diff --git a/swarmsim/distributions.nim b/swarmsim/distributions.nim
new file mode 100644
index 0000000..bf39343
--- /dev/null
+++ b/swarmsim/distributions.nim
@@ -0,0 +1,14 @@
+import std/random
+import std/math
+
+type Distribution = proc(): float
+
+proc unitUniform(): float =
+  ## Uniform distribution on [0, 1]. Used as a building block for inverse transform
+  ## samplers (https://en.wikipedia.org/wiki/Inverse_transform_sampling), as well as
+  ## for the scaled uniform distribution.
+  rand(1.float)
+
+proc Exp*(lambda: float, unitUniform = unitUniform): Distribution =
+  ## Returns an exponential `Distribution` with parameter lambda.
+  proc(): float = -ln(1 - unitUniform()) / lambda
diff --git a/swarmsim/engine/eventdrivenengine.nim b/swarmsim/engine/eventdrivenengine.nim
new file mode 100644
index 0000000..1295f0c
--- /dev/null
+++ b/swarmsim/engine/eventdrivenengine.nim
@@ -0,0 +1,50 @@
+import std/options
+import std/strformat
+
+import ./types
+import ./schedulableevent
+
+type
+  AwaitableHandle = object of RootObj
+    schedulable: SchedulableEvent
+    engine: EventDrivenEngine
+
+proc current_time*(self: EventDrivenEngine): uint64 {.inline.} = self.current_time
+
+proc schedule*(self: EventDrivenEngine, schedulable: SchedulableEvent): void =
+  if schedulable.time < self.current_time:
+    raise (ref Defect)(
+      msg: fmt"Cannot schedule an event in the past ({schedulable.time}) < ({self.current_time})")
+  self.queue.push(schedulable)
+
+proc awaitableSchedule*(self: EventDrivenEngine, schedulable: SchedulableEvent): AwaitableHandle =
+  self.schedule(schedulable)
+  AwaitableHandle(schedulable: schedulable, engine: self)
+
+proc scheduleAll*[T: SchedulableEvent](self: EventDrivenEngine, schedulables: seq[T]): void =
+  for schedulable in schedulables:
+    self.schedule(schedulable)
+
+proc nextStep*(self: EventDrivenEngine): Option[SchedulableEvent] =
+  if len(self.queue) == 0:
+    return none(SchedulableEvent)
+
+  let schedulable = self.queue.pop()
+  self.current_time = schedulable.time
+  schedulable.atScheduledTime(engine = self)
+
+  some(schedulable)
+
+proc runUntil*(self: EventDrivenEngine, until: uint64): void =
+  while self.nextStep().isSome and self.current_time < until:
+    discard
+
+proc run*(self: EventDrivenEngine): void =
+  self.runUntil(high(uint64))
+
+proc doAwait*(self: AwaitableHandle): void =
+  self.engine.runUntil(self.schedulable.time)
+
+export EventDrivenEngine
+export AwaitableHandle
+export options
diff --git a/swarmsim/engine/message.nim b/swarmsim/engine/message.nim
new file mode 100644
index 0000000..43f52b5
--- /dev/null
+++ b/swarmsim/engine/message.nim
@@ -0,0 +1,9 @@
+import std/options
+
+import ./types
+
+proc new*(T: type Message, sender: Option[Peer] = none(Peer), receiver: Peer, messageType: string): Message =
+  Message(sender: sender, receiver: receiver, messageType: messageType)
+
+export Message
+export options
diff --git a/swarmsim/engine/network.nim b/swarmsim/engine/network.nim
new file mode 100644
index 0000000..d113737
--- /dev/null
+++ b/swarmsim/engine/network.nim
@@ -0,0 +1,50 @@
+import std/options
+import std/sets
+
+import ./types
+import ./peer
+import ./eventdrivenengine
+
+type
+  ScheduledMessage = ref object of SchedulableEvent
+    message: Message
+
+proc new*(
+  T: type Network,
+  engine: EventDrivenEngine,
+  defaultLinkDelay: uint64 = 0
+): T =
+  return Network(
+    engine: engine,
+    defaultLinkDelay: defaultLinkDelay,
+    peers: HashSet[Peer]()
+  )
+
+proc add*(self: Network, peer: Peer): void =
+  # TODO: this can be very slow if the array keeps being resized, but for
+  #   now I won't care much.
