Reduced TCP Window Size andAdaptive Playout for
Legacy LAN VoIP
Niko Färber, Yi LiangNovember 29, 2000
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)
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
Load = 20%
buffer delay [ms]
late
loss
[%
]
W = {1, 2, 4, 8, 16, 32, 64}
fixed playout
adaptive playout
Load = 40%
buffer delay [ms]
late
loss
[%
]
W = {1, 2, 4, 8, 16, 32, 64}
fixed playout
adaptive playout
Delay CDF At load link is not used with prob. 1- With 1- 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)
99
W Nd
R
1-
1
dd99
Fd(d)
dmax