[ovs.git] / Documentation / faq / releases.rst

..
      Licensed under the Apache License, Version 2.0 (the "License"); you may
      not use this file except in compliance with the License. You may obtain
      a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
      License for the specific language governing permissions and limitations
      under the License.

      Convention for heading levels in Open vSwitch documentation:

      =======  Heading 0 (reserved for the title in a document)
      -------  Heading 1
      ~~~~~~~  Heading 2
      +++++++  Heading 3
      '''''''  Heading 4

      Avoid deeper levels because they do not render well.

========
Releases
========

Q: What does it mean for an Open vSwitch release to be LTS (long-term support)?

    A: All official releases have been through a comprehensive testing process
    and are suitable for production use.  Planned releases occur twice 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 2.5.x.

    For more information on the Open vSwitch release process, refer to
    :doc:`/internals/release-process`.

Q: What Linux kernel versions does each Open vSwitch release work with?

    A: The following table lists the Linux kernel versions against which the
    given versions of the Open vSwitch kernel module will successfully build.
    The Linux kernel versions are upstream kernel versions, so Linux kernels
    modified from the upstream sources may not build in some cases even if they
    are based on a supported version.  This is most notably true of Red Hat
    Enterprise Linux (RHEL) kernels, which are extensively modified from
    upstream.

    ============ ==============
    Open vSwitch Linux kernel
    ============ ==============
    1.4.x        2.6.18 to 3.2
    1.5.x        2.6.18 to 3.2
    1.6.x        2.6.18 to 3.2
    1.7.x        2.6.18 to 3.3
    1.8.x        2.6.18 to 3.4
    1.9.x        2.6.18 to 3.8
    1.10.x       2.6.18 to 3.8
    1.11.x       2.6.18 to 3.8
    2.0.x        2.6.32 to 3.10
    2.1.x        2.6.32 to 3.11
    2.3.x        2.6.32 to 3.14
    2.4.x        2.6.32 to 4.0
    2.5.x        2.6.32 to 4.3
    2.6.x        3.10 to 4.7
    2.7.x        3.10 to 4.9
    2.8.x        3.10 to 4.12
    2.9.x        3.10 to 4.13
    2.10.x       3.16 to 4.17
    2.11.x       3.16 to 4.18
    2.12.x       3.16 to 5.0
    2.14.x       3.16 to 5.5
    ============ ==============

    Open vSwitch userspace should also work with the Linux kernel module built
    into Linux 3.3 and later.

    Open vSwitch userspace is not sensitive to the Linux kernel version.  It
    should build against almost any kernel, certainly against 2.6.32 and later.

    Open vSwitch branches 2.10 through 2.14 will still compile against the
    RHEL and CentOS 7 3.10 based kernels since they have diverged from the
    Linux kernel.org 3.10 kernels.

Q: Are all features available with all datapaths?

    A: Open vSwitch supports different datapaths on different platforms.  Each
    datapath has a different feature set: the following tables try to summarize
    the status.

    Supported datapaths:

    Linux upstream
      The datapath implemented by the kernel module shipped with Linux
      upstream.  Since features have been gradually introduced into the kernel,
      the table mentions the first Linux release whose OVS module supports the
      feature.

    Linux OVS tree
      The datapath implemented by the Linux kernel module distributed with the
      OVS source tree.

    Userspace
      This datapath supports conventional system devices as well as
      DPDK and AF_XDP devices when support for those is built.  This
      is the only datapath that works on NetBSD, FreeBSD and Mac OSX.

    Hyper-V
      Also known as the Windows datapath.

    The following table lists the datapath supported features from an
    Open vSwitch user's perspective.  The "Linux upstream" column
    lists the Linux kernel version that introduced a given feature
    into its kernel module.  The "Linux OVS tree" and "Userspace"
    columns list the Open vSwitch release versions that introduced a
    given feature into the included kernel module or the userspace
    datapath, respectively.