+  self.peers.incl(peer)
+
+proc remove*(self: Network, peer: Peer) =
+  self.peers.excl(peer)
+
+proc send*(self: Network, message: Message,
+  linkDelay: Option[uint64] = none(uint64)): AwaitableHandle =
+
+  let delay = linkDelay.get(self.defaultLinkDelay)
+
+  self.engine.awaitableSchedule(
+    ScheduledMessage(
+      time: self.engine.current_time + delay,
+      message: message
+    )
+  )
+
+method atScheduledTime*(self: ScheduledMessage, engine: EventDrivenEngine) =
+  self.message.receiver.deliver(self.message)
+
+export Network
+export peer
+export eventdrivenengine
+export options
+export sets
diff --git a/swarmsim/engine/peer.nim b/swarmsim/engine/peer.nim
new file mode 100644
index 0000000..35c2ba6
--- /dev/null
+++ b/swarmsim/engine/peer.nim
@@ -0,0 +1,46 @@
+import std/tables
+import std/options
+import std/random
+
+import ./types
+import ./protocol
+
+## TODO a "readonly" pragma could probably be my first macro
+proc `peerId=`*(self: Peer, id: int): void {.error: "Cannot assign to `peerId` property of `Peer`.".}
+
+proc `protocols=`*(self: Peer, value: Table[string, Protocol]): void {.error: "Cannot assign to `protocols` property of `Peer`.".}
+
+proc `protocols`*(self: Peer): Table[string, Protocol] {.error: "Cannot read from `protocols` property of `Peer`.".}
+
+proc getProtocol*(self: Peer, protocolId: string): Option[Protocol] =
+  if self.protocols.hasKey(protocolId):
+    return self.protocols[protocolId].some
+
+  none(Protocol)
+
+proc deliver*(self: Peer, message: Message): void =
+  self.getProtocol(message.messageType).map(
+    proc (p: Protocol): void = p.deliver(message))
+
+proc initPeer(self: Peer, protocols: seq[Protocol]): Peer =
+  # XXX integer indexes or an enum would be better, but this is easier
+  for protocol in protocols:
+    self.protocols[protocol.messageType] = protocol
+
+  self
+
+proc hash*(self: Peer): int = self.peerId
+
+proc new*(
+  T: type Peer,
+  protocols: seq[Protocol],
+  peerId: Option[int] = none(int)
+): Peer =
+  # XXX I can't have put this in the init proc as that would mean allowing public
+  #   write access to every field in Peer. Not sure how to solve this in nim.
+  let peerId = peerId.get(rand(high(int)))
+  initPeer(Peer(protocols: initTable[string, Protocol](), peerId: peerId), protocols)
+
+export Peer
+export options
+export tables
diff --git a/swarmsim/engine/protocol.nim b/swarmsim/engine/protocol.nim
new file mode 100644
index 0000000..825309e
--- /dev/null
+++ b/swarmsim/engine/protocol.nim
@@ -0,0 +1,10 @@
+import ./types
+
+method uncheckedDeliver(self: Protocol, message: Message): void {.base.} =
+  raise newException(CatchableError, "Method without implementation override")
+
+proc deliver*(self: Protocol, message: Message): void =
+  assert(self.messageType == message.messageType)
+  self.uncheckedDeliver(message)
+
+export Protocol
diff --git a/swarmsim/schedulableevent.nim b/swarmsim/engine/schedulableevent.nim
similarity index 71%
rename from swarmsim/schedulableevent.nim
rename to swarmsim/engine/schedulableevent.nim
index c1fc844..739e659 100644
--- a/swarmsim/schedulableevent.nim
+++ b/swarmsim/engine/schedulableevent.nim
@@ -1,8 +1,10 @@
-import pkg/swarmsim/types
+import ./types
 
 func `<`*(self: SchedulableEvent, other: SchedulableEvent): bool =
   return self.time < other.time
 
+proc `time=`*(self: SchedulableEvent, value: float): void {.error: "Cannot assign to `time` property of `SchedulableEvent`.".}
+
 method atScheduledTime*(self: SchedulableEvent, engine: EventDrivenEngine): void {.base.} =
