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Version: The version
field identifies the version of RTP, which is currently version 2
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Padding (P): Some
protocols or algorithms require a packet to be a specific size. The
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padding field is a variable
field that fills space to make the header the proper size.
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CSRC count: The CSRC
field contains the number of CSRC identifiers that follow the
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fixed header.
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Marker: The marker
field is used in specific applications to identify groups of RTP packets.
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Payload type: This
field identifies what type of information is in the payload portion
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of the RTP packet and is
used by applications to determine how to handle the packet.
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Sequence number: The
sequence number keeps a count of RTP packets by Real-Time Transport Protocol
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incrementing the field by
one for each packet that is sent, and is used to detect
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packet loss and to maintain
the sequence of the packets that are received.
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|
Timestamp: The
timestamp field records the time when the RTP packet was
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|
created and is derived from
a clock that increments monotonically and linearly
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|
in time to allow
synchronization and jitter calculations.
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|
Synchronization source
(SSRC): The SSRC field contains a randomly
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|
generated 32-bit number to
identify individual RTP sessions for the purpose of
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|
separating individual RTP
sessions and synchronizing the data transmission
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|
across multiple end-points.
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|
Contributing source
(CSRC): The CSRC field is another layer of
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|
identification for sessions
that have the same SSRC number, but the data in the
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|
stream needs to be
differentiated further. For example, in a conference call, all
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|
the RTP packets in the
session would contain the same SSRC identifier but the
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|
CSRC could be used to
identify each caller who is speaking.
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Header