diff --git a/src/lib_base/p2p_connection.ml b/src/lib_base/p2p_connection.ml
index 17edc0fb2..070e1c460 100644
--- a/src/lib_base/p2p_connection.ml
+++ b/src/lib_base/p2p_connection.ml
@@ -53,40 +53,50 @@ module Table = Hashtbl.Make (Id)
 
 module Info = struct
 
-  type t = {
+  type 'meta t = {
     incoming : bool ;
     peer_id : P2p_peer_id.t ;
     id_point : Id.t ;
     remote_socket_port : P2p_addr.port ;
     versions : P2p_version.t list ;
+    private_node : bool ;
+    remote_metadata : 'meta ;
   }
 
-  let encoding =
+  let encoding metadata_encoding =
     let open Data_encoding in
     conv
-      (fun { incoming ; peer_id ; id_point ; remote_socket_port ; versions } ->
-         (incoming, peer_id, id_point, remote_socket_port, versions))
-      (fun (incoming, peer_id, id_point, remote_socket_port, versions) ->
-         { incoming ; peer_id ; id_point ; remote_socket_port ; versions })
-      (obj5
+      (fun { incoming ; peer_id ; id_point ; remote_socket_port ;
+             versions ; private_node ; remote_metadata } ->
+        (incoming, peer_id, id_point, remote_socket_port,
+         versions, private_node, remote_metadata))
+      (fun (incoming, peer_id, id_point, remote_socket_port,
+            versions, private_node, remote_metadata) ->
+        { incoming ; peer_id ; id_point ; remote_socket_port ;
+          versions ; private_node ; remote_metadata })
+      (obj7
          (req "incoming" bool)
          (req "peer_id" P2p_peer_id.encoding)
          (req "id_point" Id.encoding)
          (req "remote_socket_port" uint16)
-         (req "versions" (list P2p_version.encoding)))
+         (req "versions" (list P2p_version.encoding))
+         (req "private" bool)
+         (req "remote_metadata" metadata_encoding))
 
-  let pp ppf
+  let pp pp_meta ppf
       { incoming ; id_point = (remote_addr, remote_port) ;
-        remote_socket_port ; peer_id ; versions } =
+        remote_socket_port ; peer_id ; versions ; private_node ; remote_metadata } =
     let version = List.hd versions in
     let point = match remote_port with
       | None -> remote_addr, remote_socket_port
       | Some port -> remote_addr, port in
-    Format.fprintf ppf "%s %a %a (%a)"
+    Format.fprintf ppf "%s %a %a (%a)%s%a"
       (if incoming then "↘" else "↗")
       P2p_peer_id.pp peer_id
       P2p_point.Id.pp point
       P2p_version.pp version
+      (if private_node then " private" else "")
+      pp_meta remote_metadata
 
 end
 
diff --git a/src/lib_base/p2p_connection.mli b/src/lib_base/p2p_connection.mli
index 1e7f84115..756d82763 100644
--- a/src/lib_base/p2p_connection.mli
+++ b/src/lib_base/p2p_connection.mli
@@ -31,16 +31,20 @@ module Table : Hashtbl.S with type key = Id.t
 (** Information about a connection *)
 module Info : sig
 
-  type t = {
+  type 'meta t = {
     incoming : bool;
     peer_id : P2p_peer_id.t;
     id_point : Id.t;
     remote_socket_port : P2p_addr.port;
     versions : P2p_version.t list ;
+    private_node : bool ;
+    remote_metadata : 'meta ;
   }
 
-  val pp : Format.formatter -> t -> unit
-  val encoding : t Data_encoding.t
+  val pp :
+    (Format.formatter -> 'meta -> unit) ->
+    Format.formatter -> 'meta t -> unit
+  val encoding : 'meta Data_encoding.t -> 'meta t Data_encoding.t
 
 end
 
diff --git a/src/lib_client_commands/client_p2p_commands.ml b/src/lib_client_commands/client_p2p_commands.ml
index 1f1f59e33..2369c63e7 100644
--- a/src/lib_client_commands/client_p2p_commands.ml
+++ b/src/lib_client_commands/client_p2p_commands.ml
@@ -24,6 +24,8 @@ let port_arg () =
          with Failure _ ->
            failwith "Invalid peer-to-peer port"))
 
+let pp_connection_info ppf conn = P2p_connection.Info.pp (fun _ _ -> ()) ppf conn
+
 let commands () =
   let open Clic in
   let addr_parameter =
@@ -44,10 +46,10 @@ let commands () =
       let incoming, outgoing =
         List.partition (fun c -> c.P2p_connection.Info.incoming) conns in
       Lwt_list.iter_s begin fun conn ->
-        cctxt#message "  %a" P2p_connection.Info.pp conn
+        cctxt#message "  %a" pp_connection_info conn
       end incoming >>= fun () ->
       Lwt_list.iter_s begin fun conn ->
-        cctxt#message "  %a" P2p_connection.Info.pp conn
+        cctxt#message "  %a" pp_connection_info conn
       end outgoing >>= fun () ->
       cctxt#message "KNOWN PEERS" >>= fun () ->
       Lwt_list.iter_s begin fun (p, pi) ->
diff --git a/src/lib_p2p/p2p.ml b/src/lib_p2p/p2p.ml
index 6475ec3f3..bf985b86e 100644
--- a/src/lib_p2p/p2p.ml
+++ b/src/lib_p2p/p2p.ml
@@ -15,7 +15,7 @@ type 'peer_meta peer_meta_config = 'peer_meta P2p_pool.peer_meta_config = {
   score : 'peer_meta -> float ;
 }
 
