diff --git a/src/client/client_node_rpcs.ml b/src/client/client_node_rpcs.ml
index a0b7a567e..8197325af 100644
--- a/src/client/client_node_rpcs.ml
+++ b/src/client/client_node_rpcs.ml
@@ -148,6 +148,8 @@ let inject_block ?(wait = true) ?force block =
   call_service0 Services.inject_block (block, wait, force)
 let inject_operation ?(wait = true) ?force operation =
   call_service0 Services.inject_operation (operation, wait, force)
+let inject_protocol ?(wait = true) ?force protocol =
+  call_service0 Services.inject_protocol (protocol, wait, force)
 let describe ?recurse path =
   let prefix, arg = RPC.forge_request Services.describe () recurse in
   get_json (prefix @ path) arg >>=
diff --git a/src/client/client_node_rpcs.mli b/src/client/client_node_rpcs.mli
index 2f9ec342b..3fa2349cc 100644
--- a/src/client/client_node_rpcs.mli
+++ b/src/client/client_node_rpcs.mli
@@ -25,6 +25,8 @@ val inject_block:
   Block_hash.t tzresult Lwt.t
 val inject_operation:
   ?wait:bool -> ?force:bool -> MBytes.t -> Operation_hash.t tzresult Lwt.t
+val inject_protocol:
+  ?wait:bool -> ?force:bool -> Store.protocol -> Protocol_hash.t tzresult Lwt.t
 
 module Blocks : sig
 
diff --git a/src/node/db/context.ml b/src/node/db/context.ml
index a18795f2c..6f16c2b2d 100644
--- a/src/node/db/context.ml
+++ b/src/node/db/context.ml
@@ -216,7 +216,7 @@ let remove_rec (module View : VIEW) key =
   GitStore.FunView.remove_rec View.v (data_key key) >>= fun v ->
   Lwt.return (pack (module GitStore) View.s v)
 
-
+let keys (module View : VIEW) = Store.undefined_key_fn
 
 (*-- Initialisation ----------------------------------------------------------*)
 
diff --git a/src/node/db/db_proxy.ml b/src/node/db/db_proxy.ml
index 2777256e6..6e4f89bec 100644
--- a/src/node/db/db_proxy.ml
+++ b/src/node/db/db_proxy.ml
@@ -23,6 +23,8 @@ module type DISTRIBUTED_DB = sig
   val update: t -> key -> value -> bool Lwt.t
   val remove: t -> key -> bool Lwt.t
   val shutdown: t -> unit Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 type operation_state = {
@@ -106,3 +108,42 @@ module Block =
   Persist.MakeImperativeProxy
     (Store.Faked_functional_block)
     (Block_hash_table) (Block_scheduler)
+
+type protocol_state = {
+  request_protocols: Protocol_hash.t list -> unit ;
+}
+
+module Protocol_scheduler = struct
+  let name = "protocol_scheduler"
+  type rdata = Store.net_id
+  type data = float ref
+  type state = protocol_state
+  let init_request _ _ = Lwt.return (ref 0.0)
+  let request net ~get:_ ~set:_ pendings =
+    let current_time = Unix.gettimeofday () in
+    let time = current_time -. (3. +. Random.float 8.) in
+    let protocols =
+      List.fold_left
+        (fun acc (hash, last_request, Store.Net net_id) ->
+           if !last_request < time then begin
+             last_request := current_time ;
+             let prev =
+               try Block_hash_map.find net_id acc
+               with Not_found -> [] in
+             Block_hash_map.add net_id (hash :: prev) acc
+           end else
+             acc)
+        Block_hash_map.empty
+        pendings in
+    if Block_hash_map.is_empty protocols then
+      0.
+    else begin
+      Block_hash_map.iter (fun _net_id -> net.request_protocols) protocols ;
+      1. +. Random.float 4.
+    end
+end
+
+module Protocol =
+  Persist.MakeImperativeProxy
+    (Store.Faked_functional_protocol)
+    (Protocol_hash_table) (Protocol_scheduler)
diff --git a/src/node/db/db_proxy.mli b/src/node/db/db_proxy.mli
index 9370a1754..b69483202 100644
--- a/src/node/db/db_proxy.mli
+++ b/src/node/db/db_proxy.mli
@@ -23,6 +23,8 @@ module type DISTRIBUTED_DB = sig
   val update: t -> key -> value -> bool Lwt.t
   val remove: t -> key -> bool Lwt.t
   val shutdown: t -> unit Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 type operation_state = {
@@ -44,3 +46,13 @@ module Block :
                   and type key := Store.Block.key
                   and type value := Store.Block.value
                   and type state := block_state
+
+
+type protocol_state = {
+  request_protocols: Protocol_hash.t list -> unit ;
+}
+module Protocol :
+  DISTRIBUTED_DB with type store := Store.Protocol.t
+                  and type key := Store.Protocol.key
+                  and type value := Store.Protocol.value
+                  and type state := protocol_state
diff --git a/src/node/db/persist.ml b/src/node/db/persist.ml
index 43811d6ab..b0ae55440 100644
--- a/src/node/db/persist.ml
+++ b/src/node/db/persist.ml
@@ -24,6 +24,8 @@ module type STORE = sig
   val del: t -> key -> t Lwt.t
   val list: t -> key list -> key list Lwt.t
   val remove_rec: t -> key -> t Lwt.t
+
+  val keys : t -> key list Lwt.t
 end
 
 module type BYTES_STORE = sig
@@ -35,6 +37,8 @@ module type BYTES_STORE = sig
   val del: t -> key -> t Lwt.t
   val list: t -> key list -> key list Lwt.t
   val remove_rec: t -> key -> t Lwt.t
+
+  val keys : t -> key list Lwt.t
 end
 
 module type TYPED_STORE = sig
@@ -45,6 +49,8 @@ module type TYPED_STORE = sig
   val get: t -> key -> value option Lwt.t
   val set: t -> key -> value -> t Lwt.t
   val del: t -> key -> t Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 module type KEY = sig
@@ -146,6 +152,7 @@ module MakeBytesStore
   let remove_rec s k =
     S.remove_rec s (to_path k)
 
