diff --git a/PROTOCOL.md b/PROTOCOL.md
index 209754c..1923f43 100644
--- a/PROTOCOL.md
+++ b/PROTOCOL.md
@@ -85,7 +85,7 @@ version, type and ID, followed by the length of the message.
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-    |    Version    | Protocol-Type |   Hop Limit   |   Hop Count   |
+    |    Version    | Protocol-Type |    Tokens     |   Hop Limit   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            Length                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ -111,8 +111,8 @@ where such a packet came from MAY be closed.
 Protocol-Type is one of those specified in section Protocol Messages,
 or 255 for Content Messages.
 
-Hop Limit SHOULD be set to `20` on message creation, and
-MUST NOT be changed by a forwarding node.
+Tokens is the number of times this message should be copied to
+different relays.
 
 Hop Count specifies the number of nodes a message may pass. When
 creating a package, it is initialized to 0. Whenever a node forwards
diff --git a/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothInterface.scala b/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothInterface.scala
index 42d37e1..aa7ad4d 100644
--- a/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothInterface.scala
+++ b/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothInterface.scala
@@ -12,6 +12,7 @@ import com.nutomic.ensichat.core.body.ConnectionInfo
 import com.nutomic.ensichat.core.interfaces.{SettingsInterface, TransmissionInterface}
 import com.nutomic.ensichat.core.{Address, ConnectionHandler, Message}
 import com.nutomic.ensichat.service.ChatService
+import org.joda.time.{DateTime, Duration}
 
 import scala.collection.immutable.HashMap
 
@@ -169,12 +170,13 @@ class BluetoothInterface(context: Context, mainHandler: Handler,
   /**
    * Removes device from active connections.
    */
-  def onConnectionClosed(device: Device, socket: BluetoothSocket): Unit = {
-    val address = getAddressForDevice(device.id)
-    devices -= device.id
-    connections -= device.id
-    addressDeviceMap = addressDeviceMap.filterNot(_._2 == device.id)
-    connectionHandler.onConnectionClosed(address)
+  def onConnectionClosed(connectionOpened: DateTime, deviceId: Device.ID): Unit = {
+    val address = getAddressForDevice(deviceId)
+    devices -= deviceId
+    connections -= deviceId
+    addressDeviceMap = addressDeviceMap.filterNot(_._2 == deviceId)
+    val connectionDuration = new Duration(connectionOpened, DateTime.now)
+    connectionHandler.onConnectionClosed(address, connectionDuration)
   }
 
   /**
diff --git a/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothTransferThread.scala b/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothTransferThread.scala
index 240a2fd..2f389b6 100644
--- a/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothTransferThread.scala
+++ b/android/src/main/scala/com/nutomic/ensichat/bluetooth/BluetoothTransferThread.scala
@@ -9,6 +9,7 @@ import com.nutomic.ensichat.core.Message.ReadMessageException
 import com.nutomic.ensichat.core.body.ConnectionInfo
 import com.nutomic.ensichat.core.header.MessageHeader
 import com.nutomic.ensichat.core.{Address, Crypto, Message}
+import org.joda.time.DateTime
 
 /**
  * Transfers data between connnected devices.
@@ -17,8 +18,11 @@ import com.nutomic.ensichat.core.{Address, Crypto, Message}
  * @param socket An open socket to the given device.
  * @param onReceive Called when a message was received from the other device.
  */
-class BluetoothTransferThread(context: Context, device: Device, socket: BluetoothSocket, handler: BluetoothInterface,
-                     crypto: Crypto, onReceive: (Message, Device.ID) => Unit) extends Thread {
+class BluetoothTransferThread(context: Context, device: Device, socket: BluetoothSocket,
+                              handler: BluetoothInterface, crypto: Crypto,
+                              onReceive: (Message, Device.ID) => Unit) extends Thread {
+
+  private val connectionOpened = DateTime.now
 
   private val Tag = "TransferThread"
 
@@ -61,7 +65,7 @@ class BluetoothTransferThread(context: Context, device: Device, socket: Bluetoot
                              new IntentFilter(BluetoothDevice.ACTION_ACL_DISCONNECTED))
 
     send(crypto.sign(new Message(new MessageHeader(ConnectionInfo.Type,
-      Address.Null, Address.Null, 0), new ConnectionInfo(crypto.getLocalPublicKey))))
+      Address.Null, Address.Null, 0, 0), new ConnectionInfo(crypto.getLocalPublicKey))))
 
     while (socket.isConnected) {
       try {
@@ -102,7 +106,7 @@ class BluetoothTransferThread(context: Context, device: Device, socket: Bluetoot
     } catch {
       case e: IOException => Log.e(Tag, "Failed to close socket", e);
     } finally {
-      handler.onConnectionClosed(new Device(device.btDevice.get, false), null)
+      handler.onConnectionClosed(connectionOpened, device.id)
     }
   }
 
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/ConnectionHandler.scala b/core/src/main/scala/com/nutomic/ensichat/core/ConnectionHandler.scala
index 408ca89..3ff4bde 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/ConnectionHandler.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/ConnectionHandler.scala
@@ -1,15 +1,15 @@
 package com.nutomic.ensichat.core
 
 import java.security.InvalidKeyException
-import java.util.{TimerTask, Timer, Date}
+import java.util.Date
 
 import com.nutomic.ensichat.core.body._
-import com.nutomic.ensichat.core.header.{ContentHeader, MessageHeader}
+import com.nutomic.ensichat.core.header.{AbstractHeader, ContentHeader, MessageHeader}
 import com.nutomic.ensichat.core.interfaces._
 import com.nutomic.ensichat.core.internet.InternetInterface
 import com.nutomic.ensichat.core.util._
 import com.typesafe.scalalogging.Logger
-import org.joda.time.{DateTime, Duration}
+import org.joda.time.Duration
 
 import scala.concurrent.ExecutionContext.Implicits.global
 import scala.concurrent.Future
@@ -27,8 +27,6 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
 
   private val logger = Logger(this.getClass)
 
