diff --git a/.gitignore b/.gitignore
index ab918853d..dc5373a3c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -39,7 +39,7 @@
 /test/test-context
 /test/test-basic
 /test/test-data-encoding
-/test/test-p2p
+/test/test-p2p-io-scheduler
 /test/LOG
 
 *~
diff --git a/src/.merlin b/src/.merlin
index d193250dc..d351d972f 100644
--- a/src/.merlin
+++ b/src/.merlin
@@ -23,6 +23,7 @@ FLG -w -30
 FLG -w -40
 PKG base64
 PKG calendar
+PKG cmdliner
 PKG cohttp
 PKG compiler-libs.optcomp
 PKG conduit
@@ -33,12 +34,13 @@ PKG ezjsonm
 PKG git
 PKG irmin
 PKG lwt
+PKG mtime.os
 PKG ocplib-endian
 PKG ocplib-json-typed
 PKG ocplib-ocamlres
 PKG ocplib-resto.directory
 PKG result
 PKG sodium
+PKG ssl
 PKG unix
 PKG zarith
-PKG cmdliner
diff --git a/src/Makefile b/src/Makefile
index 2bbba54b5..6d4ee8cfa 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -101,7 +101,7 @@ clean::
 
 MINUTILS_LIB_INTFS := \
   minutils/mBytes.mli \
-	minutils/hex_encode.mli \
+  minutils/hex_encode.mli \
   minutils/utils.mli \
   minutils/compare.mli \
   minutils/data_encoding.mli \
@@ -187,6 +187,7 @@ UTILS_PACKAGES := \
   base64 \
   calendar \
   ezjsonm \
+  mtime.os \
   sodium \
   zarith \
   $(COVERAGEPKG) \
@@ -256,6 +257,8 @@ clean::
 
 NODE_LIB_INTFS := \
   \
+  node/net/p2p_types.mli \
+  node/net/p2p_io_scheduler.mli \
   node/net/p2p.mli \
   node/net/RPC_server.mli \
   \
@@ -286,7 +289,10 @@ NODE_LIB_IMPLS := \
   \
   compiler/node_compiler_main.ml \
   \
+  node/net/p2p_types.ml \
+  node/net/p2p_io_scheduler.ml \
   node/net/p2p.ml \
+  \
   node/net/RPC_server.ml \
   \
   node/updater/fitness.ml \
@@ -594,10 +600,8 @@ NO_DEPS := \
 compiler/embedded_cmis.cmx compiler/embedded_cmis.cmi: OPENED_MODULES=
 
 ifneq ($(MAKECMDGOALS),clean)
-ifneq ($(MAKECMDGOALS),build-deps)
 include .depend
 endif
-endif
 DEPENDS := $(filter-out $(NO_DEPS), \
   $(MINUTILS_LIB_INTFS) $(MINUTILS_LIB_IMPLS) \
   $(UTILS_LIB_INTFS) $(UTILS_LIB_IMPLS) \
diff --git a/src/node/net/p2p.ml b/src/node/net/p2p.ml
index 08cd4c6f7..3d21775d5 100644
--- a/src/node/net/p2p.ml
+++ b/src/node/net/p2p.ml
@@ -486,24 +486,12 @@ module Make (P: PARAMS) = struct
 