-type 'conn_meta conn_meta_config = 'conn_meta P2p_pool.conn_meta_config = {
+type 'conn_meta conn_meta_config = 'conn_meta P2p_socket.metadata_config = {
   conn_meta_encoding : 'conn_meta Data_encoding.t ;
   conn_meta_value : P2p_peer.Id.t -> 'conn_meta ;
   private_node : 'conn_meta -> bool ;
@@ -206,8 +206,8 @@ module Real = struct
     P2p_pool.disconnect ?wait conn
   let connection_info _net conn =
     P2p_pool.Connection.info conn
-  let connection_metadata _net conn =
-    P2p_pool.Connection.meta conn
+  let connection_remote_metadata _net conn =
+    P2p_pool.Connection.remote_metadata conn
   let connection_stat _net conn =
     P2p_pool.Connection.stat conn
   let global_stat { pool } () =
@@ -307,12 +307,14 @@ module Fake = struct
     current_inflow = 0 ;
     current_outflow = 0 ;
   }
-  let connection_info = {
+  let connection_info faked_metadata = {
     P2p_connection.Info.incoming = false ;
     peer_id = id.peer_id ;
     id_point = (Ipaddr.V6.unspecified, None) ;
     remote_socket_port = 0 ;
     versions = [] ;
+    remote_metadata = faked_metadata ;
+    private_node = false ;
   }
 
 end
@@ -329,8 +331,8 @@ type ('msg, 'peer_meta, 'conn_meta) t = {
   disconnect :
     ?wait:bool -> ('msg, 'peer_meta, 'conn_meta) connection -> unit Lwt.t ;
   connection_info :
-    ('msg, 'peer_meta, 'conn_meta) connection -> P2p_connection.Info.t ;
-  connection_metadata :
+    ('msg, 'peer_meta, 'conn_meta) connection -> 'conn_meta P2p_connection.Info.t ;
+  connection_remote_metadata :
     ('msg, 'peer_meta, 'conn_meta) connection -> 'conn_meta ;
   connection_stat : ('msg, 'peer_meta, 'conn_meta) connection -> P2p_stat.t ;
   global_stat : unit -> P2p_stat.t ;
@@ -407,7 +409,7 @@ let create ~config ~limits peer_cfg conn_cfg msg_cfg =
     find_connection = Real.find_connection net ;
     disconnect = Real.disconnect ;
     connection_info = Real.connection_info net  ;
-    connection_metadata = Real.connection_metadata net  ;
+    connection_remote_metadata = Real.connection_remote_metadata net  ;
     connection_stat = Real.connection_stat net ;
     global_stat = Real.global_stat net ;
     get_peer_metadata = Real.get_peer_metadata net ;
@@ -423,7 +425,7 @@ let create ~config ~limits peer_cfg conn_cfg msg_cfg =
     on_new_connection = Real.on_new_connection net ;
   }
 
-let faked_network peer_cfg = {
+let faked_network peer_cfg faked_metadata = {
   versions = [] ;
   peer_id = Fake.id.peer_id ;
   maintain = Lwt.return ;
@@ -432,8 +434,8 @@ let faked_network peer_cfg = {
   connections = (fun () -> []) ;
   find_connection = (fun _ -> None) ;
   disconnect = (fun ?wait:_ _ -> Lwt.return_unit) ;
-  connection_info = (fun _ -> Fake.connection_info) ;
-  connection_metadata = (fun _ -> assert false) ;
+  connection_info = (fun _ -> Fake.connection_info faked_metadata) ;
+  connection_remote_metadata = (fun _ -> faked_metadata) ;
   connection_stat = (fun _ -> Fake.empty_stat) ;
   global_stat = (fun () -> Fake.empty_stat) ;
   get_peer_metadata = (fun _ -> peer_cfg.peer_meta_initial) ;
@@ -457,7 +459,7 @@ let connections net = net.connections ()
 let disconnect net = net.disconnect
 let find_connection net = net.find_connection
 let connection_info net = net.connection_info
-let connection_metadata net = net.connection_metadata
+let connection_remote_metadata net = net.connection_remote_metadata
 let connection_stat net = net.connection_stat
 let global_stat net = net.global_stat ()
 let get_peer_metadata net = net.get_peer_metadata
@@ -524,7 +526,7 @@ let info_of_peer_info pool i =
   let meta_opt =
     match conn_opt with
     | None -> None
-    | Some conn -> Some (P2p_pool.Connection.meta conn) in
+    | Some conn -> Some (P2p_pool.Connection.remote_metadata conn) in
   P2p_peer_state.Info.{
     score ;
     trusted = trusted i ;
diff --git a/src/lib_p2p/p2p.mli b/src/lib_p2p/p2p.mli
index 306b5b06c..9c21ccfb0 100644
--- a/src/lib_p2p/p2p.mli
+++ b/src/lib_p2p/p2p.mli
@@ -147,6 +147,7 @@ type ('msg, 'peer_meta, 'conn_meta) net = ('msg, 'peer_meta, 'conn_meta) t
     nor open any listening socket *)
 val faked_network :
   'peer_meta peer_meta_config ->
+  'conn_meta ->
   ('msg, 'peer_meta, 'conn_meta) net
 