   ## Callback invoked by the event engine indicating that this event is due for execution. By
   ## default, it does nothing.
diff --git a/swarmsim/engine/types.nim b/swarmsim/engine/types.nim
new file mode 100644
index 0000000..6fc3466
--- /dev/null
+++ b/swarmsim/engine/types.nim
@@ -0,0 +1,49 @@
+import std/heapqueue
+import std/tables
+import std/sets
+import std/options
+
+type
+  SchedulableEvent* = ref object of RootObj
+    ## A `SchedulableEvent` is an event that can be scheduled for execution in an `EventDrivenEngine`
+    ## at a well-defined point in simuliation time.
+    ##
+    time*: uint64
+
+type
+  EventDrivenEngine* = ref object of RootObj
+    ## An `EventDrivenEngine` is a simple simulation engine that executes events in the order of their
+    ## scheduled time.
+    ##
+    current_time*: uint64
+    queue*: HeapQueue[SchedulableEvent]
+
+type
+  Protocol* = ref object of RootObj
+    ## A `Protocol` defines a P2P protocol. It handles messages meant for it, keeps internal state,
+    ## and may expose services to other `Protocol`s within the same `Peer`.
+    messageType*: string ## "Type" of the message accepted by this protocol.
+
+type
+  Peer* = ref object of RootObj
+    peerId*: int
+    protocols*: Table[string, Protocol]
+
+type
+  Message* = ref object of RootObj
+    ## A `Message` is a piece of data that is sent over the network. Its meaning is typically
+    ## protocol-specific.
+    messageType*: string
+    sender*: Option[Peer]
+    receiver*: Peer
+
+type
+  Network* = ref object of RootObj
+    ## A `Network` is a collection of `Peer`s that can communicate with each other.
+    ##
+    engine*: EventDrivenEngine
+    defaultLinkDelay*: uint64
+    peers*: HashSet[Peer] # TODO: use an array
+
+export heapqueue
+export option
diff --git a/swarmsim/eventdrivenengine.nim b/swarmsim/eventdrivenengine.nim
deleted file mode 100644
index 07c912e..0000000
--- a/swarmsim/eventdrivenengine.nim
+++ /dev/null
@@ -1,31 +0,0 @@
-import std/options
-
-import pkg/swarmsim/types
-import pkg/swarmsim/schedulableevent
-
-proc current_time*(self: EventDrivenEngine): uint64 {.inline.} = self.current_time
-
-proc schedule*(self: EventDrivenEngine, schedulable: SchedulableEvent): EventDrivenEngine =
-  self.queue.push(schedulable)
-  self
-
-proc scheduleAll*[T: SchedulableEvent](self: EventDrivenEngine, schedulables: seq[T]): void =
-  for schedulable in schedulables:
-    discard self.schedule(schedulable)
-
-proc nextStep*(self: EventDrivenEngine): Option[SchedulableEvent] =
-  if len(self.queue) == 0:
-    return none(SchedulableEvent)
-
-  let schedulable = self.queue.pop()
-  self.current_time = schedulable.time
-  schedulable.atScheduledTime(engine = self)
-
-  some(schedulable)
-
-proc run*(self: EventDrivenEngine): void =
-  while self.nextStep().isSome:
-    discard
-
-export EventDrivenEngine
-export options
diff --git a/swarmsim/types.nim b/swarmsim/types.nim
deleted file mode 100644
index 1db5e2c..0000000
--- a/swarmsim/types.nim
+++ /dev/null
@@ -1,15 +0,0 @@
-import std/heapqueue
-
-type
-  SchedulableEvent* = ref object of RootObj
-    ## A `SchedulableEvent` is an event that can be scheduled for execution in an `EventDrivenEngine`
-    ## at a well-defined point in simuliation time.