     (* Them we can build the net object and launch the worker. *)
     and connected buf local_nonce version gid public_key nonce listening_port =
-      let feed_ma ?(freq=1.) ma counter =
-        let rec inner old_received =
-          Lwt_unix.sleep freq >>= fun () ->
-          let received = !counter in
-          ma#add_int (received - old_received);
-          inner received in
-        Lwt.async (fun () -> Lwt.pick [cancelation (); inner !counter])
-      in
       (* net object state *)
       let last = ref (Unix.gettimeofday ()) in
       let local_nonce = ref local_nonce in
       let remote_nonce = ref nonce in
       let received = ref 0 in
       let sent = ref 0 in
-      let received_ema = new Moving_average.ema ~init:0. ~alpha:0.2 () in
-      let sent_ema = new Moving_average.ema ~init:0. ~alpha:0.2 () in
-      feed_ma received_ema received ;
-      feed_ma sent_ema sent ;
       (* net object callbaks *)
       let last_seen () = !last in
       let get_nonce nonce =
@@ -520,8 +508,8 @@ module Make (P: PARAMS) = struct
       let reader = Lwt_pipe.create ~size:2 () in
       let total_sent () = !sent in
       let total_recv () = !received in
-      let current_inflow () = received_ema#get in
-      let current_outflow () = sent_ema#get in
+      let current_inflow () = 0. in
+      let current_outflow () = 0. in
       (* net object construction *)
       let peer = { gid ; public_key ; point = (addr, port) ;
                    listening_port ; version ; last_seen ;
diff --git a/src/node/net/p2p_io_scheduler.ml b/src/node/net/p2p_io_scheduler.ml
new file mode 100644
index 000000000..0a0acb087
--- /dev/null
+++ b/src/node/net/p2p_io_scheduler.ml
@@ -0,0 +1,449 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2016.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+(* TODO decide whether we need to preallocate buffers or not. *)
+
+open P2p_types
+include Logging.Make (struct let name = "p2p.io-scheduler" end)
+
+module Inttbl = Hashtbl.Make(struct
+    type t = int
+    let equal (x: int) (y: int) = x = y
+    let hash = Hashtbl.hash
+  end)
+
+let alpha = 0.2
+
+module type IO = sig
+  val name: string
+  type in_param
+  val pop: in_param -> MBytes.t tzresult Lwt.t
+  type out_param
+  val push: out_param -> MBytes.t -> unit tzresult Lwt.t
+  val close: out_param -> error list -> unit Lwt.t
+end
+
+module Scheduler(IO : IO) = struct
+
+  type t = {
+    canceler: Canceler.t ;
+    mutable worker: unit Lwt.t ;
+    counter: Moving_average.t ;
+    max_speed: int option ;
+    mutable quota: int ;
+    quota_updated: unit Lwt_condition.t ;
+    readys: unit Lwt_condition.t ;
+    readys_high: (connection * MBytes.t tzresult) Queue.t ;
+    readys_low: (connection * MBytes.t tzresult) Queue.t ;
+  }
+
+  and connection = {
+    id: int ;
+    mutable closed: bool ;
+    canceler: Canceler.t ;
+    in_param: IO.in_param ;
+    out_param: IO.out_param ;
+    mutable current_pop: MBytes.t tzresult Lwt.t ;
+    mutable current_push: unit tzresult Lwt.t ;
+    counter: Moving_average.t ;
+    mutable quota: int ;
+    mutable last_quota: int ;
+  }
+
+  let cancel (conn : connection) err =
+    if not conn.closed then begin
+      conn.closed <- true ;
+      Lwt.catch
+        (fun () -> IO.close conn.out_param err)
+        (fun _ -> Lwt.return_unit) >>= fun () ->
+      Canceler.cancel conn.canceler
+    end else
+      Lwt.return_unit
+
+  let waiter st conn =
+    assert (Lwt.state conn.current_pop <> Sleep) ;
+    conn.current_pop <- IO.pop conn.in_param ;
+    Lwt.async begin fun () ->
+      conn.current_pop >>= fun res ->
+      conn.current_push >>= fun _ ->
+      let was_empty =
+        Queue.is_empty st.readys_high && Queue.is_empty st.readys_low in
+      if conn.quota > 0 then
+        Queue.push (conn, res) st.readys_high
+      else
+        Queue.push (conn, res) st.readys_low ;
+      if was_empty then Lwt_condition.broadcast st.readys () ;
+      Lwt.return_unit
+    end
+
+  let wait_data st =
+    let is_empty =
+      Queue.is_empty st.readys_high && Queue.is_empty st.readys_low in
+    if is_empty then Lwt_condition.wait st.readys else Lwt.return_unit
+
+  let check_quota st =
+    if st.max_speed <> None && st.quota < 0 then
+      Lwt_condition.wait st.quota_updated
+    else
+      Lwt_unix.yield ()
+
+  let rec worker_loop st =
+    check_quota st >>= fun () ->
+    Lwt.pick [
+      Canceler.cancelation st.canceler ;
+      wait_data st
+    ] >>= fun () ->
+    if Canceler.canceled st.canceler then
+      Lwt.return_unit
+    else
+      let prio, (conn, msg) =
+        if not (Queue.is_empty st.readys_high) then
+          true, (Queue.pop st.readys_high)
+        else
+          false, (Queue.pop st.readys_low)
+      in
+      match msg with
+      | Error [Lwt_utils.Canceled] ->
+          worker_loop st
+      | Error ([Exn (Lwt_pipe.Closed |
+                     Unix.Unix_error (EBADF, _, _))] as err) ->
+          cancel conn err >>= fun () ->
+          worker_loop st
+      | Error err ->
+          lwt_debug "Error %a" pp_print_error err >>= fun () ->
+          cancel conn err >>= fun () ->
+          worker_loop st
+      | Ok msg ->
+          conn.current_push <- begin
+            IO.push conn.out_param msg >>= function
+            | Ok ()
+            | Error [Lwt_utils.Canceled] ->
+                return ()
+            | Error ([Exn (Unix.Unix_error (EBADF, _, _) |
+                           Lwt_pipe.Closed)] as err) ->
+                cancel conn err >>= fun () ->
+                return ()
+            | Error err ->
+                lwt_debug "Error %a" pp_print_error err >>= fun () ->
+                cancel conn err >>= fun () ->
+                Lwt.return (Error err)
+          end ;
+          let len = MBytes.length msg in
+          Moving_average.add st.counter len ;
+          st.quota <- st.quota - len ;
+          Moving_average.add conn.counter len ;
+          if prio then conn.quota <- conn.quota - len ;
+          waiter st conn ;
+          worker_loop st
+
+  let create max_speed =
+    let st = {
+      canceler = Canceler.create () ;
+      worker = Lwt.return_unit ;
+      counter = Moving_average.create ~init:0 ~alpha ;
+      max_speed ; quota = unopt 0 max_speed ;
+      quota_updated = Lwt_condition.create () ;
+      readys = Lwt_condition.create () ;
+      readys_high = Queue.create () ;
+      readys_low = Queue.create () ;
+    } in
+    st.worker <-
+      Lwt_utils.worker IO.name
+        (fun () -> worker_loop st)
+        (fun () -> Canceler.cancel st.canceler) ;
+    st
+
+  let create_connection st in_param out_param canceler id =
+    let conn =
+      { id ; closed = false ;
+        canceler ;
+        in_param ; out_param ;
+        current_pop = Lwt.fail Not_found (* dummy *) ;
+        current_push = return () ;
+        counter = Moving_average.create ~init:0 ~alpha ;
+        quota = 0 ; last_quota = 0 ;
+      } in
+    waiter st conn ;
+    conn
+
+  let update_quota st =
+    iter_option st.max_speed ~f:begin fun quota ->
+      st.quota <- (min st.quota 0) + quota ;
+      Lwt_condition.broadcast st.quota_updated ()
+    end ;
