RTP, Real-Time Transfer Protocol related questions
RTP - October 24, 2008 at 18:10 pm by Rajmeet Ghai
Explain RTP.
Real-Time Transfer Protocol lays a standard or a way to transfer or manage real
time data over a network. It does not guarantee the delivery of data or provide
any quality of service. However it helps to manage the data. Which means that
RTP can be used deliver the necessary data to the application to make sure it
can put the received packets in the correct order Real time data examples could
be audio and video
What is RTP Multiplexing?
RTP multiplexing allows multiple media flows within a single RTP data payload
between two points. This means that it can be used to carry multiple streams of
data in one RTP packet. RTP multiplexing will reduce the bandwidth used. RTP
multiplexing will also increase scalability.
Explain the use of RTP and RTCP protocols.
Use of RTP and RTCP:-
1. RTP can be used to transfer Real time data like voice packets.
2. RTP can be used with RTCP which makes it possible to monitor data.
3. Packet loss can be detected by RTP using Sequence number
RTCP provides Qos feedback :- Packets lost, round trip time
Describe the format of RTP and RTCP packets.
The 32 bits of RTP packet format is as follows:- (L to R)
Bit 0-1:- Indicates version, currently 2
Bit 2:- P- indicates padding bytes
Bit 3:- X- Indicates presence of extension header
Bit 4-7:- CC- Contains number of CSRC identifiers that follows the header
Bit 8:- M- Current data has some special relevance (if set)
Bit 9-15:- PT- Indicates format of payload
Bit 16-31:- Sequence number
Timestamp: - 32bits – time stamp of packet
SSRC- Synchronization source identifier uniquely identifies the source of a
stream.
CSRC -Contributing source IDs enumerate contributing sources to a stream which
has been generated from multiple sources
Extension header: - first 32 bit word contains profile specific identifier and
length specifier
The 32 bits of RTCP header format is as follows:- (L to R)
Bit 0-1:- Indicates version, currently 2
Bit 2:- P- indicates padding bytes
Bit 3 to 7:- Count of number of reception report blocks
Bit 8 to 15:- Type: - Determined RTCP packet type. Type can take values from 0
to 255
16 to 31:- Length- Length of RTCP packet - 1
SR: - Sender Report for transmission and reception from active senders
RR: - Receiver report for reception from in active senders
SDES: - Source description items
BYE- indicates end of participation
APP: - Application specific functions
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