+Overview\r
+========\r
+\r
+Tested Virtual Topologies\r
+-------------------------\r
+\r
+CSIT NSH_SFC functional tests are executed on virtualized topologies created\r
+using Virtual Internet Routing Lab (VIRL) simulation platform contributed by\r
+Cisco. VIRL runs on physical baremetal servers hosted by LF FD.io project.\r
+Majority,of the tests are executed in the three node logical test topology -\r
+Traffic Generator (TG) node and two Systems Under Test (SUT) nodes connected in\r
+a loop. Some tests use two node logical test topology - TG node and SUT1 node.\r
+Both logical test topologies are shown in the figures below.\r
+\r
+::\r
+\r
+ +------------------------+ +------------------------+\r
+ | | | |\r
+ | +------------------+ | | +------------------+ |\r
+ | | <-----------------> | |\r
+ | | | | | | | |\r
+ | | DUT1 <-----------------> DUT2 | |\r
+ | +--^--^------------+ | | +------------^--^--+ |\r
+ | | | | | | | |\r
+ | | | SUT1 | | SUT2 | | |\r
+ +------------------------+ +------------------------+\r
+ | | | |\r
+ | | | |\r
+ | | +-----------+ | |\r
+ | +---------------> <---------------+ |\r
+ | | TG | |\r
+ +------------------> <------------------+\r
+ +-----------+\r
+\r
+ +------------------------+\r
+ | |\r
+ | +------------------+ |\r
+ +---------------> <--------------+\r
+ | | | | | |\r
+ | |------------> DUT1 <-----------+ |\r
+ | | | +------------------+ | | |\r
+ | | | | | |\r
+ | | | SUT1 | | |\r
+ | | +------------------------+ | |\r
+ | | | |\r
+ | | | |\r
+ | | +-----------+ | |\r
+ | +---------------> <---------------+ |\r
+ | | TG | |\r
+ +------------------> <------------------+\r
+ +-----------+\r
+\r
+SUT1 and SUT2 are two VMs (Ubuntu or Centos, depending on the test suite), TG\r
+is a Traffic Generator (TG, another Ubuntu VM). SUTs run VPP SW application in\r
+Linux user-mode as a Device Under Test (DUT) within the VM. TG runs Scapy SW\r
+application as a packet Traffic Generator. Logical connectivity between SUTs\r
+and to TG is provided using virtual NICs using VMs' virtio driver.\r
+\r
+Virtual testbeds are created on-demand whenever a verification job is started\r
+(e.g. triggered by the gerrit patch submission) and destroyed upon completion\r
+of all functional tests. Each node is a Virtual Machine and each connection\r
+that is drawn on the diagram is available for use in any test case. During the\r
+test execution, all nodes are reachable thru the Management network connected\r
+to every node via dedicated virtual NICs and virtual links (not shown above\r
+for clarity).\r
+\r
+For the test cases that require DUT (VPP) to communicate with VM over the\r
+vhost-user interfaces, a nested VM is created on SUT1 and/or SUT2 for the\r
+duration of these particular test cases only. DUT (VPP) test topology with VM\r
+is shown in the figure below including the applicable packet flow thru the VM\r
+(marked in the figure with ``***``).\r
+\r
+::\r
+\r
+ +------------------------+ +------------------------+\r
+ | +----------+ | | +----------+ |\r
+ | | VM | | | | VM | |\r
+ | | ****** | | | | ****** | |\r
+ | +--^----^--+ | | +--^----^--+ |\r
+ | *| |* | | *| |* |\r
+ | +------v----v------+ | | +------v----v------+ |\r
+ | | * * |**|***********|**| * * | |\r
+ | | ***** *******<----------------->******* ***** | |\r
+ | | * DUT1 | | | | DUT2 * | |\r
+ | +--^---------------+ | | +---------------^--+ |\r
+ | *| | | |* |\r
+ | *| SUT1 | | SUT2 |* |\r
+ +------------------------+ +------------------^-----+\r
+ *| |*\r
+ *| |*\r
+ *| +-----------+ |*\r
+ *| | | |*\r
+ *+------------------> TG <------------------+*\r
+ ******************* | |********************\r
+ +-----------+\r
+\r
+NSH_SFC Functional Tests Coverage\r
+---------------------------------\r
+\r
+Following NSH_SFC functional test areas are covered in the CSIT |release| with\r
+results listed in this report:\r
+\r
+- TODO\r
+\r
+\r