    ========================== ============== ============== ========= =======
    Feature                    Linux upstream Linux OVS tree Userspace Hyper-V
    ========================== ============== ============== ========= =======
    Connection tracking             4.3            2.5          2.6      YES
    Conntrack Fragment Reass.       4.3            2.6          2.12     YES
    Conntrack Timeout Policies      5.2            2.12         2.14     NO
    Conntrack Zone Limit            4.18           2.10         2.13     YES
    Conntrack NAT                   4.6            2.6          2.8      YES
    Tunnel - LISP                   NO             2.11         NO       NO
    Tunnel - STT                    NO             2.4          NO       YES
    Tunnel - GRE                    3.11           1.0          2.4      YES
    Tunnel - VXLAN                  3.12           1.10         2.4      YES
    Tunnel - Geneve                 3.18           2.4          2.4      YES
    Tunnel - GRE-IPv6               4.18           2.6          2.6      NO
    Tunnel - VXLAN-IPv6             4.3            2.6          2.6      NO
    Tunnel - Geneve-IPv6            4.4            2.6          2.6      NO
    Tunnel - ERSPAN                 4.18           2.10         2.10     NO
    Tunnel - ERSPAN-IPv6            4.18           2.10         2.10     NO
    Tunnel - GTP-U                  NO             NO           2.14     NO
    QoS - Policing                  YES            1.1          2.6      NO
    QoS - Shaping                   YES            1.1          NO       NO
    sFlow                           YES            1.0          1.0      NO
    IPFIX                           3.10           1.11         1.11     YES
    Set action                      YES            1.0          1.0    PARTIAL
    NIC Bonding                     YES            1.0          1.0      YES
    Multiple VTEPs                  YES            1.10         1.10     YES
    Meter action                    4.15           2.10         2.7      NO
    check_pkt_len action            5.2            2.12         2.12     NO
    ========================== ============== ============== ========= =======

    Do note, however:

    * Only a limited set of flow fields is modifiable via the set action by the
      Hyper-V datapath.

    * Userspace datapath support, in some cases, is dependent on the associated
      interface types.  For example, DPDK interfaces support ingress and egress
      policing, but not shaping.

    The following table lists features that do not *directly* impact an Open
    vSwitch user, e.g. because their absence can be hidden by the ofproto layer
    (usually this comes with a performance penalty).

    ===================== ============== ============== ========= =======
    Feature               Linux upstream Linux OVS tree Userspace Hyper-V
    ===================== ============== ============== ========= =======
    SCTP flows            3.12           YES            YES       YES
    MPLS                  3.19           YES            YES       YES
    UFID                  4.0            YES            YES       NO
    Megaflows             3.12           YES            YES       NO
    Masked set action     4.0            YES            YES       NO
    Recirculation         3.19           YES            YES       YES
    TCP flags matching    3.13           YES            YES       NO
    Validate flow actions YES            YES            N/A       NO
    Multiple datapaths    YES            YES            YES       NO
    Tunnel TSO - STT      N/A            YES            NO        YES
    ===================== ============== ============== ========= =======

Q: What DPDK version does each Open vSwitch release work with?

    A: The following table lists the DPDK version against which the given
    versions of Open vSwitch will successfully build.

    ============ =======
    Open vSwitch DPDK
    ============ =======
    2.2.x        1.6
    2.3.x        1.6
    2.4.x        2.0
    2.5.x        2.2
    2.6.x        16.07.2
    2.7.x        16.11.9
    2.8.x        17.05.2
    2.9.x        17.11.4
    2.10.x       17.11.4
    2.11.x       18.11.6
    2.12.x       18.11.6
    2.13.x       19.11.0
    ============ =======

Q: Are all the DPDK releases that OVS versions work with maintained?

    No. DPDK follows YY.MM.n (Year.Month.Number) versioning.

    Typically, all DPDK releases get a stable YY.MM.1 update with bugfixes 3
    months after the YY.MM.0 release. In some cases there may also be a
    YY.MM.2 release.

    DPDK LTS releases start once a year at YY.11.0 and are maintained for
    two years, with YY.MM.n+1 releases around every 3 months.

    The latest information about DPDK stable and LTS releases can be found
    at `DPDK stable`_.

.. _DPDK stable: http://dpdk.org/doc/guides/contributing/stable.html

Q: I get an error like this when I configure Open vSwitch:

        configure: error: Linux kernel in <dir> is version <x>, but
        version newer than <y> is not supported (please refer to the
        FAQ for advice)

    What should I do?

    A: You have the following options:

    - Use the Linux kernel module supplied with the kernel that you are using.
      (See also the following FAQ.)

    - If there is a newer released version of Open vSwitch, consider building
      that one, because it may support the kernel that you are building
      against.  (To find out, consult the table in the previous FAQ.)

    - The Open vSwitch "master" branch may support the kernel that you are
      using, so consider building the kernel module from "master".

    All versions of Open vSwitch userspace are compatible with all versions of
    the Open vSwitch kernel module, so you do not have to use the kernel module
    from one source along with the userspace programs from the same source.

