diff --git a/IPython/frontend/html/notebook/handlers.py b/IPython/frontend/html/notebook/handlers.py
index b6cb9f7..ab680c4 100644
--- a/IPython/frontend/html/notebook/handlers.py
+++ b/IPython/frontend/html/notebook/handlers.py
@@ -13,7 +13,7 @@ from tornado import websocket
 
 
 #-----------------------------------------------------------------------------
-# Handlers
+# Top-level handlers
 #-----------------------------------------------------------------------------
 
 
@@ -38,25 +38,45 @@ class NamedNotebookHandler(web.RequestHandler):
         self.render('notebook.html', notebook_id=notebook_id)
 
 
-class KernelHandler(web.RequestHandler):
+#-----------------------------------------------------------------------------
+# Kernel handlers
+#-----------------------------------------------------------------------------
+
+
+class MainKernelHandler(web.RequestHandler):
 
     def get(self):
-        self.finish(json.dumps(self.application.kernel_ids))
+        rkm = self.application.routing_kernel_manager
+        self.finish(json.dumps(rkm.kernel_ids))
 
     def post(self):
-        kernel_id = self.application.start_kernel()
+        rkm = self.application.routing_kernel_manager
+        notebook_id = self.get_argument('notebook', default=None)
+        kernel_id = rkm.start_kernel(notebook_id)
         self.set_header('Location', '/'+kernel_id)
         self.finish(json.dumps(kernel_id))
 
 
+class KernelHandler(web.RequestHandler):
+
+    SUPPORTED_METHODS = ('DELETE')
+
+    def delete(self, kernel_id):
+        rkm = self.application.routing_kernel_manager
+        self.kill_kernel(kernel_id)
+        self.set_status(204)
+        self.finish()
+
+
 class KernelActionHandler(web.RequestHandler):
 
     def post(self, kernel_id, action):
-        # TODO: figure out a better way of handling RPC style calls.
+        rkm = self.application.routing_kernel_manager
         if action == 'interrupt':
-            self.application.interrupt_kernel(kernel_id)
+            rkm.interrupt_kernel(kernel_id)
+            self.set_status(204)
         if action == 'restart':
-            new_kernel_id = self.application.restart_kernel(kernel_id)
+            new_kernel_id = rkm.restart_kernel(kernel_id)
             self.write(json.dumps(new_kernel_id))
         self.finish()
 
@@ -67,7 +87,8 @@ class ZMQStreamHandler(websocket.WebSocketHandler):
         self.stream_name = stream_name
 
     def open(self, kernel_id):
-        self.router = self.application.get_router(kernel_id, self.stream_name)
+        rkm = self.application.routing_kernel_manager
+        self.router = rkm.get_router(kernel_id, self.stream_name)
         self.client_id = self.router.register_client(self)
         logging.info("Connection open: %s, %s" % (kernel_id, self.client_id))
 
@@ -79,6 +100,10 @@ class ZMQStreamHandler(websocket.WebSocketHandler):
         logging.info("Connection closed: %s" % self.client_id)
 
 
+#-----------------------------------------------------------------------------
+# Notebook web service handlers
+#-----------------------------------------------------------------------------
+
 class NotebookRootHandler(web.RequestHandler):
 
     def get(self):
diff --git a/IPython/frontend/html/notebook/kernelmanager.py b/IPython/frontend/html/notebook/kernelmanager.py
index 9a1fe37..f5b2ecd 100644
--- a/IPython/frontend/html/notebook/kernelmanager.py
+++ b/IPython/frontend/html/notebook/kernelmanager.py
@@ -17,9 +17,13 @@ import uuid
 
 import zmq
 
+from tornado import web
+
+from .routers import IOPubStreamRouter, ShellStreamRouter
+
 from IPython.config.configurable import LoggingConfigurable
 from IPython.zmq.ipkernel import launch_kernel
-from IPython.utils.traitlets import Instance, Dict
+from IPython.utils.traitlets import Instance, Dict, List, Unicode
 
