RTCP hierarchical aggregation
Encyclopedia
The Hierarchical Aggregation (or also known as RTCP feedback hierarchy) is an optimization of the RTCP feedback model and its aim is to shift the maximum number of users limit further together with Quality of Service
(QoS) measurement[1], [2] . The RTCP bandwidth
is constant and takes just 5% of session bandwidth. Therefore the reporting interval about QoS depends, among others, on a number of session members and for very large sessions it can become very high (minutes or even hours)[2]. However the acceptable interval is about 10 seconds of reporting. Bigger values would cause time-shifted and very inaccurate reported status about the current session status and any optimization made by sender could even have a negative effect to network or QoS conditions.
The Hierarchical Aggregation is used with Source-Specific Multicast
where only a single source is allowed, i.e. IPTV
. The another type of multicast could be Any-Source Multicast
but it is not so suitable for large-scale applications with huge number of users.
Only the most modern IPTV systems use Hierarchical aggregation (June 2007).
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
(QoS) measurement
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
is constant and takes just 5% of session bandwidth. Therefore the reporting interval about QoS depends, among others, on a number of session members and for very large sessions it can become very high (minutes or even hours)[2]. However the acceptable interval is about 10 seconds of reporting. Bigger values would cause time-shifted and very inaccurate reported status about the current session status and any optimization made by sender could even have a negative effect to network or QoS conditions.
The Hierarchical Aggregation is used with Source-Specific Multicast
Source-specific multicast
Source-specific multicast is a method of delivering multicast packets in which the only packets that are delivered to a receiver are those originating from a specific source address requested by the receiver...
where only a single source is allowed, i.e. IPTV
IPTV
Internet Protocol television is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.IPTV services...
. The another type of multicast could be Any-Source Multicast
Any-source multicast
Any-source multicast is the more traditional form of multicast where you can have multiple senders on the same group/channel, as opposed to source-specific multicast where a single particular source is specified....
but it is not so suitable for large-scale applications with huge number of users.
Only the most modern IPTV systems use Hierarchical aggregation (June 2007).