+  let keys s = S.keys s >|= List.map of_path
 end
 
 module MakeTypedStore
@@ -167,6 +174,7 @@ module MakeTypedStore
 
   let raw_get = S.get
 
+  let keys = S.keys
 end
 
 module RawKey = struct
@@ -369,6 +377,8 @@ module type IMPERATIVE_PROXY = sig
   val fetch: t -> rdata -> Store.key -> Store.value Lwt.t
   val pending: t -> Store.key -> bool
   val shutdown: t -> unit Lwt.t
+
+  val keys: t -> Store.key list Lwt.t
 end
 
 module type IMPERATIVE_PROXY_SCHEDULER = sig
@@ -457,6 +467,8 @@ module MakeImperativeProxy
   let known { store } hash =
     use store (fun store -> Store.mem store hash)
 
+  let keys { store } = use store Store.keys
+
   let read { store } hash =
     use store (fun store -> Store.get store hash)
 
@@ -528,6 +540,8 @@ module MakeImperativeProxy
   let shutdown { cancel ; worker } =
     cancel () >>= fun () -> worker
 
+  let keys { store } =
+    use store (fun store -> Store.keys store)
 end
 
 (*-- Predefined Instances ----------------------------------------------------*)
diff --git a/src/node/db/persist.mli b/src/node/db/persist.mli
index 69380e0a6..ede8de0e4 100644
--- a/src/node/db/persist.mli
+++ b/src/node/db/persist.mli
@@ -27,6 +27,8 @@ module type STORE = sig
   val del: t -> key -> t Lwt.t
   val list: t -> key list -> key list Lwt.t
   val remove_rec: t -> key -> t Lwt.t
+
+  val keys : t -> key list Lwt.t
 end
 
 (** Projection of OCaml keys of some abstract type to concrete storage
@@ -55,6 +57,8 @@ module type BYTES_STORE = sig
   val del: t -> key -> t Lwt.t
   val list: t -> key list -> key list Lwt.t
   val remove_rec: t -> key -> t Lwt.t
+
+  val keys : t -> key list Lwt.t
 end
 
 module MakeBytesStore (S : STORE) (K : KEY) :
@@ -82,6 +86,8 @@ module type TYPED_STORE = sig
   val get: t -> key -> value option Lwt.t
   val set: t -> key -> value -> t Lwt.t
   val del: t -> key -> t Lwt.t
+
+  val keys: t -> key list Lwt.t (** Not always relevant, BEWARE! *)
 end
 
 (** Gives a typed view of a store (values of a given type stored under
@@ -91,6 +97,7 @@ end
 module MakeTypedStore (S : STORE) (K : KEY) (C : VALUE) :
   TYPED_STORE with type t = S.t and type key = K.t and type value = C.t
 
+
 (** {2 Persistent Sets} ******************************************************)
 
 (** Signature of a set as returned by {!MakePersistentSet} *)
@@ -194,6 +201,8 @@ module type IMPERATIVE_PROXY = sig
   val fetch: t -> rdata -> Store.key -> Store.value Lwt.t
   val pending: t -> Store.key -> bool
   val shutdown: t -> unit Lwt.t
+
+  val keys: t -> Store.key list Lwt.t
 end
 
 module type IMPERATIVE_PROXY_SCHEDULER = sig
diff --git a/src/node/db/store.ml b/src/node/db/store.ml
index 4ffc3abd1..2447b001a 100644
--- a/src/node/db/store.ml
+++ b/src/node/db/store.ml
@@ -92,11 +92,13 @@ type generic_store = FS.t
 type block_store = FS.t
 type blockchain_store = FS.t
 type operation_store = FS.t
+type protocol_store = FS.t
 
 type store = {
   block: block_store Persist.shared_ref ;
   blockchain: blockchain_store Persist.shared_ref ;
   operation: operation_store Persist.shared_ref ;
+  protocol: protocol_store Persist.shared_ref ;
   global_store: generic_store Persist.shared_ref ;
   net_init: ?expiration:Time.t -> genesis -> net_store Lwt.t ;
   net_read: net_id -> net_store tzresult Lwt.t ;
@@ -126,6 +128,8 @@ module type TYPED_IMPERATIVE_STORE = sig
   val get_exn: t -> key -> value Lwt.t
   val set: t -> key -> value -> unit Lwt.t
   val del: t -> key -> unit Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 module type IMPERATIVE_STORE = sig
@@ -146,6 +150,14 @@ module type KEY = sig
   val to_path: t -> string list
 end
 
+module type HASHKEY = sig
+  type t
+  val to_path: t -> string list
+  val of_path: string list -> t
+  val prefix : string list
+  val length : int
+end
+
 module Raw_key = struct
   type t = string list
   let to_path x = x
@@ -187,6 +199,7 @@ module Errors_value = struct
   let of_bytes b = Data_encoding.(Binary.of_bytes (list (error_encoding ()))) b
 end
 
+let undefined_key_fn = Lwt.fail_invalid_arg "function keys cannot be implemented in this module"
 
 module Make (K : KEY) (V : Persist.VALUE) = struct
   type t = FS.t
@@ -205,6 +218,8 @@ module Make (K : KEY) (V : Persist.VALUE) = struct
   let del t k = FS.del t (K.to_path k)
   let list t ks = FS.list t (List.map K.to_path ks)
   let remove_rec t k = FS.remove_rec t (K.to_path k)
+
+  let keys _t = undefined_key_fn
 end
 
 module Data_store : IMPERATIVE_STORE with type t = FS.t =
@@ -212,6 +227,7 @@ module Data_store : IMPERATIVE_STORE with type t = FS.t =
 
 include Data_store
 
+
 (*-- Typed block store under "blocks/" ---------------------------------------*)
 
 type shell_block = {
@@ -350,6 +366,7 @@ module Block = struct
 
   let raw_get t k = Raw_block.get t k
 
+  let keys _t = undefined_key_fn (** We never list keys here *)
 end
 
 module Blockchain_succ_key = struct
@@ -484,9 +501,111 @@ module Operation = struct
   let to_bytes = Raw_operation_value.to_bytes
   let hash op = Operation_hash.hash_bytes [to_bytes op]
   let raw_get t k = Raw_operation_data.get t k
+
+  let keys _t = undefined_key_fn (** We never list keys here *)
 end
 