+    if not (Queue.is_empty st.readys_low) then begin
+      let tmp = Queue.create () in
+      Queue.iter
+        (fun ((conn : connection), _ as msg) ->
+           if conn.quota > 0 then
+             Queue.push msg st.readys_high
+           else
+             Queue.push msg tmp)
+        st.readys_low ;
+      Queue.clear st.readys_low ;
+      Queue.transfer tmp st.readys_low ;
+  end
+
+  let shutdown st =
+    Canceler.cancel st.canceler >>= fun () ->
+    st.worker
+
+end
+
+type error += Connection_closed
+
+module ReadScheduler = Scheduler(struct
+    let name = "io_scheduler(read)"
+    type in_param = Lwt_unix.file_descr * int
+    let pop (fd, maxlen) =
+      Lwt.catch
+        (fun () ->
+           let buf = MBytes.create maxlen in
+           Lwt_bytes.read fd buf 0 maxlen >>= fun len ->
+           if len = 0 then
+             fail Connection_closed
+           else
+             return (MBytes.sub buf 0 len) )
+        (function
+          | Unix.Unix_error(Unix.ECONNRESET, _, _) ->
+              fail Connection_closed
+          | exn ->
+              Lwt.return (error_exn exn))
+    type out_param = MBytes.t tzresult Lwt_pipe.t
+    let push p msg =
+      Lwt.catch
+        (fun () -> Lwt_pipe.push p (Ok msg) >>= return)
+        (fun exn -> fail (Exn exn))
+    let close p err =
+      Lwt.catch
+        (fun () -> Lwt_pipe.push p (Error err))
+        (fun _ -> Lwt.return_unit)
+  end)
+
+module WriteScheduler = Scheduler(struct
+    let name = "io_scheduler(write)"
+    type in_param = MBytes.t Lwt_pipe.t
+    let pop p =
+      Lwt.catch
+        (fun () -> Lwt_pipe.pop p >>= return)
+        (fun _ -> fail (Exn Lwt_pipe.Closed))
+    type out_param = Lwt_unix.file_descr
+    let push fd buf =
+      Lwt.catch
+        (fun () ->
+           Lwt_utils.write_mbytes fd buf >>= return)
+        (function
+          | Unix.Unix_error(Unix.EPIPE, _, _)
+          | Lwt.Canceled
+          | End_of_file ->
+              fail Connection_closed
+          | exn ->
+              Lwt.return (error_exn exn))
+    let close _p _err = Lwt.return_unit
+  end)
+
+type connection = {
+  id: int ;
+  sched: t ;
+  conn: Lwt_unix.file_descr ;
+  canceler: Canceler.t ;
+  read_conn: ReadScheduler.connection ;
+  read_queue: MBytes.t tzresult Lwt_pipe.t ;
+  write_conn: WriteScheduler.connection ;
+  write_queue: MBytes.t Lwt_pipe.t ;
+  mutable partial_read: MBytes.t option ;
+}
+
+and t = {
+  mutable closed: bool ;
+  connected: connection Inttbl.t ;
+  read_scheduler: ReadScheduler.t ;
+  write_scheduler: WriteScheduler.t ;
+  max_upload_speed: int option ; (* bytes per second. *)
+  max_download_speed: int option ;
+  read_buffer_size: int ;
+  read_queue_size: int option ;
+  write_queue_size: int option ;
+}
+
+let reset_quota st =
+  let { Moving_average.average = current_inflow } =
+    Moving_average.stat st.read_scheduler.counter
+  and { Moving_average.average = current_outflow } =
+    Moving_average.stat st.write_scheduler.counter in
+  let nb_conn = Inttbl.length st.connected in
+  if nb_conn > 0 then begin
+    let fair_read_quota = current_inflow / nb_conn
+    and fair_write_quota = current_outflow / nb_conn in
+    Inttbl.iter
+      (fun _id conn ->
+         conn.read_conn.last_quota <- fair_read_quota ;
+         conn.read_conn.quota <-
+           (min conn.read_conn.quota 0) + fair_read_quota ;
+         conn.write_conn.last_quota <- fair_write_quota ;
+         conn.write_conn.quota <-
+           (min conn.write_conn.quota 0) + fair_write_quota ; )
+      st.connected
+  end ;
+  ReadScheduler.update_quota st.read_scheduler ;
+  WriteScheduler.update_quota st.write_scheduler
+
+let create
+    ?max_upload_speed ?max_download_speed
+    ?read_queue_size ?write_queue_size
+    ~read_buffer_size
+    () =
+  let st = {
+    closed = false ;
+    connected = Inttbl.create 53 ;
+    read_scheduler = ReadScheduler.create max_download_speed ;
+    write_scheduler = WriteScheduler.create max_upload_speed ;
+    max_upload_speed ;
+    max_download_speed ;
+    read_buffer_size ;
+    read_queue_size ;
+    write_queue_size ;
+  } in
+  Moving_average.on_update (fun () -> reset_quota st) ;
+  st
+
+exception Closed
+
+let register =
+  let cpt = ref 0 in
+  fun st conn ->
+  if st.closed then begin
+    Lwt.async (fun () -> Lwt_utils.safe_close conn) ;
+    raise Closed
+  end else begin
+    let id = incr cpt; !cpt in
+    let canceler = Canceler.create () in
+    let read_queue = Lwt_pipe.create ?size:st.read_queue_size ()
+    and write_queue = Lwt_pipe.create ?size:st.write_queue_size () in
+    let read_conn =
+      ReadScheduler.create_connection
+        st.read_scheduler (conn, st.read_buffer_size) read_queue canceler id
+    and write_conn =
+      WriteScheduler.create_connection
+        st.write_scheduler write_queue conn canceler id in
+    Canceler.on_cancel canceler begin fun () ->
+      Inttbl.remove st.connected id ;
+      Moving_average.destroy read_conn.counter ;
+      Moving_average.destroy write_conn.counter ;
+      Lwt_pipe.close write_queue ;
+      Lwt_pipe.close read_queue ;
+      Lwt_utils.safe_close conn
+    end ;
+    let conn = {
+      sched = st ; id ; conn ; canceler ;
+      read_queue ; read_conn ;
+      write_queue ; write_conn ;
+      partial_read = None ;
+    } in
+    Inttbl.add st.connected id conn ;
+    conn
+  end
+
+let write { write_queue } msg =
+  Lwt.catch
+    (fun () -> Lwt_pipe.push write_queue msg >>= return)
+    (fun _ -> fail Connection_closed)
+let write_now { write_queue } msg = Lwt_pipe.push_now write_queue msg
+
+let read_from conn ?pos ?len buf msg =
+  let maxlen = MBytes.length buf in
+  let pos = unopt 0 pos in
+  assert (0 <= pos && pos < maxlen) ;
+  let len = unopt (maxlen - pos) len in
+  assert (len <= maxlen - pos) ;
+  match msg with
+  | Ok msg ->
+      let msg_len = MBytes.length msg in
+      let read_len = min len msg_len in
+      MBytes.blit msg 0 buf pos read_len ;
+      if read_len < msg_len then
+        conn.partial_read <-
+          Some (MBytes.sub msg read_len (msg_len - read_len)) ;
+      Ok read_len
+  | Error _ ->
+      Error [Connection_closed]
+
+let read_now conn ?pos ?len buf =
+  match conn.partial_read with
+  | Some msg ->
+      conn.partial_read <- None ;
+      Some (read_from conn ?pos ?len buf (Ok msg))
+  | None ->
+      try
+        map_option
+          (read_from conn ?pos ?len buf)
+          (Lwt_pipe.pop_now conn.read_queue)
+      with Lwt_pipe.Closed -> Some (Error [Connection_closed])
+
+let read conn ?pos ?len buf =
+  match conn.partial_read with
+  | Some msg ->
+      conn.partial_read <- None ;
+      Lwt.return (read_from conn ?pos ?len buf (Ok msg))
+  | None ->
+      Lwt.catch
+        (fun () ->
+           Lwt_pipe.pop conn.read_queue >|= fun msg ->
+           read_from conn ?pos ?len buf msg)
+        (fun _ -> fail Connection_closed)
+
+let read_full conn ?pos ?len buf =
+  let maxlen = MBytes.length buf in
+  let pos = unopt 0 pos in
+  let len = unopt (maxlen - pos) len in
+  assert (0 <= pos && pos < maxlen) ;
+  assert (len <= maxlen - pos) ;
+  let rec loop pos len =
+    if len = 0 then
+      return ()
