diff --git a/beacon_chain/beacon_node.nim b/beacon_chain/beacon_node.nim
index d4d564de5..a1f2b8ee3 100644
--- a/beacon_chain/beacon_node.nim
+++ b/beacon_chain/beacon_node.nim
@@ -4,10 +4,10 @@ import
   chronos, chronicles, confutils, serialization/errors,
   eth/trie/db, eth/trie/backends/rocksdb_backend, eth/async_utils,
   spec/[bitfield, datatypes, digest, crypto, beaconstate, helpers, validator],
-  conf, time,
-  state_transition, fork_choice, ssz, beacon_chain_db, validator_pool, extras,
-  attestation_pool, block_pool, eth2_network, beacon_node_types,
-  mainchain_monitor, trusted_state_snapshots, version
+  conf, time, state_transition, fork_choice, ssz, beacon_chain_db,
+  validator_pool, extras, attestation_pool, block_pool, eth2_network,
+  beacon_node_types, mainchain_monitor, trusted_state_snapshots, version,
+  sync_protocol, request_manager
 
 const
   topicBeaconBlocks = "ethereum/2.1/beacon_chain/blocks"
@@ -18,13 +18,7 @@ const
   genesisFile = "genesis.json"
   testnetsBaseUrl = "https://serenity-testnets.status.im"
 
-# #################################################
-# Careful handling of beacon_node <-> sync_protocol
-# to avoid recursive dependencies
 proc onBeaconBlock*(node: BeaconNode, blck: BeaconBlock) {.gcsafe.}
-  # Forward decl for sync_protocol
-import sync_protocol, request_manager
-# #################################################
 
 func localValidatorsDir(conf: BeaconNodeConf): string =
   conf.dataDir / "validators"
@@ -88,6 +82,7 @@ proc saveValidatorKey(keyName, key: string, conf: BeaconNodeConf) =
 
 proc init*(T: type BeaconNode, conf: BeaconNodeConf): Future[BeaconNode] {.async.} =
   new result
+  result.onBeaconBlock = onBeaconBlock
   result.config = conf
   result.networkIdentity = getPersistentNetIdentity(conf)
   result.nickname = if conf.nodename == "auto": shortForm(result.networkIdentity)
@@ -654,7 +649,7 @@ proc onSecond(node: BeaconNode, moment: Moment) {.async.} =
   if missingBlocks.len > 0:
     info "Requesting detected missing blocks", missingBlocks
     node.requestManager.fetchAncestorBlocks(missingBlocks) do (b: BeaconBlock):
-      node.onBeaconBlock(b)
+      onBeaconBlock(node ,b)
 
   let nextSecond = max(Moment.now(), moment + chronos.seconds(1))
   addTimer(nextSecond) do (p: pointer):
@@ -662,7 +657,7 @@ proc onSecond(node: BeaconNode, moment: Moment) {.async.} =
 
 proc run*(node: BeaconNode) =
   waitFor node.network.subscribe(topicBeaconBlocks) do (blck: BeaconBlock):
-    node.onBeaconBlock(blck)
+    onBeaconBlock(node, blck)
 
   waitFor node.network.subscribe(topicAttestations) do (attestation: Attestation):
     node.onAttestation(attestation)
diff --git a/beacon_chain/beacon_node_types.nim b/beacon_chain/beacon_node_types.nim
index 0e5306d3f..a0a00f534 100644
--- a/beacon_chain/beacon_node_types.nim
+++ b/beacon_chain/beacon_node_types.nim
@@ -25,6 +25,7 @@ type
     attestationPool*: AttestationPool
     mainchainMonitor*: MainchainMonitor
     beaconClock*: BeaconClock
+    onBeaconBlock*: proc (node: BeaconNode, blck: BeaconBlock) {.gcsafe.}
 
     stateCache*: StateData ##\
     ## State cache object that's used as a scratch pad
diff --git a/beacon_chain/eth2_network.nim b/beacon_chain/eth2_network.nim
index 110a0ee5c..5c9bf03b3 100644
--- a/beacon_chain/eth2_network.nim
+++ b/beacon_chain/eth2_network.nim
@@ -175,17 +175,22 @@ else:
     result = waitFor daemon.identity()
     waitFor daemon.close()
 