 
+(*-- Typed operation store under "protocols/" -------------------------------*)
+
+type component = {
+  name : string ;
+  interface : string option ;
+  implementation : string ;
+}
+
+let component_encoding =
+  let open Data_encoding in
+  conv
+    (fun { name ; interface; implementation } -> (name, interface, implementation))
+    (fun (name, interface, implementation) -> { name ; interface ; implementation })
+    (obj3
+       (req "name" string)
+       (opt "interface" string)
+       (req "implementation" string))
+
+type protocol = component list
+let protocol_encoding = Data_encoding.list component_encoding
+
+module Raw_protocol_value = struct
+  type t = protocol
+  let to_bytes v = Data_encoding.Binary.to_bytes protocol_encoding v
+  let of_bytes b = Data_encoding.Binary.of_bytes protocol_encoding b
+end
+
+module Raw_protocol_key = struct
+  type t = Protocol_hash.t
+  let to_path p = "protocols" :: Protocol_hash.to_path p @ [ "contents" ]
+end
+
+module Protocol_data = Make (Raw_protocol_key) (Raw_protocol_value)
+module Raw_protocol_data = Make (Raw_protocol_key) (Raw_value)
+
+module Protocol_time_key = struct
+  type t = Protocol_hash.t
+  let to_path p = "protocols" :: Protocol_hash.to_path p @ [ "discovery_time" ]
+end
+module Protocol_time = Make (Protocol_time_key) (Time_value)
+
+module Protocol_errors_key = struct
+  type t = Protocol_hash.t
+  let to_path p = "protocols" :: Protocol_hash.to_path p @ [ "errors" ]
+end
+module Protocol_errors = Make (Protocol_errors_key) (Errors_value)
+
+module Protocol = struct
+  type t = FS.t
+  type key = Protocol_hash.t
+  type value = protocol tzresult Time.timed_data
+  let mem = Protocol_data.mem
+  let get s k =
+    Protocol_time.get s k >>= function
+    | None -> Lwt.return_none
+    | Some time ->
+        Protocol_errors.get s k >>= function
+        | Some exns -> Lwt.return (Some { Time.data = Error exns ; time })
+        | None ->
+            Protocol_data.get s k >>= function
+            | None -> Lwt.return_none
+            | Some bytes -> Lwt.return (Some { Time.data = Ok bytes ; time })
+  let get_exn s k =
+    get s k >>= function
+    | None -> Lwt.fail Not_found
+    | Some x -> Lwt.return x
+  let set s k { Time.data ; time } =
+    Protocol_time.set s k time >>= fun () ->
+    match data with
+    | Ok bytes ->
+        Protocol_data.set s k bytes >>= fun () ->
+        Protocol_errors.del s k
+    | Error exns ->
+        Protocol_errors.set s k exns >>= fun () ->
+        Protocol_data.del s k
+  let del s k =
+    Protocol_time.del s k >>= fun () ->
+    Protocol_data.del s k >>= fun () ->
+    Protocol_errors.del s k
+  let of_bytes = Raw_protocol_value.of_bytes
+  let to_bytes = Raw_protocol_value.to_bytes
+  let hash proto = Protocol_hash.hash_bytes [to_bytes proto]
+  let compare p1 p2 =
+    Protocol_hash.(compare (hash_bytes [to_bytes p1]) (hash_bytes [to_bytes p2]))
+  let equal b1 b2 = compare b1 b2 = 0
+  let raw_get t k = Raw_protocol_data.get t k
+
+  let fold s x ~f =
+    let rec dig i root acc =
+      if i <= 0 then
+        f (Protocol_hash.of_path @@ List.tl root) acc
+      else
+        FS.list s [root] >>= fun roots ->
+        Lwt_list.fold_right_s (dig (i - 1)) roots acc
+    in
+    dig Protocol_hash.path_len ["protocols"] x
+
+  let keys s = fold s [] ~f:(fun k a -> Lwt.return @@ k :: a)
+end
+
 (*- Genesis and initialization -----------------------------------------------*)
 
 let genesis_encoding =
@@ -620,6 +739,7 @@ let init root =
     { block = Persist.share t ;
       blockchain = Persist.share t ;
       operation = Persist.share t ;
+      protocol = Persist.share t ;
       global_store = Persist.share t ;
       net_init = net_init ~root ;
       net_read = net_read ~root ;
@@ -638,6 +758,7 @@ end
 
 module Faked_functional_operation = Faked_functional_typed_store (Operation)
 module Faked_functional_block = Faked_functional_typed_store (Block)
+module Faked_functional_protocol = Faked_functional_typed_store (Protocol)
 
 module Faked_functional_store : Persist.STORE with type t = t
 = struct
@@ -645,4 +766,6 @@ module Faked_functional_store : Persist.STORE with type t = t
   let set s k v = Data_store.set s k v >>= fun () -> Lwt.return s
   let del s k = Data_store.del s k >>= fun () -> Lwt.return s
   let remove_rec s k = Data_store.remove_rec s k >>= fun () -> Lwt.return s
+
+  let keys _s = invalid_arg "function keys not implementable here" (** We never use list here. *)
 end
diff --git a/src/node/db/store.mli b/src/node/db/store.mli
index a91909889..8bbc1ebf7 100644
--- a/src/node/db/store.mli
+++ b/src/node/db/store.mli
@@ -21,6 +21,7 @@ module type TYPED_IMPERATIVE_STORE = sig
   val get_exn: t -> key -> value Lwt.t
   val set: t -> key -> value -> unit Lwt.t
   val del: t -> key -> unit Lwt.t
+  val keys: t -> key list Lwt.t
 end
 
 module type IMPERATIVE_STORE = sig
@@ -39,11 +40,13 @@ type generic_store
 type block_store
 type blockchain_store
 type operation_store
+type protocol_store
 
 type store = private {
   block: block_store Persist.shared_ref ;
   blockchain: blockchain_store Persist.shared_ref ;
   operation: operation_store Persist.shared_ref ;
+  protocol: protocol_store Persist.shared_ref ;
   global_store: generic_store Persist.shared_ref ;
   net_init: ?expiration:Time.t -> genesis -> net_store Lwt.t ;
   net_read: net_id -> net_store tzresult Lwt.t ;
@@ -70,6 +73,9 @@ val pp_net_id: Format.formatter -> net_id -> unit
 (** Open or initialize a store at a given path. *)
 val init: string -> store Lwt.t
 
