Real Time Ethernet Semester Winter 2001 Technion –Israel Institute of Technology Computer Networks Laboratory & Digital laboratory Real Time Ethernet Semester Winter 2001        Students: Shay Auster & Hagit Chen       Supervisor: Vitali Suchin

Basic Ethernet Simulation Analytic Analysis Basic Ethernet Simulation Results Real-Time Ethernet Simulation Real-Time Ethernet Simulation Results What Next ?

Purposes of Simulation Compare and evaluate new system (protocol) Actual experimentation with the system is infeasible or cost ineffective

Simulation Model time slots of 2. In each new iteration we randomly choose for each station if it transmits or not : More then one transmits – Collision. No station transmits – Net is quiet.  Simulation time is forwarded in 2. Only one station transmits – Succesful transmission.  Simulation time is forwarded in package transmission time.

The Station FSM LISTEN WAIT SEND WaitTime Over PacketsToSend Collision NetQuiet Collision PacketsToSend

The Line FSM netQuiet netCollide netBusy EndOfCollision Transmit MoreThanOne EndOfTransmit No Transmittions

Efficiency Analysis slot time = 2, hence the mean contention interval  is 2/A packet trans time = P sec Channel Efficiency = P P + 2/A F = frame length ; B = network bandwidth ; L = cabel length c = speed of signal propagation P = F/B Channel Efficiency = 1 1 + 2BLe/cF

Efficiency Analysis (Cont.) p = 1 k k = num of stations The probability that some stations acquire the channel: A = kp(1-p) k-1 if kinf.  A 1/e The probability that the contection interval has exactly j slots: A(1-A) j-1 jA(1-A) j-1 = 1 A j=0 inf.  The mean num of slot per contention:

Check for RealTime Transmition RTE Simulation START Back to START Regular Ethernet Transmition no Regular Ethernet Check for RealTime Transmition Rte Transmittion Or Collision No Rte Transmittion Or Collision

The RTE Station FSM LISTEN WAIT SEND WaitTime Over Collision or PacketsToSend SEND NetQuiet WaitTime – After a collision TimeOut – After succesful transmition

The RTE Simulation Line FSM EndOfTransmit netCollide netQuiet netBusy RTE EndOfCollision MoreThanOne Transmit RTE Transmit No Transmittions

Analytic Analysis Assumptions All RTE Stations are used for the same application RTE max packet size is 1500 Bytes TimeOut of RTE station varies according to the application

Analytic Analysis TimeOut Calculation Acctual TimeOut TimeOut(sec) = Max Packet Size Sample Rate = Bytes Bytes/Sec bits bits/Sec Acctual TimeOut 1500 Bytes * 8 = 12,000 bits 1500 Bytes Transmition Time = 12,000 bits 100 Mbits/sec = 120 Sec TimeOut = Sample Rate 120 Sec -

BandWidth Calculation Analytic Analysis BandWidth Calculation RTE transmit time transmittime Ethernet transmit time TimeOut for RTE station

BandWidth Calculation (Cont.) Analytic Analysis BandWidth Calculation (Cont.) B.W. (%)= TimeOut – [Num of RTE Stations * RTE packet Transmition Time] TimeOut B.W. (%)= [ 1500 Bytes Sample Rate 120 Sec - ] - [Num of RTE Stations * 120 Sec]

BandWidth Calculation Example Analytic Analysis BandWidth Calculation Example Sample Time = 1mSec  Sample Rate = 1000 bit/sec [ ] B.W. (%)= 1500 Bytes 12 Mbit/sec 120 Sec - [ 12 Mbits/sec ] - [1 * 120 Sec] = 86.36%

Project Status 3.1.2001 – Mid-Term Presentation: Ethernet Simulation – done Analytic Analysis for basic Ethernet – done RTE Simulation – done for one RTE station Basic Analytic Analysis for RTE - done

Next on RTE Project: Finish debug RTE simulation Expand RTE Analytic Analysis Check RTE protocol performance, using RTE simulation