 #-----------------------------------------------------------------------------
 # Classes
@@ -55,7 +59,7 @@ class KernelManager(LoggingConfigurable):
 
     def start_kernel(self, **kwargs):
         """Start a new kernel."""
-        kernel_id = str(uuid.uuid4())
+        kernel_id = unicode(uuid.uuid4())
         (process, shell_port, iopub_port, stdin_port, hb_port) = launch_kernel(**kwargs)
         # Store the information for contacting the kernel. This assumes the kernel is
         # running on localhost.
@@ -186,3 +190,117 @@ class KernelManager(LoggingConfigurable):
             config=self.config, context=self.context, log=self.log
         )
 
+
+class RoutingKernelManager(LoggingConfigurable):
+    """A KernelManager that handles WebSocket routing and HTTP error handling"""
+
+    kernel_argv = List(Unicode)
+    kernel_manager = Instance(KernelManager)
+
+    _routers = Dict()
+    _session_dict = Dict()
+    _notebook_mapping = Dict()
+
+    #-------------------------------------------------------------------------
+    # Methods for managing kernels and sessions
+    #-------------------------------------------------------------------------
+
+    @property
+    def kernel_ids(self):
+        return self.kernel_manager.kernel_ids
+
+    def notebook_for_kernel(self, kernel_id):
+        notebook_ids = [k for k, v in self._notebook_mapping.iteritems() if v == kernel_id]
+        if len(notebook_ids) == 1:
+            return notebook_ids[0]
+        else:
+            return None
+
+    def delete_mapping_for_kernel(self, kernel_id):
+        notebook_id = self.notebook_for_kernel(kernel_id)
+        if notebook_id is not None:
+            del self._notebook_mapping[notebook_id]
+
+    def start_kernel(self, notebook_id=None):
+        self.log.info
+        kernel_id = self._notebook_mapping.get(notebook_id)
+        if kernel_id is None:
+            kwargs = dict()
+            kwargs['extra_arguments'] = self.kernel_argv
+            kernel_id = self.kernel_manager.start_kernel(**kwargs)
+            if notebook_id is not None:
+                self._notebook_mapping[notebook_id] = kernel_id
+            self.log.info("Kernel started for notebook %s: %s" % (notebook_id,kernel_id))
+            self.log.debug("Kernel args: %r" % kwargs)
+            self.start_session_manager(kernel_id)
+        else:
+            self.log.info("Using existing kernel: %s" % kernel_id)
+        return kernel_id
+
+    def start_session_manager(self, kernel_id):
+        sm = self.kernel_manager.create_session_manager(kernel_id)
+        self._session_dict[kernel_id] = sm
+        iopub_stream = sm.get_iopub_stream()
+        shell_stream = sm.get_shell_stream()
+        iopub_router = IOPubStreamRouter(
+            zmq_stream=iopub_stream, session=sm.session, config=self.config
+        )
+        shell_router = ShellStreamRouter(
+            zmq_stream=shell_stream, session=sm.session, config=self.config
+        )
+        self._routers[(kernel_id, 'iopub')] = iopub_router
+        self._routers[(kernel_id, 'shell')] = shell_router
+
+    def kill_kernel(self, kernel_id):
+        if kernel_id not in self.kernel_manager:
+            raise web.HTTPError(404)
+        try:
+            sm = self._session_dict.pop(kernel_id)
+        except KeyError:
+            raise web.HTTPError(404)
+        sm.stop()
+        self.kernel_manager.kill_kernel(kernel_id)
+        self.delete_mapping_for_kernel(kernel_id)
+        self.log.info("Kernel killed: %s" % kernel_id)
+
+    def interrupt_kernel(self, kernel_id):
+        if kernel_id not in self.kernel_manager:
+            raise web.HTTPError(404)
+        self.kernel_manager.interrupt_kernel(kernel_id)
+        self.log.debug("Kernel interrupted: %s" % kernel_id)
+
+    def restart_kernel(self, kernel_id):
+        if kernel_id not in self.kernel_manager:
+            raise web.HTTPError(404)
+
+        # Get the notebook_id to preserve the kernel/notebook association
+        notebook_id = self.notebook_for_kernel(kernel_id)
+        # Create the new kernel first so we can move the clients over.
+        new_kernel_id = self.start_kernel()
+
+        # Copy the clients over to the new routers.
+        old_iopub_router = self.get_router(kernel_id, 'iopub')
+        old_shell_router = self.get_router(kernel_id, 'shell')
+        new_iopub_router = self.get_router(new_kernel_id, 'iopub')
+        new_shell_router = self.get_router(new_kernel_id, 'shell')
+        new_iopub_router.copy_clients(old_iopub_router)
+        new_shell_router.copy_clients(old_shell_router)
+
+        # Now shutdown the old session and the kernel.
+        # TODO: This causes a hard crash in ZMQStream.close, which sets
+        # self.socket to None to hastily. We will need to fix this in PyZMQ
+        # itself. For now, we just leave the old kernel running :(
+        # Maybe this is fixed now, but nothing was changed really.
+        self.kill_kernel(kernel_id)
+
+        # Now save the new kernel/notebook association. We have to save it
+        # after the old kernel is killed as that will delete the mapping.
+        self._notebook_mapping[notebook_id] = kernel_id
+
+        self.log.debug("Kernel restarted: %s -> %s" % (kernel_id, new_kernel_id))
+        return new_kernel_id
+
+    def get_router(self, kernel_id, stream_name):
+        router = self._routers[(kernel_id, stream_name)]
+        return router
+
diff --git a/IPython/frontend/html/notebook/notebookapp.py b/IPython/frontend/html/notebook/notebookapp.py
index a8314bb..4b59303 100644
--- a/IPython/frontend/html/notebook/notebookapp.py
+++ b/IPython/frontend/html/notebook/notebookapp.py
@@ -27,14 +27,13 @@ tornado.ioloop = ioloop
 from tornado import httpserver
 from tornado import web
 