-    ##
-    time*: uint64
-
-type
-  EventDrivenEngine* = ref object of RootObj
-    current_time*: uint64
-    queue*: HeapQueue[SchedulableEvent]
-
-export heapqueue
diff --git a/tests/all_tests.nim b/tests/all_tests.nim
index e5a8080..4e79ee0 100644
--- a/tests/all_tests.nim
+++ b/tests/all_tests.nim
@@ -1 +1,7 @@
-import ./swarmsim/eventdrivenengine
\ No newline at end of file
+import ./swarmsim/engine/eventdrivenengine
+import ./swarmsim/engine/schedulableevent
+import ./swarmsim/engine/network
+import ./swarmsim/engine/peer
+
+{.warning[UnusedImport]: off.}
+
diff --git a/tests/swarmsim/engine/eventdrivenengine.nim b/tests/swarmsim/engine/eventdrivenengine.nim
new file mode 100644
index 0000000..1021eac
--- /dev/null
+++ b/tests/swarmsim/engine/eventdrivenengine.nim
@@ -0,0 +1,58 @@
+import unittest
+import sequtils
+import sugar
+
+import std/algorithm
+import std/tables
+
+import pkg/swarmsim/engine/schedulableevent
+import pkg/swarmsim/engine/eventdrivenengine
+
+suite "event driven engine tests":
+
+  test "should run schedulables at the right time":
+
+    let times = @[1, 10, 5].map(time => uint64(time))
+    let schedulables = times.map(time => SchedulableEvent(time: time))
+
+    let engine = EventDrivenEngine()
+
+    engine.scheduleAll(schedulables)
+
+    for time in times.sorted:
+      let result = engine.nextStep().get()
+      check(result.time == engine.current_time)
+
+    check(engine.nextStep().isNone)
+
+  test "should allow clients to wait until a scheduled event happens":
+    let times = @[1, 2, 3, 4, 5, 6, 7, 8]
+    let schedulables = times.map(time => SchedulableEvent(time: uint64(time)))
+
+    let engine = EventDrivenEngine()
+    let handles = schedulables.map(schedulable => engine.awaitableSchedule(schedulable))
+
+    check(engine.current_time == 0)
+
+    handles[4].doAwait()
+    check(engine.current_time == 5)
+
+    handles[7].doAwait()
+    check(engine.current_time == 8)
+
+
+  test "should not allow schedulables to be scheduled in the past":
+    let e1 = SchedulableEvent(time: 10)
+    let e2 = SchedulableEvent(time: 8)
+
+    let engine = EventDrivenEngine()
+    engine.schedule(e1)
+    discard engine.nextStep()
+
+    expect(Defect):
+      engine.schedule(e2)
+
+
+
+
+
diff --git a/tests/swarmsim/engine/network.nim b/tests/swarmsim/engine/network.nim
new file mode 100644
index 0000000..e9814e0
--- /dev/null
+++ b/tests/swarmsim/engine/network.nim
@@ -0,0 +1,53 @@
+import unittest
+
+import pkg/swarmsim/engine/eventdrivenengine
+import pkg/swarmsim/engine/network
+import pkg/swarmsim/engine/peer
+import pkg/swarmsim/engine/message
+import pkg/swarmsim/engine/protocol
+
+type
+  FakeProtocol = ref object of Protocol
+    received: bool
+
+method uncheckedDeliver(self: FakeProtocol, message: Message) =
+  self.received = true
+
+proc getFakeProtocol(peer: Peer, protocolId: string): FakeProtocol =
+  let protocol = peer.getProtocol(protocolId)
+  check(protocol.isSome)
+  return FakeProtocol(protocol.get())
+
+suite "network":
+  test "should dispatch message to the correct protocol within a peer":
