--- /dev/null
+ Using Open vSwitch as a Simple OpenFlow Switch
+ ==============================================
+
+Open vSwitch uses OpenFlow as its preferred method of remote flow table
+configuration. Running ovs-vswitchd(8) with the bridge.<name>.controller
+set of parameters as described in ovs-vswitchd.conf(5) will cause it to
+connect to the specified controller using OpenFlow. We recommend using
+OpenFlow in this manner, however, it is also possible to use Open vSwitch
+as a simple OpenFlow switch like that provided by the OpenFlow reference
+implementation [1].
+
+What is OpenFlow?
+-----------------
+
+OpenFlow is a flow-based switch specification designed to enable
+researchers to run experiments in live networks. OpenFlow is based on a
+simple Ethernet flow switch that exposes a standardized interface for
+adding and removing flow entries.
+
+An OpenFlow switch consists of three parts: (1) A "flow table" in
+which each flow entry is associated with an action telling the switch
+how to process the flow, (2) a "secure channel" that connects the switch
+to a remote process (a controller), allowing commands and packets to
+be sent between the controller and the switch, and (3) an OpenFlow
+protocol implementation, providing an open and standard way for a
+controller to talk to the switch.
+
+An OpenFlow switch can thus serve as a simple datapath element that
+forwards packets between ports according to flow actions defined by
+the controller using OpenFlow commands. Example actions are:
+
+ - Forward this flow's packets to the given port(s)
+ - Drop this flow's packets
+ - Encapsulate and forward this flow's packets to the controller.
+
+The OpenFlow switch is defined in detail in the OpenFlow switch
+Specification [2].
+
+Installation Procedure
+----------------------
+
+The procedure below explains how to use the Open vSwitch as a simple
+OpenFlow switch.
+
+1. Build and install the Open vSwitch kernel modules and userspace
+ programs as described in INSTALL.Linux.
+
+ It is important to run "make install", because some Open vSwitch
+ programs expect to find files in locations selected at installation
+ time.
+
+2. Load the openvswitch kernel module (which was built in step 1), e.g.:
+
+ % insmod datapath/linux-2.6/openvswitch_mod.ko
+
+ This kernel module cannot be loaded if the Linux bridge module is
+ already loaded. Thus, you may need to remove any existing bridges
+ and unload the bridge module with "rmmod bridge" before you can do
+ this.
+
+3. Create a datapath instance. The command below creates a datapath
+ identified as dp0 (see ovs-dpctl(8) for more detailed usage
+ information).
+
+ # ovs-dpctl add-dp dp0
+
+ Creating datapath dp0 creates a new network device, also named dp0.
+ This network device, called the datapath's "local port", will be
+ bridged to the physical switch ports by ovs-openflowd(8), for use in
+ in-band control.
+
+4. Use ovs-dpctl to attach the datapath to physical interfaces on the
+ machine. Say, for example, you want to create a trivial 2-port
+ switch using interfaces eth1 and eth2, you would issue the following
+ commands:
+
+ # ovs-dpctl add-if dp0 eth1
+ # ovs-dpctl add-if dp0 eth2
+
+ You can verify that the interfaces were successfully added by asking
+ ovs-dpctl to print the current status of datapath dp0:
+
+ # ovs-dpctl show dp0
+
+5. Arrange so that the switch can reach the controller over the
+ network.
+
+ - If you are using out-of-band control, at this point make sure
+ that the switch machine can reach the controller over the
+ network.
+
+ - If you are using in-band control, then at this point you must
+ configure the dp0 network device created in step 3. This
+ device is not yet bridged to any physical network (because
+ ovs-openflowd does that, and it is not yet running), so the next
+ step depends on whether connectivity is required to configure
+ the device's IP address:
+
+ * If the switch has a static IP address, you may configure
+ its IP address now, e.g.:
+
+ # ifconfig dp0 192.168.1.1
+
+ * If the switch does not have a static IP address, e.g. its
+ IP address is obtained dynamically via DHCP, then proceed
+ to step 4. The DHCP client will not be able to contact
+ the DHCP server until the secure channel has started up.
+
+ - If you are using in-band control with controller discovery, no
+ configuration is required at this point. You may proceed to
+ step 4.
+
+6. Run ovs-openflowd to start the secure channel connecting the datapath to
+ a remote controller. If the controller is running on host
+ 192.168.1.2 port 6633 (the default port), the ovs-openflowd invocation
+ would look like this:
+
+ # ovs-openflowd dp0 tcp:192.168.1.2
+
+ - If you are using in-band control with controller discovery, omit
+ the second argument to the ovs-openflowd command.
+
+ - If you are using out-of-band control, add --out-of-band to the
+ command line.
+
+ Using the "tcp:<controller_ip>" argument causes the switch to connect
+ in an insecure manner. Please see INSTALL.SSL for a description of
+ how to connect securely using SSL.
+
+7. If you are using in-band control with manual configuration, and the
+ switch obtains its IP address dynamically, then you may now obtain
+ the switch's IP address, e.g. by invoking a DHCP client. The
+ secure channel will only be able to connect to the controller after
+ an IP address has been obtained.
+
+8. The secure channel should connect to the controller within a few
+ seconds. It may take a little longer if controller discovery is in
+ use, because the switch must then also obtain its own IP address
+ and the controller's location via DHCP.
+
+References
+----------
+
+ [1] OpenFlow Reference Implementation.
+ <http://www.openflowswitch.org/wp/downloads/>
+
+ [2] OpenFlow Switch Specification.
+ <http://openflowswitch.org/documents/openflow-spec-latest.pdf>
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