TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

increased linearly in the absence of loss, and transmission rate being decreased multiplicatively
when congestion is detected. RAP uses the ratio of short-term to long-term averages of RTT to
fine tune the sending rate. The RAP protocol was applied in the context of unicast video delivery
[80] [81]. The video is a layered constant-bit rate. All the layers have the same throughput. The rate
control algorithm used by the server adapts the video quality to network state by adding and
dropping layers to efficiently use the available bandwidth. The algorithm takes into consideration
the status of the receiver buffer, making sure that base layer packets are always available for
playback. In [82], the authors propose a spectrum of window-based congestion controls schemes
which perform TCP-Friendly compatibility under RED control. These window-based schemes use
history information to improve traffic fairness. The proposed schemes are fundamentally different
from memoryless schemes such as AIMD and can maintain TCP-compatibility or fairness across
connections using history information for different protocols.
In [83] Zhang et al. present an end-to-end transport architecture for multimedia streaming
over the Internet. They propose a new multimedia streaming TCP-friendly protocol (MSTFP) that
combines forward estimation of network conditions with information feedback control to optimally
track the network conditions. This scheme improves end-to-end QoS by allocating resources
according to network status and media characteristics.
The TCP-friendly congestion control mechanism that was developed recently is TCP-friendly
Rate Control Protocol (TFRC) [84]. It seems to be more robust protocol and is recently accepted as
an RFC by the IETF. TFRC provides sufficient responsiveness by taking into consideration all the
parameters that affect the TCP rate such as loss, Round-Trip Time (RTT) and retransmission
timeout value. The key advantage of TFRC is that it has a more stable rate during the session
lifetime. The calculated rate is obtained by using the TFRC is [84] (see Eq. 1):
R
TCP
≅
RTT
2 (3
2
RTO
bp
+ t
3
s
3bp
) p(1
+ 32 p
8
)
(Eq. 1)
Where RTCP is the target transmission rate or the allowed transmission rate, s is the packet
size, RTT is the round trip time, p is the loss rate, t RTO is the TCP retransmission timeout value and
b is the number of packets acknowledged by a single TCP acknowledgement.
3.2.1.11 Media Caching
Multimedia Caching is an important technique for enhancing the performance of streaming
system. Proxy caching has been the key factor in the scalability of the Web, because it reduces the
network load and access latency. Video caching aims to store some part of the video near the
clients. It allows improving the quality of the delivered stream when there is a presence of
bottleneck links between the server and the client. Many works has experienced the media proxy
caching [85], [86], [87], [88], [89], and [90].
3.2.1.12 Video Smoothing
The rate of the encoded video stream is in general a variable bit rate having a bursty behavior.
The bursty nature of this traffic causes in the majority of case network congestion. In order to
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