+    else
+      read conn ~pos ~len buf >>=? fun read_len ->
+      loop (pos + read_len) (len - read_len) in
+  loop pos len
+
+let convert ~ws ~rs =
+  { Stat.total_sent = ws.Moving_average.total ;
+    total_recv = rs.Moving_average.total ;
+    current_outflow = ws.average ;
+    current_inflow = rs.average ;
+  }
+
+let global_stat { read_scheduler ; write_scheduler } =
+  let rs = Moving_average.stat read_scheduler.counter
+  and ws = Moving_average.stat write_scheduler.counter in
+  convert ~rs ~ws
+
+let stat { read_conn ; write_conn} =
+  let rs = Moving_average.stat read_conn.counter
+  and ws = Moving_average.stat write_conn.counter in
+  convert ~rs ~ws
+
+let close conn =
+  Inttbl.remove conn.sched.connected conn.id ;
+  Lwt_pipe.close conn.write_queue ;
+  Canceler.cancelation conn.canceler >>= fun () ->
+  conn.write_conn.current_push >>= fun res ->
+  Lwt.return res
+
+let iter_connection { connected } f =
+  Inttbl.iter f connected
+
+let shutdown st =
+  st.closed <- true ;
+  ReadScheduler.shutdown st.read_scheduler >>= fun () ->
+  WriteScheduler.shutdown st.write_scheduler >>= fun () ->
+  Inttbl.fold
+    (fun _gid conn acc -> close conn >>= fun _ -> acc)
+    st.connected
+    Lwt.return_unit
diff --git a/src/node/net/p2p_io_scheduler.mli b/src/node/net/p2p_io_scheduler.mli
new file mode 100644
index 000000000..9e5d20139
--- /dev/null
+++ b/src/node/net/p2p_io_scheduler.mli
@@ -0,0 +1,93 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2016.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+(** IO Scheduling. This module implements generic IO scheduling
+    between file descriptors. In order to use IO scheduling, the
+    [register] function must be used to make a file descriptor managed
+    by a [scheduler].. It will return a value of type [connection]
+    that must be used to perform IO on the managed file descriptor
+    using this module's dedicated IO functions (read, write, etc.).
+
+    Each connection is allowed a read (resp. write) quota, which is
+    for now fairly distributed among connections.
+
+    To each connection is associated a read (resp. write) queue where
+    data is copied to (resp. read from), at a rate of
+    max_download_speed / num_connections (resp. max_upload_speed /
+    num_connections).
+*)
+
+open P2p_types
+
+type connection
+(** Type of a connection. *)
+
+type t
+(** Type of an IO scheduler. *)
+
+val create:
+  ?max_upload_speed:int ->
+  ?max_download_speed:int ->
+  ?read_queue_size:int ->
+  ?write_queue_size:int ->
+  read_buffer_size:int ->
+  unit -> t
+(** [create ~max_upload_speed ~max_download_speed ~read_queue_size
+    ~write_queue_size ()] is an IO scheduler with specified (global)
+    max upload (resp. download) speed, and specified read
+    (resp. write) queue sizes for connections. *)
+
+val register: t -> Lwt_unix.file_descr -> connection
+(** [register sched fd] is a [connection] managed by [sched]. *)
+
+type error += Connection_closed
+
+val write: connection -> MBytes.t -> unit tzresult Lwt.t
+(** [write conn msg] returns [Ok ()] when [msg] has been added to
+    [conn]'s write queue, or fail with an error. *)
+
+val write_now: connection -> MBytes.t -> bool
+(** [write_now conn msg] is [true] iff [msg] has been (immediately)
+    added to [conn]'s write queue, [false] if it has been dropped. *)
+
+val read_now:
+  connection -> ?pos:int -> ?len:int -> MBytes.t -> int tzresult option
+(** [read_now conn ~pos ~len buf] blits at most [len] bytes from
+    [conn]'s read queue and returns the number of bytes written in
+    [buf] starting at [pos]. *)
+
+val read:
+  connection -> ?pos:int -> ?len:int -> MBytes.t -> int tzresult Lwt.t
+(** Like [read_now], but waits till [conn] read queue has at least one
+    element instead of failing. *)
+
+val read_full:
+  connection -> ?pos:int -> ?len:int -> MBytes.t -> unit tzresult Lwt.t
+(** Like [read], but blits exactly [len] bytes in [buf]. *)
+
+val stat: connection -> Stat.t
+(** [stat conn] is a snapshot of current bandwidth usage for
+    [conn]. *)
+
+val global_stat: t -> Stat.t
+(** [global_stat sched] is a snapshot of [sched]'s bandwidth usage
+    (sum of [stat conn] for each [conn] in [sched]). *)
+
+val iter_connection: t -> (int -> connection -> unit) -> unit
+(** [iter_connection sched f] applies [f] on each connection managed
+    by [sched]. *)
+
+val close: connection -> unit tzresult Lwt.t
+(** [close conn] cancels [conn] and returns after any pending data has
+    been sent. *)
+
+val shutdown: t -> unit Lwt.t
+(** [shutdown sched] returns after all connections managed by [sched]
+    have been closed and [sched]'s inner worker has successfully
+    canceled. *)
diff --git a/src/node/net/p2p_types.ml b/src/node/net/p2p_types.ml
new file mode 100644
index 000000000..846ba75a3
--- /dev/null
+++ b/src/node/net/p2p_types.ml
@@ -0,0 +1,46 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2016.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+open Logging.Net
+
+module Canceler = Lwt_utils.Canceler
+
+module Stat = struct
+
+  type t = {
+    total_sent : int ;
+    total_recv : int ;
+    current_inflow : int ;
+    current_outflow : int ;
+  }
+
+  let print_size ppf sz =
+    let ratio n = (float_of_int sz /. float_of_int (1 lsl n)) in
+    if sz < 1 lsl 10 then
+      Format.fprintf ppf "%d B" sz
+    else if sz < 1 lsl 20 then
+      Format.fprintf ppf "%.2f kiB" (ratio 10)
+    else
+      Format.fprintf ppf "%.2f MiB" (ratio 20)
+
+  let pp ppf stat =
+    Format.fprintf ppf
+      "sent: %a (%a/s) recv: %a (%a/s)"
+      print_size stat.total_sent print_size stat.current_outflow
+      print_size stat.total_recv print_size stat.current_inflow
+
+end
+
+module Gid = struct
+  include Crypto_box.Public_key_hash
+  let pp = pp_short
+  module Map = Map.Make (Crypto_box.Public_key_hash)
+  module Set = Set.Make (Crypto_box.Public_key_hash)
+  module Table = Hash.Hash_table (Crypto_box.Public_key_hash)
+end
diff --git a/src/node/net/p2p_types.mli b/src/node/net/p2p_types.mli
new file mode 100644
index 000000000..27e596452
--- /dev/null
+++ b/src/node/net/p2p_types.mli
@@ -0,0 +1,26 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2016.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+module Canceler = Lwt_utils.Canceler
+
+
+(** Bandwidth usage statistics *)
+
+module Stat : sig
+
+  type t = {
+    total_sent : int ;
+    total_recv : int ;
+    current_inflow : int ;
+    current_outflow : int ;
+  }
+
+  val pp: Format.formatter -> t -> unit
+
+end
diff --git a/src/tezos-deps.opam b/src/tezos-deps.opam
index 0637af7dc..c1914a775 100644
--- a/src/tezos-deps.opam
+++ b/src/tezos-deps.opam
@@ -26,6 +26,7 @@ depends: [
   "lwt" {>= "2.7.0" }
   "lwt_ssl"
   "menhir"
+  "mtime"
   "ocp-ocamlres" {>= "dev" }
   "ocplib-endian"
   "ocplib-json-typed"
diff --git a/src/utils/moving_average.ml b/src/utils/moving_average.ml
index 00b79977c..eea6a4334 100644
--- a/src/utils/moving_average.ml
+++ b/src/utils/moving_average.ml
@@ -7,31 +7,80 @@
 (*                                                                        *)
 (**************************************************************************)
 