 (** Main network initialisation function *)
@@ -185,8 +186,8 @@ val find_connection :
 val connection_info :
   ('msg, 'peer_meta, 'conn_meta) net ->
   ('msg, 'peer_meta, 'conn_meta) connection ->
-  P2p_connection.Info.t
-val connection_metadata :
+  'conn_meta P2p_connection.Info.t
+val connection_remote_metadata :
   ('msg, 'peer_meta, 'conn_meta) net ->
   ('msg, 'peer_meta, 'conn_meta) connection ->
   'conn_meta
diff --git a/src/lib_p2p/p2p_pool.ml b/src/lib_p2p/p2p_pool.ml
index 04aae29c3..6520e5601 100644
--- a/src/lib_p2p/p2p_pool.ml
+++ b/src/lib_p2p/p2p_pool.ml
@@ -207,16 +207,10 @@ type 'msg message_config = {
   versions : P2p_version.t list;
 }
 
-type 'conn_meta conn_meta_config = {
-  conn_meta_encoding : 'conn_meta Data_encoding.t ;
-  conn_meta_value : P2p_peer.Id.t -> 'conn_meta ;
-  private_node : 'conn_meta -> bool ;
-}
-
 type ('msg, 'peer_meta, 'conn_meta) t = {
   config : config ;
   peer_meta_config : 'peer_meta peer_meta_config ;
-  conn_meta_config : 'conn_meta conn_meta_config ;
+  conn_meta_config : 'conn_meta P2p_socket.metadata_config ;
   message_config : 'msg message_config ;
   my_id_points : unit P2p_point.Table.t ;
   known_peer_ids :
@@ -602,8 +596,8 @@ module Connection = struct
   let info { conn } =
     P2p_socket.info conn
 
-  let meta { conn } =
-    P2p_socket.meta conn
+  let remote_metadata { conn } =
+    P2p_socket.remote_metadata conn
 
   let find_by_peer_id pool peer_id =
     Option.apply
@@ -727,7 +721,7 @@ and authenticate pool ?point_info canceler fd point =
       ~incoming (P2p_io_scheduler.register pool.io_sched fd) point
       ?listening_port:pool.config.listening_port
       pool.config.identity pool.message_config.versions
-      pool.conn_meta_config.conn_meta_encoding
+      pool.conn_meta_config
   end ~on_error: begin fun err ->
     begin match err with
       | [ Canceled ] ->
@@ -825,10 +819,7 @@ and authenticate pool ?point_info canceler fd point =
           ?incoming_message_queue_size:pool.config.incoming_message_queue_size
           ?outgoing_message_queue_size:pool.config.outgoing_message_queue_size
           ?binary_chunks_size:pool.config.binary_chunks_size
-          ~private_node:pool.conn_meta_config.private_node
-          auth_fd
-          (pool.conn_meta_config.conn_meta_value info.peer_id)
-          pool.encoding >>=? fun conn ->
+          auth_fd pool.encoding >>=? fun conn ->
         lwt_debug "authenticate: %a -> Connected %a"
           P2p_point.Id.pp point
           P2p_peer.Id.pp info.peer_id >>= fun () ->
@@ -936,16 +927,16 @@ and create_connection pool p2p_conn id_point point_info peer_info _version =
       messages ; canceler ; answerer ; wait_close = false ;
       last_sent_swap_request = None } in
   ignore (Lazy.force answerer) ;
+  let conn_meta = P2p_socket.remote_metadata p2p_conn in
   Option.iter point_info ~f:begin fun point_info ->
     let point = P2p_point_state.Info.point point_info in
-    let conn_meta = P2p_socket.meta p2p_conn in
     P2p_point_state.set_running
       ~known_private:(pool.conn_meta_config.private_node conn_meta)
       point_info peer_id conn;
     P2p_point.Table.add pool.connected_points point point_info ;
   end ;
   log pool (Connection_established (id_point, peer_id)) ;
-  P2p_peer_state.set_running peer_info id_point conn (P2p_socket.meta conn.conn) ;
+  P2p_peer_state.set_running peer_info id_point conn conn_meta ;
   P2p_peer.Table.add pool.connected_peer_ids peer_id peer_info ;
   Lwt_condition.broadcast pool.events.new_connection () ;
   Lwt_canceler.on_cancel canceler begin fun () ->
diff --git a/src/lib_p2p/p2p_pool.mli b/src/lib_p2p/p2p_pool.mli
index 7981de35c..a4673e3c0 100644
--- a/src/lib_p2p/p2p_pool.mli
+++ b/src/lib_p2p/p2p_pool.mli
@@ -131,12 +131,6 @@ type 'peer_meta peer_meta_config = {
   score : 'peer_meta -> float ;
 }
 
