-      GNUNET_break (0);
-      disconnect_client (client);
-      return;
-    }
-    session = session->next;
-  }
-
-  session = GNUNET_malloc (sizeof (struct ConsensusSession));
-  session->join_msg = (struct GNUNET_CONSENSUS_JoinMessage *) GNUNET_copy_message (m);
-  session->client = client;
-  GNUNET_SERVER_client_keep (client);
-
-  GNUNET_CONTAINER_DLL_insert (sessions_head, sessions_tail, session);
-
-  // Initialize session later if local peer identity is not known yet.
-  if (NULL == my_peer)
-  {
-    GNUNET_SERVER_disable_receive_done_warning (client);
-    return;
-  }
-
-  initialize_session (session);
-}
-
-
-/**
- * Called when a client performs an insert operation.
- *
- * @param cls (unused)
- * @param client client handle
- * @param message message sent by the client
- */
-void
-client_insert (void *cls,
-             struct GNUNET_SERVER_Client *client,
-             const struct GNUNET_MessageHeader *m)
-{
-  struct ConsensusSession *session;
-  struct GNUNET_CONSENSUS_ElementMessage *msg;
-  struct GNUNET_CONSENSUS_Element *element;
-  struct GNUNET_HashCode key;
-  int element_size;
-
-  session = sessions_head;
-  while (NULL != session)
-  {
-    if (session->client == client)
-      break;
-  }
-
-  if (NULL == session)
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "client tried to insert, but client is not in any session\n");
-    GNUNET_SERVER_client_disconnect (client);
-    return;
-  }
-
-  msg = (struct GNUNET_CONSENSUS_ElementMessage *) m;
-  element_size = ntohs (msg->header.size )- sizeof (struct GNUNET_CONSENSUS_ElementMessage);
-
-  element = GNUNET_malloc (sizeof (struct GNUNET_CONSENSUS_Element) + element_size);
-
-  element->type = msg->element_type;
-  element->size = element_size;
-  memcpy (&element[1], &msg[1], element_size);
-  element->data = &element[1];
-
-  GNUNET_assert (NULL != element->data);
-
-  GNUNET_CRYPTO_hash (element, element_size, &key);
-
-  GNUNET_CONTAINER_multihashmap_put (session->values, &key, element,
-                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
-
-  strata_insert (session->strata, &key);
-
-  GNUNET_SERVER_receive_done (client, GNUNET_OK);
-
-  send_next (session);
-}
-
-
-
-
-/**
- * Functions of this signature are called whenever writing operations
- * on a stream are executed
- *
- * @param cls the closure from GNUNET_STREAM_write
- * @param status the status of the stream at the time this function is called;
- *          GNUNET_STREAM_OK if writing to stream was completed successfully;
- *          GNUNET_STREAM_TIMEOUT if the given data is not sent successfully
- *          (this doesn't mean that the data is never sent, the receiver may
- *          have read the data but its ACKs may have been lost);
- *          GNUNET_STREAM_SHUTDOWN if the stream is shutdown for writing in the
- *          mean time; GNUNET_STREAM_SYSERR if the stream is broken and cannot
- *          be processed.
- * @param size the number of bytes written
- */
-static void 
-write_strata_done (void *cls, enum GNUNET_STREAM_Status status, size_t size)
+static int
+hash_cmp (const void *h1, const void *h2)
 {
-  GNUNET_assert (GNUNET_STREAM_OK == status);
-  /* just wait for the ibf */
+  return GNUNET_CRYPTO_hash_cmp ((struct GNUNET_HashCode *) h1, (struct GNUNET_HashCode *) h2);
 }
 
