Class A jitter scenario

1
Class A jitter scenario

• Using the Simula RPR V2.3 Java simulator
• Students implementing the scenario
• Bjornar Libaek
• Petter Teigen
• Based on cls09_fairness1.pdf dated june 23.
  2003 from Dave James
• In RPR version 2.3, the D shaper does not shape
  the transit traffic. I believe this results in
  the class A jitter shown. We are in the process
  of changing the simulator so that shaper D will
  shape the STQ traffic. Results from these
  simulations are hopefully available tomorrow
  (June 31. 2003)

2
Scenario (From Harry Peng)
1 km
1 km
1 km
1 km
1940 km
S1
S2
S29
S30
S31
S32
S59
S60
S61
S62
1
29
1
31
29
30

• 2000 km between S30 and S31
• 1 km between S1 and S2, S2 and S3, . S29 and S30
• 1 km between S31and S32, ., S61 and S62
• 5 us per km
• 1000M lineRate
• Total distance 1940 29 31 2000
• STQ size 1 off Ring circumfernce
• .01(5e-6 s/km 2000 km 1e9
  bit/s)
• 100 kbits or 12.5 kilobytes
• S61 b) Dual Queue design

3
Additional scenario info.

• S0 to S30 are producing at full speed
• S31 to S60 clients are producing A1 traffic at 3
  of line rate.
• S61 client is producing A0 traffic at 1 of line
  rate
• All Mac clients have small add buffers (two
  frames).
• Two STQ sizes 12.5 Kbytes and 25 K bytes
• Other RPR parameters are defaults.

4
The next 6 pages show

1. Class A1 traffic from S 31 to S60 (STQ 12.5
   Kbytes)
2. Class C traffic from S1 to S30 (STQ 12.5
   Kbytes)
3. Class A0 traffic from S61 (STQ 12.5 Kbytes)
4. Class A1 traffic from S 31 to S60 (STQ 25
   Kbytes)
5. Class C traffic from S1 to S30 (STQ 25 Kbytes)
6. Class A0 traffic from S61 (STQ 25Kbytes)

Frames are plotted when they reach Station 62,
the legend shows the sender station
5
STQ size 12.5 Kbytes
6
STQ size 12.5 Kbytes
7
STQ size 12.5 Kbytes
8
STQ size 25 Kbytes
9
STQ size 25 Kbytes
10
STQ size 25 Kbytes
11
Conclusion

• All class A1 traffic has a long period from time
  12 ms in which it is not allowed to send.
• With 12.5 Kbyte STQ size this lasts about 20 ms,
  with 25 Kbyte STQ size this is lasts about 50
  ms.
• Class A0 traffic from S61 to S62 behaves as the
  class A1 traffic.
• Shaper D running negative is probably the cause
  for the class A1 delay.
• Stay tuned for results when shaper D shapes STQ
  traffic.