-  private val CheckMessageRetryInterval = Duration.standardMinutes(1)
-
   private var transmissionInterfaces = Set[TransmissionInterface]()
 
   private lazy val seqNumGenerator = new SeqNumGenerator(settings)
@@ -83,12 +81,13 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
     FutureHelper {
       val messageId = settings.get("message_id", 0L)
       val header = new ContentHeader(crypto.localAddress, target, seqNumGenerator.next(),
-        body.contentType, Some(messageId), Some(new Date()))
+        body.contentType, Some(messageId), Some(new Date()), AbstractHeader.InitialForwardingTokens)
       settings.put("message_id", messageId + 1)
 
       val msg = new Message(header, body)
       val encrypted = crypto.encryptAndSign(msg)
       router.forwardMessage(encrypted)
+      forwardMessageToRelays(encrypted)
       onNewMessage(msg)
     }
   }
@@ -98,7 +97,7 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
     val seqNum = seqNumGenerator.next()
     val targetSeqNum = localRoutesInfo.getRoute(target).map(_.seqNum).getOrElse(-1)
     val body = new RouteRequest(target, seqNum, targetSeqNum, 0)
-    val header = new MessageHeader(body.protocolType, crypto.localAddress, Address.Broadcast, seqNum)
+    val header = new MessageHeader(body.protocolType, crypto.localAddress, Address.Broadcast, seqNum, 0)
 
     val signed = crypto.sign(new Message(header, body))
     logger.trace(s"sending new $signed")
@@ -108,7 +107,7 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
   private def replyRoute(target: Address, replyTo: Address): Unit = {
     val seqNum = seqNumGenerator.next()
     val body = new RouteReply(seqNum, 0)
-    val header = new MessageHeader(body.protocolType, crypto.localAddress, replyTo, seqNum)
+    val header = new MessageHeader(body.protocolType, crypto.localAddress, replyTo, seqNum, 0)
 
     val signed = crypto.sign(new Message(header, body))
     logger.trace(s"sending new $signed")
@@ -118,7 +117,7 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
   private def routeError(address: Address, packetSource: Option[Address]): Unit =  {
     val destination = packetSource.getOrElse(Address.Broadcast)
     val header = new MessageHeader(RouteError.Type, crypto.localAddress, destination,
-                                   seqNumGenerator.next())
+                                   seqNumGenerator.next(), 0)
     val seqNum = localRoutesInfo.getRoute(address).map(_.seqNum).getOrElse(-1)
     val body = new RouteError(address, seqNum)
 
@@ -211,6 +210,7 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
 
     if (msg.header.target != crypto.localAddress) {
       router.forwardMessage(msg)
+      forwardMessageToRelays(msg)
       return
     }
 
@@ -234,6 +234,20 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
     onNewMessage(plainMsg)
   }
 
+  private def forwardMessageToRelays(message: Message): Unit = {
+    var tokens = message.header.tokens
+    val relays = database.pickLongestConnectionDevice(connections())
+    var index = 0
+    while (tokens > 1) {
+      val forwardTokens = tokens / 2
+      val headerCopy = message.header.asInstanceOf[ContentHeader].copy(tokens = forwardTokens)
+      router.forwardMessage(message.copy(header = headerCopy), relays.lift(index))
+      tokens -= forwardTokens
+      database.updateMessageForwardingTokens(message, tokens)
+      index += 1
+    }
+  }
+
   /**
     * Tries to send messages in [[MessageBuffer]] again, after we acquired a new route.
     */
@@ -244,11 +258,8 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
   }
 
   private def noRouteFound(message: Message): Unit = {
-    if (message.header.origin == crypto.localAddress) {
-      messageBuffer.addMessage(message)
-      requestRoute(message.header.target)
-    } else
-      routeError(message.header.target, Option(message.header.origin))
+    messageBuffer.addMessage(message)
+    requestRoute(message.header.target)
   }
 
   /**
@@ -317,13 +328,23 @@ final class ConnectionHandler(settings: SettingsInterface, database: Database,
                                 settings.get(SettingsInterface.KeyUserStatus, "")))
     callbacks.onConnectionsChanged()
     resendMissingRouteMessages()
+    messageBuffer.getAllMessages
+      .filter(_.header.tokens > 1)
+      .foreach(forwardMessageToRelays)
     true
   }
 
-  def onConnectionClosed(address: Address): Unit = {
+  /**
+    * Called by [[TransmissionInterface]] when a connection is closed.
+    *
+    * @param address The address of the connected device.
+    * @param duration The time that we were connected to the device.
+    */
+  def onConnectionClosed(address: Address, duration: Duration): Unit = {
     localRoutesInfo.connectionClosed(address)
       .foreach(routeError(_, None))
     callbacks.onConnectionsChanged()
+    database.insertOrUpdateKnownDevice(address, duration)
   }
 
   def connections(): Set[Address] = transmissionInterfaces.flatMap(_.getConnections)
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/Router.scala b/core/src/main/scala/com/nutomic/ensichat/core/Router.scala
index 02159b8..fd0de6c 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/Router.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/Router.scala
@@ -7,6 +7,8 @@ import com.nutomic.ensichat.core.util.LocalRoutesInfo
 
