diff --git a/IPython/parallel/client/client.py b/IPython/parallel/client/client.py
index bee991a..4f3acf7 100644
--- a/IPython/parallel/client/client.py
+++ b/IPython/parallel/client/client.py
@@ -370,7 +370,7 @@ class Client(HasTraits):
         self.session = Session(**extra_args)
         
         self._query_socket = self._context.socket(zmq.DEALER)
-        self._query_socket.setsockopt(zmq.IDENTITY, util.asbytes(self.session.session))
+        self._query_socket.setsockopt(zmq.IDENTITY, self.session.bsession)
         if self._ssh:
             tunnel.tunnel_connection(self._query_socket, url, sshserver, **ssh_kwargs)
         else:
@@ -496,7 +496,7 @@ class Client(HasTraits):
         content = msg.content
         self._config['registration'] = dict(content)
         if content.status == 'ok':
-            ident = util.asbytes(self.session.session)
+            ident = self.session.bsession
             if content.mux:
                 self._mux_socket = self._context.socket(zmq.DEALER)
                 self._mux_socket.setsockopt(zmq.IDENTITY, ident)
@@ -512,7 +512,7 @@ class Client(HasTraits):
                 self._notification_socket.setsockopt(zmq.SUBSCRIBE, b'')
             # if content.query:
             #     self._query_socket = self._context.socket(zmq.DEALER)
-            #     self._query_socket.setsockopt(zmq.IDENTITY, self.session.session)
+            #     self._query_socket.setsockopt(zmq.IDENTITY, self.session.bsession)
             #     connect_socket(self._query_socket, content.query)
             if content.control:
                 self._control_socket = self._context.socket(zmq.DEALER)
diff --git a/IPython/parallel/controller/hub.py b/IPython/parallel/controller/hub.py
index c3fe1c1..9dde8fb 100755
--- a/IPython/parallel/controller/hub.py
+++ b/IPython/parallel/controller/hub.py
@@ -288,7 +288,7 @@ class HubFactory(RegistrationFactory):
         # resubmit stream
         r = ZMQStream(ctx.socket(zmq.DEALER), loop)
         url = util.disambiguate_url(self.client_info['task'][-1])
-        r.setsockopt(zmq.IDENTITY, util.asbytes(self.session.session))
+        r.setsockopt(zmq.IDENTITY, self.session.bsession)
         r.connect(url)
 
         self.hub = Hub(loop=loop, session=self.session, monitor=sub, heartmonitor=self.heartmonitor,
diff --git a/IPython/parallel/controller/scheduler.py b/IPython/parallel/controller/scheduler.py
index b7f63eb..b063123 100644
--- a/IPython/parallel/controller/scheduler.py
+++ b/IPython/parallel/controller/scheduler.py
@@ -177,7 +177,7 @@ class TaskScheduler(SessionFactory):
     ident = CBytes() # ZMQ identity. This should just be self.session.session
                      # but ensure Bytes
     def _ident_default(self):
-        return asbytes(self.session.session)
+        return self.session.bsession
     
     def start(self):
         self.engine_stream.on_recv(self.dispatch_result, copy=False)
diff --git a/IPython/zmq/kernelmanager.py b/IPython/zmq/kernelmanager.py
index a688d41..841a1b9 100644
--- a/IPython/zmq/kernelmanager.py
+++ b/IPython/zmq/kernelmanager.py
@@ -188,7 +188,7 @@ class ShellSocketChannel(ZMQSocketChannel):
     def run(self):
         """The thread's main activity.  Call start() instead."""
         self.socket = self.context.socket(zmq.DEALER)
-        self.socket.setsockopt(zmq.IDENTITY, self.session.session.encode("ascii"))
+        self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.iostate = POLLERR|POLLIN
         self.ioloop.add_handler(self.socket, self._handle_events, 
@@ -395,7 +395,7 @@ class SubSocketChannel(ZMQSocketChannel):
         """The thread's main activity.  Call start() instead."""
         self.socket = self.context.socket(zmq.SUB)
         self.socket.setsockopt(zmq.SUBSCRIBE,b'')
-        self.socket.setsockopt(zmq.IDENTITY, self.session.session.encode("ascii"))
+        self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.iostate = POLLIN|POLLERR
         self.ioloop.add_handler(self.socket, self._handle_events, 
@@ -483,7 +483,7 @@ class StdInSocketChannel(ZMQSocketChannel):
     def run(self):
         """The thread's main activity.  Call start() instead."""
         self.socket = self.context.socket(zmq.DEALER)
-        self.socket.setsockopt(zmq.IDENTITY, self.session.session.encode("ascii"))
+        self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.iostate = POLLERR|POLLIN
         self.ioloop.add_handler(self.socket, self._handle_events, 
@@ -562,7 +562,7 @@ class HBSocketChannel(ZMQSocketChannel):
 