+
 /**
- * Functions of this signature are called whenever writing operations
- * on a stream are executed
- *
- * @param cls the closure from GNUNET_STREAM_write
- * @param status the status of the stream at the time this function is called;
- *          GNUNET_STREAM_OK if writing to stream was completed successfully;
- *          GNUNET_STREAM_TIMEOUT if the given data is not sent successfully
- *          (this doesn't mean that the data is never sent, the receiver may
- *          have read the data but its ACKs may have been lost);
- *          GNUNET_STREAM_SHUTDOWN if the stream is shutdown for writing in the
- *          mean time; GNUNET_STREAM_SYSERR if the stream is broken and cannot
- *          be processed.
- * @param size the number of bytes written
+ * Create the sorted list of peers for the session,
+ * add the local peer if not in the join message.
  */
-static void 
-write_strata (void *cls, enum GNUNET_STREAM_Status status, size_t size)
+static void
+initialize_session_peer_list (struct ConsensusSession *session,
+                              struct GNUNET_CONSENSUS_JoinMessage *join_msg)
 {
-  struct ConsensusPeerInformation *cpi;
-  struct StrataMessage *strata_msg;
-  size_t msize;
-  int i;
-  uint64_t *key_dst;
-  uint32_t *hash_dst;
-  uint8_t *count_dst;
-
-  cpi = cls;
-  cpi->wh = NULL;
-
-  GNUNET_assert (GNUNET_STREAM_OK == status);
-
-  GNUNET_assert (GNUNET_YES == cpi->is_outgoing);
-
-  /* FIXME: handle this */
-  GNUNET_assert (GNUNET_STREAM_OK == status);
+  unsigned int local_peer_in_list;
+  uint32_t listed_peers;
+  const struct GNUNET_PeerIdentity *msg_peers;
+  struct GNUNET_PeerIdentity *peers;
+  unsigned int i;
 
-  msize = (sizeof *strata_msg) + (STRATA_COUNT * IBF_BUCKET_SIZE * STRATA_IBF_BUCKETS);
+  GNUNET_assert (NULL != join_msg);
 
-  strata_msg = GNUNET_malloc (msize);
-  strata_msg->header.size = htons (msize);
-  strata_msg->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_DELTA_ESTIMATE);
+  /* peers in the join message, may or may not include the local peer */
+  listed_peers = ntohl (join_msg->num_peers);
+  
+  session->num_peers = listed_peers;
 
-  /* for correct message alignment, copy bucket types seperately */
-  key_dst = (uint64_t *) &strata_msg[1];
+  msg_peers = (struct GNUNET_PeerIdentity *) &join_msg[1];
 
-  for (i = 0; i < STRATA_COUNT; i++)
+  local_peer_in_list = GNUNET_NO;
+  for (i = 0; i < listed_peers; i++)
   {
-    memcpy (key_dst, cpi->session->strata[i]->id_sum, STRATA_IBF_BUCKETS * sizeof *key_dst);
-    key_dst += STRATA_IBF_BUCKETS;
+    if (0 == memcmp (&msg_peers[i], &my_peer, sizeof (struct GNUNET_PeerIdentity)))
+    {
+      local_peer_in_list = GNUNET_YES;
+      break;
+    }
   }
 
-  hash_dst = (uint32_t *) key_dst;
+  if (GNUNET_NO == local_peer_in_list)
+    session->num_peers++;
 
-  for (i = 0; i < STRATA_COUNT; i++)
-  {
-    memcpy (hash_dst, cpi->session->strata[i]->hash_sum, STRATA_IBF_BUCKETS * sizeof *hash_dst);
-    hash_dst += STRATA_IBF_BUCKETS;
-  }
+  peers = GNUNET_malloc (session->num_peers * sizeof (struct GNUNET_PeerIdentity));
+
+  if (GNUNET_NO == local_peer_in_list)
+    peers[session->num_peers - 1] = my_peer;
+
+  memcpy (peers, msg_peers, listed_peers * sizeof (struct GNUNET_PeerIdentity));
+  qsort (peers, session->num_peers, sizeof (struct GNUNET_PeerIdentity), &hash_cmp);
 
-  count_dst = (uint8_t *) hash_dst;
+  session->info = GNUNET_malloc (session->num_peers * sizeof (struct ConsensusPeerInformation));
 
-  for (i = 0; i < STRATA_COUNT; i++)
+  for (i = 0; i < session->num_peers; ++i)
   {
-    memcpy (count_dst, cpi->session->strata[i]->count, STRATA_IBF_BUCKETS);
-    count_dst += STRATA_IBF_BUCKETS;
+    /* initialize back-references, so consensus peer information can
+     * be used as closure */
+    session->info[i].session = session;
+    session->info[i].peer_id = peers[i];
   }
 
