TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

By using our PBNM tool, we allocated 1.5Mbit/s for each AF class (i.e. AF1, 2, 3 and 4), all of
which are bounded. We limit the amount of EF traffic to 15% of the bandwidth capacity rate, i.e.
1.5Mbit and we allocated 3.5Mbit for the best effort traffic that are allowed to borrow any available
bandwidth. To get distinguish class of service, we used CBQ as our packet scheduler, In our
implementation, CBQ is used to classify EF, AF, and BE traffic so that each user can get
appropriate resources based on packet marking. The scheduler of the Diffserv core router employs
GRED queuing discipline to support multiple drop priorities as required for the AF PHB group.
The network is load using n IP traffic generator. One traffic generator is composed of a traffic
sender and a traffic receiver. The traffic sender generates a UDP packet of 1024 bytes with IP and
UDP headers according to a Poisson distribution with parameter λ = 128 packet/s that gives
1Mbit/s per traffic generator. In our test, and since our Ethernet links are 10 Mbit/s, we have taken
n=5, n=7 and n=10 in order to load the network differently each time. Each source can be either on
or off during exponentially distribution on/off period with an average of λ = λ = s .
on off
1
Edge router performs policy for particular video traffic, which is identified by a couple
. Policy determines whether the video traffic is in or out-of profile. This
task is done by a token bucket (r,b) (r is the rate at which the token are placed in the bucket and b
the size of bucket) optional parameters can be used such as a peak rate (p), a minimum policed unit
(m), and a maximum datagram size (M).
The token bucket and peak rate parameters require that traffic obeys the rule that over all time
periods, the amount of data sent cannot exceed M+min[pT, rT+b-M] [173]. M is the maximum
datagram size, and T is the length of time period. Datagrams which arrive at an element and cause a
violation of the M+min[pT, rT+b-M] bound are considered out of profile (non-conformant) and
require a decision from the PDP.
In our experiment, we take these parameters for the token bucket: r=600Kbit/s and b=2K, to
handle user traffic. This means that video traffic must not exceed 600Kbit/s otherwise it will be
considered as out-of-profile traffic.
For a testing purpose, we transmit a high quality MPEG-4 simple profile video stream to see
the reaction of our system. Figure 5-29 shows the MPEG-4 video stream sent by video application.
The average rate of this video is about 800Kbit/s and the peak rate is about 1.4Mbit/s. Video
traffic is not conform to the traffic specification, the exceed traffic is considered out-of-profile.
Edge router marks the video traffic according to the dynamic policy provisioning.
In our experiment, in profile traffic will be marked with Gold PHB as much as there is no
congestion and when congestion occurs it will be marked with Bronze PHB. Out-of-profile traffic
will be marked either by Gold or Silver or it can be dropped (according to network status)
dynamically.
133