What is voice-over-ip?
Conversation between parties over ip.
Need to maintain conversation, min-delay.
Rule of thumb:
<150ms: good, >400 ms: bad
IP address, port no., encoding algorithms
Value-added services: call forwarding, screening, recording.
Maximize: low playout delay, low late loss rate
Choosing the right timeout
d is packet timeout delay.
If long, we have less packet loss, less interactivity.
If short, we have more interactivity, higher loss.
Adaptive solution, minimize both packet delay and loss.
di = (1-ɑ) di-1 + ɑ (ri-ti)
Each ACK/NAK takes ~ one RTT.
alternative: Forward Error Correction (FEC)
Send enough bits to allow recovery w/o retransmission (2-d parity in ch.5)
Simple way to do so:
Create redundant chunk by XORing n chunks.
send n+redundant chunk.
Reconstruct original n chunk, if 1 lost chunk.
Send 2 streams
one higher, one lower quality stream, interleave to conceal loss.
If packet lost, still have most of every original chunks.