 object Router extends Comparator[Int] {
 
+  private val HopLimit = 20
+
   /**
    * Compares which sequence number is newer.
    *
@@ -50,7 +52,7 @@ private[core] class Router(routesInfo: LocalRoutesInfo, send: (Address, Message)
    * true.
    */
   def forwardMessage(msg: Message, nextHopOption: Option[Address] = None): Unit = {
-    if (msg.header.hopCount + 1 >= msg.header.hopLimit)
+    if (msg.header.hopCount + 1 >= Router.HopLimit)
       return
 
     val nextHop = nextHopOption.getOrElse(msg.header.target)
@@ -79,10 +81,8 @@ private[core] class Router(routesInfo: LocalRoutesInfo, send: (Address, Message)
    */
   private def incHopCount(msg: Message): Message = {
     val updatedHeader = msg.header match {
-      case ch: ContentHeader => new ContentHeader(ch.origin, ch.target, ch.seqNum, ch.contentType,
-                                    ch.messageId, ch.time, ch.hopCount + 1, ch.hopLimit)
-      case mh: MessageHeader => new MessageHeader(mh.protocolType, mh.origin, mh.target, mh.seqNum,
-                                    mh.hopCount + 1, mh.hopLimit)
+      case ch: ContentHeader => ch.copy(hopCount = ch.hopCount + 1)
+      case mh: MessageHeader => mh.copy(hopCount = mh.hopCount + 1)
     }
     new Message(updatedHeader, msg.crypto, msg.body)
   }
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/header/AbstractHeader.scala b/core/src/main/scala/com/nutomic/ensichat/core/header/AbstractHeader.scala
index a2a4589..97e1073 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/header/AbstractHeader.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/header/AbstractHeader.scala
@@ -8,7 +8,7 @@ import com.nutomic.ensichat.core.util.BufferUtils
 
 object AbstractHeader {
 
-  val DefaultHopLimit = 20
+  val InitialForwardingTokens = 3
 
   val Version = 0
 
@@ -25,7 +25,7 @@ object AbstractHeader {
 trait AbstractHeader {
 
   def protocolType: Int
-  def hopLimit: Int
+  def tokens: Int
   def hopCount: Int
   def origin: Address
   def target: Address
@@ -41,7 +41,7 @@ trait AbstractHeader {
 
     BufferUtils.putUnsignedByte(b, AbstractHeader.Version)
     BufferUtils.putUnsignedByte(b, protocolType)
-    BufferUtils.putUnsignedByte(b, hopLimit)
+    BufferUtils.putUnsignedByte(b, tokens)
     BufferUtils.putUnsignedByte(b, hopCount)
 
     BufferUtils.putUnsignedInt(b, length + contentLength)
@@ -63,7 +63,7 @@ trait AbstractHeader {
   override def equals(a: Any): Boolean = a match {
     case o: AbstractHeader =>
       protocolType  == o.protocolType &&
-        hopLimit    == o.hopLimit &&
+        tokens      == o.tokens &&
         hopCount    == o.hopCount &&
         origin      == o.origin &&
         target      == o.target &&
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/header/ContentHeader.scala b/core/src/main/scala/com/nutomic/ensichat/core/header/ContentHeader.scala
index dd9c7a7..f58ce36 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/header/ContentHeader.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/header/ContentHeader.scala
@@ -25,7 +25,7 @@ object ContentHeader {
     val time        = BufferUtils.getUnsignedInt(b)
 
     val ch = new ContentHeader(mh.origin, mh.target, mh.seqNum, contentType, Some(messageId),
-      Some(new Date(time * 1000)), mh.hopCount)
+      Some(new Date(time * 1000)), mh.tokens, mh.hopCount)
 
     val remaining = new Array[Byte](b.remaining())
     b.get(remaining, 0, b.remaining())
@@ -45,8 +45,8 @@ final case class ContentHeader(override val origin: Address,
                     contentType: Int,
                     override val messageId: Some[Long],
                     override val time: Some[Date],
-                    override val hopCount: Int = 0,
-                    override val hopLimit: Int = AbstractHeader.DefaultHopLimit)
+                    override val tokens: Int,
+                    override val hopCount: Int = 0)
   extends AbstractHeader {
 
   override val protocolType = ContentHeader.ContentMessageType
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/header/MessageHeader.scala b/core/src/main/scala/com/nutomic/ensichat/core/header/MessageHeader.scala
index 9b77509..2f859a4 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/header/MessageHeader.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/header/MessageHeader.scala
@@ -23,7 +23,7 @@ object MessageHeader {
     if (version != AbstractHeader.Version)
       throw new ReadMessageException("Failed to parse message with unsupported version " + version)
     val protocolType = BufferUtils.getUnsignedByte(b)
-    val hopLimit = BufferUtils.getUnsignedByte(b)
+    val tokens = BufferUtils.getUnsignedByte(b)
     val hopCount = BufferUtils.getUnsignedByte(b)
 
     val length = BufferUtils.getUnsignedInt(b)
@@ -34,7 +34,7 @@ object MessageHeader {
 
     val seqNum = BufferUtils.getUnsignedShort(b)
 
-    (new MessageHeader(protocolType, origin, target, seqNum, hopCount, hopLimit), length.toInt)
+    (new MessageHeader(protocolType, origin, target, seqNum, tokens, hopCount), length.toInt)
   }
 
