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. UDP is connection less protocol and so routing and forwarding functions are executed for any information unit in arrival to a node. Information units with the same destination address can use different path and so the latency can be different. A variable delay increases the jitter. I think that RTP should use a layer 4 connection oriented protocol (like TCP) but without retransmissions of information units with excessive delay or errors (like UDP). What do you think about this? ----- Original Message ----- From: "Dean Anderson" <dean@xxxxxxx> To: "Daniele Giordano" <d.giordano@xxxxxxxxxx> Cc: <ietf@xxxxxxxx> Sent: Monday, March 28, 2005 2:00 AM Subject: Re: reduce jitter in routed network for voip applications > On Sun, 27 Mar 2005, Daniele Giordano wrote: > > > voip applications use connectionless layer 4 protocols and this increases > > jitter. A layer 4 connection oriented protocol limits jitter but it must not > > use packet checks in voip applications. > > Connection oriented protocols don't limit jitter. Jitter is the same no > matter what. However, a very late packet is discarded by a jitter buffer. > (you don't care what joe said 10 seconds ago--if it didn't get here in the > jitter buffer, its too late.) But it would not be discarded by a > connection oriented protocol. You'd hear what joe said 10 seconds ago, and > then you would have to wait 10 seconds to hear what joe just said. This is > OK for streaming a song. Its not fine for two way voice. > > > Is there an intefrace between TCP and UDP? Isn't there a "TDP" (transfer > > datagram protocol) that joins the two features? > > What do you think about this? > > Right protocol for the right purpose. We already have RTSP for streaming, > and RTP for voip. > > -- > Av8 Internet Prepared to pay a premium for better service? > www.av8.net faster, more reliable, better service > 617 344 9000 > > > > _______________________________________________ > Ietf mailing list > Ietf@xxxxxxxx > https://www1.ietf.org/mailman/listinfo/ietf > _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf