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Change-Id: I71bcf634033c78866d6808a4604b33629710ec23
Signed-off-by: ahothan <ahothan@cisco.com>

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+.. This work is licensed under a Creative Commons Attribution 4.0 International
+.. License.
+.. http://creativecommons.org/licenses/by/4.0
+.. (c) Cisco Systems, Inc
+
+Traffic Description
+===================
+
+The general packet path model followed by NFVbench requires injecting traffic into an arbitrary
+number of service chains, where each service chain is identified by 2 edge networks (left and right).
+In the current multi-chaining model:
+
+- all service chains share the same left and right edge networks
+- each port associated to the traffic generator is dedicated to send traffic to one edge network
+
+In an OpenStack deployment, this corresponds to all chains sharing the same 2 neutron networks.
+If VLAN encapsulation is used, all traffic sent to a port will have the same VLAN id.
+
+Basic Packet Description
+------------------------
+
+The code to create the UDP packet is located in TRex.create_pkt() (nfvbench/traffic_gen/trex.py).
+
+NFVbench always generates UDP packets (even when doing L2 forwarding).
+The final size of the frame containing each UDP packet will be based on the requested L2 frame size.
+When taking into account the minimum payload size requirements from the traffic generator for
+the latency streams, the minimum L2 frame size is 64 byte (no vlan tagging) or
+68 bytes (with vlan tagging).
+
+Flows Specification
+-------------------
+
+Mac Addresses
+.............
+The source MAC address is always the local port MAC address (for each port).
+The destination MAC address is based on the configuration and can be:
+
+- the traffic generator peer port MAC address in the case of L2 loopback at the switch level
+  or when using a loopback cable
+- the dest MAC as specified by the configuration file (EXT chain no ARP)
+- the dest MAC as discovered by ARP (EXT chain)
+- the VM MAC as dicovered from Neutron API (PVP, PVVP chains)
+
+NFVbench does not currently range on the MAC addresses.
+
+IP addresses
+............
+The source IP address is fixed per chain.
+The destination IP address is variable within a distinct range per chain.
+
+UDP ports
+.........
+The source and destination ports are fixed for all packets and can be set in the configuratoon
+file (default is 53).
+
+Payload User Data
+.................
+The length of the user data is based on the requested L2 frame size and takes into account the
+size of the L2 header - including the VLAN tag if applicable.
+
+
+IMIX Support
+------------
+In the case of IMIX, each direction is made of 4 streams:
+- 1 latency stream
+- 1 stream for each IMIX frame size
+
+The IMIX ratio is encoded into the number of consecutive packets sent by each stream in turn.
+
+Service Chains and Streams
+--------------------------
+A stream identifies one "stream" of packets with same characteristics such as rate and destination address.
+NFVbench will create 2 streams per service chain per direction:
+
+- 1 latency stream set to 1000pps
+- 1 main traffic stream set to the requested Tx rate less the latency stream rate (1000pps)
+
+For example, a benchmark with 1 chain (fixed rate) will result in a total of 4 streams.
+A benchmark with 20 chains will results in a total of 80 streams (fixed rate, it is more with IMIX).
+
+The overall flows are split equally between the number of chains by using the appropriate destination
+MAC address.
+
+For example, in the case of 10 chains, 1M flows and fixed rate, there will be a total of 40 streams.
+Each of the 20 non-latency stream will generate packets corresponding to 50,000 flows (unique src/dest address tuples).