 }
@@ -48,8 +48,8 @@ final case class MessageHeader(override val protocolType: Int,
                     override val origin: Address,
                     override val target: Address,
                     override val seqNum: Int,
-                    override val hopCount: Int = 0,
-                    override val hopLimit: Int = AbstractHeader.DefaultHopLimit)
+                    override val tokens: Int,
+                    override val hopCount: Int = 0)
   extends AbstractHeader {
 
   def length: Int = MessageHeader.Length
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetConnectionThread.scala b/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetConnectionThread.scala
index 4235964..b559128 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetConnectionThread.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetConnectionThread.scala
@@ -8,6 +8,7 @@ import com.nutomic.ensichat.core.body.ConnectionInfo
 import com.nutomic.ensichat.core.header.MessageHeader
 import com.nutomic.ensichat.core.{Address, Crypto, Message}
 import com.typesafe.scalalogging.Logger
+import org.joda.time.DateTime
 
 /**
  * Encapsulates an active connection to another node.
@@ -17,6 +18,8 @@ private[core] class InternetConnectionThread(socket: Socket, crypto: Crypto,
                                              onReceive: (Message, InternetConnectionThread) => Unit)
                                              extends Thread {
 
+  val connectionOpened = DateTime.now
+
   private val logger = Logger(this.getClass)
 
   private val inStream: InputStream =
@@ -47,7 +50,7 @@ private[core] class InternetConnectionThread(socket: Socket, crypto: Crypto,
     logger.info("Connection opened to " + socket.getInetAddress)
 
     send(crypto.sign(new Message(new MessageHeader(ConnectionInfo.Type,
-      Address.Null, Address.Null, 0), new ConnectionInfo(crypto.getLocalPublicKey))))
+      Address.Null, Address.Null, 0, 0), new ConnectionInfo(crypto.getLocalPublicKey))))
 
     try {
       socket.setKeepAlive(true)
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetInterface.scala b/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetInterface.scala
index f68905d..d3f9ce1 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetInterface.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/internet/InternetInterface.scala
@@ -7,6 +7,7 @@ import com.nutomic.ensichat.core.interfaces.{SettingsInterface, TransmissionInte
 import com.nutomic.ensichat.core.util.FutureHelper
 import com.nutomic.ensichat.core.{Address, ConnectionHandler, Crypto, Message}
 import com.typesafe.scalalogging.Logger
+import org.joda.time.{DateTime, Duration}
 
 import scala.concurrent.ExecutionContext.Implicits.global
 import scala.concurrent.Future
@@ -102,7 +103,8 @@ private[core] class InternetInterface(connectionHandler: ConnectionHandler, cryp
       logger.trace("Connection closed to " + ad)
       connections -= connectionThread
       addressDeviceMap -= ad
-      connectionHandler.onConnectionClosed(ad)
+      val connectionDuration = new Duration(connectionThread.connectionOpened, DateTime.now)
+      connectionHandler.onConnectionClosed(ad, connectionDuration)
     }
   }
 
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/util/Database.scala b/core/src/main/scala/com/nutomic/ensichat/core/util/Database.scala
index ec8d464..8cd4a3f 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/util/Database.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/util/Database.scala
@@ -1,13 +1,15 @@
 package com.nutomic.ensichat.core.util
 
 import java.io.File
+import java.sql.DriverManager
 import java.util.Date
 
 import com.nutomic.ensichat.core.body.Text
 import com.nutomic.ensichat.core.header.ContentHeader
-import com.nutomic.ensichat.core.interfaces.CallbackInterface
+import com.nutomic.ensichat.core.interfaces.{CallbackInterface, SettingsInterface}
 import com.nutomic.ensichat.core.{Address, Message, User}
 import com.typesafe.scalalogging.Logger
+import org.joda.time
 import slick.driver.H2Driver.api._
 
 import scala.concurrent.Await
@@ -19,10 +21,15 @@ import scala.concurrent.duration.Duration
  *
  * @param path The database file.
  */
-class Database(path: File, callbackInterface: CallbackInterface) {
+class Database(path: File, settings: SettingsInterface, callbackInterface: CallbackInterface) {
 
   private val logger = Logger(this.getClass)
 
+  private val DatabaseVersionKey = "database_version"
+  private val DatabaseVersion = 2
+
+  private val DatabasePath = "jdbc:h2:" + path.getAbsolutePath + ";DATABASE_TO_UPPER=false"
+
   private class Messages(tag: Tag) extends Table[Message](tag, "MESSAGES") {
     def id        = primaryKey("id", (origin, messageId))
     def origin    = column[String]("origin")
@@ -30,20 +37,23 @@ class Database(path: File, callbackInterface: CallbackInterface) {
     def messageId = column[Long]("message_id")
     def text      = column[String]("text")
     def date      = column[Long]("date")
-    def * = (origin, target, messageId, text, date).<> [Message, (String, String, Long, String, Long)]( { tuple =>
-      val header = new ContentHeader(new Address(tuple._1),
-        new Address(tuple._2),
-        -1,
-        Text.Type,
-        Some(tuple._3),
-        Some(new Date(tuple._5)))
-      val body = new Text(tuple._4)
-      new Message(header, body)
-    }, { message =>
+    def tokens    = column[Int]("tokens")
+    def * = (origin, target, messageId, text, date, tokens) <> [Message, (String, String, Long, String, Long, Int)]( {
+      tuple =>
+        val header = new ContentHeader(new Address(tuple._1),
+          new Address(tuple._2),
+          -1,
+          Text.Type,
+          Some(tuple._3),
+          Some(new Date(tuple._5)),
+          tuple._6)
+        val body = new Text(tuple._4)
+        new Message(header, body)
+    }, message =>
       Option((message.header.origin.toString(), message.header.target.toString(),
         message.header.messageId.get, message.body.asInstanceOf[Text].text,
-        message.header.time.get.getTime))
-    })
+        message.header.time.get.getTime, message.header.tokens))
+    )
   }
   private val messages = TableQuery[Messages]
 