-class type ma = object
-  method add_float : float -> unit
-  method add_int : int -> unit
-  method get : float
-end
+open Lwt.Infix
 
-class virtual base ?(init = 0.) () = object (self)
-  val mutable acc : float = init
-  method virtual add_float : float -> unit
-  method add_int x = self#add_float (float_of_int x)
-  method get = acc
-end
+module Inttbl = Hashtbl.Make(struct
+    type t = int
+    let equal (x: int) (y: int) = x = y
+    let hash = Hashtbl.hash
+  end)
 
-class sma ?init () = object
-  inherit base ?init ()
-  val mutable i = match init with None -> 0 | _ -> 1
-  method add_float x =
-    acc <- (acc +. (x -. acc) /. (float_of_int @@ succ i)) ;
-    i <- succ i
-end
+type t = {
+  id: int;
+  alpha: int ;
+  mutable total: int ;
+  mutable current: int ;
+  mutable average: int ;
+}
 
-class ema ?init ~alpha () = object
-  inherit base ?init ()
-  val alpha = alpha
-  method add_float x =
-      acc <- alpha *. x +. (1. -. alpha) *. acc
-end
+let counters = Inttbl.create 51
 
+let updated = Lwt_condition.create ()
+
+let update_hook = ref []
+let on_update f = update_hook := f :: !update_hook
+
+let worker_loop () =
+  let prev = ref @@ Mtime.elapsed () in
+  let rec inner sleep =
+    sleep >>= fun () ->
+    let sleep = Lwt_unix.sleep 1. in
+    let now = Mtime.elapsed () in
+    let elapsed = int_of_float (Mtime.(to_ms now -. to_ms !prev)) in
+    prev := now;
+    Inttbl.iter
+      (fun _ c ->
+         c.average <-
+           (c.alpha * c.current) / elapsed + (1000 - c.alpha) * c.average / 1000;
+         c.current <- 0)
+      counters ;
+    List.iter (fun f -> f ()) !update_hook ;
+    Lwt_condition.broadcast updated () ;
+    inner sleep
+  in
+  inner (Lwt_unix.sleep 1.)
+
+let worker =
+  lazy begin
+    Lwt.async begin fun () ->
+      let (_cancelation, cancel, _on_cancel) = Lwt_utils.canceler () in
+      Lwt_utils.worker "counter" ~run:worker_loop ~cancel
+    end
+  end
+
+let create =
+  let cpt = ref 0 in
+  fun ~init ~alpha ->
+    Lazy.force worker ;
+    let id = !cpt in
+    incr cpt ;
+    assert (0. < alpha && alpha <= 1.) ;
+    let alpha = int_of_float (1000. *. alpha) in
+    let c = { id ; alpha ; total = 0 ; current = 0 ; average = init } in
+    Inttbl.add counters id c ;
+    c
+
+let add c x =
+  c.total <- c.total + x ;
+  c.current <- c.current + x
+
+let destroy c =
+  Inttbl.remove counters c.id
+
+type stat = {
+  total: int ;
+  average: int ;
+}
+
+let stat ({ total ; average } : t) : stat =
+  { total ; average }
diff --git a/src/utils/moving_average.mli b/src/utils/moving_average.mli
index a5768ee51..24acbe95b 100644
--- a/src/utils/moving_average.mli
+++ b/src/utils/moving_average.mli
@@ -7,28 +7,18 @@
 (*                                                                        *)
 (**************************************************************************)
 
-(** Moving averages. The formulas are from Wikipedia
-    [https://en.wikipedia.org/wiki/Moving_average] *)
+type t
 
-class type ma = object
-  method add_float : float -> unit
-  method add_int : int -> unit
-  method get : float
-end
-(** Common class type for objects computing a cumulative moving
-    average of some flavor. In a cumulative moving average, the data
-    arrive in an ordered datum stream, and the user would like to get
-    the average of all of the data up until the current datum
-    point. The method [add_float] and [add_int] are used to add the
-    next datum. The method [get] and [get_exn] are used to compute the
-    moving average up until the current datum point. *)
+val create: init:int -> alpha:float -> t
+val destroy: t -> unit
 
-class sma : ?init:float -> unit -> ma
-(** [sma ?init ()] is an object that computes the Simple Moving
-    Average of a datum stream. [SMA(n+1) = SMA(n) + (x_(n+1) / SMA(n))
-    / (n+1)] *)
+val add: t -> int -> unit
 
-class ema : ?init:float -> alpha:float -> unit -> ma
-(** [ema ?init ~alpha ()] is an object that computes the Exponential
-    Moving Average of a datum stream. [EMA(n+1) = alpha * x_(n+1) +
-    (1 - alpha) * x_n] *)
+val on_update: (unit -> unit) -> unit
+val updated: unit Lwt_condition.t
+
+type stat = {
+  total: int ;
+  average: int ;
+}
+val stat: t -> stat
diff --git a/test/Makefile b/test/Makefile
index 429836541..36e6a356d 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,5 +1,9 @@
 
-TESTS :=  data-encoding store context state basic basic.sh
+TESTS := \
+  data-encoding \
+  store context state \
+  basic basic.sh \
+  p2p-io-scheduler
 
 all: test
 
@@ -36,6 +40,7 @@ PACKAGES := \
   irmin.unix \
   lwt \
   lwt.unix \
+  mtime.os \
   ocplib-endian \
   ocplib-ocamlres \
   ocplib-json-typed.bson \
@@ -66,7 +71,7 @@ ${NODELIB} ${CLIENTLIB}:
 	${MAKE} -C ../src $@
 
 .PHONY: build-test run-test test
-build-test: ${addprefix build-test-,${TESTS}} test-p2p
+build-test: ${addprefix build-test-,${TESTS}}
 run-test:
 	@$(patsubst %,${MAKE} run-test-% ; , ${TESTS}) \
 	  echo && echo "Success" && echo
@@ -177,13 +182,35 @@ clean::
 ############################################################################
 ## p2p test program
 
-TEST_P2P_INTFS =
+.PHONY:build-test-io_schduler
+build-test-p2p-io-scheduler: test-p2p-io-scheduler
+run-test-p2p-io-scheduler:
+	./test-p2p-io-scheduler \
+	   --delay 20 --clients 8 \
+	   --max-upload-speed $$((1 << 18)) \
+	   --max-download-speed $$((1 << 20))
 
-TEST_P2P_IMPLS = \
-  test_p2p.ml
+TEST_P2P_IO_SCHEDULER_IMPLS = \
+  lib/process.ml \
+  test_p2p_io_scheduler.ml
+
+${TEST_P2P_IO_SCHEDULER_IMPLS:.ml=.cmx}: ${NODELIB}
+test-p2p-io-scheduler: ${NODELIB} ${TEST_P2P_IO_SCHEDULER_IMPLS:.ml=.cmx}
+	ocamlfind ocamlopt -linkall -linkpkg ${OCAMLFLAGS} -o $@ $^
+
+clean::
+	rm -f test-p2p-io_scheduler
+
+############################################################################
+## lwt pipe test program
+
+build-test-lwt-pipe: test-lwt-pipe
+
+TEST_PIPE_IMPLS = \
+  test_lwt_pipe.ml
 