+  template tcpEndPoint(address, port): auto =
+    MultiAddress.init(address, IPPROTO_TCP, port)
+
   proc createEth2Node*(conf: BeaconNodeConf): Future[Eth2Node] {.async.} =
     var
       (extIp, extTcpPort, extUdpPort) = setupNat(conf)
       hostAddress = tcpEndPoint(globalListeningAddr, Port conf.tcpPort)
       announcedAddresses = if extIp != globalListeningAddr: @[]
                            else: @[tcpEndPoint(extIp, extTcpPort)]
+      keyFile = conf.ensureNetworkIdFile
 
-      daemon = await newDaemonApi({PSGossipSub},
-                                  id = conf.ensureNetworkIdFile,
-                                  hostAddresses = @[hostAddress],
-                                  announcedAddresses = announcedAddresses)
+    info "Starting LibP2P deamon", hostAddress, announcedAddresses, keyFile
+    let daemon = await newDaemonApi({PSGossipSub},
+                                    id = keyFile,
+                                    hostAddresses = @[hostAddress],
+                                    announcedAddresses = announcedAddresses)
 
     return await Eth2Node.init(daemon)
 
@@ -195,7 +200,7 @@ else:
     result.addresses = @[tcpEndPoint(ip, port)]
 
   proc isSameNode*(bootstrapNode: BootstrapAddr, id: Eth2NodeIdentity): bool =
-    bootstrapNode == id
+    bootstrapNode.peer == id.peer
 
   proc shortForm*(id: Eth2NodeIdentity): string =
     # TODO: Make this shorter
diff --git a/beacon_chain/libp2p_backend.nim b/beacon_chain/libp2p_backend.nim
index 254b0258c..c3d949e7f 100644
--- a/beacon_chain/libp2p_backend.nim
+++ b/beacon_chain/libp2p_backend.nim
@@ -22,6 +22,7 @@ type
     connectionState*: ConnectionState
     awaitedMessages: Table[CompressedMsgId, FutureBase]
     protocolStates*: seq[RootRef]
+    maxInactivityAllowed*: Duration
 
   ConnectionState* = enum
     None,
@@ -95,6 +96,7 @@ proc init*(T: type Eth2Node, daemon: DaemonAPI): Future[T] {.async.} =
   new result
   result.daemon = daemon
   result.daemon.userData = result
+  result.maxInactivityAllowed = 15.minutes # TODO: Read this from the config
   init result.peers
 
   newSeq result.protocolStates, allProtocols.len
@@ -319,7 +321,7 @@ proc implementSendProcBody(sendProc: SendProc) =
     else:
       quote: `sendBytes`(`UntypedResponder`(`peer`).stream, `bytes`)
 
-  sendProc.useStandardBody(nil, sendCallGenerator)
+  sendProc.useStandardBody(nil, nil, sendCallGenerator)
 
 proc p2pProtocolBackendImpl*(p: P2PProtocol): Backend =
   var
diff --git a/beacon_chain/libp2p_spec_backend.nim b/beacon_chain/libp2p_spec_backend.nim
index cb17794e6..3eb4e44a6 100644
--- a/beacon_chain/libp2p_spec_backend.nim
+++ b/beacon_chain/libp2p_spec_backend.nim
@@ -1,7 +1,7 @@
 import
   tables, deques, options, algorithm, std_shims/[macros_shim, tables_shims],
   ranges/ptr_arith, chronos, chronicles, serialization, faststreams/input_stream,
-  eth/p2p/p2p_protocol_dsl, libp2p/daemon/daemonapi,
+  eth/async_utils, eth/p2p/p2p_protocol_dsl, libp2p/daemon/daemonapi,
   ssz
 
 export
@@ -9,10 +9,10 @@ export
 
 const
   # Compression nibble
-  NoCompression* = uint 0
+  NoCompression* = byte 0
 
   # Encoding nibble
-  SszEncoding* = uint 1
+  SszEncoding* = byte 1
 
   beaconChainProtocol = "/eth/serenity/beacon/rpc/1"
 
@@ -27,13 +27,13 @@ type
   Peer* = ref object
     network*: Eth2Node
     id*: PeerID
-    lastSentMsgId*: uint64
+    lastReqId*: uint64
     rpcStream*: P2PStream
     connectionState*: ConnectionState
     awaitedMessages: Table[CompressedMsgId, FutureBase]
-    outstandingRequests*: seq[Deque[OutstandingRequest]]
+    outstandingRequests*: Table[uint64, OutstandingRequest]
     protocolStates*: seq[RootRef]
-    maxInactivityAllowed: Duration
+    maxInactivityAllowed*: Duration
 