+(** Lwt exn returned when function keys is not implemented *)
+val undefined_key_fn : 'a Lwt.t
+
 (** {2 Generic interface} ****************************************************)
 
 (** The generic primitives do work on the direct root, but in a
@@ -107,6 +113,16 @@ type block = {
 val shell_block_encoding: shell_block Data_encoding.t
 val block_encoding: block Data_encoding.t
 
+(** Protocol *)
+type component = {
+  name : string ;
+  interface : string option ;
+  implementation : string ;
+}
+
+type protocol = component list
+val protocol_encoding : protocol Data_encoding.t
+
 (** {2 Block and operations store} ********************************************)
 
 module Block : sig
@@ -177,6 +193,19 @@ module Operation : sig
 
 end
 
+module Protocol : sig
+  val of_bytes: MBytes.t -> protocol option
+  val to_bytes: protocol -> MBytes.t
+  val hash: protocol -> Protocol_hash.t
+
+  include TYPED_IMPERATIVE_STORE
+    with type t = protocol_store
+     and type key = Protocol_hash.t
+     and type value = protocol tzresult Time.timed_data
+
+  val raw_get: t -> Protocol_hash.t -> MBytes.t option Lwt.t
+end
+
 (**/**) (* For testing only *)
 
 (* module LwtUnixStore : sig *)
@@ -198,4 +227,9 @@ module Faked_functional_block :
                        and type value = Block.value
                        and type key = Block.key
 
+module Faked_functional_protocol :
+  Persist.TYPED_STORE with type t = Protocol.t
+                       and type value = Protocol.value
+                       and type key = Protocol.key
+
 module Faked_functional_store : Persist.STORE with type t = t
diff --git a/src/node/shell/messages.ml b/src/node/shell/messages.ml
index eba85a1a0..22e32f68c 100644
--- a/src/node/shell/messages.ml
+++ b/src/node/shell/messages.ml
@@ -25,8 +25,8 @@ type message =
   | Get_operations of Operation_hash.t list
   | Operation of MBytes.t
 
-  | Current_protocol of net_id
-  | Protocol_inventory of Protocol_hash.t
+  | Get_protocols of Protocol_hash.t list
+  | Protocol of MBytes.t
 
 
 let to_frame msg =
@@ -54,10 +54,10 @@ let to_frame msg =
   | Operation b ->
       [ S 2703 ; B b ]
 
-  | Current_protocol (Net net_id) ->
-      [ S 2800 ; bh net_id ]
-  | Protocol_inventory p ->
-      [ S 2801 ; ph p ]
+  | Get_protocols protos ->
+      [ S 2800 ; F (List.map ph protos) ]
+  | Protocol p ->
+      [ S 2801 ; B p ]
 
 let from_frame msg =
 
@@ -82,9 +82,9 @@ let from_frame msg =
         Some (Get_operations (List.map oph ops))
     | [ S 2703 ; B contents ] -> Some (Operation contents)
 
-    | [ S 2800 ; B netid ] -> Some (Current_protocol (net netid))
+    | [ S 2800 ; F protos ] -> Some (Get_protocols (List.map ph protos))
 
-    | [ S 2801 ; p ] -> Some (Protocol_inventory (ph p))
+    | [ S 2801 ; B contents ] -> Some (Protocol contents)
 
     | _ -> None
 
diff --git a/src/node/shell/messages.mli b/src/node/shell/messages.mli
index 0f8c1601a..2c3df42cc 100644
--- a/src/node/shell/messages.mli
+++ b/src/node/shell/messages.mli
@@ -22,8 +22,9 @@ type message =
   | Get_operations of Operation_hash.t list
   | Operation of MBytes.t
 
-  | Current_protocol of Store.net_id
-  | Protocol_inventory of Protocol_hash.t
+  | Get_protocols of Protocol_hash.t list
+  | Protocol of MBytes.t
+
 
 (** Converts a high level message to a network frame *)
 val to_frame: message -> Netbits.frame
diff --git a/src/node/shell/node.ml b/src/node/shell/node.ml
index f14d5e1b7..67291fac5 100644
--- a/src/node/shell/node.ml
+++ b/src/node/shell/node.ml
@@ -24,6 +24,13 @@ let inject_operation validator ?force bytes =
   let hash = Operation_hash.hash_bytes [bytes] in
   Lwt.return (hash, t)
 
+let inject_protocol state ?force:_ proto =
+  (* TODO: Validate the protocol *)
+  let proto_bytes = Store.Protocol.to_bytes proto in
+  let hash = Protocol_hash.hash_bytes [proto_bytes] in
+  let t = State.Protocol.store state proto_bytes >>|? ignore in
+  Lwt.return (hash, t)
+
 let process_operation state validator bytes =
   State.Operation.store state bytes >>= function
   | Error _ | Ok None -> Lwt.return_unit
@@ -38,6 +45,13 @@ let process_operation state validator bytes =
           Prevalidator.register_operation prevalidator hash ;
           Lwt.return_unit
 
+let process_protocol state _validator bytes =
+  State.Protocol.store state bytes >>= function
+  | Error _ | Ok None -> Lwt.return_unit
+  | Ok (Some (hash, _proto)) ->
+      (* TODO: Store only pending protocols... *)
+      lwt_log_info "process Protocol %a" Protocol_hash.pp_short hash
+
 let process_block state validator bytes =
   State.Block.store state bytes >>= function
   | Error _ | Ok None -> Lwt.return_unit
@@ -144,23 +158,20 @@ let process state validator msg =
       process_operation state validator content >>= fun () ->
       Lwt.return_nil
 