-  cpi->wh = GNUNET_STREAM_write (cpi->socket, strata_msg, msize, GNUNET_TIME_UNIT_FOREVER_REL,
-                                 write_strata_done, cpi);
-
-  GNUNET_assert (NULL != cpi->wh);
+  GNUNET_free (peers);
 }
 
 
 /**
- * Functions of this signature are called whenever writing operations
- * on a stream are executed
+ * Called when another peer wants to do a set operation with the
+ * local peer.
  *
- * @param cls the closure from GNUNET_STREAM_write
- * @param status the status of the stream at the time this function is called;
- *          GNUNET_STREAM_OK if writing to stream was completed successfully;
- *          GNUNET_STREAM_TIMEOUT if the given data is not sent successfully
- *          (this doesn't mean that the data is never sent, the receiver may
- *          have read the data but its ACKs may have been lost);
- *          GNUNET_STREAM_SHUTDOWN if the stream is shutdown for writing in the
- *          mean time; GNUNET_STREAM_SYSERR if the stream is broken and cannot
- *          be processed.
- * @param size the number of bytes written
+ * @param cls closure
+ * @param other_peer the other peer
+ * @param context_msg message with application specific information from
+ *        the other peer
+ * @param request request from the other peer, use GNUNET_SET_accept
+ *        to accept it, otherwise the request will be refused
+ *        Note that we don't use a return value here, as it is also
+ *        necessary to specify the set we want to do the operation with,
+ *        whith sometimes can be derived from the context message.
+ *        Also necessary to specify the timeout.
  */
-static void 
-write_ibf (void *cls, enum GNUNET_STREAM_Status status, size_t size)
+static void
+set_listen_cb (void *cls,
+               const struct GNUNET_PeerIdentity *other_peer,
+               const struct GNUNET_MessageHeader *context_msg,
+               struct GNUNET_SET_Request *request)
 {
+  struct ConsensusSession *session = cls;
+  struct GNUNET_CONSENSUS_RoundContextMessage *msg = (struct GNUNET_CONSENSUS_RoundContextMessage *) context_msg;
   struct ConsensusPeerInformation *cpi;
-  struct DifferenceDigest *digest;
-  int msize;
-  uint64_t *key_dst;
-  uint32_t *hash_dst;
-  uint8_t *count_dst;
-  int num_buckets;
-
-  cpi = cls;
-  cpi->wh = NULL;
-
-  GNUNET_assert (GNUNET_STREAM_OK == status);
-
-  GNUNET_assert (IBF_STATE_TRANSMITTING == cpi->ibf_state);
+  struct GNUNET_SET_OperationHandle *set_op;
+  struct RoundInfo round_info;
+  int index;
+  int cmp;
 
-  if (cpi->ibf_bucket_counter == (1 << cpi->ibf_order))
+  if (NULL == context_msg)
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "ibf completely written\n");
-    /* we now wait for values / requests / another IBF because peer could not decode with our IBF */
+    GNUNET_break_op (0);
     return;
   }
 
-  /* remaining buckets */
-  num_buckets = (1 << cpi->ibf_order) - cpi->ibf_bucket_counter;
-
-  /* limit to maximum */
-  if (num_buckets > BUCKETS_PER_MESSAGE)
-    num_buckets = BUCKETS_PER_MESSAGE;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "writing ibf buckets at %d/%d\n", cpi->ibf_bucket_counter, (1<<cpi->ibf_order));
-
-  msize = (sizeof *digest) + (num_buckets * IBF_BUCKET_SIZE);
-
-  digest = GNUNET_malloc (msize);
-  digest->header.size = htons (msize);
-  digest->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_DIFFERENCE_DIGEST);
-  digest->order = cpi->ibf_order;
+  index = get_peer_idx (other_peer, session);
 