   ConnectionState* = enum
     None,
@@ -69,6 +69,7 @@ type
     id*: uint64
     future*: FutureBase
     timeoutAt*: Moment
+    responseThunk*: ThunkProc
 
   ProtocolConnection* = object
     stream*: P2PStream
@@ -96,13 +97,9 @@ type
     networkStateInitializer*: NetworkStateInitializer
     handshake*: HandshakeStep
     disconnectHandler*: DisconnectionHandler
-    dispatcher: Dispatcher
 
   ProtocolInfo* = ptr ProtocolInfoObj
 
-  Dispatcher* = object
-    messages*: seq[MessageInfo]
-
   SpecOuterMsgHeader {.packed.} = object
     compression {.bitsize: 4.}: uint
     encoding {.bitsize: 4.}: uint
@@ -112,6 +109,10 @@ type
     reqId: uint64
     methodId: uint16
 
+  ErrorResponse {.packed.} = object
+    outerHeader: SpecOuterMsgHeader
+    innerHeader: SpecInnerMsgHeader
+
   PeerStateInitializer* = proc(peer: Peer): RootRef {.gcsafe.}
   NetworkStateInitializer* = proc(network: Eth2Node): RootRef {.gcsafe.}
 
@@ -121,6 +122,7 @@ type
   ThunkProc* = proc(peer: Peer,
                     stream: P2PStream,
                     reqId: uint64,
+                    reqFuture: FutureBase,
                     msgData: ByteStreamVar): Future[void] {.gcsafe.}
 
   MessageContentPrinter* = proc(msg: pointer): string {.gcsafe.}
@@ -147,6 +149,14 @@ const
   BreachOfProtocol* = FaultOrError
     # TODO: We should lobby for more disconnection reasons.
 
+template isOdd(val: SomeInteger): bool =
+  type T = type(val)
+  (val and T(1)) != 0
+
+proc init(T: type SpecOuterMsgHeader,
+          compression, encoding: byte, msgLen: uint64): T =
+  T(compression: compression, encoding: encoding, msgLen: msgLen)
+
 proc readPackedObject(stream: P2PStream, T: type): Future[T] {.async.} =
   await stream.transp.readExactly(addr result, sizeof result)
 
@@ -154,6 +164,10 @@ proc appendPackedObject(stream: OutputStreamVar, value: auto) =
   let valueAsBytes = cast[ptr byte](unsafeAddr(value))
   stream.append makeOpenArray(valueAsBytes, sizeof(value))
 
+proc getThunk(protocol: ProtocolInfo, methodId: uint16): ThunkProc =
+  if methodId.int >= protocol.messages.len: return nil
+  protocol.messages[methodId.int].thunk
+
 include libp2p_backends_common
 include eth/p2p/p2p_backends_helpers
 include eth/p2p/p2p_tracing
@@ -178,7 +192,8 @@ proc init*(T: type Peer, network: Eth2Node, id: PeerID): Peer =
   result.id = id
   result.network = network
   result.awaitedMessages = initTable[CompressedMsgId, FutureBase]()
-  result.connectionState = Connected
+  result.maxInactivityAllowed = 15.minutes # TODO: read this from the config
+  result.connectionState = None
   newSeq result.protocolStates, allProtocols.len
   for i in 0 ..< allProtocols.len:
     let proto = allProtocols[i]
@@ -189,52 +204,51 @@ proc init*[MsgName](T: type ResponderWithId[MsgName],
                     peer: Peer, reqId: uint64): T =
   T(peer: peer, reqId: reqId)
 
-proc performProtocolHandshakes*(peer: Peer) {.async.} =
-  var subProtocolsHandshakes = newSeqOfCap[Future[void]](allProtocols.len)
-  for protocol in allProtocols:
-    if protocol.handshake != nil:
-      subProtocolsHandshakes.add((protocol.handshake)(peer, peer.rpcStream))
-
-  await all(subProtocolsHandshakes)
-  debug "All protocols initialized", peer
-
-proc initializeConnection*(peer: Peer) {.async.} =
-  let daemon = peer.network.daemon
+proc sendMsg*(peer: Peer, data: Bytes) {.gcsafe, async.} =
   try:
-    peer.rpcStream = await daemon.openStream(peer.id, @[beaconChainProtocol])
-    await performProtocolHandshakes(peer)
+    var unsentBytes = data.len
+    while true:
+      # TODO: this looks wrong.
+      # We are always trying to write the same data.
+      # Find all other places where such code is used.
+      unsentBytes -= await peer.rpcStream.transp.write(data)
+      if unsentBytes <= 0: return
   except CatchableError:
-    await reraiseAsPeerDisconnected(peer, "Failed to perform handshake")
+    await peer.disconnect(FaultOrError)
+    # this is usually a "(32) Broken pipe":
+    # FIXME: this exception should be caught somewhere in addMsgHandler() and
+    # sending should be retried a few times
+    raise
 
