TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

Diffserv architecture defines, at a lower level, four types of data-path elements: traffic
classifiers, actions elements, meters and queuing elements [168]. Combining these elements into
higher-level blocks creates a Traffic Condition Block (TCB), which can be managed by policy-based
network management tools. The configuration of Diffserv TCB using PBNM involves the use of
administratively prescribed rules that specify actions in response to defined criteria. All the
information needed to perform this task such as profiles, user information, network configuration
data, and IP infrastructure data such as network addresses and name server information are stored
in a policy repository. These configurations do not change frequently because they are not
associated with specific application or traffic but with the network management. The more difficult
part in the configuration is to have the traffic entering the network appropriately marked (audio,
video and other data). Since, the user is signed up for the service, edge devices could be configured
to mark user’s traffic with the appropriate PHB. With a known IP address and/or IP port number,
the administrator can specify a policy that refers to user application IP address and marks traffic
coming from that address appropriately.
In the actual configuration, when the user signs up for a particular multimedia service, he/she
must specify his/her traffic profile and the action that must be taken when the traffic exceed this
predefined profile (out of profile traffic). Generally, the out of profile traffic is dropped or marked
as best effort traffic. This model is static and does neither respond to application needs nor favor
an optimal utilization of network resources.
It is obvious that the solutions suggested by the IETF IP Diffserv working group makes it
possible to privilege some MPEG-4 streams among others by the marking. The marking is
performed according to the importance of the Audio Visual Object within the scene. In Chapter 4,
Section 4.1, we have presented an algorithm that allows the server to distinguish between most
important objects and lower important objects based on application level information found in
objects descriptor or provided by the MPEG-7 framework. It is clear that IP Diffserv network will
be deployed for next generation Internet since it provides QoS support for end-applications with
scalable manner.
Open issues regarding the design of an efficient Diffserv PHB for the transport of packet
video applications such as MPEG-4 video applications are summarized in the following: (1) what is
the appropriate PHB that guarantee the better QoS for Audio Visual Stream?, (2) What is the IP
packet marking policy (marking at the server or marking when entering the network)?, (3) Is it
suitable to modify the marking of IP packets with respect to network states? (4) What is the most
flexible network architecture to cope with all these requirements?
There are many available algorithms for metering and marking packets at the boundary of the
differentiated services (Diffserv) domain. Among these algorithm we find, Time Sliding Window
Algorithm (TSW) such as Time Sliding Window Three Color Marker (TSWTCM) [130]and Three
Color Marker algorithm (TCM) such as Two Rate Three Color Marker (TRTCM) [131].
The TSW algorithm is based on rate estimation using a window. It provides a smooth rate
estimation of the IP traffic throughput. The algorithm can mark the packet as out of profile one the
traffic exceeds a certain target rate. It can be used to mark in profile traffic with EF PHB and out of
profile traffic with AF PHB.
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