-type 'conn_meta conn_meta_config = {
-  conn_meta_encoding : 'conn_meta Data_encoding.t ;
-  conn_meta_value : P2p_peer.Id.t -> 'conn_meta ;
-  private_node : 'conn_meta -> bool ;
-}
-
 type 'msg message_config = {
   encoding : 'msg encoding list ;
   versions : P2p_version.t list;
@@ -145,7 +139,7 @@ type 'msg message_config = {
 val create:
   config ->
   'peer_meta peer_meta_config ->
-  'conn_meta conn_meta_config ->
+  'conn_meta P2p_socket.metadata_config ->
   'msg message_config ->
   P2p_io_scheduler.t ->
   ('msg, 'peer_meta,'conn_meta) pool Lwt.t
@@ -224,8 +218,8 @@ val disconnect:
 
 module Connection : sig
 
-  val info: ('msg, 'peer_meta,'conn_meta) connection -> P2p_connection.Info.t
-  val meta: ('msg, 'peer_meta,'conn_meta) connection -> 'conn_meta
+  val info: ('msg, 'peer_meta,'conn_meta) connection -> 'conn_meta P2p_connection.Info.t
+  val remote_metadata: ('msg, 'peer_meta,'conn_meta) connection -> 'conn_meta
 
   val stat:  ('msg, 'peer_meta,'conn_meta) connection -> P2p_stat.t
   (** [stat conn] is a snapshot of current bandwidth usage for
diff --git a/src/lib_p2p/p2p_socket.ml b/src/lib_p2p/p2p_socket.ml
index f4f3fe3a8..bcea2af46 100644
--- a/src/lib_p2p/p2p_socket.ml
+++ b/src/lib_p2p/p2p_socket.ml
@@ -7,15 +7,7 @@
 (*                                                                        *)
 (**************************************************************************)
 
-(* TODO patch Data_encoding for continuation-based binary writer/reader. *)
 (* TODO test `close ~wait:true`. *)
-(* TODO nothing in welcoming message proves that the incoming peer is
-        the owner of the public key... only the first message will
-        really proves it. Should this to be changed? Not really
-        important, but... an attacker might forge a random public key
-        with enough proof of work (hard task), open a connection, wait
-        infinitly. This would avoid the real peer to talk with us. And
-        this might also have an influence on its "score". *)
 
 include Logging.Make(struct let name = "p2p.connection" end)
 
@@ -150,20 +142,60 @@ module Connection_message = struct
 
 end
 
+type 'meta metadata_config = {
+  conn_meta_encoding : 'meta Data_encoding.t ;
+  conn_meta_value : P2p_peer.Id.t -> 'meta ;
+  private_node : 'meta -> bool ;
+}
+
+module Metadata = struct
+
+  let write metadata_config cryptobox_data fd message =
+    let encoded_message_len =
+      Data_encoding.Binary.length metadata_config.conn_meta_encoding message in
+    let buf = MBytes.create encoded_message_len in
+    match
+      Data_encoding.Binary.write
+        metadata_config.conn_meta_encoding message buf 0 encoded_message_len
+    with
+    | None ->
+        fail P2p_errors.Encoding_error
+    | Some last ->
+        fail_unless (last = encoded_message_len)
+          P2p_errors.Encoding_error >>=? fun () ->
+        Crypto.write_chunk cryptobox_data fd buf
+
+  let read metadata_config fd cryptobox_data =
+    Crypto.read_chunk fd cryptobox_data >>=? fun buf ->
+    let length = MBytes.length buf in
+    match
+      Data_encoding.Binary.read
+        metadata_config.conn_meta_encoding buf 0 length
+    with
+    | None ->
+        fail P2p_errors.Decoding_error
+    | Some (read_len, message) ->
+        if read_len <> length then
+          fail P2p_errors.Decoding_error
+        else
+          return message
+
+end
+
 module Ack = struct
 
-  type 'a t = Ack of 'a | Nack
+  type t = Ack | Nack
 
-  let encoding ack_encoding =
+  let encoding =
     let open Data_encoding in
-    let ack_encoding = obj1 (req "ack" ack_encoding) in
+    let ack_encoding = obj1 (req "ack" empty) in
     let nack_encoding = obj1 (req "nack" empty) in
     let ack_case tag =
       case tag ack_encoding
         (function
-          | Ack param -> Some param
+          | Ack -> Some ()
           | _ -> None)
-        (fun param -> Ack param) in
+        (fun () -> Ack) in
     let nack_case tag =
       case tag nack_encoding
         (function
@@ -173,11 +205,10 @@ module Ack = struct
         (fun _ -> Nack) in
     union [
       ack_case (Tag 0) ;
-      nack_case (Tag 1) ;
+      nack_case (Tag 255) ;
     ]
 
-  let write ack_encoding cryptobox_data fd message =
-    let encoding = encoding ack_encoding in
+  let write cryptobox_data fd message =
     let encoded_message_len =
       Data_encoding.Binary.length encoding message in
     let buf = MBytes.create encoded_message_len in
@@ -189,8 +220,7 @@ module Ack = struct
           P2p_errors.Encoding_error >>=? fun () ->
         Crypto.write_chunk cryptobox_data fd buf
 
-  let read ack_encoding fd cryptobox_data =
-    let encoding = encoding ack_encoding in
+  let read fd cryptobox_data =
     Crypto.read_chunk fd cryptobox_data >>=? fun buf ->
     let length = MBytes.length buf in
     match Data_encoding.Binary.read encoding buf 0 length with
@@ -206,13 +236,12 @@ end
 
 type 'conn_meta authenticated_fd = {
   fd: P2p_io_scheduler.connection ;
-  info: P2p_connection.Info.t ;
+  info: 'conn_meta P2p_connection.Info.t ;
   cryptobox_data: Crypto.data ;
-  ack_encoding: 'conn_meta Data_encoding.t ;
 }
 