-proc handleConnectingBeaconChainPeer(daemon: DaemonAPI, stream: P2PStream) {.async, gcsafe.} =
-  let peer = daemon.peerFromStream(stream)
-  peer.rpcStream = stream
-  await performProtocolHandshakes(peer)
+proc sendMsg*[T](responder: ResponderWithId[T], data: Bytes): Future[void] =
+  return sendMsg(responder.peer, data)
 
-proc accepts(d: Dispatcher, methodId: uint16): bool =
-  methodId.int < d.messages.len
+proc sendErrorResponse(peer: Peer, reqId: uint64,
+                       responseCode: ResponseCode): Future[void] =
+  var resp = ErrorResponse(
+    outerHeader: SpecOuterMsgHeader.init(
+      compression = NoCompression,
+      encoding = SszEncoding,
+      msgLen = uint64 sizeof(SpecInnerMsgHeader)),
+    innerHeader: SpecInnerMsgHeader(
+      reqId: reqId,
+      methodId: uint16(responseCode)))
 
-proc invokeThunk(peer: Peer,
-                 protocol: ProtocolInfo,
-                 stream: P2PStream,
-                 methodId: int,
-                 reqId: uint64,
-                 msgContents: ByteStreamVar): Future[void] =
-  template raiseInvalidMsgId =
-    raise newException(InvalidMsgIdError,
-      "ETH2 message with an invalid id " & $methodId)
+  # TODO: don't allocate the Bytes sequence here
+  return peer.sendMsg @(makeOpenArray(cast[ptr byte](addr resp), sizeof resp))
 
-  if methodId >= protocol.dispatcher.messages.len: raiseInvalidMsgId()
-  var thunk = protocol.dispatcher.messages[methodId].thunk
-  if thunk == nil: raiseInvalidMsgId()
-
-  return thunk(peer, stream, reqId, msgContents)
-
-proc recvAndDispatchMsg*(peer: Peer, protocol: ProtocolInfo, stream: P2PStream):
-                         Future[PeerLoopExitReason] {.async.} =
+proc recvAndDispatchMsg*(peer: Peer): Future[PeerLoopExitReason] {.async.} =
   template fail(reason) =
     return reason
 
+  # For now, we won't try to handle the presence of multiple sub-protocols
+  # since the spec is not defining how they will be mapped to P2P streams.
+  doAssert allProtocols.len == 1
+
+  var
+    stream = peer.rpcStream
+    protocol = allProtocols[0]
+
   var outerHeader = await stream.readPackedObject(SpecOuterMsgHeader)
 
   if outerHeader.compression != NoCompression:
@@ -246,44 +260,51 @@ proc recvAndDispatchMsg*(peer: Peer, protocol: ProtocolInfo, stream: P2PStream):
   if outerHeader.msgLen <= SpecInnerMsgHeader.sizeof.uint64:
     fail ProtocolViolation
 
-  var innerHeader = await stream.readPackedObject(SpecInnerMsgHeader)
+  let
+    innerHeader = await stream.readPackedObject(SpecInnerMsgHeader)
+    reqId = innerHeader.reqId
 
   var msgContent = newSeq[byte](outerHeader.msgLen - SpecInnerMsgHeader.sizeof.uint64)
   await stream.transp.readExactly(addr msgContent[0], msgContent.len)
 
   var msgContentStream = memoryStream(msgContent)
 
-  if protocol.dispatcher.accepts(innerHeader.methodId):
-    try:
-      await invokeThunk(peer, protocol, stream,
-                        innerHeader.methodId.int,
-                        innerHeader.reqId,
-                        msgContentStream)
-    except SerializationError:
-      fail ProtocolViolation
-    except CatchableError:
-      warn ""
+  if reqId.isOdd:
+    peer.outstandingRequests.withValue(reqId, req):
+      let thunk = req.responseThunk
+      let reqFuture = req.future
+      peer.outstandingRequests.del(reqId)
 