 ${TEST_BASIC_IMPLS:.ml=.cmx}: ${NODELIB}
-test-p2p: ${NODELIB} ${TEST_P2P_IMPLS:.ml=.cmx}
+test-lwt-pipe: ${NODELIB} ${TEST_PIPE_IMPLS:.ml=.cmx}
 	ocamlfind ocamlopt -linkall -linkpkg ${OCAMLFLAGS} -o $@ $^
 
 clean::
diff --git a/test/lib/process.ml b/test/lib/process.ml
new file mode 100644
index 000000000..2a60b2bbc
--- /dev/null
+++ b/test/lib/process.ml
@@ -0,0 +1,79 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2017.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+include Logging.Make (struct let name = "process" end)
+
+open Error_monad
+
+exception Exited of int
+
+let detach ?(prefix = "") f =
+  Lwt_io.flush_all () >>= fun () ->
+  match Lwt_unix.fork () with
+  | 0 ->
+      Random.self_init () ;
+      let template = Format.asprintf "%s$(section): $(message)" prefix in
+      let logger =
+        Lwt_log.channel
+          ~template ~close_mode:`Keep ~channel:Lwt_io.stderr () in
+      Logging.init (Manual logger) ;
+      Lwt_main.run begin
+        lwt_log_notice "PID: %d" (Unix.getpid ()) >>= fun () ->
+        f ()
+      end ;
+      exit 0
+  | pid ->
+      Lwt.catch
+        (fun () ->
+           Lwt_unix.waitpid [] pid >>= function
+           | (_,Lwt_unix.WEXITED 0) ->
+               Lwt.return_unit
+           | (_,Lwt_unix.WEXITED n) ->
+               Lwt.fail (Exited n)
+           | (_,Lwt_unix.WSIGNALED _)
+           | (_,Lwt_unix.WSTOPPED _) ->
+               Lwt.fail Exit)
+        (function
+          | Lwt.Canceled ->
+              Unix.kill pid Sys.sigkill ;
+              Lwt.return_unit
+          | exn -> Lwt.fail exn)
+
+let handle_error f =
+  Lwt.catch
+    f
+    (fun exn -> Lwt.return (error_exn exn)) >>= function
+  | Ok () -> Lwt.return_unit
+  | Error err ->
+      lwt_log_error "%a" Error_monad.pp_print_error err >>= fun () ->
+      exit 1
+
+let rec wait processes =
+  Lwt.catch
+    (fun () ->
+       Lwt.nchoose_split processes >>= function
+       | (_, []) -> lwt_log_notice "All done!"
+       | (_, processes) -> wait processes)
+    (function
+      | Exited n ->
+          lwt_log_notice "Early error!" >>= fun () ->
+          List.iter Lwt.cancel processes ;
+          Lwt.catch
+            (fun () -> Lwt.join processes)
+            (fun _ -> Lwt.return_unit) >>= fun () ->
+          lwt_log_notice "A process finished with error %d !" n >>= fun () ->
+          Pervasives.exit n
+      | exn ->
+          lwt_log_notice "Unexpected error!%a"
+            Error_monad.pp_exn exn >>= fun () ->
+          List.iter Lwt.cancel processes ;
+          Lwt.catch
+            (fun () -> Lwt.join processes)
+            (fun _ -> Lwt.return_unit) >>= fun () ->
+          Pervasives.exit 2)
diff --git a/test/lib/process.mli b/test/lib/process.mli
new file mode 100644
index 000000000..c1933cc11
--- /dev/null
+++ b/test/lib/process.mli
@@ -0,0 +1,15 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2017.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+open Error_monad
+exception Exited of int
+
+val detach: ?prefix:string -> (unit -> unit Lwt.t) -> unit Lwt.t
+val handle_error: (unit -> (unit, error list) result Lwt.t) -> unit Lwt.t
+val wait: unit Lwt.t list -> unit Lwt.t
diff --git a/test/test_p2p.ml b/test/test_p2p.ml
deleted file mode 100644
index bf1c44617..000000000
--- a/test/test_p2p.ml
+++ /dev/null
@@ -1,167 +0,0 @@
-open Lwt.Infix
-open P2p
-
-include Logging.Make (struct let name = "test-p2p" end)
-
-module Param = struct
-
-  let dump_encoding = Data_encoding.(Variable.list (tup2 string string))
-
-  type msg =
-    | Create of string * string
-    | Update of string * string
-    | Delete of string
-    | Dump of (string * string) list
-
-  let encodings = [
-    Encoding { tag = 0x10;
-               encoding = Data_encoding.(tup2 string string);
-               wrap = (function (k, v) -> Create (k, v));
-               unwrap = (function Create (k, v) -> Some (k, v) | _ -> None);
-               max_length = Some 0x400;
-             };
-    Encoding { tag = 0x11;
-               encoding = Data_encoding.(tup2 string string);
-               wrap = (function (k, v) -> Update (k, v));
-               unwrap = (function Create (k, v) -> Some (k, v) | _ -> None);
-               max_length = Some 0x400;
-             };
-    Encoding { tag = 0x12;
-               encoding = Data_encoding.string;
-               wrap = (function x -> Delete x);
-               unwrap = (function Delete x -> Some x | _ -> None);
-               max_length = Some 0x400;
-             };
-    Encoding { tag = 0x13;
-               encoding = dump_encoding;
-               wrap = (function x -> Dump x);
-               unwrap = (function Dump x -> Some x | _ -> None);
-               max_length = Some 0x10000;
-             };
-  ]
-
-  type metadata = unit
-  let initial_metadata = ()
-  let metadata_encoding = Data_encoding.empty
-  let score () = 0.
-
-  let supported_versions = [ { name = "TEST"; major = 0; minor = 0; } ]
-end
-
-module Net = Make(Param)
-
-let print_peer_info { Net.gid; addr; port; version = { name; major; minor } } =
-  Printf.sprintf "%s:%d (%s.%d.%d)" (Ipaddr.to_string addr) port name major minor
-
-let string_of_gid gid = Format.asprintf "%a" pp_gid gid
-
-let net_monitor config limits num_nets net =
-  let my_gid_str = string_of_gid @@ Net.gid net in
-  let send_msgs_to_neighbours neighbours =
-    Lwt_list.iter_p begin fun p ->
-      let { Net.gid } = Net.peer_info net p in
-      let remote_gid_str = string_of_gid gid in
-      Net.send net p (Create (my_gid_str, remote_gid_str)) >>= fun _ ->
-      lwt_log_notice "(%s) Done sending msg to %s" my_gid_str remote_gid_str
-    end neighbours >>= fun () ->
-    lwt_log_notice "(%s) Done sending all msgs." my_gid_str
-  in
-  let rec inner () =
-    let neighbours = Net.peers net in
