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