-from .kernelmanager import KernelManager
+from .kernelmanager import KernelManager, RoutingKernelManager
 from .sessionmanager import SessionManager
 from .handlers import (
     NBBrowserHandler, NewHandler, NamedNotebookHandler,
-    KernelHandler, KernelActionHandler, ZMQStreamHandler,
+    MainKernelHandler, KernelHandler, KernelActionHandler, ZMQStreamHandler,
     NotebookRootHandler, NotebookHandler
 )
-from .routers import IOPubStreamRouter, ShellStreamRouter
 from .notebookmanager import NotebookManager
 
 from IPython.core.application import BaseIPythonApplication
@@ -65,12 +64,13 @@ LOCALHOST = '127.0.0.1'
 
 class NotebookWebApplication(web.Application):
 
-    def __init__(self, kernel_manager, log, kernel_argv, config):
+    def __init__(self, routing_kernel_manager, notebook_manager, log):
         handlers = [
             (r"/", NBBrowserHandler),
             (r"/new", NewHandler),
             (r"/%s" % _notebook_id_regex, NamedNotebookHandler),
-            (r"/kernels", KernelHandler),
+            (r"/kernels", MainKernelHandler),
+            (r"/kernels/%s" % _kernel_id_regex, KernelHandler),
             (r"/kernels/%s/%s" % (_kernel_id_regex, _kernel_action_regex), KernelActionHandler),
             (r"/kernels/%s/iopub" % _kernel_id_regex, ZMQStreamHandler, dict(stream_name='iopub')),
             (r"/kernels/%s/shell" % _kernel_id_regex, ZMQStreamHandler, dict(stream_name='shell')),
@@ -83,82 +83,10 @@ class NotebookWebApplication(web.Application):
         )
         web.Application.__init__(self, handlers, **settings)
 
