Each RTP session is identified by a network address and a pair of ports: one for RTP data and one for RTCP data.. The RTP data port should be even, and the RTCP port should be one above
Trang 1Each RTP session is identified by a network address and a pair
of ports: one for RTP data and one for RTCP data The RTP data port should be even, and the RTCP port should be one above the RTP port For example, if media data is being sent on UDP port 5004, the control channel will be sent to the same address
on UDP port 5005
As noted in Chapter 4 , RTP Data Transfer Protocol, the latest revision of the RTP
specification relaxes the requirement that the RTCP port is odd-numbered, and
allows nonadjacent RTP and RTCP ports For compatibility with older
implementations, it is still wise to use adjacent ports where possible, with the
RTCP data being sent on the higher, odd-numbered, port.
All participants in a session should send compound RTCP
packets and, in turn, will receive the compound RTCP packets
sent by all other participants Note that feedback is sent to all
participants in a multiparty session: either unicast to a
translator, which then redistributes the data, or directly via
multicast The peer-to-peer nature of RTCP gives each
participant in a session knowledge of all other participants: their presence, reception quality, andoptionallypersonal details such
as name, e-mail address, location, and phone number
Trang 2RTP Sessions
The RTP Data Transfer Packet
Packet Validation
Translators and Mixers
This chapter explains the RTP data transfer protocol, the means
by which real-time media is exchanged The discussion focuses
on the "on-the-wire" aspects of RTPthat is, the packet formats and requirements for interoperability; the design of a system using RTP is explained in later chapters