-  | Current_protocol net_id ->
-      lwt_log_info "process Current_protocol" >>= fun () ->
-      if not (State.Net.is_active state net_id) then
-        Lwt.return_nil
-      else begin
-        match State.Net.get state net_id with
-        | Error _ -> Lwt.return_nil
-        | Ok net ->
-            State.Net.Blockchain.head net >>= fun head ->
-            Lwt.return [Protocol_inventory head.protocol_hash]
-      end
+  | Get_protocols protos ->
+      lwt_log_info "process Get_protocols" >>= fun () ->
+      Lwt_list.map_p (State.Protocol.raw_read state) protos >>= fun protos ->
+      let cons_protocol acc = function
+        | Some proto -> Protocol proto :: acc
+        | None -> acc in
+      Lwt.return (List.fold_left cons_protocol [] protos)
 
-  | Protocol_inventory _ ->
-      lwt_log_info "process Protocol_inventory" >>= fun () ->
-      (* TODO... *)
+  | Protocol content ->
+      lwt_log_info "process Protocol" >>= fun () ->
+      process_protocol state validator content >>= fun () ->
       Lwt.return_nil
 
+
 type t = {
   state: State.t ;
   validator: Validator.worker ;
@@ -170,6 +181,8 @@ type t = {
     ?force:bool -> MBytes.t -> (Block_hash.t * unit tzresult Lwt.t) Lwt.t ;
   inject_operation:
     ?force:bool -> MBytes.t -> (Operation_hash.t * unit tzresult Lwt.t) Lwt.t ;
+  inject_protocol:
+    ?force:bool -> Store.protocol -> (Protocol_hash.t * unit tzresult Lwt.t) Lwt.t ;
   shutdown: unit -> unit Lwt.t ;
 }
 
@@ -184,6 +197,11 @@ let request_blocks net _net_id blocks =
           For now simply broadcast the request to all our neighbours. *)
   P2p.broadcast (Messages.(to_frame (Get_blocks blocks))) net
 
+let request_protocols net protocols =
+  (* TODO improve the lookup strategy.
+          For now simply broadcast the request to all our neighbours. *)
+  P2p.broadcast (Messages.(to_frame (Get_protocols protocols))) net
+
 let init_p2p net_params =
   match net_params with
   | None ->
@@ -200,8 +218,9 @@ let create
   lwt_log_info "reading state..." >>= fun () ->
   let request_operations = request_operations p2p in
   let request_blocks = request_blocks p2p in
+  let request_protocols = request_protocols p2p in
   State.read
-    ~request_operations ~request_blocks
+    ~request_operations ~request_blocks ~request_protocols
     ~store_root ~context_root ~ttl:(48 * 3600) (* 2 days *)
     ?patch_context () >>= fun state ->
   let validator = Validator.create_worker p2p state in
@@ -264,6 +283,7 @@ let create
     global_validator ;
     inject_block = inject_block state validator ;
     inject_operation = inject_operation validator ;
+    inject_protocol = inject_protocol state ;
     shutdown ;
   }
 
@@ -310,6 +330,7 @@ module RPC = struct
 
   let inject_block node = node.inject_block
   let inject_operation node = node.inject_operation
+  let inject_protocol node = node.inject_protocol
 
   let raw_block_info node hash =
     State.Valid_block.read_exn node.state hash >|= convert
@@ -449,6 +470,11 @@ module RPC = struct
                 State.Net.Mempool.for_block net b >|= fun ops ->
                 Updater.empty_result, ops
 
+  let protocols { state } = State.Protocol.keys state
+
+  let protocol_content node hash =
+    State.Protocol.read node.state hash
+
   let preapply node block ~timestamp ~sort ops =
     begin
       match block with
@@ -539,6 +565,9 @@ module RPC = struct
   let operation_watcher node =
     State.Operation.create_watcher node.state
 
+  let protocol_watcher node =
+    State.Protocol.create_watcher node.state
+
   let validate node net_id block =
     Validator.get node.validator net_id >>=? fun net_v ->
     Validator.fetch_block net_v block >>=? fun _ ->
diff --git a/src/node/shell/node.mli b/src/node/shell/node.mli
index f1ffe52c6..d5368fa7c 100644
--- a/src/node/shell/node.mli
+++ b/src/node/shell/node.mli
@@ -29,6 +29,8 @@ module RPC : sig
     t -> ?force:bool -> MBytes.t -> (Block_hash.t * unit tzresult Lwt.t) Lwt.t
   val inject_operation:
     t -> ?force:bool -> MBytes.t -> (Operation_hash.t * unit tzresult Lwt.t) Lwt.t
+  val inject_protocol:
+    t -> ?force:bool -> Store.protocol -> (Protocol_hash.t * unit tzresult Lwt.t) Lwt.t
 
   val raw_block_info:
     t -> Block_hash.t -> block_info Lwt.t
@@ -54,6 +56,13 @@ module RPC : sig
   val pending_operations:
     t -> block -> (error Updater.preapply_result * Operation_hash_set.t) Lwt.t
 
+  val protocols:
+    t -> Protocol_hash.t list Lwt.t
+  val protocol_content:
+    t -> Protocol_hash.t -> Store.protocol tzresult Time.timed_data option Lwt.t
+  val protocol_watcher:
+    t -> (Protocol_hash.t * Store.protocol) Lwt_stream.t * (unit -> unit)
+
   val context_dir:
     t -> block -> 'a RPC.directory option Lwt.t
 
diff --git a/src/node/shell/node_rpc.ml b/src/node/shell/node_rpc.ml
index 9a58865f0..a938ec44c 100644
--- a/src/node/shell/node_rpc.ml
+++ b/src/node/shell/node_rpc.ml
@@ -332,6 +332,42 @@ let get_operations node hash () =
   | Some bytes -> RPC.Answer.return bytes
   | None -> raise Not_found
 