-  key_dst = (uint64_t *) &digest[1];
-
-  memcpy (key_dst, cpi->ibf->id_sum, num_buckets * sizeof *key_dst);
-  key_dst += num_buckets;
-
-  hash_dst = (uint32_t *) key_dst;
-
-  memcpy (hash_dst, cpi->ibf->id_sum, num_buckets * sizeof *hash_dst);
-  hash_dst += num_buckets;
-
-  count_dst = (uint8_t *) hash_dst;
+  if (index < 0)
+  {
+    GNUNET_break_op (0);
+    return;
+  }
 
-  memcpy (count_dst, cpi->ibf->count, num_buckets * sizeof *count_dst);
+  round_info.round = ntohl (msg->round);
+  round_info.exp_round = ntohl (msg->exp_round);
+  round_info.exp_subround = ntohl (msg->exp_subround);
 
-  cpi->ibf_bucket_counter += num_buckets;
+  cpi = &session->info[index];
 
-  cpi->wh = GNUNET_STREAM_write (cpi->socket, digest, msize, GNUNET_TIME_UNIT_FOREVER_REL,
-                                 write_ibf, cpi);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d got set request from P%d\n", session->local_peer_idx, index);
 
-  GNUNET_assert (NULL != cpi->wh);
+  switch (session->current_round)
+  {
+    case CONSENSUS_ROUND_EXCHANGE:
+      cmp = rounds_compare (session, &round_info);
+      if (cmp > 0)
+      {
+        /* the other peer is too late */
+        GNUNET_break_op (0);
+        return;
+      }
+      /* kill old request, if any. this is legal,
+       * as the other peer would not make a new request if it would want to
+       * complete the old one! */
+      if (NULL != cpi->set_op)
+      {
+        GNUNET_SET_operation_cancel (cpi->set_op);
+        cpi->set_op = NULL;
+      }
+      set_op = GNUNET_SET_accept (request, GNUNET_SET_RESULT_ADDED,
+                                       set_result_cb, &session->info[index]);
+      if (cmp == 0)
+      {
+        cpi->set_op = set_op;
+        GNUNET_SET_commit (set_op, session->element_set);
+        GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d commited to set request from P%d\n", session->local_peer_idx, index);
+      }
+      else
+      {
+        /* if there's a exp subround running, mark it as finished, as the set op has been canceled! */
+        cpi->delayed_set_op = set_op;
+        cpi->delayed_round_info = round_info;
+        cpi->exp_subround_finished = GNUNET_YES;
+        GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%d delaying set request from P%d\n", session->local_peer_idx, index);
+      }
+      break;
+    default:
+      GNUNET_break_op (0);
+      return;
+  }
 }
 
 
 /**
- * Functions of this signature are called whenever writing operations
- * on a stream are executed
+ * Initialize the session, continue receiving messages from the owning client
  *
- * @param cls the closure from GNUNET_STREAM_write
- * @param status the status of the stream at the time this function is called;
- *          GNUNET_STREAM_OK if writing to stream was completed successfully;
- *          GNUNET_STREAM_TIMEOUT if the given data is not sent successfully
- *          (this doesn't mean that the data is never sent, the receiver may
- *          have read the data but its ACKs may have been lost);
- *          GNUNET_STREAM_SHUTDOWN if the stream is shutdown for writing in the
- *          mean time; GNUNET_STREAM_SYSERR if the stream is broken and cannot
- *          be processed.
- * @param size the number of bytes written
+ * @param session the session to initialize
+ * @param join_msg the join message from the client
  */
-static void 
-write_requests_and_elements (void *cls, enum GNUNET_STREAM_Status status, size_t size)
+static void
+initialize_session (struct ConsensusSession *session,
+                    struct GNUNET_CONSENSUS_JoinMessage *join_msg)
 {
-  struct ConsensusPeerInformation *cpi;
-  uint64_t key;
-  struct GNUNET_HashCode hashcode;
-  int side;
-  int msize;
-
-  GNUNET_assert (GNUNET_STREAM_OK == status);
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "transmitting value\n");
-
-  cpi = cls;
-  cpi->wh = NULL;
+  struct ConsensusSession *other_session;
 