-    let nb_neighbours = List.length neighbours in
-    if nb_neighbours < num_nets - 1 then begin
-      log_notice "(%s) I have %d peers" my_gid_str nb_neighbours;
-      Lwt_unix.sleep 1. >>= inner end
-    else begin
-      log_notice "(%s) I know all my %d peers" my_gid_str nb_neighbours;
-      Lwt.async (fun () -> send_msgs_to_neighbours neighbours);
-      let rec recv_peer_msgs acc =
-        if List.length acc = num_nets - 1 then begin
-          (* Print total sent/recv *)
-          let peers = Net.peers net in
-          ListLabels.iter peers ~f:begin fun p ->
-            let pi = Net.peer_info net p in
-            log_info "%a -> %a %d %d %.2f %.2f" pp_gid (Net.gid net) pp_gid pi.gid
-              pi.total_sent pi.total_recv pi.current_inflow pi.current_outflow;
-          end;
-          ListLabels.iter acc ~f:(fun (k, v) -> log_info "%s %s" k v);
-          Lwt.return_unit
-        end
-        else begin
-          lwt_log_notice "(%s) recv_peers_msgs: Got %d, need %d"
-            my_gid_str (List.length acc) (num_nets - 1) >>= fun () ->
-          Net.recv net >>= function
-          | p, (Create (their_gid, my_gid)) ->
-              lwt_log_notice "(%s) Got a message from %s" my_gid_str their_gid >>= fun () ->
-              recv_peer_msgs ((their_gid, my_gid) :: acc)
-          | _ -> assert false
-        end
-      in
-      recv_peer_msgs []
-    end
-  in inner ()
-
-let range n =
-  let rec inner acc = function
-    | -1 -> acc
-    | n -> inner (n :: acc) (pred n)
-  in
-  if n < 0 then invalid_arg "range"
-  else inner [] (pred n)
-
-let main () =
-  let incoming_port = ref @@ Some 11732 in
-  let discovery_port = ref @@ Some 10732 in
-  let closed_network = ref false in
-
-  let max_packet_size = ref 1024 in
-  let peer_answer_timeout = ref 10. in
-  let blacklist_time = ref 100. in
-  let num_networks = ref 0 in
-
-  let make_net nb_neighbours n =
-    let config = {
-      incoming_port = Utils.map_option !incoming_port ~f:(fun p ->  p + n);
-      discovery_port = !discovery_port;
-      known_peers = [];
-      peers_file = "";
-      closed_network = !closed_network;
-    }
-    in
-    let limits = {
-      max_message_size = !max_packet_size;
-      peer_answer_timeout = !peer_answer_timeout;
-      expected_connections = nb_neighbours;
-      min_connections = nb_neighbours;
-      max_connections = nb_neighbours;
-      blacklist_time = !blacklist_time;
-    }
-    in
-    Net.bootstrap ~config ~limits >|= fun net ->
-    config, limits, net
-  in
-  let spec = Arg.[
-      "-start-port", Int (fun p -> incoming_port := Some p), " Incoming port";
-      "-dport", Int (fun p -> discovery_port := Some p), " Discovery port";
-      "-closed", Set closed_network, " Closed network mode";
-
-      "-max-packet-size", Set_int max_packet_size, "int Max size of packets";
-      "-peer-answer-timeout", Set_float peer_answer_timeout, "float Number of seconds";
-      "-blacklist-time", Set_float blacklist_time, "float Number of seconds";
-      "-v", Unit (fun () -> Lwt_log_core.(add_rule "*" Info)), " Log up to info msgs";
-      "-vv", Unit (fun () -> Lwt_log_core.(add_rule "*" Debug)), " Log up to debug msgs";
-    ]
-  in
-  let anon_fun num_peers = num_networks := int_of_string num_peers in
-  let usage_msg = "Usage: %s <num_peers>.\nArguments are:" in
-  Arg.parse spec anon_fun usage_msg;
-    let nets = range !num_networks in
-    Lwt_list.map_p (make_net (pred !num_networks)) nets >>= fun nets ->
-    Lwt_list.iter_p (fun (cfg, limits, net) -> net_monitor cfg limits !num_networks net) nets >>= fun () ->
-    lwt_log_notice "All done!"
-
-let () =
-  Sys.catch_break true;
-  try
-    Lwt_main.run @@ main ()
-  with _ -> ()
diff --git a/test/test_p2p_io_scheduler.ml b/test/test_p2p_io_scheduler.ml
new file mode 100644
index 000000000..e41fca204
--- /dev/null
+++ b/test/test_p2p_io_scheduler.ml
@@ -0,0 +1,232 @@
+(**************************************************************************)
+(*                                                                        *)
+(*    Copyright (c) 2014 - 2016.                                          *)
+(*    Dynamic Ledger Solutions, Inc. <contact@tezos.com>                  *)
+(*                                                                        *)
+(*    All rights reserved. No warranty, explicit or implicit, provided.   *)
+(*                                                                        *)
+(**************************************************************************)
+
+open Error_monad
+open P2p_types
+include Logging.Make (struct let name = "test-p2p-io-scheduler" end)
+
+exception Error of error list
+
+let rec listen ?port addr =
+  let tentative_port =
+    match port with
+    | None -> 1024 + Random.int 8192
+    | Some port -> port in
+  let uaddr = Ipaddr_unix.V6.to_inet_addr addr in
+  let main_socket = Lwt_unix.(socket PF_INET6 SOCK_STREAM 0) in
+  Lwt_unix.(setsockopt main_socket SO_REUSEADDR true) ;
+  Lwt.catch begin fun () ->
+    Lwt_unix.Versioned.bind_2 main_socket
+      (ADDR_INET (uaddr, tentative_port)) >>= fun () ->
+    Lwt_unix.listen main_socket 50 ;
+    Lwt.return (main_socket, tentative_port)
+  end begin function
+    | Unix.Unix_error
+        ((Unix.EADDRINUSE | Unix.EADDRNOTAVAIL), _, _) when port = None ->
+        listen addr
+    | exn -> Lwt.fail exn
+  end
+
+let accept main_socket =
+  Lwt_unix.accept main_socket >>= fun (fd, sockaddr) ->
+  return fd
+
+let rec accept_n main_socket n =
+  if n <= 0 then
+    return []
+  else
+    accept_n main_socket (n-1) >>=? fun acc ->
+    accept main_socket >>=? fun conn ->
+    return (conn :: acc)
+
+let connect addr port =
+  let fd = Lwt_unix.socket PF_INET6 SOCK_STREAM 0 in
+  let uaddr =
+    Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
+  Lwt_unix.connect fd uaddr >>= fun () ->