@@ -51,12 +61,21 @@ class Database(path: File, callbackInterface: CallbackInterface) {
     def address = column[String]("address", O.PrimaryKey)
     def name    = column[String]("name")
     def status  = column[String]("status")
-    def wrappedAddress = address.<> [Address, String](new Address(_), a => Option(a.toString()))
+    def wrappedAddress = address <> [Address, String](new Address(_), a => Option(a.toString))
     def * = (wrappedAddress, name, status) <> (User.tupled, User.unapply)
   }
   private val contacts = TableQuery[Contacts]
 
-  private val db = Database.forURL("jdbc:h2:" + path.getAbsolutePath, driver = "org.h2.Driver")
+  private class KnownDevices(tag: Tag) extends Table[(Address, time.Duration)](tag, "KNOWN_DEVICES") {
+    def address                 = column[String]("address", O.PrimaryKey)
+    def totalConnectionSeconds  = column[Long]("total_connection_seconds")
+    def * = (address, totalConnectionSeconds) <> [(Address, time.Duration), (String, Long)](
+      tuple => (new Address(tuple._1), time.Duration.standardSeconds(tuple._2)),
+      tuple => Option((tuple._1.toString, tuple._2.getStandardSeconds)))
+  }
+  private val knownDevices = TableQuery[KnownDevices]
+
+  private val db = Database.forURL(DatabasePath, driver = "org.h2.Driver")
 
   // Create tables if database doesn't exist.
   {
@@ -64,7 +83,25 @@ class Database(path: File, callbackInterface: CallbackInterface) {
     val dbFile = new File(path.getAbsolutePath + ".mv.db")
     if (!dbFile.exists()) {
       logger.info("Database does not exist, creating tables")
-      Await.result(db.run((messages.schema ++ contacts.schema).create), Duration.Inf)
+      val query = (messages.schema ++ contacts.schema ++ knownDevices.schema).create
+      Await.result(db.run(query), Duration.Inf)
+      settings.put(DatabaseVersionKey, DatabaseVersion)
+    }
+  }
+
+  // Apparently, slick doesn't support ALTER TABLE, so we have to write raw SQL for this...
+  {
+    val oldVersion = settings.get(DatabaseVersionKey, 0)
+    if (oldVersion != DatabaseVersion) {
+      logger.info(s"Upgrading database from version $oldVersion to $DatabaseVersion")
+      val connection = DriverManager.getConnection(DatabasePath)
+      if (oldVersion <= 2) {
+        connection.createStatement().executeUpdate("ALTER TABLE MESSAGES ADD COLUMN (tokens INT);")
+        connection.commit()
+        Await.result(db.run(knownDevices.schema.create), Duration.Inf)
+      }
+      connection.close()
+      settings.put(DatabaseVersionKey, DatabaseVersion)
     }
   }
 
@@ -122,4 +159,30 @@ class Database(path: File, callbackInterface: CallbackInterface) {
     callbackInterface.onContactsUpdated()
   }
 
+  def insertOrUpdateKnownDevice(address: Address, connectionTime: time.Duration): Unit = {
+    val query = knownDevices.insertOrUpdate((address, connectionTime))
+    Await.result(db.run(query), Duration.Inf)
+  }
+
+  /**
+    * Returns neighbors sorted by connection time, according to [[KnownDevices]].
+    */
+  def pickLongestConnectionDevice(connections: Set[Address]): List[Address] = {
+    val map = Await.result(db.run(knownDevices.result), Duration.Inf).toMap
+    connections
+      .toList
+      .sortBy(map(_).getMillis)
+      .reverse
+  }
+
+  def updateMessageForwardingTokens(message: Message, tokens: Int): Unit = {
+    val query = messages.filter { c =>
+        c.origin === message.header.origin.toString &&
+        c.messageId === message.header.messageId
+      }
+      .map(_.tokens)
+      .update(tokens)
+    Await.result(db.run(query), Duration.Inf)
+  }
+
 }
diff --git a/core/src/main/scala/com/nutomic/ensichat/core/util/MessageBuffer.scala b/core/src/main/scala/com/nutomic/ensichat/core/util/MessageBuffer.scala
index b82da3c..988a405 100644
--- a/core/src/main/scala/com/nutomic/ensichat/core/util/MessageBuffer.scala
+++ b/core/src/main/scala/com/nutomic/ensichat/core/util/MessageBuffer.scala
@@ -82,6 +82,8 @@ class MessageBuffer(retryMessageSending: (Address) => Unit) {
     ret.map(_.message)
   }
 
+  def getAllMessages: Set[Message] = values.map(_.message)
+
   private def handleTimeouts(): Unit = {
     values = values.filter { e =>
       e.retryCount < MaxRetryCount
diff --git a/core/src/test/scala/com/nutomic/ensichat/core/MessageTest.scala b/core/src/test/scala/com/nutomic/ensichat/core/MessageTest.scala
index 2af4609..0b624a7 100644
--- a/core/src/test/scala/com/nutomic/ensichat/core/MessageTest.scala
+++ b/core/src/test/scala/com/nutomic/ensichat/core/MessageTest.scala
@@ -40,7 +40,7 @@ class MessageTest extends TestCase {
   }
 
