Why are you trying to do this? Surely the hardware and OS can handle more throughput than the application. Why not use an application load tester such as Apache's JMeter?
An apt-cache search on my Debian box had these results:
Code:
$ apt-cache search traffic generator
bittwist - libpcap based Ethernet packet generator
d-itg - Distributed Internet Traffic Generator
mgen - packet generator for IP network performance tests
mz - versatile packet creation and network traffic generation tool
ostinato - Packet/Traffic Generator and Analyzer
sip-tester - Performance testing tool for the SIP protocol
It sounds like any of them but sip-tester could do the job.