INSTALL.OpenFlow

   1             Using Open vSwitch as a Simple OpenFlow Switch
   2             ==============================================
   3
   4 Open vSwitch uses OpenFlow as its preferred method of remote flow
   5 table configuration.  This is the simplest method of using it with an
   6 OpenFlow controller.  The ovs-vsctl "set-controller" command can also
   7 be used in conjunction with ovs-vswitchd to set the controller for one
   8 or more bridges.  We recommend using OpenFlow in this manner and in this
   9 case you should not run ovs-openflowd.  Directions for setting up
  10 ovs-vswitchd can be found in INSTALL.Linux.
  11
  12 However, it is also possible to use Open vSwitch as a simple OpenFlow
  13 switch like that provided by the OpenFlow reference implementation
  14 [1].  The remainder of this file describes how to use it in that
  15 manner.
  16
  17 What is OpenFlow?
  18 -----------------
  19
  20 OpenFlow is a flow-based switch specification designed to enable
  21 researchers to run experiments in live networks.  OpenFlow is based on a
  22 simple Ethernet flow switch that exposes a standardized interface for
  23 adding and removing flow entries.
  24
  25 An OpenFlow switch consists of three parts: (1) A "flow table" in
  26 which each flow entry is associated with an action telling the switch
  27 how to process the flow, (2) a "secure channel" that connects the switch
  28 to a remote process (a controller), allowing commands and packets to
  29 be sent between the controller and the switch, and (3) an OpenFlow
  30 protocol implementation, providing an open and standard way for a
  31 controller to talk to the switch.
  32
  33 An OpenFlow switch can thus serve as a simple datapath element that
  34 forwards packets between ports according to flow actions defined by
  35 the controller using OpenFlow commands.  Example actions are:
  36
  37     - Forward this flow's packets to the given port(s)
  38     - Drop this flow's packets
  39     - Encapsulate and forward this flow's packets to the controller.
  40
  41 The OpenFlow switch is defined in detail in the OpenFlow switch
  42 Specification [2].
  43
  44 Installation Procedure
  45 ----------------------
  46
  47 The procedure below explains how to use the Open vSwitch as a simple
  48 OpenFlow switch.
  49
  50 1. Build and install the Open vSwitch kernel modules and userspace
  51    programs as described in INSTALL.Linux.
  52
  53    It is important to run "make install", because some Open vSwitch
  54    programs expect to find files in locations selected at installation
  55    time.
  56
  57 2. Load the openvswitch kernel module (which was built in step 1), e.g.:
  58
  59       % insmod datapath/linux-2.6/openvswitch_mod.ko
  60
  61    This kernel module cannot be loaded if the Linux bridge module is
  62    already loaded.  Thus, you may need to remove any existing bridges
  63    and unload the bridge module with "rmmod bridge" before you can do
  64    this.
  65
  66 3. Create a datapath instance.  The command below creates a datapath
  67    identified as dp0 (see ovs-dpctl(8) for more detailed usage
  68    information).
  69
  70       # ovs-dpctl add-dp dp0
  71
  72    Creating datapath dp0 creates a new network device, also named dp0.
  73    This network device, called the datapath's "local port", will be
  74    bridged to the physical switch ports by ovs-openflowd(8).  It is
  75    optionally used for in-band control as described in step 5.
  76
  77 4. Use ovs-dpctl to attach the datapath to physical interfaces on the
  78    machine.  Say, for example, you want to create a trivial 2-port
  79    switch using interfaces eth1 and eth2, you would issue the following
  80    commands:
  81
  82       # ovs-dpctl add-if dp0 eth1
  83       # ovs-dpctl add-if dp0 eth2
  84
  85    You can verify that the interfaces were successfully added by asking
  86    ovs-dpctl to print the current status of datapath dp0:
  87
  88       # ovs-dpctl show dp0
  89
  90 5. Arrange so that the switch can reach the controller over the network.
  91    This can be done in two ways.  The switch may be configured for
  92    out-of-band control, which means it uses a network separate from the
  93    data traffic that it controls.  Alternatively, the switch may be
  94    configured to contact the controller over one of the network devices
  95    under its control.  In-band control is often more convenient than
  96    out-of-band, because it is not necessary to maintain two independent
  97    networks.
  98
  99       - If you are using out-of-band control, at this point make sure
 100         that the switch machine can reach the controller over the
 101         network.
 102
 103       - If you are using in-band control, then at this point you must
 104         configure the dp0 network device created in step 3.  This
 105         device is not yet bridged to any physical network (because
 106         ovs-openflowd does that, and it is not yet running), so the next
 107         step depends on whether connectivity is required to configure
 108         the device's IP address:
 109
 110            * If the switch has a static IP address, you may configure
 111              its IP address now, e.g.:
 112
 113                 # ifconfig dp0 192.168.1.1
 114
 115            * If the switch does not have a static IP address, e.g. its
 116              IP address is obtained dynamically via DHCP, then proceed
 117              to the next step.  The DHCP client will not be able to
 118              contact the DHCP server until the secure channel has
 119              started.  The address will be obtained in step 7.
 120
 121       - If you are using in-band control with controller discovery, no
 122         configuration is required at this point.  You may proceed to
 123         the next step.
 124
 125 6. Run ovs-openflowd to start the secure channel connecting the datapath to
 126    a remote controller.  If the controller is running on host
 127    192.168.1.2 port 6633 (the default port), the ovs-openflowd invocation
 128    would look like this:
 129
 130       # ovs-openflowd dp0 tcp:192.168.1.2
 131
 132    - If you are using in-band control with controller discovery, omit
 133      the second argument to the ovs-openflowd command.
 134
 135    - If you are using out-of-band control, add --out-of-band to the
 136      command line.
 137
 138    Using the "tcp:<controller_ip>" argument causes the switch to connect
 139    in an insecure manner.  Please see INSTALL.SSL for a description of
 140    how to connect securely using SSL.
 141
 142 7. If you are using in-band control with manual configuration, and the
 143    switch obtains its IP address dynamically, then you may now obtain
 144    the switch's IP address, e.g. by invoking a DHCP client.  The
 145    secure channel will only be able to connect to the controller after
 146    an IP address has been obtained.
 147
 148 8. The secure channel should connect to the controller within a few
 149    seconds.  It may take a little longer if controller discovery is in
 150    use, because the switch must then also obtain its own IP address
 151    and the controller's location via DHCP.
 152
 153 References
 154 ----------
 155
 156     [1] OpenFlow Reference Implementation.
 157         <http://www.openflowswitch.org/wp/downloads/>
 158
 159     [2] OpenFlow Switch Specification.
 160         <http://openflowswitch.org/documents/openflow-spec-latest.pdf>