-proc sendMsg*(peer: Peer, data: Bytes) {.gcsafe, async.} =
-  try:
-    var unsentBytes = data.len
-    while true:
-      unsentBytes -= await peer.rpcStream.transp.write(data)
-      if unsentBytes <= 0: return
-  except:
-    await peer.disconnect(FaultOrError)
-    # this is usually a "(32) Broken pipe":
-    # FIXME: this exception should be caught somewhere in addMsgHandler() and
-    # sending should be retried a few times
-    raise
+      try:
+        await thunk(peer, stream, reqId, reqFuture, msgContentStream)
+      except SerializationError:
+        debug "Error during deserialization", err = getCurrentExceptionMsg()
+        fail ProtocolViolation
+      except CatchableError:
+        # TODO
+        warn ""
+    do:
+      debug "Ignoring late or invalid response ID", peer, id = reqId
+      # TODO: skip the message
+  else:
+    let thunk = protocol.getThunk(innerHeader.methodId)
+    if thunk != nil:
+      try:
+        await thunk(peer, stream, reqId, nil, msgContentStream)
+      except SerializationError:
+        debug "Error during deserialization", err = getCurrentExceptionMsg()
+        fail ProtocolViolation
+      except CatchableError:
+        # TODO
+        warn ""
+    else:
+      debug "P2P request method not found", methodId = innerHeader.methodId
+      await peer.sendErrorResponse(reqId, MethodNotFound)
 
-proc sendMsg*[T](responder: ResponderWithId[T], data: Bytes): Future[void] =
-  return sendMsg(responder.peer, data)
-
-proc dispatchMessages*(peer: Peer, protocol: ProtocolInfo, stream: P2PStream):
-                       Future[PeerLoopExitReason] {.async.} =
+proc dispatchMessages*(peer: Peer): Future[PeerLoopExitReason] {.async.} =
   while true:
-    let dispatchedMsgFut = recvAndDispatchMsg(peer, protocol, stream)
+    let dispatchedMsgFut = recvAndDispatchMsg(peer)
+    doAssert peer.maxInactivityAllowed.milliseconds > 0
     yield dispatchedMsgFut or sleepAsync(peer.maxInactivityAllowed)
     if not dispatchedMsgFut.finished:
       return InactivePeer
@@ -295,87 +316,70 @@ proc dispatchMessages*(peer: Peer, protocol: ProtocolInfo, stream: P2PStream):
       if status == Success: continue
       return status
 
-proc registerRequest(peer: Peer,
-                     protocol: ProtocolInfo,
-                     timeout: Duration,
-                     responseFuture: FutureBase,
-                     responseMethodId: uint16): uint64 =
-  inc peer.lastSentMsgId
-  result = peer.lastSentMsgId
+proc performProtocolHandshakes*(peer: Peer) {.async.} =
+  peer.initProtocolStates allProtocols
 
-  let timeoutAt = Moment.fromNow(timeout)
-  let req = OutstandingRequest(id: result,
-                               future: responseFuture,
-                               timeoutAt: timeoutAt)
-  peer.outstandingRequests[responseMethodId.int].addLast req
+  # Please note that the ordering of operations here is important!
+  #
+  # We must first start all handshake procedures and give them a
+  # chance to send any initial packages they might require over
+  # the network and to yield on their `nextMsg` waits.
+  #
+  var subProtocolsHandshakes = newSeqOfCap[Future[void]](allProtocols.len)
+  for protocol in allProtocols:
+    if protocol.handshake != nil:
+      subProtocolsHandshakes.add((protocol.handshake)(peer, peer.rpcStream))
 
-  let requestResolver = protocol.dispatcher.messages[responseMethodId.int].requestResolver
-  proc timeoutExpired(udata: pointer) = requestResolver(nil, responseFuture)
+  # The `dispatchMesssages` loop must be started after this.
+  # Otherwise, we risk that some of the handshake packets sent by
+  # the other peer may arrrive too early and be processed before
+  # the handshake code got a change to wait for them.
+  #
+  var messageProcessingLoop = peer.dispatchMessages()
+  messageProcessingLoop.callback = proc(p: pointer) {.gcsafe.} =
+    if messageProcessingLoop.failed:
+      debug "Ending dispatchMessages loop", peer,
+            err = messageProcessingLoop.error.msg
+    else:
+      debug "Ending dispatchMessages", peer,
+            exitCode = messageProcessingLoop.read
+    traceAsyncErrors peer.disconnect(ClientShutdown)
 
