[spp] [PATCH 01/10] docs: add spp_mirror in overview section

[x-fn-spp@sl.ntt-tx.co.jp]

From: Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>

Add overview of spp_mirror beside spp_vf.

Signed-off-by: Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>
Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
---
 docs/guides/spp_vf/overview.rst | 71 +++++++++++++++++++++++++++++++++--------
 1 file changed, 58 insertions(+), 13 deletions(-)

diff --git a/docs/guides/spp_vf/overview.rst b/docs/guides/spp_vf/overview.rst
index 4773213..dd957d4 100644
--- a/docs/guides/spp_vf/overview.rst
+++ b/docs/guides/spp_vf/overview.rst
@@ -6,24 +6,44 @@
 Overview
 ========
 
-SPP_VF provides SR-IOV like network functionality using DPDK for NFV.
+This section describes an overview of SPP's extensions, ``spp_vf`` and
+``spp_mirror``.
+SPP provides a connectivity between DPDK processes as a virtual patch panel.
+However, It is not sufficient considering more practical usecases.
+For instance, you might need a classification for incoming packets if you have
+multiple processes as destinations. You might also need to duplicate packets
+for monitoring or inspection.
 
-PP_VF distributes incoming packets to VMs with referring to virtual
-MAC address like Virtual Function(VF) of SR-IOV.
-Virtual MAC address can be defined by commands from spp
-controller(``spp_vf.py``).
+``spp_vf`` is a SPP secondary process for forwarding packets to multiple
+destination ports with a MAC address classification. It is also supported to
+merge from several source ports to aggregate packets to a destination port.
 
-SPP_VF is multi-process and multi-thread applications. A SPP_VF process
-is referred to as ``spp_vf`` in this document. Each ``spp_vf`` has
-one manager thread and component threads. The manager thread provides
-function for command processing and creating the component threads.
-The component threads have its own multiple components, ports and
-classifier tables including Virtual MAC address.
+``spp_mirror`` is an another kind of secondary process to duplicate incoming
+packets. This feature is intended to use as a
+`TaaS
+<https://docs.openstack.org/dragonflow/latest/specs/tap_as_a_service.html>`_
+feature for port mirroring introduced in OpenStack.
 
 
+spp_vf
+------
+
+``spp_vf`` provides a SR-IOV like network feature.
+
+``spp_vf`` forwards incoming packets to several destination VMs by referring
+MAC address like as a Virtual Function (VF) of SR-IOV.
+
+``spp_vf`` is a  multi-process and multi-thread application.
+Each of ``spp_vf`` has one manager thread and worker threads called as
+components.
+The manager thread provides a function for parsing a command and creating the
+components.
+The component threads have its own multiple components, ports and classifier
+tables including Virtual MAC address.
+
 This is an example of network configuration, in which one
 ``classifier_mac``,
-one merger and four forwarders are running in SPP_VF process
+one merger and four forwarders are running in ``spp_vf`` process
 for two destinations of vhost interface.
 Incoming packets from rx on host1 are sent to each of vhosts of VM
 by looking up destination MAC address in the packet.
@@ -31,4 +51,29 @@ by looking up destination MAC address in the packet.
 .. figure:: ../images/spp_vf/spp_vf_overview.*
     :width: 70%
 
-    Overview of SPP VF
+    Overview of spp_vf
+
+
+SPP Mirror
+----------
+
+``spp_mirror`` is an implementation of
+`TaaS
+<https://docs.openstack.org/dragonflow/latest/specs/tap_as_a_service.html>`_
+as a SPP secondary process for port mirroring.
+TaaS stands for TAP as a Service.
+
+``spp_mirror`` consists of one manager thread and worker threads as similar to
+``spp_vf``, but just one worker role for mirroring.
+:numref:`figure_spp_mirror_overview` shows an overview of use of ``spp_mirror``
+in which ``spp_mirror`` process receives packets from ``ring:0`` in ``spp_vf``
+for duplicating the packets for monitoring.
+Worker thread ``mirror`` has two of tx rings for forwaring the packets to the
+destination and a monitor application running on VM3.
+
+.. _figure_spp_mirror_overview:
+
+.. figure:: ../images/spp_vf/spp_mirror_overview.*
+   :width: 70%
+
+   Overview of spp_mirror
-- 
2.7.4