     def _create_socket(self):
         self.socket = self.context.socket(zmq.REQ)
-        self.socket.setsockopt(zmq.IDENTITY, self.session.session.encode("ascii"))
+        self.socket.setsockopt(zmq.IDENTITY, self.session.bsession)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.poller = zmq.Poller()
         self.poller.register(self.socket, zmq.POLLIN)
diff --git a/IPython/zmq/session.py b/IPython/zmq/session.py
index 55df686..4636f91 100644
--- a/IPython/zmq/session.py
+++ b/IPython/zmq/session.py
@@ -242,7 +242,15 @@ class Session(Configurable):
     session = CUnicode(u'', config=True,
         help="""The UUID identifying this session.""")
     def _session_default(self):
-        return unicode(uuid.uuid4())
+        u = unicode(uuid.uuid4())
+        self.bsession = u.encode('ascii')
+        return u
+    
+    def _session_changed(self, name, old, new):
+        self.bsession = self.session.encode('ascii')
+    
+    # bsession is the session as bytes
+    bsession = CBytes(b'')
     
     username = Unicode(os.environ.get('USER',u'username'), config=True,
         help="""Username for the Session. Default is your system username.""")
@@ -296,9 +304,11 @@ class Session(Configurable):
         pack/unpack : callables
             You can also set the pack/unpack callables for serialization
             directly.
-        session : bytes
+        session : unicode (must be ascii)
             the ID of this Session object.  The default is to generate a new 
             UUID.
+        bsession : bytes
+            The session as bytes
         username : unicode
             username added to message headers.  The default is to ask the OS.
         key : bytes
@@ -311,6 +321,8 @@ class Session(Configurable):
         super(Session, self).__init__(**kwargs)
         self._check_packers()
         self.none = self.pack({})
+        # ensure self._session_default() if necessary, so bsession is defined:
+        self.session
 
     @property
     def msg_id(self):
diff --git a/IPython/zmq/tests/test_session.py b/IPython/zmq/tests/test_session.py
index 42ac635..b2b522c 100644
--- a/IPython/zmq/tests/test_session.py
+++ b/IPython/zmq/tests/test_session.py
@@ -185,4 +185,26 @@ class TestSession(SessionTestCase):
         content = dict(code='whoda',stuff=object())
         themsg = self.session.msg('execute',content=content)
         pmsg = theids
+    
+    def test_session_id(self):
+        session = ss.Session()
+        # get bs before us
+        bs = session.bsession
+        us = session.session
+        self.assertEquals(us.encode('ascii'), bs)
+        session = ss.Session()
+        # get us before bs
+        us = session.session
+        bs = session.bsession
+        self.assertEquals(us.encode('ascii'), bs)
+        # change propagates:
+        session.session = 'something else'
+        bs = session.bsession
+        us = session.session
+        self.assertEquals(us.encode('ascii'), bs)
+        session = ss.Session(session='stuff')
+        # get us before bs
+        self.assertEquals(session.bsession, session.session.encode('ascii'))
+        self.assertEquals(b'stuff', session.bsession)
+