-let kick { fd ; ack_encoding ; cryptobox_data ; _ } =
-  Ack.write ack_encoding fd cryptobox_data Nack >>= fun _ ->
+let kick { fd ; cryptobox_data ; _ } =
+  Ack.write fd cryptobox_data Nack >>= fun _ ->
   P2p_io_scheduler.close fd >>= fun _ ->
   Lwt.return_unit
 
@@ -222,7 +251,7 @@ let kick { fd ; ack_encoding ; cryptobox_data ; _ } =
 let authenticate
     ~proof_of_work_target
     ~incoming fd (remote_addr, remote_socket_port as point)
-    ?listening_port identity supported_versions ack_encoding =
+    ?listening_port identity supported_versions metadata_config =
   let local_nonce_seed = Crypto_box.random_nonce () in
   lwt_debug "Sending authenfication to %a" P2p_point.Id.pp point >>= fun () ->
   Connection_message.write fd
@@ -248,16 +277,21 @@ let authenticate
   let (local_nonce, remote_nonce) =
     Crypto_box.generate_nonces ~incoming ~sent_msg ~recv_msg in
   let cryptobox_data = { Crypto.channel_key ; local_nonce ; remote_nonce } in
+  let local_metadata = metadata_config.conn_meta_value remote_peer_id in
+  Metadata.write metadata_config fd cryptobox_data local_metadata >>=? fun () ->
+  Metadata.read metadata_config fd cryptobox_data >>=? fun remote_metadata ->
   let info =
     { P2p_connection.Info.peer_id = remote_peer_id ;
       versions = msg.versions ; incoming ;
       id_point ; remote_socket_port ;
+      private_node = metadata_config.private_node remote_metadata ;
+      remote_metadata ;
     } in
-  return (info, { fd ; info ; cryptobox_data ; ack_encoding })
+  return (info, { fd ; info ; cryptobox_data })
 
-type connection = {
+type 'meta connection = {
   id : int ;
-  info : P2p_connection.Info.t ;
+  info : 'meta P2p_connection.Info.t ;
   fd : P2p_io_scheduler.connection ;
   cryptobox_data : Crypto.data ;
 }
@@ -268,9 +302,9 @@ let next_conn_id =
 
 module Reader = struct
 
-  type 'msg t = {
+  type ('msg, 'meta) t = {
     canceler: Lwt_canceler.t ;
-    conn: connection ;
+    conn: 'meta connection ;
     encoding: 'msg Data_encoding.t ;
     messages: (int * 'msg) tzresult Lwt_pipe.t ;
     mutable worker: unit Lwt.t ;
@@ -355,9 +389,9 @@ end
 
 module Writer = struct
 
-  type 'msg t = {
+  type ('msg, 'meta) t = {
     canceler: Lwt_canceler.t ;
-    conn: connection ;
+    conn: 'meta connection ;
     encoding: 'msg Data_encoding.t ;
     messages: (MBytes.t list * unit tzresult Lwt.u option) Lwt_pipe.t ;
     mutable worker: unit Lwt.t ;
@@ -480,30 +514,26 @@ module Writer = struct
 end
 
 type ('msg, 'meta) t = {
-  conn : connection ;
-  meta : 'meta ;
-  reader : 'msg Reader.t ;
-  writer : 'msg Writer.t ;
-  private_node : bool ;
+  conn : 'meta connection ;
+  reader : ('msg, 'meta) Reader.t ;
+  writer : ('msg, 'meta) Writer.t ;
 }
 
 let equal { conn = { id = id1 } } { conn = { id = id2 } } = id1 = id2
 
-let pp ppf { conn } = P2p_connection.Info.pp ppf conn.info
+let pp ppf { conn } = P2p_connection.Info.pp (fun _ _ -> ()) ppf conn.info
 let info { conn } = conn.info
-let meta { meta } = meta
-let private_node { private_node } = private_node
+let remote_metadata { conn } = conn.info.remote_metadata
+let private_node { conn } = conn.info.private_node
 
 let accept
     ?incoming_message_queue_size ?outgoing_message_queue_size
     ?binary_chunks_size
-    ~private_node
-    { fd ; info ; cryptobox_data ; ack_encoding }
-    ack_param
+    ({ fd ; info ; cryptobox_data } : 'meta authenticated_fd)
     encoding =
   protect begin fun () ->
-    Ack.write ack_encoding fd cryptobox_data (Ack ack_param) >>=? fun () ->
-    Ack.read ack_encoding fd cryptobox_data
+    Ack.write fd cryptobox_data Ack >>=? fun () ->
+    Ack.read fd cryptobox_data
   end ~on_error:begin fun err ->
     P2p_io_scheduler.close fd >>= fun _ ->
     match err with
@@ -511,7 +541,7 @@ let accept
     | [ P2p_errors.Decipher_error ] -> fail P2p_errors.Invalid_auth
     | err -> Lwt.return (Error err)
   end >>=? function
-  | Ack meta ->
+  | Ack ->
       let canceler = Lwt_canceler.create () in
       let conn = { id = next_conn_id () ; fd ; info ; cryptobox_data } in
       let reader =
@@ -521,8 +551,7 @@ let accept
           ?size:outgoing_message_queue_size ?binary_chunks_size
           conn encoding canceler
       in
-      let conn = { conn ; reader ; writer ; meta ;
-                   private_node = private_node meta } in
+      let conn = { conn ; reader ; writer } in
       Lwt_canceler.on_cancel canceler begin fun () ->
         P2p_io_scheduler.close fd >>= fun _ ->
         Lwt.return_unit
diff --git a/src/lib_p2p/p2p_socket.mli b/src/lib_p2p/p2p_socket.mli
index a04c6f529..56457254e 100644
--- a/src/lib_p2p/p2p_socket.mli
+++ b/src/lib_p2p/p2p_socket.mli
@@ -19,7 +19,14 @@
 