+let list_protocols node {Services.Protocols.monitor; contents} =
+  let monitor = match monitor with None -> false | Some x -> x in
+  let include_contents = match contents with None -> false | Some x -> x in
+  Node.RPC.protocols node >>= fun protocols ->
+  Lwt_list.map_p
+    (fun hash ->
+       if include_contents then
+         Node.RPC.protocol_content node hash >>= function
+         | None | Some { Time.data = Error _ } -> Lwt.return (hash, None)
+         | Some { Time.data = Ok bytes }->
+             Lwt.return (hash, Some bytes)
+       else
+         Lwt.return (hash, None))
+    protocols >>= fun protocols ->
+  if not monitor then
+    RPC.Answer.return protocols
+  else
+    let stream, shutdown = Node.RPC.protocol_watcher node in
+    let first_request = ref true in
+    let next () =
+      if not !first_request then
+        Lwt_stream.get stream >>= function
+        | None -> Lwt.return_none
+        | Some (h, op) when include_contents -> Lwt.return (Some [h, Some op])
+        | Some (h, _) -> Lwt.return (Some [h, None])
+      else begin
+        first_request := false ;
+        Lwt.return (Some protocols)
+      end in
+    RPC.Answer.return_stream { next ; shutdown }
+
+let get_protocols node hash () =
+  Node.RPC.protocol_content node hash >>= function
+  | Some bytes -> RPC.Answer.return bytes
+  | None -> raise Not_found
+
 let build_rpc_directory node =
   let dir = RPC.empty in
   let dir = RPC.register0 dir Services.Blocks.list (list_blocks node) in
@@ -351,6 +387,10 @@ let build_rpc_directory node =
     RPC.register0 dir Services.Operations.list (list_operations node) in
   let dir =
     RPC.register1 dir Services.Operations.bytes (get_operations node) in
+  let dir =
+    RPC.register0 dir Services.Protocols.list (list_protocols node) in
+  let dir =
+    RPC.register1 dir Services.Protocols.bytes (get_protocols node) in
   let dir =
     let implementation (net_id, pred, time, fitness, operations, header) =
       Node.RPC.block_info node (`Head 0) >>= fun bi ->
@@ -383,6 +423,13 @@ let build_rpc_directory node =
         (if blocking then wait else return ()) >>=? fun () -> return hash
       end >>= RPC.Answer.return in
     RPC.register0 dir Services.inject_operation implementation in
+  let dir =
+    let implementation (proto, blocking, force) =
+      Node.RPC.inject_protocol ?force node proto >>= fun (hash, wait) ->
+      begin
+        (if blocking then wait else return ()) >>=? fun () -> return hash
+      end >>= RPC.Answer.return in
+    RPC.register0 dir Services.inject_protocol implementation in
   let dir =
     let implementation () =
       RPC.Answer.return Data_encoding.Json.(schema (Error_monad.error_encoding ())) in
diff --git a/src/node/shell/node_rpc_services.ml b/src/node/shell/node_rpc_services.ml
index 75d8bea6e..4b85cd97e 100644
--- a/src/node/shell/node_rpc_services.ml
+++ b/src/node/shell/node_rpc_services.ml
@@ -383,6 +383,56 @@ module Operations = struct
 
 end
 
+module Protocols = struct
+  let protocols_arg =
+    let name = "protocol_id" in
+    let descr =
+      "A protocol identifier in hexadecimal." in
+    let construct = Protocol_hash.to_b48check in
+    let destruct h =
+      try Ok (Protocol_hash.of_b48check h)
+      with _ -> Error "Can't parse hash" in
+    RPC.Arg.make ~name ~descr ~construct ~destruct ()
+
+  let bytes =
+    RPC.service
+      ~input: empty
+      ~output:
+        (obj1 (req "data"
+                 (describe ~title: "Tezos protocol"
+                    (Time.timed_encoding @@
+                     RPC.Error.wrap @@
+                     Store.protocol_encoding))))
+      RPC.Path.(root / "protocols" /: protocols_arg)
+
+  type list_param = {
+    contents: bool option ;
+    monitor: bool option ;
+  }
+
+  let list_param_encoding =
+    conv
+      (fun {contents; monitor} -> (contents, monitor))
+      (fun (contents, monitor) -> {contents; monitor})
+      (obj2
+         (opt "contents" bool)
+         (opt "monitor" bool))
+
+  let list =
+    RPC.service
+      ~input: list_param_encoding
+      ~output:
+        (obj1
+           (req "protocols"
+              (list
+                 (obj2
+                    (req "hash" Protocol_hash.encoding)
+                    (opt "contents"
+                       (dynamic_size Store.protocol_encoding)))
+              )))
+      RPC.Path.(root / "protocols")
+end
+
 let forge_block =
   RPC.service
     ~description: "Forge a block header"
@@ -480,6 +530,59 @@ let inject_operation =
        (obj1 (req "injectedOperation" Operation_hash.encoding)))
     RPC.Path.(root / "inject_operation")
 
+let inject_protocol =
+  let proto =
+    (list
+       (obj3
+          (req "name"
+             (describe ~title:"OCaml module name"
+                string))
+          (opt "interface"
+             (describe
+                ~description:"Content of the .mli file"
+                string))
+          (req "implementation"
+             (describe
+                ~description:"Content of the .ml file"
+                string))))
+  in
+  let proto_of_rpc =
+    List.map (fun (name, interface, implementation) ->
+        { Store.name; interface; implementation })
+  in
+  let rpc_of_proto =
+    List.map (fun { Store.name; interface; implementation } ->
+                (name, interface, implementation))
+  in
+  RPC.service
+    ~description:
+      "Inject a protocol in node. Returns the ID of the protocol."
+    ~input:
+      (conv
+         (fun (proto, blocking, force) -> (rpc_of_proto proto, Some blocking, force))
+         (fun (proto, blocking, force) -> (proto_of_rpc proto, unopt true blocking, force))
+         (obj3
+            (req "protocol"
+               (describe ~title: "Tezos protocol"
+                  proto))
+            (opt "blocking"
+               (describe
+                  ~description:
+                    "Should the RPC wait for the protocol to be \
+                     validated before to answer. (default: true)"
+                  bool))
+            (opt "force"
+               (describe
+                  ~description:
+                    "Should we inject protocol that is invalid. (default: false)"
+                  bool))))
+    ~output:
+      (RPC.Error.wrap @@
+       describe
+         ~title: "Hash of the injected protocol" @@
+       (obj1 (req "injectedProtocol" Protocol_hash.encoding)))
+    RPC.Path.(root / "inject_protocol")
+
 let describe =
   RPC.Description.service
     ~description: "RPCs documentation and input/output schema"
diff --git a/src/node/shell/node_rpc_services.mli b/src/node/shell/node_rpc_services.mli
index 6aa778939..055de2ec6 100644
--- a/src/node/shell/node_rpc_services.mli
+++ b/src/node/shell/node_rpc_services.mli
@@ -97,6 +97,19 @@ module Operations : sig
      list_param, (Operation_hash.t * Store.operation option) list) RPC.service
 end
 
