| Documentation to "simulation of a packet processing system" PPS |

| Globals | |
|---|---|
![]() | EXIT (or hitting ESC) quits the program. |
![]() | With these three buttons referred to as play, pause and stop the simulation process can be initiated, paused, stopped and
reset. The current status is represented by an highlighted (blue) button. From status stop the user can From status play the user can From status paused the user can |
![]() | The distribution bars can be clicked for a larger view. |
| Source | |
|---|---|
![]() | "Source" simulates an infinite number of statistically independent sources. The probability of packet generation after a certain time converges towards a negative exponential distribution in this case, which is simulated here. Hence, the time between packet generations will be distributed according to:
To is the estimated value in msecs an must be supplied by the user.Once a packet is to be generated, its length must be calculated. This length is composed by a constant offset "Dat. offs." and a part that can be Negative Exponential- or Uniform- distributed. The chosen distribution is highlighted in blue/yellow. It is also possible to disable the distributed part. If Negative Exponential Distribution (EXD) is chosen, packet lengths will be distributed according to:
Lo is the estimated value in bytes and must be supplied by the user.If Uniform Distribution (UFD) is chosen, packet lengths between 1 and Max. will be generated with equal probability. |
| Buffer | |
![]() | The "buffer" is the instance between source and processor. Its current fillstate is indicated by
a bar graph. All generated packets, i.e. a certain number of bytes, will be stored here by the source, enough space provided. If a packet cannot be completely stored in the buffer (because the remaining size is smaller than the packet length), it will be rejected and an overrun condition is signalled by a red top field of the bar graph. The frequency of this event is also referred to as packet loss probability B. The processor then takes out bytes at processing speed. Shouldn't there be enough bytes left for a simulation step, those remaining will be withdrawn and an underrun condition is indicated (red lower field). Note: These (non-linear) effects cause temporary reductions of either generation or processing rate and may direct into stable systems showing unstable behaviour (bouncing buffer distribution graph). The buffer size s has to be supplied by the user. |
| Processor | |
![]() | The processor takes bytes out of the buffer at processing speed (eps).
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