-  GNUNET_assert (IBF_STATE_DECODING == cpi->ibf_state);
+  initialize_session_peer_list (session, join_msg);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "session with %u peers\n", session->num_peers);
+  compute_global_id (session, &join_msg->session_id);
 
-  for (;;)
+  /* check if some local client already owns the session.
+   * it is only legal to have a session with an existing global id
+   * if all other sessions with this global id are finished.*/
+  other_session = sessions_head;
+  while (NULL != other_session)
   {
-    int res;
-    res = ibf_decode (cpi->ibf, &side, &key);
-    if (GNUNET_SYSERR == res)
-    {
-      cpi->ibf_order++;
-      prepare_ibf (cpi);
-      cpi->ibf = ibf_dup (cpi->session->ibfs[cpi->ibf_order]);
-      cpi->ibf_state = IBF_STATE_TRANSMITTING;
-      write_ibf (cls, status, size);
-      return;
-    }
-    if (GNUNET_NO == res)
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "transmitted all values\n");
-      return;
-    }
-    if (-1 == side)
-    {
-      struct GNUNET_CONSENSUS_Element *element;
-      struct GNUNET_MessageHeader *element_msg;
-      ibf_hashcode_from_key (key, &hashcode);
-      /* FIXME: this only transmits one element stored with the key */
-      element = GNUNET_CONTAINER_multihashmap_get (cpi->session->values, &hashcode);
-      if (NULL == element)
-        continue;
-      msize = sizeof (struct GNUNET_MessageHeader) + element->size;
-      element_msg = GNUNET_malloc (msize);
-      element_msg->size = htons (msize);
-      element_msg->type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_ELEMENTS);
-      GNUNET_assert (NULL != element->data);
-      memcpy (&element_msg[1], element->data, element->size);
-      cpi->wh = GNUNET_STREAM_write (cpi->socket, element_msg, msize, GNUNET_TIME_UNIT_FOREVER_REL,
-                                     write_requests_and_elements, cpi);
-      GNUNET_free (element_msg);
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO, "transmitted value\n");
-
-      GNUNET_assert (NULL != cpi->wh);
-      return;
-    }
-    else
+    if ((other_session != session) && 
+        (0 == GNUNET_CRYPTO_hash_cmp (&session->global_id, &other_session->global_id)))
     {
-      struct ElementRequest *msg;
-      size_t msize;
-      uint64_t *p;
-
-      msize = (sizeof *msg) + sizeof (uint64_t);
-      msg = GNUNET_malloc (msize);
-      msg->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_ELEMENTS_REQUEST);
-      msg->header.size = htons (msize);
-      p = (uint64_t *) &msg[1];
-      *p = key;
-
-      cpi->wh = GNUNET_STREAM_write (cpi->socket, msg, msize, GNUNET_TIME_UNIT_FOREVER_REL,
-                                     write_requests_and_elements, cpi);
-      GNUNET_assert (NULL != cpi->wh);
-      GNUNET_free (msg);
-      return;
+      if (CONSENSUS_ROUND_FINISH != other_session->current_round)
+      {
+        GNUNET_break (0);
+        destroy_session (session);
+        return;
+      }
+      break;
     }
+    other_session = other_session->next;
   }
 
+  session->local_peer_idx = get_peer_idx (&my_peer, session);
+  GNUNET_assert (-1 != session->local_peer_idx);
+  session->element_set = GNUNET_SET_create (cfg, GNUNET_SET_OPERATION_UNION);
+  GNUNET_assert (NULL != session->element_set);
+  session->set_listener = GNUNET_SET_listen (cfg, GNUNET_SET_OPERATION_UNION,
+                                             &session->global_id,
+                                             set_listen_cb, session);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "%d is the local peer\n", session->local_peer_idx);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "session %s initialized\n", GNUNET_h2s (&session->global_id));
 }
 
 
-
-/*
-static void
-select_best_group (struct ConsensusSession *session)
+static struct ConsensusSession *
+get_session_by_client (struct GNUNET_SERVER_Client *client)
 {
+  struct ConsensusSession *session;
+
+  session = sessions_head;
+  while (NULL != session)
+  {
+    if (session->client == client)
+      return session;
+    session = session->next;
+  }
+  return NULL;
 }
-*/
 