+module Protocols : sig
+  val bytes:
+    (unit, unit * Protocol_hash.t, unit,
+     Store.protocol tzresult Time.timed_data) RPC.service
+  type list_param = {
+    contents: bool option ;
+    monitor: bool option ;
+  }
+  val list:
+    (unit, unit,
+     list_param, (Protocol_hash.t * Store.protocol option) list) RPC.service
+end
+
 val forge_block:
   (unit, unit,
    Updater.net_id option * Block_hash.t option * Time.t option *
@@ -115,5 +128,9 @@ val inject_operation:
   (unit, unit,
    (MBytes.t * bool * bool option), Operation_hash.t tzresult) RPC.service
 
+val inject_protocol:
+  (unit, unit,
+   (Store.protocol * bool * bool option), Protocol_hash.t tzresult) RPC.service
+
 val describe:
   (unit, unit, bool option, RPC.Description.directory_descr) RPC.service
diff --git a/src/node/shell/state.ml b/src/node/shell/state.ml
index b4433eb6e..3fb1853dd 100644
--- a/src/node/shell/state.ml
+++ b/src/node/shell/state.ml
@@ -82,6 +82,9 @@ type t = {
   operation_db: Db_proxy.Operation.t ;
   operation_watchers:
     (Operation_hash.t * Store.operation) Watcher.t list ref ;
+  protocol_db: Db_proxy.Protocol.t ;
+  protocol_watchers:
+    (Protocol_hash.t * Store.protocol) Watcher.t list ref ;
   valid_block_state: valid_block_state Persist.shared_ref ;
 }
 
@@ -154,6 +157,15 @@ module InvalidOperations =
   Persist.MakeBufferedPersistentSet
     (Store.Faked_functional_store) (InvalidOperations_key) (Operation_hash_set)
 
+module InvalidProtocols_key = struct
+  include Protocol_hash
+  let prefix = ["state"; "invalid_protocols"]
+  let length = path_len
+end
+module InvalidProtocols =
+  Persist.MakeBufferedPersistentSet
+    (Store.Faked_functional_store) (InvalidProtocols_key) (Protocol_hash_set)
+
 module InvalidBlocks_key = struct
   include Block_hash
   let prefix = ["state"; "invalid_blocks"]
@@ -236,6 +248,66 @@ module Operation = struct
 
 end
 
+module Protocol = struct
+  type key = Store.Protocol.key
+
+  type component = Store.component = {
+    name: string;
+    interface: string option;
+    implementation: string
+  }
+
+  type t = Store.protocol
+
+  type protocol = t
+  exception Invalid of key * error list
+  let of_bytes = Store.Protocol.of_bytes
+  let to_bytes = Store.Protocol.to_bytes
+  let known t k = Db_proxy.Protocol.known t.protocol_db k
+  let read t k = Db_proxy.Protocol.read t.protocol_db k
+  let read_exn t k =
+    Db_proxy.Protocol.read t.protocol_db k >>= function
+    | None -> Lwt.fail Not_found
+    | Some { data = Error e } -> Lwt.fail (Invalid (k, e))
+    | Some { data = Ok data ; time }  -> Lwt.return { Time.data ; time }
+  let hash = Store.Protocol.hash
+  let raw_read t k =
+    Persist.use t.store.Store.protocol
+      (fun store -> Store.Protocol.raw_get store k)
+  let prefetch t net_id ks =
+    List.iter (Db_proxy.Protocol.prefetch t.protocol_db net_id) ks
+  let fetch t net_id k = Db_proxy.Protocol.fetch t.protocol_db net_id k
+  let store t bytes =
+    match of_bytes bytes with
+    | None -> fail Cannot_parse
+    | Some proto ->
+        let h = hash proto in
+        Db_proxy.Protocol.store t.protocol_db h (Time.make_timed (Ok proto))
+        >>= function
+        | true ->
+            Watcher.notify !(t.protocol_watchers) (h, proto) ;
+            return (Some (h, proto))
+        | false ->
+            return None
+  let mark_invalid t k e =
+    Db_proxy.Protocol.update t.protocol_db k (Time.make_timed (Error e))
+    >>= function
+    | true ->
+        Persist.update t.store.global_store (fun store ->
+            InvalidProtocols.set store k >>= fun store ->
+            Lwt.return (Some store)) >>= fun _ ->
+        Lwt.return true
+    | false -> Lwt.return false
+
+  let invalid state =
+    Persist.use state.store.global_store InvalidProtocols.read
+
+  let create_watcher t = Watcher.create_stream t.protocol_watchers ()
+
+  let keys { protocol_db } = Db_proxy.Protocol.keys protocol_db
+
+end
+
 let iter_predecessors
     (type t)
     (compare: t -> t -> int)
@@ -458,7 +530,7 @@ module Valid_block = struct
     hash: Block_hash.t ;
     pred: Block_hash.t ;
     timestamp: Time.t ;
-    fitness: Protocol.fitness ;
+    fitness: Fitness.fitness ;
     operations: Operation_hash.t list ;
     discovery_time: Time.t ;
     protocol_hash: Protocol_hash.t ;
@@ -785,6 +857,8 @@ module Valid_block = struct
       | Error exns ->
           locked_store_invalid vstate hash exns >>= fun _changed ->
           Lwt.return vstate
+
+    let keys _ = Store.undefined_key_fn
   end
 