   def testSerializeSigned(): Unit = {
-    val header = new MessageHeader(ConnectionInfo.Type, AddressTest.a4, AddressTest.a2, 0)
+    val header = new MessageHeader(ConnectionInfo.Type, AddressTest.a4, AddressTest.a2, 0, 3)
     val m = new Message(header, ConnectionInfoTest.generateCi())
 
     val signed = crypto.sign(m)
diff --git a/core/src/test/scala/com/nutomic/ensichat/core/RouterTest.scala b/core/src/test/scala/com/nutomic/ensichat/core/RouterTest.scala
index 88ca751..677626a 100644
--- a/core/src/test/scala/com/nutomic/ensichat/core/RouterTest.scala
+++ b/core/src/test/scala/com/nutomic/ensichat/core/RouterTest.scala
@@ -46,7 +46,7 @@ class RouterTest extends TestCase {
         assertEquals(msg.header.seqNum,       m.header.seqNum)
         assertEquals(msg.header.protocolType, m.header.protocolType)
         assertEquals(msg.header.hopCount + 1, m.header.hopCount)
-        assertEquals(msg.header.hopLimit,     m.header.hopLimit)
+        assertEquals(msg.header.tokens,       m.header.tokens)
         assertEquals(msg.body, m.body)
         assertEquals(msg.crypto, m.crypto)
       }, _ => ())
@@ -93,14 +93,14 @@ class RouterTest extends TestCase {
 
   def testHopLimit(): Unit = Range(19, 22).foreach { i =>
     val msg = new Message(
-      new ContentHeader(AddressTest.a1, AddressTest.a2, 1, 1, Some(1), Some(new Date()), i), new Text(""))
+      new ContentHeader(AddressTest.a1, AddressTest.a2, 1, 1, Some(1), Some(new Date()), 3, i), new Text(""))
     val router = new Router(new LocalRoutesInfo(neighbors), (a, m) => fail(), _ => ())
     router.forwardMessage(msg)
   }
 
   private def generateMessage(sender: Address, receiver: Address, seqNum: Int): Message = {
     val header = new ContentHeader(sender, receiver, seqNum, UserInfo.Type, Some(5),
-      Some(new GregorianCalendar(2014, 6, 10).getTime))
+      Some(new GregorianCalendar(2014, 6, 10).getTime), 3)
     new Message(header, new UserInfo("", ""))
   }
 
diff --git a/core/src/test/scala/com/nutomic/ensichat/core/header/MessageHeaderTest.scala b/core/src/test/scala/com/nutomic/ensichat/core/header/MessageHeaderTest.scala
index cd444b9..e1c660b 100644
--- a/core/src/test/scala/com/nutomic/ensichat/core/header/MessageHeaderTest.scala
+++ b/core/src/test/scala/com/nutomic/ensichat/core/header/MessageHeaderTest.scala
@@ -11,9 +11,9 @@ object MessageHeaderTest {
     0)
 
   val h2 = new MessageHeader(ContentHeader.ContentMessageType, Address.Null, Address.Broadcast,
-    ContentHeader.SeqNumRange.last, 0xff)
+    ContentHeader.SeqNumRange.last, 0xff, 3)
 
-  val h3 = new MessageHeader(ContentHeader.ContentMessageType, Address.Broadcast, Address.Null, 0)
+  val h3 = new MessageHeader(ContentHeader.ContentMessageType, Address.Broadcast, Address.Null, 0, 3)
 
   val headers = Set(h1, h2, h3)
 
diff --git a/core/src/test/scala/com/nutomic/ensichat/core/util/RouteMessageInfoTest.scala b/core/src/test/scala/com/nutomic/ensichat/core/util/RouteMessageInfoTest.scala
index bc6e2b5..b8659af 100644
--- a/core/src/test/scala/com/nutomic/ensichat/core/util/RouteMessageInfoTest.scala
+++ b/core/src/test/scala/com/nutomic/ensichat/core/util/RouteMessageInfoTest.scala
@@ -13,7 +13,7 @@ class RouteMessageInfoTest extends TestCase {
     * Test case in which we have an entry with the same type, origin and target.
     */
   def testSameMessage(): Unit = {
-    val header = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1)
+    val header = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1, 0)
     val msg = new Message(header, new RouteRequest(AddressTest.a3, 2, 3, 1))
     val rmi = new RouteMessageInfo()
     assertFalse(rmi.isMessageRedundant(msg))
@@ -24,12 +24,12 @@ class RouteMessageInfoTest extends TestCase {
     * Forward a message with a seqnum that is older than the latest.
     */
   def testSeqNumOlder(): Unit = {
-    val header1 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1)
+    val header1 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1, 0)
     val msg1 = new Message(header1, new RouteRequest(AddressTest.a3, 0, 0, 0))
     val rmi = new RouteMessageInfo()
     assertFalse(rmi.isMessageRedundant(msg1))
 
-    val header2 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 3)
+    val header2 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 3, 0)
     val msg2 = new Message(header2, new RouteRequest(AddressTest.a3, 2, 0, 0))
     assertTrue(rmi.isMessageRedundant(msg2))
   }
@@ -38,12 +38,12 @@ class RouteMessageInfoTest extends TestCase {
     * Announce a route with a metric that is worse than the existing one.
     */
   def testMetricWorse(): Unit = {
-    val header1 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1)
+    val header1 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1, 0)
     val msg1 = new Message(header1, new RouteRequest(AddressTest.a3, 1, 0, 2))
     val rmi = new RouteMessageInfo()
     assertFalse(rmi.isMessageRedundant(msg1))
 
