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Figure 2-29 Interaction between Client and Server 
The client sends a SETUP message to the media server, which responds with an OK 
message. Next, the client sends a PLAY message to the media server, and the media 
server responds with an OK message. Now the client is ready to receive media chunks 
from the server. After some time the client sends a PAUSE message, and the media 
server responds with an OK message. When the client is finished, it sends a 
TEARDOWN message, and the media server confirms with an OK message. 
In many ways the RTSP protocol has many similarities with HTTP and SIP. All have 
American Standard Code for Information Interchange (
ASCII)text based messages. The 
client sends standard methods such as SETUP, PLAY and PAUSE, and the server 
responds with standardized reply codes such as 200 OK. However, one major difference 
from HTTP is that the RTSP servers keep track of the state of the client for each 
ongoing RTSP session. To ensure this the servers uses the session and sequence numbers 
which are a part of each RTSP request and response. The session number is the same 
through the entire session, while the sequence number is incremented by one for each 
message the client sends. 
2.7.2
 
Real-Time Protocol 
Real-Time Protocol (RTP) is a protocol which typically runs on top of UDP and can 
therefore be viewed as a sub-layer of the transport layer. 

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2.7 Background information: : Streaming Protocols 
Page 27 of 93 
Figure 2-30: RTP can be viewed as a sublayer of the transport layer 
The media chunk is encapsulated in a RTP packet which its self is encapsulated in a UDP 
segment. The receiver extracts the RTP packet from the UDP segment and then extracts 
the media chunk from RTP packet. The media chunk along with the RTP header forms 
the RTP packet. The RTP header includes i.a. a sequence number and a timestamp.