Virtual Traffic Classifier


This chapter provides an overview of the virtual Traffic Classifier, a contribution to OPNFV Yardstick from the EU Project TNOVA. Additional documentation is available in TNOVAresults.


The virtual Traffic Classifier VNF, the VTC, comprises of a VNFC. The VNFC contains both the Traffic Inspection module, and the Traffic forwarding module, needed to run the VNF. The exploitation of DPI methods for traffic classification is built around two basic assumptions:

  • third parties unaffiliated with either source or recipient are able to

inspect each IP packet’s payload

  • the classifier knows the relevant syntax of each application’s packet

payloads (protocol signatures, data patterns, etc.).

The proposed DPI based approach will only use an indicative, small number of the initial packets from each flow in order to identify the content and not inspect each packet.

In this respect it follows the PBFS. This method uses a table to track each session based on the 5-tuples (src address, dest address, src port,dest port, transport protocol) that is maintained for each flow.


  • Traffic Inspection: The process of packet analysis and application

identification of network traffic that passes through the VTC.

  • Traffic Forwarding: The process of packet forwarding from an incoming

network interface to a pre-defined outgoing network interface.

  • Traffic Rule Application: The process of packet tagging, based on a

predefined set of rules. Packet tagging may include e.g. ToS field modification.


The Traffic Inspection module is the most computationally intensive component of the VNF. It implements filtering and packet matching algorithms in order to support the enhanced traffic forwarding capability of the VNF. The component supports a flow table (exploiting hashing algorithms for fast indexing of flows) and an inspection engine for traffic classification.

The implementation used for these experiments exploits the nDPI library. The packet capturing mechanism is implemented using libpcap. When the DPI engine identifies a new flow, the flow register is updated with the appropriate information and transmitted across the Traffic Forwarding module, which then applies any required policy updates.

The Traffic Forwarding moudle is responsible for routing and packet forwarding. It accepts incoming network traffic, consults the flow table for classification information for each incoming flow and then applies pre-defined policies marking e.g. ToS/DSCP multimedia traffic for QoS enablement on the forwarded traffic. It is assumed that the traffic is forwarded using the default policy until it is identified and new policies are enforced.

The expected response delay is considered to be negligible, as only a small number of packets are required to identify each flow.

Graphical Overview

|                            |
| Virtual Traffic Classifier |
|                            |
|     Analysing/Forwarding   |
|        ------------>       |
|     ethA          ethB     |
|                            |
     |              ^
     |              |
     v              |
|                            |
|     Virtual Switch         |
|                            |


run the with root privileges


sudo ./pfbridge -a eth1 -b eth2

Development Environment

Ubuntu 14.04