Reduced TCP Window Size and Adaptive Playout for Legacy LAN VoIP

1. Reduced TCP Window Size andAdaptive Playout forLegacy LAN VoIP Niko Färber, Yi Liang November 29, 2000

2. Outline • Buffer Delay vs. Late Loss • Load = 20, 40 % • TCP window size = 1, 2, 4, 8, 16, 32, 64 packets • Adaptive/Fixed playout • Adaptive playout over time • Load = 10, 40% • TCP window size = 32 packets • Analysis/Modeling of queuing delay • Fd(d) (CDF of delay) • n(t), d(t) (n = number of simultaneous transmissions) • fn(n) (PDF of simultaneous transmissions) • Fd(d | n) (conditional PDF of delay)

3. Simulation conditions • Balanced N-N communication, N=16 hosts, 1 switch • File size PDF: Log-Normal • Idle time ~ file size • 70 KB buffer • 10 Mbps • Full duplex • Drop tail

4. fixed playout adaptive playout Load = 20% late loss [%] W = {1, 2, 4, 8, 16, 32, 64} buffer delay [ms]

5. fixed playout adaptive playout Load = 40% W = {1, 2, 4, 8, 16, 32, 64} late loss [%] buffer delay [ms]

6. Adaptive Playout, Load = 10%

7. Adaptive Playout, Load = 10%

8. Adaptive Playout, Load = 10%

9. Adaptive Playout, Load = 40%

10. Adaptive Playout, Load = 40%

11. Adaptive Playout, Load = 40%

12. Delay CDF • At load l link is not used with prob. 1-l • With 1-l prob. voice packets see empty queue(and therefore experience zero queuing delay) • Empirical model for significant delay range(99 % of packet delays are less than d99) Fd(d) 1 1-l d99 d dmax

13. Delay CDF, Load = 10% Fd(d) d [ms]

14. Delay CDF, Load = 20% Fd(d) d [ms]

15. Delay CDF, Load = 30% Fd(d) d [ms]

16. Delay CDF, Load = 40% Fd(d) d [ms]

17. Delay CDF, Load = 50% Fd(d) d [ms]

18. Delay and Simultaneous Txs d(t) [ms] 3 2 n(t) 1 t [s]

19. PDF of Simultaneous Txs l = 10%, W=32 Binominal (fn(0) matched) fn(n) n

20. Cond. Delay PDF, 0 simult. Tx fd(d | n=0) d [ms]

21. Cond. Delay PDF, 1 simult. Tx fd(d | n=1) d [ms]

22. Cond. Delay PDF, 2 simult. Txs fd(d | n=2) d [ms]

23. Cond. Delay PDF, 3 simult. Txs fd(d | n=3) d [ms]

24. Mean and Std of Cond. Delay PDF d [ms] sd md n