OPENFLOW-1.1+

   1                 OpenFlow 1.1+ support in Open vSwitch
   2                 =====================================
   3
   4 Open vSwitch support for OpenFlow 1.1, 1.2, and 1.3 is a work in
   5 progress.  This file describes the work still to be done.
   6
   7 The Plan
   8 --------
   9
  10 OpenFlow version support is not a build-time option.  A single build
  11 of Open vSwitch must be able to handle all supported versions of
  12 OpenFlow.  Ideally, even at runtime it should be able to support all
  13 protocol versions at the same time on different OpenFlow bridges (and
  14 perhaps even on the same bridge).
  15
  16 At the same time, it would be a shame to litter the core of the OVS
  17 code with lots of ugly code concerned with the details of various
  18 OpenFlow protocol versions.
  19
  20 The primary approach to compatibility is to abstract most of the
  21 details of the differences from the core code, by adding a protocol
  22 layer that translates between OF1.x and a slightly higher-level
  23 abstract representation.  The core of this approach is the many struct
  24 ofputil_* structures in lib/ofp-util.h.
  25
  26 As a consequence of this approach, OVS cannot use OpenFlow protocol
  27 definitions that closely resemble those in the OpenFlow specification,
  28 because openflow.h in different versions of the OpenFlow specification
  29 defines the same identifier with different values.  Instead,
  30 openflow-common.h contains definitions that are common to all the
  31 specifications and separate protocol version-specific headers contain
  32 protocol-specific definitions renamed so as not to conflict,
  33 e.g. OFPAT10_ENQUEUE and OFPAT11_ENQUEUE for the OpenFlow 1.0 and 1.1
  34 values for OFPAT_ENQUEUE.  Generally, in cases of conflict, the
  35 protocol layer will define a more abstract OFPUTIL_* or struct
  36 ofputil_*.
  37
  38 Here are the current approaches in a few tricky areas:
  39
  40     * Port numbering.  OpenFlow 1.0 has 16-bit port numbers and later
  41       OpenFlow versions have 32-bit port numbers.  For now, OVS
  42       support for later protocol versions requires all port numbers to
  43       fall into the 16-bit range, translating the reserved OFPP_* port
  44       numbers.
  45
  46     * Actions.  OpenFlow 1.0 and later versions have very different
  47       ideas of actions.  OVS reconciles by translating all the
  48       versions' actions (and instructions) to and from a common
  49       internal representation.
  50
  51 OpenFlow 1.1
  52 ------------
  53
  54 The list of remaining work items for OpenFlow 1.1 is below.  It is
  55 probably incomplete.
  56
  57     * Implement Write-Actions instruction.
  58
  59     * The new in_phy_port field in OFPT_PACKET_IN needs some kind of
  60       implementation.  It has a sensible interpretation for tunnels
  61       but in general the physical port is not in the datapath for OVS
  62       so the value is not necessarily meaningful.  We might have to
  63       just fix it as the same as in_port.
  64
  65     * On OF1.1+ flow_mods, updates by MODIFY are now much better
  66       specified.  Check that OVS implements the new behavior, fix it
  67       if not.
  68
  69     * OFPT_TABLE_MOD stats.  This is new in OF1.1, so we need to
  70       implement it.  It should be implemented so that the default OVS
  71       behavior does not change.
  72
  73     * MPLS.  Simon Horman maintains a patch series that adds this
  74       feature.  This is partially merged.
  75
  76     * SCTP.  Joe Stringer maintains a patch series that adds this
  77       feature.  It has received review comments that need to be
  78       addressed before it is merged.
  79
  80     * Match and set double-tagged VLANs (QinQ).  This requires kernel
  81       work for reasonable performance.
  82
  83     * VLANs tagged with 88a8 Ethertype.  This requires kernel work for
  84       reasonable performance.
  85
  86     * Groups.