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 does not include support for LISP.
    Work is in progress to add support for LISP to the upstream Linux version
    of the Open vSwitch kernel module. For now, if you need this feature, use
    the kernel module from the Open vSwitch distribution instead of the
    upstream Linux kernel module.

    Certain features require kernel support to function or to have reasonable
    performance. If the ovs-vswitchd log file indicates that a feature is not
    supported, consider upgrading to a newer upstream Linux release or using
    the kernel module paired with the userspace distribution.

Q: Why do tunnels not work when using a kernel module other than the one
packaged with Open vSwitch?

    A: Support for tunnels was added to the upstream Linux kernel module after
    the rest of Open vSwitch. As a result, some kernels may contain support for
    Open vSwitch but not tunnels. The minimum kernel version that supports each
    tunnel protocol is:

    ======== ============
    Protocol Linux Kernel
    ======== ============
    GRE      3.11
    VXLAN    3.12
    Geneve   3.18
    ERSPAN   4.18
    LISP     not upstream
    STT      not upstream
    ======== ============

    If you are using a version of the kernel that is older than the one listed
    above, it is still possible to use that tunnel protocol. However, you must
    compile and install the kernel module included with the Open vSwitch
    distribution rather than the one on your machine. If problems persist after
    doing this, check to make sure that the module that is loaded is the one
    you expect.

Q: Why are UDP tunnel checksums not computed for VXLAN or Geneve?

    A: Generating outer UDP checksums requires kernel support that was not part
    of the initial implementation of these protocols. If using the upstream
    Linux Open vSwitch module, you must use kernel 4.0 or newer. The
    out-of-tree modules from Open vSwitch release 2.4 and later support UDP
    checksums.

Q: What features are not available when using the userspace datapath?

    A: Tunnel 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.

Q: Should userspace or kernel be upgraded first to minimize downtime?

    A. In general, the Open vSwitch userspace should be used with the kernel
    version included in the same release or with the version from upstream
    Linux.  However, when upgrading between two releases of Open vSwitch it is
    best to migrate userspace first to reduce the possibility of
    incompatibilities.

Q: What happened to the bridge compatibility feature?

    A: Bridge compatibility was a feature of Open vSwitch 1.9 and earlier.
    When it was enabled, Open vSwitch imitated the interface of the Linux
    kernel "bridge" module.  This allowed users to drop Open vSwitch into
    environments designed to use the Linux kernel bridge module without
    adapting the environment to use Open vSwitch.

    Open vSwitch 1.10 and later do not support bridge compatibility.  The
    feature was dropped because version 1.10 adopted a new internal
    architecture that made bridge compatibility difficult to maintain.  Now
    that many environments use OVS directly, it would be rarely useful in any
    case.