   let iter_predecessors =
@@ -1216,12 +1290,14 @@ let () =
 (** Whole protocol state : read and store. *)
 
 let read
-    ~request_operations ~request_blocks
+    ~request_operations ~request_blocks ~request_protocols
     ~store_root ~context_root ~ttl ?patch_context () =
   Store.init store_root >>= fun store ->
   lwt_log_info "Initialising the distributed database..." >>= fun () ->
   let operation_db =
     Db_proxy.Operation.create { request_operations } store.operation in
+  let protocol_db =
+    Db_proxy.Protocol.create { request_protocols } store.protocol in
   let block_db =
     Db_proxy.Block.create { request_blocks } store.block in
   Valid_block.create
@@ -1233,6 +1309,8 @@ let read
     nets = Block_hash_table.create 7 ;
     operation_db ;
     operation_watchers = ref [] ;
+    protocol_db ;
+    protocol_watchers = ref [] ;
     block_db ; block_watchers = ref [] ;
     valid_block_state ;
   }
diff --git a/src/node/shell/state.mli b/src/node/shell/state.mli
index e5084f6b9..7ea0dfdda 100644
--- a/src/node/shell/state.mli
+++ b/src/node/shell/state.mli
@@ -39,6 +39,7 @@ type error +=
 val read:
   request_operations: (net_id -> Operation_hash.t list -> unit) ->
   request_blocks: (net_id -> Block_hash.t list -> unit) ->
+  request_protocols: (Protocol_hash.t list -> unit) ->
   store_root:string ->
   context_root:string ->
   ttl:int ->
@@ -342,6 +343,78 @@ module Valid_block : sig
 
 end
 
+(** {2 Protocol database} ****************************************************)
+
+(** The local and distributed database of protocols. *)
+module Protocol : sig
+
+  type key = Protocol_hash.t
+
+  type component = Store.component = {
+    name : string ;
+    interface : string option ;
+    implementation : string ;
+  }
+
+  type t = Store.protocol
+
+  type protocol = t
+
+  (** Is a protocol stored in the local database ? *)
+  val known: state -> key -> bool Lwt.t
+
+  (** Read a protocol in the local database. This returns [None]
+      when the protocol does not exist in the local database; this returns
+      [Some (Error _)] when [mark_invalid] was used. This also returns
+      the time when the protocol was stored on the local database. *)
+  val read:
+    state -> key -> protocol tzresult Time.timed_data option Lwt.t
+
+  (** Read a protocol in the local database. This throws [Not_found]
+      when the protocol does not exist in the local database or when
+      [mark_invalid] was used. *)
+  val read_exn:
+    state -> key -> protocol Time.timed_data Lwt.t
+  exception Invalid of key * error list
+
+  (** Read an operation in the local database (without parsing). *)
+  val raw_read: state -> key -> MBytes.t option Lwt.t
+
+  (** Read a protocol from the distributed database. This may block
+      while the block is fetched from the P2P network. *)
+  val fetch:
+    state -> Store.net_id -> key -> protocol tzresult Time.timed_data Lwt.t
+
+  (** Request protocols on the P2P network without waiting for answers. *)
+  val prefetch: state -> Store.net_id -> key list -> unit
+
+  (** Add a protocol to the local database. This returns [Ok None]
+      if the protocol was already stored in the database, or returns
+      the parsed operation if not. It may also fails when the shell
+      part of the operation cannot be parsed or when the operation
+      does not belong to an active "network". For a given sequence of
+      bytes, it is guaranted that at most one call to [store] returns
+      [Some _]. *)
+  val store:
+    state -> MBytes.t -> (Protocol_hash.t * protocol) option tzresult Lwt.t
+
+  (** Mark a protocol as invalid in the local database. This returns
+      [false] if the protocol was previously stored in the local
+      database. The protocol is not removed from the local database,
+      but its content is replaced by a list of errors. *)
+  val mark_invalid: state -> key -> error list -> bool Lwt.t
+
+  (** Returns the list known-invalid procols. *)
+  val invalid: state -> Protocol_hash_set.t Lwt.t
+
+  (** Create a stream of all the newly locally-stored protocols.
+      The returned function allows to terminate the stream. *)
+  val create_watcher:
+    state -> (key * protocol) Lwt_stream.t * (unit -> unit)
+
+  val keys: state -> key list Lwt.t
+end
+
 (** {2 Network} ****************************************************************)
 
 (** Data specific to a given network. *)
diff --git a/src/node/updater/updater.ml b/src/node/updater/updater.ml
index c7a7e2167..32a5971fd 100644
--- a/src/node/updater/updater.ml
+++ b/src/node/updater/updater.ml
@@ -131,7 +131,7 @@ let get_basedir () =
 let init dir =
   basedir := Some dir
 
-type component = {
+type component = Store.component = {
   name : string ;
   interface : string option ;
   implementation : string ;
diff --git a/src/proto/environment/persist.mli b/src/proto/environment/persist.mli
index 25657f2c8..e7fc1d792 100644
--- a/src/proto/environment/persist.mli
+++ b/src/proto/environment/persist.mli
@@ -18,6 +18,8 @@ module type STORE = sig
   val del: t -> key -> t Lwt.t
   val list: t -> key list -> key list Lwt.t
   val remove_rec: t -> key -> t Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 (** Projection of OCaml keys of some abstract type to concrete storage
@@ -57,6 +59,8 @@ module type BYTES_STORE = sig
   val del: t -> key -> t Lwt.t
   val list: t -> key list -> key list Lwt.t
   val remove_rec: t -> key -> t Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 module MakeBytesStore (S : STORE) (K : KEY) :
@@ -73,6 +77,8 @@ module type TYPED_STORE = sig
   val get: t -> key -> value option Lwt.t
   val set: t -> key -> value -> t Lwt.t
   val del: t -> key -> t Lwt.t
+
+  val keys: t -> key list Lwt.t
 end
 
 (** Gives a typed view of a store (values of a given type stored under