 (** {1 Types} *)
 
-type 'conn_meta authenticated_fd
+type 'meta metadata_config = {
+  conn_meta_encoding : 'meta Data_encoding.t ;
+  conn_meta_value : P2p_peer.Id.t -> 'meta ;
+  private_node : 'meta -> bool ;
+}
+(** Type for the parameter negotiation mechanism. *)
+
+type 'meta authenticated_fd
 (** Type of a connection that successfully passed the authentication
     phase, but has not been accepted yet. Parametrized by the type
     of expected parameter in the `ack` message. *)
@@ -31,8 +38,8 @@ type ('msg, 'meta) t
 val equal: ('mst, 'meta) t -> ('msg, 'meta) t -> bool
 
 val pp: Format.formatter -> ('msg, 'meta) t -> unit
-val info: ('msg, 'meta) t -> P2p_connection.Info.t
-val meta: ('msg, 'meta) t -> 'meta
+val info: ('msg, 'meta) t -> 'meta P2p_connection.Info.t
+val remote_metadata: ('msg, 'meta) t -> 'meta
 val private_node: ('msg, 'meta) t -> bool
 
 (** {1 Low-level functions (do not use directly)} *)
@@ -42,14 +49,15 @@ val authenticate:
   incoming:bool ->
   P2p_io_scheduler.connection -> P2p_point.Id.t ->
   ?listening_port: int ->
-  P2p_identity.t -> P2p_version.t list -> 'conn_meta Data_encoding.t ->
-  (P2p_connection.Info.t * 'conn_meta authenticated_fd) tzresult Lwt.t
+  P2p_identity.t -> P2p_version.t list ->
+  'meta metadata_config ->
+  ('meta P2p_connection.Info.t * 'meta authenticated_fd) tzresult Lwt.t
 (** (Low-level) (Cancelable) Authentication function of a remote
     peer. Used in [P2p_connection_pool], to promote a
     [P2P_io_scheduler.connection] into an [authenticated_fd] (auth
     correct, acceptation undecided). *)
 
-val kick: 'conn_meta authenticated_fd -> unit Lwt.t
+val kick: 'meta authenticated_fd -> unit Lwt.t
 (** (Low-level) (Cancelable) [kick afd] notifies the remote peer that
     we refuse this connection and then closes [afd]. Used in
     [P2p_connection_pool] to reject an [aunthenticated_fd] which we do
@@ -59,9 +67,8 @@ val accept:
   ?incoming_message_queue_size:int ->
   ?outgoing_message_queue_size:int ->
   ?binary_chunks_size: int ->
-  private_node:('conn_meta -> bool) ->
-  'conn_meta authenticated_fd -> 'conn_meta ->
-  'msg Data_encoding.t -> ('msg, 'conn_meta) t tzresult Lwt.t
+  'meta authenticated_fd ->
+  'msg Data_encoding.t -> ('msg, 'meta) t tzresult Lwt.t
 (** (Low-level) (Cancelable) Accepts a remote peer given an
     authenticated_fd. Used in [P2p_connection_pool], to promote an
     [authenticated_fd] to the status of an active peer. *)
diff --git a/src/lib_p2p/test/test_p2p_pool.ml b/src/lib_p2p/test/test_p2p_pool.ml
index 780896d3d..7c55690f0 100644
--- a/src/lib_p2p/test/test_p2p_pool.ml
+++ b/src/lib_p2p/test/test_p2p_pool.ml
@@ -33,7 +33,7 @@ let peer_meta_config : metadata P2p_pool.peer_meta_config = {
   score = fun () -> 0. ;
 }
 
-let conn_meta_config : metadata P2p_pool.conn_meta_config = {
+let conn_meta_config : metadata P2p_socket.metadata_config = {
   conn_meta_encoding = Data_encoding.empty ;
   conn_meta_value = (fun _ -> ()) ;
   private_node = (fun _ -> false) ;
diff --git a/src/lib_p2p/test/test_p2p_socket.ml b/src/lib_p2p/test/test_p2p_socket.ml
index ca65a9f70..902103185 100644
--- a/src/lib_p2p/test/test_p2p_socket.ml
+++ b/src/lib_p2p/test/test_p2p_socket.ml
@@ -21,6 +21,13 @@ let id0 =
 
 let versions = P2p_version.[{ name = "TEST" ; minor = 0 ; major = 0 }]
 