    To use bridge compatibility, install OVS 1.9 or earlier, including the
    accompanying kernel modules (both the main and bridge compatibility
    modules), following the instructions that come with the release.  Be sure
    to start the ovs-brcompatd daemon.
Commit	Line	Data
11e02906 SF	1	..
	2	Licensed under the Apache License, Version 2.0 (the "License"); you may
	3	not use this file except in compliance with the License. You may obtain
	4	a copy of the License at
	5
	6	http://www.apache.org/licenses/LICENSE-2.0
	7
	8	Unless required by applicable law or agreed to in writing, software
	9	distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	10	WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	11	License for the specific language governing permissions and limitations
	12	under the License.
	13
	14	Convention for heading levels in Open vSwitch documentation:
	15
	16	======= Heading 0 (reserved for the title in a document)
	17	------- Heading 1
	18	~~~~~~~ Heading 2
	19	+++++++ Heading 3
	20	''''''' Heading 4
	21
	22	Avoid deeper levels because they do not render well.
	23
	24	========
	25	Releases
	26	========
	27
	28	Q: What does it mean for an Open vSwitch release to be LTS (long-term support)?
	29
	30	A: All official releases have been through a comprehensive testing process
	31	and are suitable for production use. Planned releases occur twice a year.
	32	If a significant bug is identified in an LTS release, we will provide an
	33	updated release that includes the fix. Releases that are not LTS may not
	34	be fixed and may just be supplanted by the next major release. The current
	35	LTS release is 2.5.x.
	36
5813d810 SF	37	For more information on the Open vSwitch release process, refer to
5813d810 SF	38	:doc:`/internals/release-process`.
11e02906 SF	39
	40	Q: What Linux kernel versions does each Open vSwitch release work with?
	41
	42	A: The following table lists the Linux kernel versions against which the
	43	given versions of the Open vSwitch kernel module will successfully build.
	44	The Linux kernel versions are upstream kernel versions, so Linux kernels
	45	modified from the upstream sources may not build in some cases even if they
	46	are based on a supported version. This is most notably true of Red Hat
	47	Enterprise Linux (RHEL) kernels, which are extensively modified from
	48	upstream.
	49
	50	============ ==============
	51	Open vSwitch Linux kernel
	52	============ ==============
	53	1.4.x 2.6.18 to 3.2
	54	1.5.x 2.6.18 to 3.2
	55	1.6.x 2.6.18 to 3.2
	56	1.7.x 2.6.18 to 3.3
	57	1.8.x 2.6.18 to 3.4
	58	1.9.x 2.6.18 to 3.8
	59	1.10.x 2.6.18 to 3.8
	60	1.11.x 2.6.18 to 3.8
	61	2.0.x 2.6.32 to 3.10
	62	2.1.x 2.6.32 to 3.11
	63	2.3.x 2.6.32 to 3.14
	64	2.4.x 2.6.32 to 4.0
	65	2.5.x 2.6.32 to 4.3
	66	2.6.x 3.10 to 4.7
27b5fbb2	67	2.7.x 3.10 to 4.9
49705e1b	68	2.8.x 3.10 to 4.12
4a67e420	69	2.9.x 3.10 to 4.13
dff2a6e9 GR	70	2.10.x 3.16 to 4.17
	71	2.11.x 3.16 to 4.18
	72	2.12.x 3.16 to 5.0
	73	2.14.x 3.16 to 5.5
11e02906 SF	74	============ ==============
	75
	76	Open vSwitch userspace should also work with the Linux kernel module built
	77	into Linux 3.3 and later.
	78
	79	Open vSwitch userspace is not sensitive to the Linux kernel version. It
	80	should build against almost any kernel, certainly against 2.6.32 and later.
	81
dff2a6e9 GR	82	Open vSwitch branches 2.10 through 2.14 will still compile against the
	83	RHEL and CentOS 7 3.10 based kernels since they have diverged from the
	84	Linux kernel.org 3.10 kernels.
	85
11e02906 SF	86	Q: Are all features available with all datapaths?
	87
	88	A: Open vSwitch supports different datapaths on different platforms. Each
	89	datapath has a different feature set: the following tables try to summarize
	90	the status.
	91
	92	Supported datapaths:
	93
	94	Linux upstream
	95	The datapath implemented by the kernel module shipped with Linux
	96	upstream. Since features have been gradually introduced into the kernel,
	97	the table mentions the first Linux release whose OVS module supports the
	98	feature.
	99
	100	Linux OVS tree
	101	The datapath implemented by the Linux kernel module distributed with the
	102	OVS source tree.
	103
	104	Userspace
653eedff BP	105	This datapath supports conventional system devices as well as
	106	DPDK and AF_XDP devices when support for those is built. This
	107	is the only datapath that works on NetBSD, FreeBSD and Mac OSX.
11e02906 SF	108
	109	Hyper-V
	110	Also known as the Windows datapath.
	111
653eedff BP	112	The following table lists the datapath supported features from an
	113	Open vSwitch user's perspective. The "Linux upstream" column