-    val header2 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 2)
+    val header2 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 2, 0)
     val msg2 = new Message(header2, new RouteRequest(AddressTest.a3, 1, 0, 4))
     assertTrue(rmi.isMessageRedundant(msg2))
   }
@@ -52,12 +52,12 @@ class RouteMessageInfoTest extends TestCase {
     * Announce route with a better metric.
     */
   def testMetricBetter(): Unit = {
-    val header1 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1)
+    val header1 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1, 0)
     val msg1 = new Message(header1, new RouteReply(0, 4))
     val rmi = new RouteMessageInfo()
     assertFalse(rmi.isMessageRedundant(msg1))
 
-    val header2 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 2)
+    val header2 = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 2, 0)
     val msg2 = new Message(header2, new RouteReply(0, 2))
     assertFalse(rmi.isMessageRedundant(msg2))
   }
@@ -68,7 +68,7 @@ class RouteMessageInfoTest extends TestCase {
   def testTimeout(): Unit = {
     val rmi = new RouteMessageInfo()
     DateTimeUtils.setCurrentMillisFixed(DateTime.now.getMillis)
-    val header = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1)
+    val header = new MessageHeader(RouteRequest.Type, AddressTest.a1, AddressTest.a2, 1, 0)
     val msg = new Message(header, new RouteRequest(AddressTest.a3, 0, 0, 0))
     assertFalse(rmi.isMessageRedundant(msg))
 
diff --git a/integration/src/main/scala/com.nutomic.ensichat.integration/LocalNode.scala b/integration/src/main/scala/com.nutomic.ensichat.integration/LocalNode.scala
index 2d88e60..4a59ec9 100644
--- a/integration/src/main/scala/com.nutomic.ensichat.integration/LocalNode.scala
+++ b/integration/src/main/scala/com.nutomic.ensichat.integration/LocalNode.scala
@@ -45,12 +45,12 @@ class LocalNode(val index: Int, configFolder: File) extends CallbackInterface {
   private val databaseFile = new File(configFolder, "database")
   private val keyFolder    = new File(configFolder, "keys")
 
-  private val database = new Database(databaseFile, this)
   private val settings = new SettingsInterface {
     private var values = Map[String, Any]()
     override def get[T](key: String, default: T): T = values.get(key).map(_.asInstanceOf[T]).getOrElse(default)
     override def put[T](key: String, value: T): Unit = values += (key -> value.asInstanceOf[Any])
   }
+  private val database = new Database(databaseFile, settings, this)
 
   val crypto            = new Crypto(settings, keyFolder)
   val connectionHandler = new ConnectionHandler(settings, database, this, crypto, 0, port)
diff --git a/integration/src/main/scala/com.nutomic.ensichat.integration/Main.scala b/integration/src/main/scala/com.nutomic.ensichat.integration/Main.scala
index c4b4476..3e7dee7 100644
--- a/integration/src/main/scala/com.nutomic.ensichat.integration/Main.scala
+++ b/integration/src/main/scala/com.nutomic.ensichat.integration/Main.scala
@@ -20,40 +20,141 @@ import scalax.file.Path
  */
 object Main extends App {
 
-  val nodes = createMesh()
-  System.out.println("\n\nAll nodes connected!\n\n")
+  // NOTE: These tests are somewhat fragile, and might fail randomly. It helps to run only
+  //       one of the following functions at a time.
+  testNeighborSending()
+  testMeshMessageSending()
+  testIndirectRelay()
+  testNeighborRelay()
+  testMessageDeliveryOnConnect()
+  testSendDelayed()
+  testRouteChange()
 
-  sendMessages(nodes)
-  System.out.println("\n\nMessages sent!\n\n")
+  private def testNeighborSending(): Unit = {
+    val node1 = Await.result(createNode(1), Duration.Inf)
+    val node2 = Await.result(createNode(2), Duration.Inf)
 
-  // Stop node 1, forcing route errors and messages to use the (longer) path via nodes 7 and 8.
-  nodes(1).connectionHandler.stop()
-  System.out.println("Node 1 stopped")
-  sendMessages(nodes)
-  System.out.println("\n\nMessages after route change sent!\n\n")
+    connectNodes(node1, node2)
+    sendMessage(node1, node2)
 
-  // Create new node 9, send message from node 0 to its address, before actually connecting it.
-  // The message is automatically delivered when node 9 connects as neighbor.
-  val node9 = Await.result(createNode(9), Duration.Inf)
-  val timer = new Timer()
-  timer.schedule(new TimerTask {
-    override def run(): Unit = {
-      connectNodes(nodes(0), node9)
-    }
-  }, Duration(10, TimeUnit.SECONDS).toMillis)
-  sendMessage(nodes(0), node9, 30)
+    Set(node1, node2).foreach(_.stop())
 
