RTP Transport and Many-to-many Transmission

RTP uses a connectionless transport (usually UDP):

Retransmission is undesirable (generally it would be too late)
Since RTP handles flow control and sequencing we don’t need this from the transport protocol
RTP is packet oriented
Enables us to easily use multicast (when there are many endpoints that want the same source stream)
- multicast address identifies a group
- these multicast groups can be dynamic

Transcript

[slide106] RTP because it's carried on top of UDP, can of course be one-to-many. Whereas with TCP, we can only have one-to-one mappings. That means that we can actually use multicast. However, we have a problem. We're sending it on top of UDP. UDP has no flow control. Right? So if we're not careful, and it's blasting away, and the network's going into congestion, whoops, we've got a problem. And we can't solve that by UDP. We have to solve it by some other mechanism.

So not surprisingly, if you look at television services, for instance, IPTV, Telia's IPTV, the traffic is being sent out as UDP multicast.