+type metadata = unit
+let conn_meta_config : metadata P2p_socket.metadata_config = {
+  conn_meta_encoding = Data_encoding.empty ;
+  conn_meta_value = (fun _ -> ()) ;
+  private_node = (fun _ -> false) ;
+}
+
 let rec listen ?port addr =
   let tentative_port =
     match port with
@@ -95,7 +102,8 @@ let accept sched main_socket =
   raw_accept sched main_socket >>= fun (fd, point) ->
   P2p_socket.authenticate
     ~proof_of_work_target
-    ~incoming:true fd point id1 versions Data_encoding.unit
+    ~incoming:true fd point id1 versions
+    conn_meta_config
 
 let raw_connect sched addr port =
   let fd = Lwt_unix.socket PF_INET6 SOCK_STREAM 0 in
@@ -109,7 +117,8 @@ let connect sched addr port id =
   raw_connect sched addr port >>= fun fd ->
   P2p_socket.authenticate
     ~proof_of_work_target
-    ~incoming:false fd (addr, port) id versions Data_encoding.unit >>=? fun (info, auth_fd) ->
+    ~incoming:false fd
+    (addr, port) id versions conn_meta_config >>=? fun (info, auth_fd) ->
   _assert (not info.incoming) __LOC__ "" >>=? fun () ->
   _assert (P2p_peer.Id.compare info.peer_id id1.peer_id = 0)
     __LOC__ "" >>=? fun () ->
@@ -172,9 +181,7 @@ module Kick = struct
 
   let client _ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>= fun conn ->
+    P2p_socket.accept auth_fd encoding >>= fun conn ->
     _assert (is_rejected conn) __LOC__ "" >>=? fun () ->
     return ()
 
@@ -188,9 +195,7 @@ module Kicked = struct
 
   let server _ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>= fun conn ->
+    P2p_socket.accept auth_fd encoding >>= fun conn ->
     _assert (Kick.is_rejected conn) __LOC__ "" >>=? fun () ->
     return ()
 
@@ -212,9 +217,7 @@ module Simple_message = struct
 
   let server ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.write_sync conn simple_msg >>=? fun () ->
     P2p_socket.read conn >>=? fun (_msg_size, msg) ->
     _assert (MBytes.compare simple_msg2 msg = 0) __LOC__ "" >>=? fun () ->
@@ -224,9 +227,7 @@ module Simple_message = struct
 
   let client ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.write_sync conn simple_msg2 >>=? fun () ->
     P2p_socket.read conn >>=? fun (_msg_size, msg) ->
     _assert (MBytes.compare simple_msg msg = 0) __LOC__ "" >>=? fun () ->
@@ -248,8 +249,7 @@ module Chunked_message = struct
   let server ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
     P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      ~binary_chunks_size:21 auth_fd () encoding >>=? fun conn ->
+      ~binary_chunks_size:21 auth_fd encoding >>=? fun conn ->
     P2p_socket.write_sync conn simple_msg >>=? fun () ->
     P2p_socket.read conn >>=? fun (_msg_size, msg) ->
     _assert (MBytes.compare simple_msg2 msg = 0) __LOC__ "" >>=? fun () ->
@@ -260,8 +260,7 @@ module Chunked_message = struct
   let client ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
     P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      ~binary_chunks_size:21 auth_fd () encoding >>=? fun conn ->
+      ~binary_chunks_size:21 auth_fd encoding >>=? fun conn ->
     P2p_socket.write_sync conn simple_msg2 >>=? fun () ->
     P2p_socket.read conn >>=? fun (_msg_size, msg) ->
     _assert (MBytes.compare simple_msg msg = 0) __LOC__ "" >>=? fun () ->
@@ -282,9 +281,7 @@ module Oversized_message = struct
 
   let server ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.write_sync conn simple_msg >>=? fun () ->
     P2p_socket.read conn >>=? fun (_msg_size, msg) ->
     _assert (MBytes.compare simple_msg2 msg = 0) __LOC__ "" >>=? fun () ->
@@ -294,9 +291,7 @@ module Oversized_message = struct
 
   let client ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.write_sync conn simple_msg2 >>=? fun () ->
     P2p_socket.read conn >>=? fun (_msg_size, msg) ->
     _assert (MBytes.compare simple_msg msg = 0) __LOC__ "" >>=? fun () ->
@@ -316,18 +311,14 @@ module Close_on_read = struct
 
   let server ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     sync ch >>=? fun () ->
     P2p_socket.close conn >>= fun _stat ->
     return ()
 
   let client ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     sync ch >>=? fun () ->
     P2p_socket.read conn >>= fun err ->
     _assert (is_connection_closed err) __LOC__ "" >>=? fun () ->
@@ -346,18 +337,14 @@ module Close_on_write = struct
 
   let server ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.close conn >>= fun _stat ->
     sync ch >>=? fun ()->
     return ()
 
   let client ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     sync ch >>=? fun ()->
     Lwt_unix.sleep 0.1 >>= fun () ->
     P2p_socket.write_sync conn simple_msg >>= fun err ->
@@ -387,9 +374,7 @@ module Garbled_data = struct
 
   let server _ch sched socket =
     accept sched socket >>=? fun (_info, auth_fd) ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.raw_write_sync conn garbled_msg >>=? fun () ->
     P2p_socket.read conn >>= fun err ->
     _assert (is_connection_closed err) __LOC__ "" >>=? fun () ->
@@ -398,9 +383,7 @@ module Garbled_data = struct
 