 
 /**
- * Called when a client performs the conclude operation.
+ * Called when a client wants to join a consensus session.
  *
- * @param cls (unused)
- * @param client client handle
- * @param message message sent by the client
+ * @param cls unused
+ * @param client client that sent the message
+ * @param m message sent by the client
  */
 static void
-client_conclude (void *cls,
+client_join (void *cls,
              struct GNUNET_SERVER_Client *client,
-             const struct GNUNET_MessageHeader *message)
+             const struct GNUNET_MessageHeader *m)
 {
   struct ConsensusSession *session;
-  int i;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "conclude requested\n");
 
-  session = sessions_head;
-  while ((session != NULL) && (session->client != client))
-    session = session->next;
-  if (NULL == session)
-  {
-    /* client not found */
-    GNUNET_break (0);
-    GNUNET_SERVER_client_disconnect (client);
-    return;
-  }
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "join message sent by client\n");
 
-  if (GNUNET_YES == session->conclude_requested)
+  session = get_session_by_client (client);
+  if (NULL != session)
   {
-    /* client requested conclude twice */
     GNUNET_break (0);
-    disconnect_client (client);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
     return;
   }
-
-  session->conclude_requested = GNUNET_YES;
-
-  for (i = 0; i < session->num_peers; i++)
-  {
-    if ( (GNUNET_YES == session->info[i].is_outgoing) &&
-         (GNUNET_YES == session->info[i].hello) )
-    {
-      /* kick off transmitting strata by calling the write continuation */
-      write_strata (&session->info[i], GNUNET_STREAM_OK, 0);
-    }
-  }
-
+  session = GNUNET_new (struct ConsensusSession);
+  session->client = client;
+  session->client_mq = GNUNET_MQ_queue_for_server_client (client);
+  GNUNET_CONTAINER_DLL_insert (sessions_head, sessions_tail, session);
+  initialize_session (session, (struct GNUNET_CONSENSUS_JoinMessage *) m);
   GNUNET_SERVER_receive_done (client, GNUNET_OK);
-  send_next (session);
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "join done\n");
 }
 
 
 /**
- * Called when a client sends an ack
+ * Called when a client performs an insert operation.
  *
  * @param cls (unused)
  * @param client client handle
- * @param message message sent by the client
+ * @param m message sent by the client
  */
 void
-client_ack (void *cls,
-             struct GNUNET_SERVER_Client *client,
-             const struct GNUNET_MessageHeader *message)
+client_insert (void *cls,
+               struct GNUNET_SERVER_Client *client,
+               const struct GNUNET_MessageHeader *m)
 {
   struct ConsensusSession *session;
-  struct GNUNET_CONSENSUS_AckMessage *msg;
-  struct PendingElement *pending;
-  struct GNUNET_CONSENSUS_Element *element;
-  struct GNUNET_HashCode key;
+  struct GNUNET_CONSENSUS_ElementMessage *msg;
+  struct GNUNET_SET_Element *element;
+  ssize_t element_size;
 
-  session = sessions_head;
-  while (NULL != session)
-  {
-    if (session->client == client)
-      break;
-  }
+  session = get_session_by_client (client);
 
   if (NULL == session)
   {
-    GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "client tried to ack, but client is not in any session\n");
+    GNUNET_break (0);
     GNUNET_SERVER_client_disconnect (client);
     return;
   }
 
-  pending = session->approval_pending_head;
-
-  GNUNET_CONTAINER_DLL_remove (session->approval_pending_head, session->approval_pending_tail, pending);
-
-  msg = (struct GNUNET_CONSENSUS_AckMessage *) message;
-
-  if (msg->keep)
+  if (CONSENSUS_ROUND_BEGIN != session->current_round)
   {
-    element = pending->element;
-    GNUNET_CRYPTO_hash (element, element->size, &key);
+    GNUNET_break (0);
+    GNUNET_SERVER_client_disconnect (client);
+    return;
+  }
 
