FAQ: Add additional entries.

Does some cleanup and adds entries that cover:

    - OVS isn't Linux-specific.
    - Point out PORTING guide.
    - Explanation of LTS releases.
    - Supported versions of OpenFlow.
    - Missing features from userspace datapath and upstream kernel
      module.

Signed-off-by: Justin Pettit <jpettit@nicira.com>

diff --git a/FAQ b/FAQ
index 18ecc91..3cd1fa3 100644 (file)
--- a/FAQ
+++ b/FAQ
@@ -35,23 +35,42 @@ A: Open vSwitch can currently run on any Linux-based virtualization
 
 Q: How can I try Open vSwitch?
 
-A: Open vSwitch is as source code to be built on a Linux system.  You
-   can build and experiment with Open vSwitch on any Linux machine.
-   Packages for various Linux distributions are underway and will be linked
-   to from this website as they materialize.
+A: The Open vSwitch source code can be built on a Linux system.  You can
+   build and experiment with Open vSwitch on any Linux machine.
+   Packages for various Linux distributions are available on many
+   platforms, including: Debian, Ubuntu, Fedora.
 
    You may also download and run a virtualization platform that already
-   has Open vSwitch integrated.  For example, download the ISO for Xen
-   Cloud Platform.  Be aware that the version integrated with a
-   particular platform may not be the most recent Open vSwitch release.
+   has Open vSwitch integrated.  For example, download a recent ISO for
+   XenServer or Xen Cloud Platform.  Be aware that the version
+   integrated with a particular platform may not be the most recent Open
+   vSwitch release.
+
+Q: Does Open vSwitch only work on Linux?
+
+A: No, Open vSwitch has been ported to a number of different operating
+   systems and hardware platforms.  Most of the development work occurs
+   on Linux, but the code should be portable to any POSIX system.  We've
+   seen Open vSwitch ported to a number of different platforms,
+   including FreeBSD, Windows, and even non-POSIX embedded systems.
+
+   By definition, the Open vSwitch Linux kernel module only works on
+   Linux and will provide the highest performance.  However, a userspace
+   datapath is available that should be very portable.
+
+Q: What's involved with porting Open vSwitch to a new platform or
+   switching ASIC?
+
+A: The PORTING document describes how one would go about porting Open
+   vSwitch to a new operating system or hardware platform.
 
 Q: Why would I use Open vSwitch instead of the Linux bridge?
 
 A: Open vSwitch is specially designed to make it easier to manage VM
-   network configuration and monitoring state spread across many
-   physical hosts in dynamic virtualized environments.  Please see
-   WHY-OVS for a more detailed description of how Open vSwitch relates
-   to the Linux Bridge.
+   network configuration and monitor state spread across many physical
+   hosts in dynamic virtualized environments.  Please see WHY-OVS for a
+   more detailed description of how Open vSwitch relates to the Linux
+   Bridge.
 
 Q: How is Open vSwitch related to distributed virtual switches like the
    VMware vNetwork distributed switch or the Cisco Nexus 1000V?
@@ -84,24 +103,65 @@ A: Open vSwitch is intended to be a useful component for building
    support all as a primitive building block rather than choose a
    particular point in the distributed design space.
 
-Q: What does it mean for an Open vSwitch release to be "stable"?
-
-A: A stable Open vSwitch release is code that has been through a
-   comprehensive testing process and is suitable for production use.
-   Planned stable releases will occur several times a year.  If a
-   significant bug is identified in a stable release, we will provide an
-   updated stable release that includes the fix.  Developers looking to
-   test the latest Open vSwitch code can use an "unstable" release or
-   directly access the code via git.
-
 Q: How can I contribute to the Open vSwitch Community?
 
 A: You can start by joining the mailing lists and helping to answer
-   questions.  You can also suggest improvements to documentation or offer
-   to write a configuration cookbook entry.
+   questions.  You can also suggest improvements to documentation.  If
+   you have a feature or bug you would like to work on, send a mail to
+   one of the mailing lists:
+
+       http://openvswitch.org/mlists/
+
+
+
+Releases
+--------
+
+Q: What does it mean for an Open vSwitch release to be LTS (long-term
+   support)?
 
-   If you have a feature or bug you would like to work on send a mail to
-   dev mailing list.
+A: All official releases have been through a comprehensive testing
+   process and are suitable for production use.  Planned releases will
+   occur several times a year.  If a significant bug is identified in an
+   LTS release, we will provide an updated release that includes the
+   fix.  Releases that are not LTS may not be fixed and may just be
+   supplanted by the next major release.  The current LTS release is
+   1.4.x.
+
+Q: What features are not available in the Open vSwitch kernel datapath
+   that ships as part of the upstream Linux kernel?
+
+A: The kernel module in upstream Linux 3.3 and later does not include
+   the following features:
+
+       - Bridge compatibility, that is, support for the ovs-brcompatd
+         daemon that (if you enable it) lets "brctl" and other Linux
+         bridge tools transparently work with Open vSwitch instead.
+
+         We do not expect bridge compatibility to ever be available in
+         upstream Linux.  If you need bridge compatibility, use the
+         kernel module from the Open vSwitch distribution instead of the
+         upstream Linux kernel module.
+
+       - Tunnel and patch virtual ports, that is, interfaces with type
+         "gre", "ipsec_gre", "capwap", or "patch".  It is possible to
+         create tunnels in Linux and attach them to Open vSwitch as
+         system devices.  However, they cannot be dynamically created
+         through the OVSDB protocol or set the tunnel ids as a flow
+         action.
+
+         Work is in progress in adding these features to the upstream
+         Linux version of the Open vSwitch kernel module.  For now, if
+         you need these features, use the kernel module from the Open
+         vSwitch distribution instead of the upstream Linux kernel
+         module.
+
+Q: What features are not available when using the userspace datapath?
+
+A: Tunnel and patch virtual ports are not supported, as described in the
+   previous answer.  It is also not possible to use queue-related
+   actions.  On Linux kernels before 2.6.39, maximum-sized VLAN packets
+   may not be transmitted.
 
 
 Configuration Problems
@@ -251,7 +311,7 @@ A: Many drivers in Linux kernels before version 3.3 had VLAN-related
          that works around bugs in kernel drivers.  To enable VLAN
          splinters on interface eth0, use the command:
 
-             ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true
+           ovs-vsctl set interface eth0 other-config:enable-vlan-splinters=true
 
          For VLAN splinters to be effective, Open vSwitch must know
          which VLANs are in use.  See the "VLAN splinters" section in
@@ -344,6 +404,15 @@ A: The configuration for VLANs in the Open vSwitch database (e.g. via
 Controllers
 -----------
 
+Q: What versions of OpenFlow does Open vSwitch support?
+
+A: Open vSwitch supports OpenFlow 1.0.  It also includes a number of
+   extensions that bring many of the features from later versions of
+   OpenFlow.  Work is underway to provide support for later versions and
+   can be tracked here:
+
+       http://openvswitch.org/development/openflow-1-x-plan/
+
 Q: I'm getting "error type 45250 code 0".  What's that?
 
 A: This is a Open vSwitch extension to OpenFlow error codes.  Open
@@ -416,6 +485,7 @@ Q: My OpenFlow controller doesn't see the VLANs that I expect.
 
 A: See answer under "VLANs", above.
 
+
 Contact 
 -------