-  addTimer(timeoutAt, timeoutExpired, nil)
+  # The handshake may involve multiple async steps, so we wait
+  # here for all of them to finish.
+  #
+  await all(subProtocolsHandshakes)
+
+  peer.connectionState = Connected
+  debug "Peer connection initialized", peer
+
+proc initializeConnection*(peer: Peer) {.async.} =
+  let daemon = peer.network.daemon
+  try:
+    peer.connectionState = Connecting
+    peer.rpcStream = await daemon.openStream(peer.id, @[beaconChainProtocol])
+    await performProtocolHandshakes(peer)
+  except CatchableError:
+    await reraiseAsPeerDisconnected(peer, "Failed to perform handshake")
+
+proc handleConnectingBeaconChainPeer(daemon: DaemonAPI, stream: P2PStream) {.async, gcsafe.} =
+  let peer = daemon.peerFromStream(stream)
+  peer.rpcStream = stream
+  peer.connectionState = Connecting
+  await performProtocolHandshakes(peer)
 
 proc resolvePendingFutures(peer: Peer, protocol: ProtocolInfo,
-                           methodId: int, msg: pointer, reqId: uint64) =
-  logScope:
-    msg = protocol.dispatcher.messages[methodId].name
-    msgContents = protocol.dispatcher.messages[methodId].printer(msg)
-    receivedReqId = reqId
-    remotePeer = peer.id
-
-  template resolve(future) =
-    (protocol.dispatcher.messages[methodId].requestResolver)(msg, future)
-
-  template outstandingReqs: auto =
-    peer.outstandingRequests[methodId]
+                           methodId: int, msg: pointer, reqFuture: FutureBase) =
 
   let msgId = (protocolIdx: protocol.index, methodId: methodId)
+
   if peer.awaitedMessages[msgId] != nil:
-    let msgInfo = protocol.dispatcher.messages[methodId]
+    let msgInfo = protocol.messages[methodId]
     msgInfo.nextMsgResolver(msg, peer.awaitedMessages[msgId])
     peer.awaitedMessages[msgId] = nil
 
-  # TODO: This is not completely sound because we are still using a global
-  # `reqId` sequence (the problem is that we might get a response ID that
-  # matches a request ID for a different type of request). To make the code
-  # correct, we can use a separate sequence per response type, but we have
-  # to first verify that the other Ethereum clients are supporting this
-  # correctly (because then, we'll be reusing the same reqIds for different
-  # types of requests). Alternatively, we can assign a separate interval in
-  # the `reqId` space for each type of response.
-  if reqId > peer.lastSentMsgId:
-    warn "RLPx response without a matching request"
-    return
-
-  var idx = 0
-  while idx < outstandingReqs.len:
-    template req: auto = outstandingReqs()[idx]
-
-    if req.future.finished:
-      doAssert req.timeoutAt <= Moment.now()
-      # Here we'll remove the expired request by swapping
-      # it with the last one in the deque (if necessary):
-      if idx != outstandingReqs.len - 1:
-        req = outstandingReqs.popLast
-        continue
-      else:
-        outstandingReqs.shrink(fromLast = 1)
-        # This was the last item, so we don't have any
-        # more work to do:
-        return
-
-    if req.id == reqId:
-      resolve req.future
-      # Here we'll remove the found request by swapping
-      # it with the last one in the deque (if necessary):
-      if idx != outstandingReqs.len - 1:
-        req = outstandingReqs.popLast
-      else:
-        outstandingReqs.shrink(fromLast = 1)
-      return
-
-    inc idx
-
-  debug "late or duplicate reply for a network request"
+  if reqFuture != nil and not reqFuture.finished:
+    protocol.messages[methodId].requestResolver(msg, reqFuture)
 
 proc initProtocol(name: string, version: int,
                   peerInit: PeerStateInitializer,
@@ -423,28 +427,72 @@ proc prepareRequest(peer: Peer,
                     stream: OutputStreamVar,
                     timeout: Duration,
                     responseFuture: FutureBase): DelayedWriteCursor =
+  assert peer != nil and
+         protocol != nil and
+         responseFuture != nil and
+         responseMethodId.int < protocol.messages.len
 
-  let reqId = registerRequest(peer, protocol, timeout,
-                              responseFuture, responseMethodId)
+  doAssert timeout.milliseconds > 0
 
   result = stream.delayFixedSizeWrite sizeof(SpecOuterMsgHeader)
 