-  // Create new node 10, send message from node 7 to its address, before connecting it to the mesh.
-  // The message is delivered after node 7 starts a route discovery triggered by the message buffer.
-  val node10 = Await.result(createNode(10), Duration.Inf)
-  timer.schedule(new TimerTask {
-    override def run(): Unit = {
-      connectNodes(nodes(0), node10)
-      timer.cancel()
-    }
-  }, Duration(5, TimeUnit.SECONDS).toMillis)
-  sendMessage(nodes(7), node10, 30)
-  System.out.println("\n\nMessages after delay sent!\n\n")
+    System.out.println("Test neighbor sending successful!")
+  }
+
+  private def testNeighborRelay(): Unit = {
+    val nodes = createNodes(3)
+
+    connectNodes(nodes(0), nodes(1))
+
+    val timer = new Timer()
+    timer.schedule(new TimerTask {
+      override def run(): Unit = {
+        nodes(0).stop()
+        connectNodes(nodes(1), nodes(2))
+      }
+    }, Duration(10, TimeUnit.SECONDS).toMillis)
+    sendMessage(nodes(0), nodes(2), 30)
+
+    timer.cancel()
+    nodes.foreach(_.stop())
+
+    System.out.println("Test neighbor relay successful!")
+  }
+
+  private def testIndirectRelay(): Unit = {
+    val nodes = createNodes(5)
+
+
+    connectNodes(nodes(0), nodes(1))
+    connectNodes(nodes(1), nodes(2))
+    connectNodes(nodes(2), nodes(3))
+
+    val timer = new Timer()
+    timer.schedule(new TimerTask {
+      override def run(): Unit = {
+        nodes(0).stop()
+        connectNodes(nodes(3), nodes(4))
+      }
+    }, Duration(10, TimeUnit.SECONDS).toMillis)
+    sendMessage(nodes(0), nodes(4), 30)
+
+    timer.cancel()
+    nodes.foreach(_.stop())
+
+    System.out.println("Test indirect sending successful!")
+  }
+
+  private def testMeshMessageSending(): Unit = {
+    val nodes = createMesh()
+
+    sendMessages(nodes)
+
+    nodes.foreach(_.stop())
+
+    System.out.println("Test mesh message sending successful!")
+  }
+
+  /**
+    * Stop node 1, forcing route errors and messages to use the (longer) path via nodes 7 and 8.
+    */
+  private def testRouteChange() {
+    val nodes = createMesh()
+    nodes(1).connectionHandler.stop()
+    sendMessages(nodes)
+
+    nodes.foreach(_.stop())
+
+    System.out.println("Test route change successful!")
+  }
+
+  /**
+    * Create new node 9, send message from node 0 to its address, before actually connecting it.
+    * The message is automatically delivered when node 9 connects as neighbor.
+    */
+  private def testMessageDeliveryOnConnect() {
+    val nodes = createMesh()
+    val node9 = Await.result(createNode(9), Duration.Inf)
+    val timer = new Timer()
+    timer.schedule(new TimerTask {
+      override def run(): Unit = {
+        connectNodes(nodes(0), node9)
+        timer.cancel()
+      }
+    }, Duration(10, TimeUnit.SECONDS).toMillis)
+    sendMessage(nodes(0), node9, 30)
+
+    (nodes :+ node9).foreach(_.stop())
+
+    System.out.println("Test message delivery on connect successful!")
+  }
+
+  /**
+    * Create new node 10, send message from node 7 to its address, before connecting it to the mesh.
+    * The message is delivered after node 7 starts a route discovery triggered by the message buffer.
+    */
+  private def testSendDelayed(): Unit = {
+    val nodes = createMesh()
+    val timer = new Timer()
+    val node10 = Await.result(createNode(10), Duration.Inf)
+    timer.schedule(new TimerTask {
+      override def run(): Unit = {
+        connectNodes(nodes(0), node10)
+        timer.cancel()
+      }
+    }, Duration(5, TimeUnit.SECONDS).toMillis)
+    sendMessage(nodes(7), node10, 30)
+
+    (nodes :+ node10).foreach(_.stop())
+
+    System.out.println("Test send delayed successful!")
+  }
+
+  private def createNodes(count: Int): Seq[LocalNode] = {
+    val nodes = Await.result(Future.sequence((0 until count).map(createNode)), Duration.Inf)
+    nodes.foreach(n => System.out.println(s"Node ${n.index} has address ${n.crypto.localAddress}"))
+    nodes
+  }
 
   /**
     * Creates a new mesh with a predefined layout.
@@ -68,8 +169,7 @@ object Main extends App {
     * @return List of [[LocalNode]]s, ordered from 0 to 8.
     */
   private def createMesh(): Seq[LocalNode] = {
-    val nodes = Await.result(Future.sequence(0.to(8).map(createNode)), Duration.Inf)
-    sys.addShutdownHook(nodes.foreach(_.stop()))
+    val nodes = createNodes(9)
 
     connectNodes(nodes(0), nodes(1))
     connectNodes(nodes(0), nodes(2))
@@ -82,7 +182,6 @@ object Main extends App {
     connectNodes(nodes(3), nodes(7))
     connectNodes(nodes(0), nodes(8))
     connectNodes(nodes(7), nodes(8))
-    nodes.foreach(n => System.out.println(s"Node ${n.index} has address ${n.crypto.localAddress}"))
 
     nodes
   }
@@ -119,7 +218,6 @@ object Main extends App {
     sendMessage(nodes(3), nodes(5))
     sendMessage(nodes(4), nodes(6))
     sendMessage(nodes(2), nodes(3))
-    sendMessage(nodes(0), nodes(3))
     sendMessage(nodes(3), nodes(6))
     sendMessage(nodes(3), nodes(2))
   }
diff --git a/server/src/main/scala/com/nutomic/ensichat/server/Main.scala b/server/src/main/scala/com/nutomic/ensichat/server/Main.scala
index 530bd59..2af3d3a 100644
--- a/server/src/main/scala/com/nutomic/ensichat/server/Main.scala
+++ b/server/src/main/scala/com/nutomic/ensichat/server/Main.scala
@@ -22,7 +22,7 @@ object Main extends App with CallbackInterface {
 
   private lazy val settings          = new Settings(ConfigFile)
   private lazy val crypto            = new Crypto(settings, KeyFolder)
-  private lazy val database          = new Database(DatabaseFile, this)
+  private lazy val database          = new Database(DatabaseFile, settings, this)
   private lazy val connectionHandler = new ConnectionHandler(settings, database, this, crypto, 7)
 
   init()