Hi Daniele,
Daniele Giordano wrote:
RTP is transparent at the transport layer. We analyse TCP and UDP: TCP is connection oriented and so the communication begins with the definition of a virtual circuit. A virtual circuit is a temporary connection of sequence nodes with relative reservation of bandwidth. A connection oriented service gives the certainty that all information units use the same nodes with a same medium latency. Same latency maintains reduced the jitter.
[chop udp discussion]
What do you think about this?
TCP does induce delay variation when retransmission is considered.
End-to-end retransmission of VoIP is not useful in many cases. TCP by default does this.
The additional mechanisms in TCP to throttle transmissions when multiple duplicate ACKs are seen will reduce the rate of transmission in some cases for VoIP. This will also cause packet delay variation.
TCP is not well suited to VoIP for these reasons.
Additionally, UDP and TCP packets travel through the network at the same rate (if no differential forwarding is used). The premise that TCP and UDP have different properties on the forwarding plane is thus flawed.
Greg
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