+  inc peer.lastReqId, 2
+  let reqId = peer.lastReqId
+
   stream.appendPackedObject SpecInnerMsgHeader(
-    reqId: reqId,
-    methodId: requestMethodId)
+    reqId: reqId, methodId: requestMethodId)
+
+  template responseMsgInfo: auto =
+    protocol.messages[responseMethodId.int]
+
+  let
+    requestResolver = responseMsgInfo.requestResolver
+    timeoutAt = Moment.fromNow(timeout)
+
+  peer.outstandingRequests[reqId + 1] = OutstandingRequest(
+    id: reqId,
+    future: responseFuture,
+    timeoutAt: timeoutAt,
+    responseThunk: responseMsgInfo.thunk)
+
+  proc timeoutExpired(udata: pointer) =
+    requestResolver(nil, responseFuture)
+    peer.outstandingRequests.del(reqId + 1)
+
+  addTimer(timeoutAt, timeoutExpired, nil)
 
 proc prepareResponse(responder: ResponderWithId,
                      stream: OutputStreamVar): DelayedWriteCursor =
   result = stream.delayFixedSizeWrite sizeof(SpecOuterMsgHeader)
 
+  stream.appendPackedObject SpecInnerMsgHeader(
+    reqId: responder.reqId + 1,
+    methodId: uint16(Success))
+
+proc prepareMsg(peer: Peer, methodId: uint16,
+                stream: OutputStreamVar): DelayedWriteCursor =
+  result = stream.delayFixedSizeWrite sizeof(SpecOuterMsgHeader)
+
+  inc peer.lastReqId, 2
+  stream.appendPackedObject SpecInnerMsgHeader(
+    reqId: peer.lastReqId, methodId: methodId)
+
+proc finishOuterHeader(headerCursor: DelayedWriteCursor) =
+  var outerHeader = SpecOuterMsgHeader.init(
+    compression = NoCompression,
+    encoding = SszEncoding,
+    msgLen = uint64(headerCursor.totalBytesWrittenAfterCursor))
+
+  headerCursor.endWrite makeOpenArray(cast[ptr byte](addr outerHeader),
+                                      sizeof outerHeader)
+
 proc implementSendProcBody(sendProc: SendProc) =
   let
     msg = sendProc.msg
     delayedWriteCursor = ident "delayedWriteCursor"
     peer = sendProc.peerParam
 
-  proc preludeGenerator(stream: NimNode): NimNode =
-    result = newStmtList()
+  proc preSerializationStep(stream: NimNode): NimNode =
     case msg.kind
     of msgRequest:
       let
@@ -453,15 +501,22 @@ proc implementSendProcBody(sendProc: SendProc) =
         protocol = sendProc.msg.protocol.protocolInfoVar
         timeout = sendProc.timeoutParam
 
-      result.add quote do:
-        let `delayedWriteCursor` = `prepareRequest`(
+      quote do:
+        var `delayedWriteCursor` = prepareRequest(
           `peer`, `protocol`, `requestMethodId`, `responseMethodId`,
           `stream`, `timeout`, `resultIdent`)
+
     of msgResponse:
-      result.add quote do:
-        let `delayedWriteCursor` = `prepareResponse`(`peer`, `stream`)
-    else:
-      discard
+      quote do:
+        var `delayedWriteCursor` = prepareResponse(`peer`, `stream`)
+
+    of msgHandshake, msgNotification:
+      let methodId = newLit(msg.id)
+      quote do:
+        var `delayedWriteCursor` = prepareMsg(`peer`, `methodId`, `stream`)
+
+  proc postSerializationStep(stream: NimNode): NimNode =
+    newCall(bindSym "finishOuterHeader", delayedWriteCursor)
 
   proc sendCallGenerator(peer, bytes: NimNode): NimNode =
     let
@@ -471,7 +526,7 @@ proc implementSendProcBody(sendProc: SendProc) =
 
     if msg.kind == msgRequest:
       # In RLPx requests, the returned future was allocated here and passed
-      # to `registerRequest`. It's already assigned to the result variable
+      # to `prepareRequest`. It's already assigned to the result variable
       # of the proc, so we just wait for the sending operation to complete
       # and we return in a normal way. (the waiting is done, so we can catch
       # any possible errors).
@@ -481,7 +536,10 @@ proc implementSendProcBody(sendProc: SendProc) =
       # `sendMsg` call.
       quote: return `sendCall`
 