+    let engine = EventDrivenEngine()
+
+    var protocols: seq[Protocol] = newSeq[Protocol]()
+
+    protocols.add(FakeProtocol(messageType: "protocol1", received: false))
+    protocols.add(FakeProtocol(messageType: "protocol2", received: false))
+
+    let peer = Peer.new(protocols = protocols)
+    let network = Network.new(engine = engine, defaultLinkDelay = 20)
+
+    network.add(peer)
+
+    let m1 = Message.new(receiver = peer, messageType = "protocol1")
+    let m2 = Message.new(receiver = peer, messageType = "protocol2")
+
+    let message2handle = network.send(m2, linkDelay = uint64(10).some)
+    let message1handle = network.send(m1, linkDelay = uint64(5).some)
+
+    check(not peer.getFakeProtocol("protocol1").received)
+    check(not peer.getFakeProtocol("protocol2").received)
+
+    message1Handle.doAwait()
+
+    check(peer.getFakeProtocol("protocol1").received)
+    check(not peer.getFakeProtocol("protocol2").received)
+
+    message2Handle.doAwait()
+
+    check(peer.getFakeProtocol("protocol1").received)
+    check(peer.getFakeProtocol("protocol2").received)
+
diff --git a/tests/swarmsim/engine/peer.nim b/tests/swarmsim/engine/peer.nim
new file mode 100644
index 0000000..73f76da
--- /dev/null
+++ b/tests/swarmsim/engine/peer.nim
@@ -0,0 +1,20 @@
+import std/unittest
+import std/sets
+
+import pkg/swarmsim/engine/peer
+
+suite "peer":
+  test "should allow inclusion and membership tests on a HashSet":
+    var peerSet = HashSet[Peer]()
+
+    let p1 = Peer.new(protocols = @[], peerId = 1.some)
+    let p2 = Peer.new(protocols = @[], peerId = 2.some)
+
+    peerSet.incl(p1)
+
+    check(peerSet.contains(p1))
+    check(not peerSet.contains(p2))
+
+    peerSet.excl(p1)
+
+    check(not peerSet.contains(p1))
diff --git a/tests/swarmsim/engine/schedulableevent.nim b/tests/swarmsim/engine/schedulableevent.nim
new file mode 100644
index 0000000..5bfd762
--- /dev/null
+++ b/tests/swarmsim/engine/schedulableevent.nim
@@ -0,0 +1,11 @@
+import unittest
+
+import pkg/swarmsim/engine/schedulableevent
+
+suite "schedulable event":
+  test "should be ordered by time":
+    let e1 = SchedulableEvent(time: 1)
+    let e2 = SchedulableEvent(time: 3)
+
+    check(e1 < e2)
+    check(not (e2 < e1))
diff --git a/tests/swarmsim/eventdrivenengine.nim b/tests/swarmsim/eventdrivenengine.nim
deleted file mode 100644
index 1f809a2..0000000
--- a/tests/swarmsim/eventdrivenengine.nim
+++ /dev/null
@@ -1,25 +0,0 @@
-import unittest
-import sequtils
-import sugar
-
-import std/algorithm
-
-import pkg/swarmsim/schedulableevent
-import pkg/swarmsim/eventdrivenengine
-
-suite "event driven engine tests":
-
-  test "should run schedulables at the right time":
-
-    let times = @[1, 10, 5].map(time => uint64(time))
-    let schedulables = times.map(time => SchedulableEvent(time: time))
-
-    let engine = EventDrivenEngine()
-
-    engine.scheduleAll(schedulables)
-
-    for time in times.sorted:
-      let result = engine.nextStep().get()
-      check(result.time == engine.current_time)
-
-    check(engine.nextStep().isNone)