Ankur Khetrapal

Hybrid Testbed

 

INTRODUCTION

The HYBRID TESTBED is simply an integration of physical components into simulation. It enables us to have a realistic overview of the system, as it consists of only a few physical servers, a few physical clients and the rest hundreds of the APs and STAs are realized in simulation.



THE STRUCTURE

The HYBRID TEST BED consists of the following parts:


PACKET CAPTURE

The packet capture code catches the packets on the interfaces of the both the networks. The packet capture code uses the libpcap library to capture the packets. Two different packet capture codes are required to listen on the two different network interfaces. Filters are set in the packet capture code so that it does not catch unnecessary data from the networks. The stored packets are placed in a buffer in order to ensure no packet is overwritten.

Source: pac2.cpp


EXTERNAL INTERFACE

The external interface has many callback functions which include functions that bind the external interface to the socket, initialize the nodes on which the external interface runs and another important function INTERFACE RECEIVE. This function is important because it polls the receive function after a delay to receive packets from the socket. The external interface has a SENDDATA function which sends the packet from the source node to the destination node inside qualnet simulation.

Source: Interfaceudp_app.cpp, Interfaceudp.cpp


RAW SOCKET

As soon as the packet reaches the destination node inside Qualnet a call is made to the raw socket code. The raw socket code enables us to receive the code find the destination address without distorting the packet and then sends it to the client. The importance of the raw socket code is that while transferring the packet it does not strip of the headers and therefore the packet is received at the client contain all its headers therefore the client considers it to be the correct packet.

Source: raw2.cpp

NOTE: The source code of the Hybrid Testbed is not available for download as it is a property of Network Labs, ECE Dept, IISc.

 

STRUCTURAL DIAGRAM

 

 

PACKET FLOW

 

RESULTS

1. Throughputs of 3.6 Mbps on an 11 Mbps connection have been achieved.
2. Deadlocks and race conditions are avoided by implementing the system as a multithreaded application.
3. Ping RTTs have decreased considerably.
4. Negligible packet drops are observed.


Download Report (Currently Inactive)