-    GNUNET_CONTAINER_multihashmap_put (session->values, &key, element,
-                                       GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
-    strata_insert (session->strata, &key);
+  msg = (struct GNUNET_CONSENSUS_ElementMessage *) m;
+  element_size = ntohs (msg->header.size) - sizeof (struct GNUNET_CONSENSUS_ElementMessage);
+  if (element_size < 0)
+  {
+    GNUNET_break (0);
+    return;
   }
 
+  element = GNUNET_malloc (sizeof (struct GNUNET_SET_Element) + element_size);
+  element->type = msg->element_type;
+  element->size = element_size;
+  memcpy (&element[1], &msg[1], element_size);
+  element->data = &element[1];
+  GNUNET_SET_add_element (session->element_set, element, NULL, NULL);
+  GNUNET_free (element);
   GNUNET_SERVER_receive_done (client, GNUNET_OK);
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: element added\n", session->local_peer_idx);
 }
 
+
 /**
- * Task that disconnects from core.
+ * Called when a client performs the conclude operation.
  *
- * @param cls core handle
- * @param tc context information (why was this task triggered now)
+ * @param cls (unused)
+ * @param client client handle
+ * @param message message sent by the client
  */
 static void
-disconnect_core (void *cls,
-                 const struct GNUNET_SCHEDULER_TaskContext *tc)
-{
-  GNUNET_CORE_disconnect (core);
-  core = NULL;
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "disconnected from core\n");
-}
-
-
-static void
-core_startup (void *cls,
-              struct GNUNET_CORE_Handle *core,
-              const struct GNUNET_PeerIdentity *peer)
+client_conclude (void *cls,
+                 struct GNUNET_SERVER_Client *client,
+                 const struct GNUNET_MessageHeader *message)
 {
   struct ConsensusSession *session;
+  struct GNUNET_CONSENSUS_ConcludeMessage *cmsg;
 
-  my_peer = GNUNET_memdup(peer, sizeof (struct GNUNET_PeerIdentity));
-  /* core can't be disconnected directly in the core startup callback, schedule a task to do it! */
-  GNUNET_SCHEDULER_add_now (&disconnect_core, core);
-  GNUNET_log(GNUNET_ERROR_TYPE_INFO, "connected to core\n");
 
-  session = sessions_head;
-  while (NULL != session)
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "conclude requested\n");
+  cmsg = (struct GNUNET_CONSENSUS_ConcludeMessage *) message;
+  session = get_session_by_client (client);
+  if (NULL == session)
   {
-    if (NULL != session->join_msg)
-      initialize_session (session);
-    session = session->next;
+    /* client not found */
+    GNUNET_break (0);
+    GNUNET_SERVER_client_disconnect (client);
+    return;
+  }
+  if (CONSENSUS_ROUND_BEGIN != session->current_round)
+  {
+    /* client requested conclude twice */
+    GNUNET_break (0);
+    return;
+  }
+  if (session->num_peers <= 1)
+  {
+    /* FIXME: what to do here? */
+    //send_client_conclude_done (session);
+  }
+  else
+  {
+    session->conclude_timeout = GNUNET_TIME_relative_ntoh (cmsg->timeout);
+    /* the 'begin' round is over, start with the next, actual round */
+    round_over (session, NULL);
   }
+
+  GNUNET_assert (CONSENSUS_ROUND_BEGIN != session->current_round);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
 }
 
 
@@ -1862,58 +1185,33 @@ static void
 shutdown_task (void *cls,
                const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-
-  /* FIXME: complete; write separate destructors for different data types */
-
-  while (NULL != incoming_sockets_head)
-  {
-    struct IncomingSocket *socket;
-    socket = incoming_sockets_head;
-    if (NULL == socket->cpi)
-    {
-      GNUNET_STREAM_close (socket->socket);
-    }
-    incoming_sockets_head = incoming_sockets_head->next;
-    GNUNET_free (socket);
-  }
-
   while (NULL != sessions_head)
-  {
-    struct ConsensusSession *session;
-    int i;
-
-    session = sessions_head;
-
-    for (i = 0; session->num_peers; i++)
-    {
-      struct ConsensusPeerInformation *cpi;
-      cpi = &session->info[i];
-      if ((NULL != cpi) && (NULL != cpi->socket))
-      {
-        GNUNET_STREAM_close (cpi->socket);
-      }
-    }
-
-    if (NULL != session->client)
-      GNUNET_SERVER_client_disconnect (session->client);
+    destroy_session (sessions_head);
 