+  return fd
+
+let simple_msgs =
+  [|
+    MBytes.create (1 lsl 6) ;
+    MBytes.create (1 lsl 7) ;
+    MBytes.create (1 lsl 8) ;
+    MBytes.create (1 lsl 9) ;
+    MBytes.create (1 lsl 10) ;
+    MBytes.create (1 lsl 11) ;
+    MBytes.create (1 lsl 12) ;
+    MBytes.create (1 lsl 13) ;
+    MBytes.create (1 lsl 14) ;
+    MBytes.create (1 lsl 15) ;
+    MBytes.create (1 lsl 16) ;
+  |]
+let nb_simple_msgs = Array.length simple_msgs
+
+let receive conn =
+  let buf = MBytes.create (1 lsl 16) in
+  let rec loop () =
+    P2p_io_scheduler.read conn buf >>= function
+    | Ok _ -> loop ()
+    | Error [P2p_io_scheduler.Connection_closed] ->
+        Lwt.return ()
+    | Error err -> Lwt.fail (Error err)
+  in
+  loop ()
+
+let server
+    ?(display_client_stat = true)
+    ?max_download_speed ?read_queue_size ~read_buffer_size
+    main_socket n =
+  let sched =
+    P2p_io_scheduler.create
+      ?max_download_speed
+      ?read_queue_size
+      ~read_buffer_size
+      () in
+  Moving_average.on_update begin fun () ->
+    log_notice "Stat: %a" Stat.pp (P2p_io_scheduler.global_stat sched) ;
+    if display_client_stat then
+      P2p_io_scheduler.iter_connection sched
+        (fun id conn ->
+           log_notice " client(%d) %a" id Stat.pp (P2p_io_scheduler.stat conn)) ;
+  end ;
+  (* Accept and read message until the connection is closed. *)
+  accept_n main_socket n >>=? fun conns ->
+  let conns = List.map (P2p_io_scheduler.register sched) conns in
+  Lwt.join (List.map receive conns) >>= fun () ->
+  iter_p P2p_io_scheduler.close conns >>=? fun () ->
+  log_notice "OK %a" Stat.pp (P2p_io_scheduler.global_stat sched) ;
+  return ()
+
+let max_size ?max_upload_speed () =
+  match max_upload_speed with
+  | None -> nb_simple_msgs
+  | Some max_upload_speed ->
+      let rec loop n =
+        if n <= 1 then 1
+        else if MBytes.length simple_msgs.(n-1) <= max_upload_speed then n
+        else loop (n - 1)
+      in
+      loop nb_simple_msgs
+
+let rec send conn nb_simple_msgs =
+  Lwt_main.yield () >>= fun () ->
+  let msg = simple_msgs.(Random.int nb_simple_msgs) in
+  P2p_io_scheduler.write conn msg >>=? fun () ->
+  send conn nb_simple_msgs
+
+let client ?max_upload_speed ?write_queue_size addr port time n =
+  let sched =
+    P2p_io_scheduler.create
+      ?max_upload_speed ?write_queue_size ~read_buffer_size:(1 lsl 12) () in
+  connect addr port >>=? fun conn ->
+  let conn = P2p_io_scheduler.register sched conn in
+  let nb_simple_msgs = max_size ?max_upload_speed () in
+  Lwt.pick [ send conn nb_simple_msgs ;
+             Lwt_unix.sleep time >>= return ] >>=? fun () ->
+  P2p_io_scheduler.close conn >>=? fun () ->
+  let stat = P2p_io_scheduler.stat conn in
+  lwt_log_notice "Client OK %a" Stat.pp stat >>= fun () ->
+  return ()
+
+let run
+    ?display_client_stat
+    ?max_download_speed ?max_upload_speed
+    ~read_buffer_size ?read_queue_size ?write_queue_size
+    addr port time n =
+  Logging.init Stderr ;
+  listen ?port addr >>= fun (main_socket, port) ->
+  let server =
+    Process.detach ~prefix:"server " begin fun () ->
+      Process.handle_error begin fun () ->
+        server
+          ?display_client_stat ?max_download_speed
+          ~read_buffer_size ?read_queue_size
+          main_socket n
+      end
+    end in
+  let client n =
+    let prefix = Printf.sprintf "client(%d) " n in
+    Process.detach ~prefix begin fun () ->
+      Lwt_utils.safe_close main_socket >>= fun () ->
+      Process.handle_error begin fun () ->
+        client ?max_upload_speed ?write_queue_size addr port time n
+      end
+    end in
+  Process.wait (server :: List.map client Utils.(1 -- n))
+
+let () = Random.self_init ()
+
+let addr = ref Ipaddr.V6.localhost
+let port = ref None
+
+let max_download_speed = ref None
+let max_upload_speed = ref None
+
+let read_buffer_size = ref (1 lsl 14)
+let read_queue_size = ref (Some 1)
+let write_queue_size = ref (Some 1)
+
+let delay = ref 60.
+let clients = ref 8
+
+let display_client_stat = ref None
+
+let spec =
+  Arg.[
+
+    "--port", Int (fun p -> port := Some p), " Listening port";
+
+    "--addr", String (fun p -> addr := Ipaddr.V6.of_string_exn p),
+    " Listening addr";
+
+    "--max-download-speed", Int (fun i -> max_download_speed := Some i),
+    " Max download speed in B/s (default: unbounded)";
+
+    "--max-upload-speed", Int (fun i -> max_upload_speed := Some i),
+    " Max upload speed in B/s (default: unbounded)";
+
+    "--read-buffer-size", Set_int read_buffer_size,
+    " Size of the read buffers";
+
+    "--read-queue-size", Int (fun i ->
+        read_queue_size := if i <= 0 then None else Some i),
+    " Size of the read queue (0=unbounded)";
+
+    "--write-queue-size", Int (fun i ->
+        write_queue_size := if i <= 0 then None else Some i),
+    " Size of the write queue (0=unbounded)";
+
+    "--delay", Set_float delay,  " Client execution time.";
+    "--clients", Set_int clients,  " Number of concurrent clients.";
+
+    "--hide-clients-stat", Unit (fun () -> display_client_stat := Some false),
+    " Hide the client bandwidth statistic." ;
+
+    "--display_clients_stat", Unit (fun () -> display_client_stat := Some true),
+    " Display the client bandwidth statistic." ;
+
+  ]
+
+let () =
+  let anon_fun num_peers = raise (Arg.Bad "No anonymous argument.") in
+  let usage_msg = "Usage: %s <num_peers>.\nArguments are:" in
+  Arg.parse spec anon_fun usage_msg
+
+let () =
+  Sys.catch_break true ;
+  Lwt_main.run
+    (run
+       ?display_client_stat:!display_client_stat
+       ?max_download_speed:!max_download_speed
+       ?max_upload_speed:!max_upload_speed
+       ~read_buffer_size:!read_buffer_size
+       ?read_queue_size:!read_queue_size
+       ?write_queue_size:!write_queue_size
+       !addr !port !delay !clients)