  87
  88 OpenFlow 1.2
  89 ------------
  90
  91 OpenFlow 1.2 support requires OpenFlow 1.1 as a prerequisite, plus the
  92 following additional work.  (This is based on the change log at the
  93 end of the OF1.2 spec.  I didn't compare the specs carefully yet.)
  94
  95     * OFPT_FLOW_MOD:
  96
  97         * MODIFY and MODIFY_STRICT commands now never insert new flows
  98           in the table.  We will still need variations that do,
  99           though, both to support older OpenFlow protocols and to get
 100           sensible behavior for the internal implementation of the
 101           NXAST_LEARN action.
 102
 103         * New flag OFPFF_RESET_COUNTS.
 104
 105         * New cookie field behavior.
 106
 107         * Add ability to delete flow in all tables.
 108
 109         * Update DESIGN to describe OF1.2 behavior also.
 110
 111 OpenFlow 1.3
 112 ------------
 113
 114 OpenFlow 1.3 support requires OpenFlow 1.2 as a prerequisite, plus the
 115 following additional work.  (This is based on the change log at the
 116 end of the OF1.3 spec, reusing most of the section titles directly.  I
 117 didn't compare the specs carefully yet.)
 118
 119     * Add support for multipart requests.
 120
 121     * Add OFPMP_TABLE_FEATURES statistics.
 122
 123     * More flexible table miss support.
 124
 125     * IPv6 extension header handling support.  Fully implementing this
 126       requires kernel support.  This likely will take some careful and
 127       probably time-consuming design work.  The actual coding, once
 128       that is all done, is probably 2 or 3 days work.
 129
 130     * Per-flow meters.  Similar to IPv6 extension headers in kernel
 131       and design requirements.  Might be politically difficult to add
 132       directly to the kernel module, since its functionality overlaps
 133       with tc.  Ideally, therefore, we could implement these somehow
 134       with tc, but I haven't investigated whether that makes sense.
 135
 136     * Per-connection event filtering.  OF1.3 adopted Open vSwitch's
 137       existing design for this feature so implementation should be
 138       easy.
 139
 140     * Auxiliary connections.  These are optional, so a minimal
 141       implementation would not need them.  An implementation in
 142       generic code might be a week's worth of work.  The value of an
 143       implementation in generic code is questionable, though, since
 144       much of the benefit of axuiliary connections is supposed to be
 145       to take advantage of hardware support.  (We could make the
 146       kernel module somehow send packets across the auxiliary
 147       connections directly, for some kind of "hardware" support, if we
 148       judged it useful enough.)
 149
 150     * MPLS BoS matching.  (Included in Simon's MPLS series?)
 151
 152     * Provider Backbone Bridge tagging.  I don't plan to implement
 153       this (but we'd accept an implementation).
 154
 155     * Rework tag order.  I'm not sure whether we need to do anything
 156       for this.
 157
 158     * Duration for queue stats.  (Duration for port stats is already
 159       implemented.)
 160
 161     * On-demand flow counters.  I think this might be a real
 162       optimization in some cases for the software switch.
 163
 164 How to contribute
 165 -----------------
 166
 167 If you plan to contribute code for a feature, please let everyone know
 168 on ovs-dev before you start work.  This will help avoid duplicating
 169 work.
 170
 171 Please consider the following:
 172
 173     * Testing.  Please test your code.
 174
 175     * Unit tests.  Please consider writing some.  The tests directory
 176       has many examples that you can use as a starting point.
 177
 178     * ovs-ofctl.  If you add a feature that is useful for some
 179       ovs-ofctl command then you should add support for it there.
 180
 181     * Documentation.  If you add a user-visible feature, then you
 182       should document it in the appropriate manpage and mention it in
 183       NEWS as well.
 184
 185     * Coding style (see the CodingStyle file at the top of the source
 186       tree).
 187
 188     * The patch submission guidelines (see SubmittingPatches).  I
 189       recommend using "git send-email", which automatically follows a
 190       lot of those guidelines.
 191
 192 Bug Reporting
 193 -------------
 194
 195 Please report problems to bugs@openvswitch.org.