-    sessions_head = sessions_head->next;
-    GNUNET_free (session);
-  }
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "handled shutdown request\n");
+}
 
-  if (NULL != core)
-  {
-    GNUNET_CORE_disconnect (core);
-    core = NULL;
-  }
 
-  if (NULL != listener)
-  {
-    GNUNET_STREAM_listen_close (listener);
-    listener = NULL;
-  } 
+/**
+ * Clean up after a client after it is
+ * disconnected (either by us or by itself)
+ *
+ * @param cls closure, unused
+ * @param client the client to clean up after
+ */
+void
+handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
+{
+  struct ConsensusSession *session;
 
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "handled shutdown request\n");
+  session = get_session_by_client (client);
+  if (NULL == session)
+    return;
+  if ((CONSENSUS_ROUND_BEGIN == session->current_round) ||
+      (CONSENSUS_ROUND_FINISH == session->current_round))
+    destroy_session (session);
+  else
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO, "client disconnected, but waiting for consensus to finish\n");
 }
 
 
@@ -1925,39 +1223,30 @@ shutdown_task (void *cls,
  * @param c configuration to use
  */
 static void
-run (void *cls, struct GNUNET_SERVER_Handle *server, const struct GNUNET_CONFIGURATION_Handle *c)
+run (void *cls, struct GNUNET_SERVER_Handle *server,
+     const struct GNUNET_CONFIGURATION_Handle *c)
 {
-  /* core is only used to retrieve the peer identity */
-  static const struct GNUNET_CORE_MessageHandler core_handlers[] = {
-    {NULL, 0, 0}
-  };
   static const struct GNUNET_SERVER_MessageHandler server_handlers[] = {
-    {&client_join, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_JOIN, 0},
-    {&client_insert, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_INSERT, 0},
     {&client_conclude, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_CONCLUDE,
         sizeof (struct GNUNET_CONSENSUS_ConcludeMessage)},
-    {&client_ack, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_ACK,
-        sizeof (struct GNUNET_CONSENSUS_AckMessage)},
+    {&client_insert, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_INSERT, 0},
+    {&client_join, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_JOIN, 0},
     {NULL, NULL, 0, 0}
   };
 
   cfg = c;
   srv = server;
-
+  if (GNUNET_OK != GNUNET_CRYPTO_get_host_identity (cfg, &my_peer))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "could not retrieve host identity\n");
+    GNUNET_break (0);
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
   GNUNET_SERVER_add_handlers (server, server_handlers);
-
   GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &shutdown_task, NULL);
-
-  listener = GNUNET_STREAM_listen (cfg, GNUNET_APPLICATION_TYPE_CONSENSUS,
-                                   listen_cb, NULL,
-                                   GNUNET_STREAM_OPTION_END);
-
-
-  /* we have to wait for the core_startup callback before proceeding with the consensus service startup */
-  core = GNUNET_CORE_connect (c, NULL, &core_startup, NULL, NULL, NULL, GNUNET_NO, NULL, GNUNET_NO, core_handlers);
-  GNUNET_assert (NULL != core);
-
-  GNUNET_log(GNUNET_ERROR_TYPE_INFO, "consensus running\n");
+  GNUNET_SERVER_disconnect_notify (server, handle_client_disconnect, NULL);
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "consensus running\n");
 }
 
 
@@ -1973,7 +1262,7 @@ main (int argc, char *const *argv)
 {
   int ret;
   ret = GNUNET_SERVICE_run (argc, argv, "consensus", GNUNET_SERVICE_OPTION_NONE, &run, NULL);
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "exit\n");
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "exit (%d)\n", GNUNET_OK != ret);
   return (GNUNET_OK == ret) ? 0 : 1;
 }