	114	lists the Linux kernel version that introduced a given feature
	115	into its kernel module. The "Linux OVS tree" and "Userspace"
	116	columns list the Open vSwitch release versions that introduced a
	117	given feature into the included kernel module or the userspace
	118	datapath, respectively.
11e02906	119
4ea96698 DB	120	========================== ============== ============== ========= =======
	121	Feature Linux upstream Linux OVS tree Userspace Hyper-V
	122	========================== ============== ============== ========= =======
653eedff	123	Connection tracking 4.3 2.5 2.6 YES
5623ed2d	124	Conntrack Fragment Reass. 4.3 2.6 2.12 YES
2078901a	125	Conntrack Timeout Policies 5.2 2.12 2.14 NO
a7f33fdb	126	Conntrack Zone Limit 4.18 2.10 2.13 YES
13ede8c1	127	Conntrack NAT 4.6 2.6 2.8 YES
653eedff BP	128	Tunnel - LISP NO 2.11 NO NO
	129	Tunnel - STT NO 2.4 NO YES
	130	Tunnel - GRE 3.11 1.0 2.4 YES
	131	Tunnel - VXLAN 3.12 1.10 2.4 YES
	132	Tunnel - Geneve 3.18 2.4 2.4 YES
	133	Tunnel - GRE-IPv6 4.18 2.6 2.6 NO
	134	Tunnel - VXLAN-IPv6 4.3 2.6 2.6 NO
	135	Tunnel - Geneve-IPv6 4.4 2.6 2.6 NO
	136	Tunnel - ERSPAN 4.18 2.10 2.10 NO
	137	Tunnel - ERSPAN-IPv6 4.18 2.10 2.10 NO
8c2b63b7	138	Tunnel - GTP-U NO NO 2.14 NO
653eedff BP	139	QoS - Policing YES 1.1 2.6 NO
	140	QoS - Shaping YES 1.1 NO NO
	141	sFlow YES 1.0 1.0 NO
	142	IPFIX 3.10 1.11 1.11 YES
	143	Set action YES 1.0 1.0 PARTIAL
	144	NIC Bonding YES 1.0 1.0 YES
	145	Multiple VTEPs YES 1.10 1.10 YES
13ede8c1	146	Meter action 4.15 2.10 2.7 NO
cbff5189	147	check_pkt_len action 5.2 2.12 2.12 NO
4ea96698	148	========================== ============== ============== ========= =======
11e02906 SF	149
	150	Do note, however:
	151
	152	* Only a limited set of flow fields is modifiable via the set action by the
	153	Hyper-V datapath.
11e02906	154
b50268e8 DB	155	* Userspace datapath support, in some cases, is dependent on the associated
	156	interface types. For example, DPDK interfaces support ingress and egress
	157	policing, but not shaping.
	158
11e02906 SF	159	The following table lists features that do not directly impact an Open
	160	vSwitch user, e.g. because their absence can be hidden by the ofproto layer
	161	(usually this comes with a performance penalty).
	162
	163	===================== ============== ============== ========= =======
	164	Feature Linux upstream Linux OVS tree Userspace Hyper-V
	165	===================== ============== ============== ========= =======
	166	SCTP flows 3.12 YES YES YES
	167	MPLS 3.19 YES YES YES
	168	UFID 4.0 YES YES NO
	169	Megaflows 3.12 YES YES NO
	170	Masked set action 4.0 YES YES NO
	171	Recirculation 3.19 YES YES YES
	172	TCP flags matching 3.13 YES YES NO
	173	Validate flow actions YES YES N/A NO
	174	Multiple datapaths YES YES YES NO
	175	Tunnel TSO - STT N/A YES NO YES
	176	===================== ============== ============== ========= =======
	177
	178	Q: What DPDK version does each Open vSwitch release work with?
	179
	180	A: The following table lists the DPDK version against which the given
	181	versions of Open vSwitch will successfully build.
	182
489b23fe	183	============ =======
11e02906	184	Open vSwitch DPDK
489b23fe	185	============ =======
11e02906 SF	186	2.2.x 1.6
	187	2.3.x 1.6
	188	2.4.x 2.0
	189	2.5.x 2.2
489b23fe	190	2.6.x 16.07.2
b5355b0d	191	2.7.x 16.11.9
dad35c4f	192	2.8.x 17.05.2
bafb398b IS	193	2.9.x 17.11.4
bafb398b IS	194	2.10.x 17.11.4
486139d9 TK	195	2.11.x 18.11.6
	196	2.12.x 18.11.6
	197	2.13.x 19.11.0
489b23fe	198	============ =======
11e02906	199
6b71df2f KT	200	Q: Are all the DPDK releases that OVS versions work with maintained?
	201
	202	No. DPDK follows YY.MM.n (Year.Month.Number) versioning.
	203
	204	Typically, all DPDK releases get a stable YY.MM.1 update with bugfixes 3
	205	months after the YY.MM.0 release. In some cases there may also be a
	206	YY.MM.2 release.
	207
	208	DPDK LTS releases start once a year at YY.11.0 and are maintained for
	209	two years, with YY.MM.n+1 releases around every 3 months.
	210
	211	The latest information about DPDK stable and LTS releases can be found
	212	at `DPDK stable`_.
	213
	214	.. _DPDK stable: http://dpdk.org/doc/guides/contributing/stable.html
	215
8f60b9bb	216	Q: I get an error like this when I configure Open vSwitch:
11e02906	217
8f60b9bb SF	218	configure: error: Linux kernel in <dir> is version <x>, but
	219	version newer than <y> is not supported (please refer to the
	220	FAQ for advice)
11e02906	221
8f60b9bb	222	What should I do?
11e02906 SF	223
	224	A: You have the following options:
	225
	226	- Use the Linux kernel module supplied with the kernel that you are using.