-        self.kernel_manager = kernel_manager
+        self.routing_kernel_manager = routing_kernel_manager
         self.log = log
-        self.kernel_argv = kernel_argv
-        self.config = config
-        self._routers = {}
-        self._session_dict = {}
-        self.notebook_manager = NotebookManager(config=self.config)
-
-    #-------------------------------------------------------------------------
-    # Methods for managing kernels and sessions
-    #-------------------------------------------------------------------------
-
-    @property
-    def kernel_ids(self):
-        return self.kernel_manager.kernel_ids
-
-    def start_kernel(self):
-        kwargs = dict()
-        kwargs['extra_arguments'] = self.kernel_argv
-        kernel_id = self.kernel_manager.start_kernel(**kwargs)
-        self.log.info("Kernel started: %s" % kernel_id)
-        self.log.debug("Kernel args: %r" % kwargs)
-        self.start_session_manager(kernel_id)
-        return kernel_id
-
-    def start_session_manager(self, kernel_id):
-        sm = self.kernel_manager.create_session_manager(kernel_id)
-        self._session_dict[kernel_id] = sm
-        iopub_stream = sm.get_iopub_stream()
-        shell_stream = sm.get_shell_stream()
-        iopub_router = IOPubStreamRouter(
-            zmq_stream=iopub_stream, session=sm.session, config=self.config
-        )
-        shell_router = ShellStreamRouter(
-            zmq_stream=shell_stream, session=sm.session, config=self.config
-        )
-        self._routers[(kernel_id, 'iopub')] = iopub_router
-        self._routers[(kernel_id, 'shell')] = shell_router
-
-    def kill_kernel(self, kernel_id):
-        sm = self._session_dict.pop(kernel_id)
-        sm.stop()
-        self.kernel_manager.kill_kernel(kernel_id)
-        self.log.info("Kernel killed: %s" % kernel_id)
-
-    def interrupt_kernel(self, kernel_id):
-        self.kernel_manager.interrupt_kernel(kernel_id)
-        self.log.debug("Kernel interrupted: %s" % kernel_id)
-
-    def restart_kernel(self, kernel_id):
-        # Create the new kernel first so we can move the clients over.
-        new_kernel_id = self.start_kernel()
-
-        # Copy the clients over to the new routers.
-        old_iopub_router = self.get_router(kernel_id, 'iopub')
-        old_shell_router = self.get_router(kernel_id, 'shell')
-        new_iopub_router = self.get_router(new_kernel_id, 'iopub')
-        new_shell_router = self.get_router(new_kernel_id, 'shell')
-        new_iopub_router.copy_clients(old_iopub_router)
-        new_shell_router.copy_clients(old_shell_router)
-
-        # Now shutdown the old session and the kernel.
-        # TODO: This causes a hard crash in ZMQStream.close, which sets
-        # self.socket to None to hastily. We will need to fix this in PyZMQ
-        # itself. For now, we just leave the old kernel running :(
-        # Maybe this is fixed now, but nothing was changed really.
-        self.kill_kernel(kernel_id)
-
-        self.log.debug("Kernel restarted: %s -> %s" % (kernel_id, new_kernel_id))
-        return new_kernel_id
-
-    def get_router(self, kernel_id, stream_name):
-        router = self._routers[(kernel_id, stream_name)]
-        return router
+        self.notebook_manager = notebook_manager
 
-    
 
 #-----------------------------------------------------------------------------
 # Aliases and Flags
@@ -196,6 +124,7 @@ class IPythonNotebookApp(BaseIPythonApplication):
     """
     
     classes = [IPKernelApp, ZMQInteractiveShell, ProfileDir, Session,
+               RoutingKernelManager, NotebookManager,
                KernelManager, SessionManager, RichIPythonWidget]
     flags = Dict(flags)
     aliases = Dict(aliases)
@@ -232,12 +161,16 @@ class IPythonNotebookApp(BaseIPythonApplication):
             if a.startswith('-') and a.lstrip('-') in notebook_flags:
                 self.kernel_argv.remove(a)
 