   let client _ch sched addr port =
     connect sched addr port id2 >>=? fun auth_fd ->
-    P2p_socket.accept
-      ~private_node:(fun _ -> false)
-      auth_fd () encoding >>=? fun conn ->
+    P2p_socket.accept auth_fd encoding >>=? fun conn ->
     P2p_socket.read conn >>= fun err ->
     _assert (is_decoding_error err) __LOC__ "" >>=? fun () ->
     P2p_socket.close conn >>= fun _stat ->
diff --git a/src/lib_shell/distributed_db.ml b/src/lib_shell/distributed_db.ml
index b68781523..d2ea4f8c5 100644
--- a/src/lib_shell/distributed_db.ml
+++ b/src/lib_shell/distributed_db.ml
@@ -499,7 +499,7 @@ module P2p_reader = struct
     | Get_current_head chain_id ->
         may_handle state chain_id @@ fun chain_db ->
         let { Connection_metadata.disable_mempool } =
-          P2p.connection_metadata chain_db.global_db.p2p state.conn in
+          P2p.connection_remote_metadata chain_db.global_db.p2p state.conn in
         begin
           if disable_mempool then
             Chain.head chain_db.chain_state >>= fun head ->
@@ -963,7 +963,7 @@ module Advertise = struct
         Message.Current_head (chain_id, State.Block.header head, Mempool.empty) in
       let send_mempool state =
         let { Connection_metadata.disable_mempool } =
-          P2p.connection_metadata chain_db.global_db.p2p state.conn in
+          P2p.connection_remote_metadata chain_db.global_db.p2p state.conn in
         let msg = if disable_mempool then msg_disable_mempool else msg_mempool in
         ignore @@ P2p.try_send chain_db.global_db.p2p state.conn msg
       in
diff --git a/src/lib_shell/node.ml b/src/lib_shell/node.ml
index 08cc43b0a..57dfb4886 100644
--- a/src/lib_shell/node.ml
+++ b/src/lib_shell/node.ml
@@ -96,7 +96,7 @@ let init_p2p p2p_params =
       let conn_metadata_cfg = connection_metadata_cfg c_meta in
       lwt_log_notice "P2P layer is disabled" >>= fun () ->
       return
-        (P2p.faked_network peer_metadata_cfg, conn_metadata_cfg)
+        (P2p.faked_network peer_metadata_cfg c_meta, conn_metadata_cfg)
   | Some (config, limits) ->
       let c_meta = init_connection_metadata (Some config) in
       let conn_metadata_cfg = connection_metadata_cfg c_meta in
diff --git a/src/lib_shell_services/p2p_services.ml b/src/lib_shell_services/p2p_services.ml
index 00a8fdab5..c29b2260a 100644
--- a/src/lib_shell_services/p2p_services.ml
+++ b/src/lib_shell_services/p2p_services.ml
@@ -54,6 +54,11 @@ let monitor_encoding = Data_encoding.(obj1 (dft "monitor" bool false))
 
 module Connections = struct
 
+  type connection_info = Connection_metadata.t P2p_connection.Info.t
+
+  let connection_info_encoding =
+    P2p_connection.Info.encoding Connection_metadata.encoding
+
   module S = struct
 
     let list =
@@ -61,14 +66,14 @@ module Connections = struct
         ~description:"List the running P2P connection."
         ~query: RPC_query.empty
         ~input: Data_encoding.empty
-        ~output: (Data_encoding.list P2p_connection.Info.encoding)
+        ~output: (Data_encoding.list connection_info_encoding)
         RPC_path.(root / "network" / "connections")
 
     let info =
       RPC_service.post_service
         ~query: RPC_query.empty
         ~input: Data_encoding.empty
-        ~output: P2p_connection.Info.encoding
+        ~output: connection_info_encoding
         ~description:"Details about the current P2P connection to the given peer."
         RPC_path.(root / "network" / "connections" /: P2p_peer.Id.rpc_arg)
 
diff --git a/src/lib_shell_services/p2p_services.mli b/src/lib_shell_services/p2p_services.mli
index df444438c..a3de8364d 100644
--- a/src/lib_shell_services/p2p_services.mli
+++ b/src/lib_shell_services/p2p_services.mli
@@ -46,9 +46,11 @@ module Connections : sig
 
   open RPC_context
 
-  val list: #simple -> P2p_connection.Info.t list tzresult Lwt.t
+  type connection_info = Connection_metadata.t P2p_connection.Info.t
 
-  val info: #simple -> P2p_peer.Id.t -> P2p_connection.Info.t tzresult Lwt.t
+  val list: #simple -> connection_info list tzresult Lwt.t
+
+  val info: #simple -> P2p_peer.Id.t -> connection_info tzresult Lwt.t
 
   val kick: #simple -> ?wait:bool -> P2p_peer.Id.t -> unit tzresult Lwt.t
 
@@ -57,12 +59,12 @@ module Connections : sig
     val list :
       ([ `POST ], unit,
        unit, unit, unit,
-       P2p_connection.Info.t list) RPC_service.t
+       connection_info list) RPC_service.t
 
     val info :
       ([ `POST ], unit,
        unit * P2p_peer.Id.t, unit, unit,
-       P2p_connection.Info.t) RPC_service.t
+       connection_info) RPC_service.t
 
     val kick :
       ([ `POST ], unit,