In several of the SSIM documents Input EPS and Output EPS are mentioned when estimating the System perfomance on different hardware platforms.
In SSIM, every event is passed through below queues in same order:
1) Input queue -- event reaches SSIM and put in this queue.
2) Archive queue -- event is archived if configured
3) Forwarding queue -- event is kept in queue and forwarded to configured service
Input EPS : It refers to the rate at which events reach SSIM server.
Output EPS : It refers to the rate at which events gets processed by SSIM server.