-  sendProc.useStandardBody(preludeGenerator, sendCallGenerator)
+  sendProc.useStandardBody(
+    preSerializationStep,
+    postSerializationStep,
+    sendCallGenerator)
 
 proc p2pProtocolBackendImpl*(p: P2PProtocol): Backend =
   let
@@ -492,7 +550,7 @@ proc p2pProtocolBackendImpl*(p: P2PProtocol): Backend =
     Format = ident "SSZ"
     Response = bindSym "Response"
     ResponderWithId = bindSym "ResponderWithId"
-    perProtocolMsgId = ident"perProtocolMsgId"
+    perProtocolMsgId = ident "perProtocolMsgId"
 
     mount = bindSym "mount"
 
@@ -508,6 +566,7 @@ proc p2pProtocolBackendImpl*(p: P2PProtocol): Backend =
     stream = ident "stream"
     protocol = ident "protocol"
     response = ident "response"
+    reqFutureVar = ident "reqFuture"
     msgContents = ident "msgContents"
     receivedMsg = ident "receivedMsg"
 
@@ -546,12 +605,12 @@ proc p2pProtocolBackendImpl*(p: P2PProtocol): Backend =
     else:
       newStmtList()
 
-    let callResolvePendingFutures = if msg.kind == msgResponse:
-      newCall(resolvePendingFutures,
-              peerVar, protocol.protocolInfoVar,
-              msgIdLit, newCall("addr", receivedMsg), reqIdVar)
-    else:
-      newStmtList()
+    let callResolvePendingFutures = newCall(
+      resolvePendingFutures, peerVar,
+                             protocol.protocolInfoVar,
+                             msgIdLit,
+                             newCall("addr", receivedMsg),
+                             reqFutureVar)
 
     var userHandlerParams = @[peerVar]
     if msg.kind == msgRequest:
@@ -565,6 +624,7 @@ proc p2pProtocolBackendImpl*(p: P2PProtocol): Backend =
       proc `thunkName`(`peerVar`: `Peer`,
                        `stream`: `P2PStream`,
                        `reqIdVar`: uint64,
+                       `reqFutureVar`: FutureBase,
                        `msgContents`: `ByteStreamVar`) {.async, gcsafe.} =
         var `receivedMsg` = `mount`(`Format`, `msgContents`, `msgRecName`)
         `traceMsg`
diff --git a/beacon_chain/sync_protocol.nim b/beacon_chain/sync_protocol.nim
index 9ab26f2fb..ecd777790 100644
--- a/beacon_chain/sync_protocol.nim
+++ b/beacon_chain/sync_protocol.nim
@@ -4,10 +4,6 @@ import
   spec/[datatypes, crypto, digest, helpers], eth/rlp,
   beacon_node_types, eth2_network, beacon_chain_db, block_pool, time, ssz
 
-from beacon_node import onBeaconBlock
-  # Careful handling of beacon_node <-> sync_protocol
-  # to avoid recursive dependencies
-
 type
   ValidatorChangeLogEntry* = object
     case kind*: ValidatorSetDeltaFlags
@@ -49,7 +45,7 @@ proc fromHeaderAndBody(b: var BeaconBlock, h: BeaconBlockHeader, body: BeaconBlo
 proc importBlocks(node: BeaconNode,
                   blocks: openarray[BeaconBlock]) =
   for blk in blocks:
-    node.onBeaconBlock(blk)
+    node.onBeaconBlock(node, blk)
   info "Forward sync imported blocks", len = blocks.len
 
 proc mergeBlockHeadersAndBodies(headers: openarray[BeaconBlockHeader], bodies: openarray[BeaconBlockBody]): Option[seq[BeaconBlock]] =
@@ -105,7 +101,7 @@ p2pProtocol BeaconSync(version = 1,
       let bestDiff = cmp((latestFinalizedEpoch, bestSlot), (m.latestFinalizedEpoch, m.bestSlot))
       if bestDiff >= 0:
         # Nothing to do?
-        trace "Nothing to sync", peer = peer.remote
+        debug "Nothing to sync", peer
       else:
         # TODO: Check for WEAK_SUBJECTIVITY_PERIOD difference and terminate the
         # connection if it's too big.
@@ -124,7 +120,7 @@ p2pProtocol BeaconSync(version = 1,
             if lastSlot <= s:
               info "Slot did not advance during sync", peer
               break
-  
+
             s = lastSlot + 1
           else:
             break