	227	(See also the following FAQ.)
	228
	229	- If there is a newer released version of Open vSwitch, consider building
	230	that one, because it may support the kernel that you are building
	231	against. (To find out, consult the table in the previous FAQ.)
	232
	233	- The Open vSwitch "master" branch may support the kernel that you are
	234	using, so consider building the kernel module from "master".
	235
	236	All versions of Open vSwitch userspace are compatible with all versions of
	237	the Open vSwitch kernel module, so you do not have to use the kernel module
	238	from one source along with the userspace programs from the same source.
	239
	240	Q: What features are not available in the Open vSwitch kernel datapath that
	241	ships as part of the upstream Linux kernel?
	242
	243	A: The kernel module in upstream Linux does not include support for LISP.
	244	Work is in progress to add support for LISP to the upstream Linux version
	245	of the Open vSwitch kernel module. For now, if you need this feature, use
	246	the kernel module from the Open vSwitch distribution instead of the
	247	upstream Linux kernel module.
	248
	249	Certain features require kernel support to function or to have reasonable
	250	performance. If the ovs-vswitchd log file indicates that a feature is not
	251	supported, consider upgrading to a newer upstream Linux release or using
	252	the kernel module paired with the userspace distribution.
	253
	254	Q: Why do tunnels not work when using a kernel module other than the one
	255	packaged with Open vSwitch?
	256
	257	A: Support for tunnels was added to the upstream Linux kernel module after
	258	the rest of Open vSwitch. As a result, some kernels may contain support for
	259	Open vSwitch but not tunnels. The minimum kernel version that supports each
	260	tunnel protocol is:
	261
	262	======== ============
	263	Protocol Linux Kernel
	264	======== ============
	265	GRE 3.11
	266	VXLAN 3.12
	267	Geneve 3.18
da5b26ad	268	ERSPAN 4.18
11e02906 SF	269	LISP not upstream
	270	STT not upstream
	271	======== ============
	272
	273	If you are using a version of the kernel that is older than the one listed
	274	above, it is still possible to use that tunnel protocol. However, you must
	275	compile and install the kernel module included with the Open vSwitch
	276	distribution rather than the one on your machine. If problems persist after
	277	doing this, check to make sure that the module that is loaded is the one
	278	you expect.
	279
	280	Q: Why are UDP tunnel checksums not computed for VXLAN or Geneve?
	281
	282	A: Generating outer UDP checksums requires kernel support that was not part
	283	of the initial implementation of these protocols. If using the upstream
	284	Linux Open vSwitch module, you must use kernel 4.0 or newer. The
	285	out-of-tree modules from Open vSwitch release 2.4 and later support UDP
	286	checksums.
	287
	288	Q: What features are not available when using the userspace datapath?
	289
	290	A: Tunnel virtual ports are not supported, as described in the previous
	291	answer. It is also not possible to use queue-related actions. On Linux
	292	kernels before 2.6.39, maximum-sized VLAN packets may not be transmitted.
	293
	294	Q: Should userspace or kernel be upgraded first to minimize downtime?
	295
	296	A. In general, the Open vSwitch userspace should be used with the kernel
	297	version included in the same release or with the version from upstream
	298	Linux. However, when upgrading between two releases of Open vSwitch it is
	299	best to migrate userspace first to reduce the possibility of
	300	incompatibilities.
	301
	302	Q: What happened to the bridge compatibility feature?
	303
	304	A: Bridge compatibility was a feature of Open vSwitch 1.9 and earlier.
	305	When it was enabled, Open vSwitch imitated the interface of the Linux
	306	kernel "bridge" module. This allowed users to drop Open vSwitch into
	307	environments designed to use the Linux kernel bridge module without
	308	adapting the environment to use Open vSwitch.
	309
	310	Open vSwitch 1.10 and later do not support bridge compatibility. The
	311	feature was dropped because version 1.10 adopted a new internal
	312	architecture that made bridge compatibility difficult to maintain. Now
	313	that many environments use OVS directly, it would be rarely useful in any
	314	case.
	315
	316	To use bridge compatibility, install OVS 1.9 or earlier, including the
	317	accompanying kernel modules (both the main and bridge compatibility
	318	modules), following the instructions that come with the release. Be sure
	319	to start the ovs-brcompatd daemon.