1. 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

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

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

4. 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.

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

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

7. 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

8. 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:

10. 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

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

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

13. 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

14. 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 -

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

16. 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]

17. 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%

19. 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

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