-    def init_kernel_manager(self):
+    def init_configurables(self):
         # Don't let Qt or ZMQ swallow KeyboardInterupts.
         signal.signal(signal.SIGINT, signal.SIG_DFL)
 
         # Create a KernelManager and start a kernel.
         self.kernel_manager = KernelManager(config=self.config, log=self.log)
+        self.routing_kernel_manager = RoutingKernelManager(config=self.config, log=self.log,
+            kernel_manager=self.kernel_manager, kernel_argv=self.kernel_argv
+        )
+        self.notebook_manager = NotebookManager(config=self.config, log=self.log)
 
     def init_logging(self):
         super(IPythonNotebookApp, self).init_logging()
@@ -248,9 +181,9 @@ class IPythonNotebookApp(BaseIPythonApplication):
 
     def initialize(self, argv=None):
         super(IPythonNotebookApp, self).initialize(argv)
-        self.init_kernel_manager()
+        self.init_configurables()
         self.web_app = NotebookWebApplication(
-            self.kernel_manager, self.log, self.kernel_argv, self.config
+            self.routing_kernel_manager, self.notebook_manager, self.log
         )
         self.http_server = httpserver.HTTPServer(self.web_app)
         self.http_server.listen(self.port)
diff --git a/IPython/frontend/html/notebook/notebookmanager.py b/IPython/frontend/html/notebook/notebookmanager.py
index d66d359..e8f8d10 100644
--- a/IPython/frontend/html/notebook/notebookmanager.py
+++ b/IPython/frontend/html/notebook/notebookmanager.py
@@ -15,7 +15,7 @@ import uuid
 
 from tornado import web
 
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import LoggingConfigurable
 from IPython.nbformat import current
 from IPython.utils.traitlets import Unicode, List, Dict
 
@@ -25,7 +25,7 @@ from IPython.utils.traitlets import Unicode, List, Dict
 #-----------------------------------------------------------------------------
 
 
-class NotebookManager(Configurable):
+class NotebookManager(LoggingConfigurable):
 
     notebook_dir = Unicode(os.getcwd())
     filename_ext = Unicode(u'.ipynb')
diff --git a/IPython/frontend/html/notebook/static/js/kernel.js b/IPython/frontend/html/notebook/static/js/kernel.js
index e7f9f9b..44a5a6d 100644
--- a/IPython/frontend/html/notebook/static/js/kernel.js
+++ b/IPython/frontend/html/notebook/static/js/kernel.js
@@ -28,9 +28,10 @@ var IPython = (function (IPython) {
         return msg;
     }
 
-    Kernel.prototype.start_kernel = function (callback) {
+    Kernel.prototype.start_kernel = function (notebook_id, callback) {
         var that = this;
-        $.post(this.base_url,
+        var qs = $.param({notebook:notebook_id});
+        $.post(this.base_url + '?' + qs,
             function (kernel_id) {
                 that._handle_start_kernel(kernel_id, callback);
             }, 
diff --git a/IPython/frontend/html/notebook/static/js/notebook.js b/IPython/frontend/html/notebook/static/js/notebook.js
index 2db0cec..999c85c 100644
--- a/IPython/frontend/html/notebook/static/js/notebook.js
+++ b/IPython/frontend/html/notebook/static/js/notebook.js
@@ -391,7 +391,8 @@ var IPython = (function (IPython) {
 
     Notebook.prototype.start_kernel = function () {
         this.kernel = new IPython.Kernel();
-        this.kernel.start_kernel($.proxy(this.kernel_started, this));
+        var notebook_id = IPython.save_widget.get_notebook_id();
+        this.kernel.start_kernel(notebook_id, $.proxy(this.kernel_started, this));
     };