Information Technology Reference
In-Depth Information
0.4
CB,
m=
1
CB,
m=
2
CB,
m=
4
CB,
m=
16
CB : Consonant Broadcasting
GCB : Grouped Consonant Broadcasting
GCB,
m=
1
GCB,
m=
2
GCB,
m=
4
GCB,
m=
16
0.3
3
b
5
b
7
b
9
b
Network bandwidth (multiples of video bit-rate
b
)
Figure 18.8
Client buffer to video size ratio versus network bandwidth
example, with a latency constraint of 15 seconds, CB and GCB requires 1,920 and 104 channels
respectively with
m
16. The trade-offs
in network bandwidth and client buffer requirement in these two cases are 5.47% and 2.76%
respectively for
m
=
4, and 7,680 and 434 channels respectively with
m
=
16.
On the other hand, if the number of network channels available is the limiting factor, then
GCB can achieve lower network bandwidth requirement than CB for a given start-up latency by
observing the result in Figure 18.10. For example, given a maximum of 64 channels and start-
up latency of 3.75 minutes, GCB requires 4
b
network bandwidth, while CB requires 4.12
b
.
Moreover, in Figure 18.11, we observe that, by further increasing the network bandwidth, CB
cannot achieve lower start-up latency as the number of network channels limits the number of
video segments
N
defined in equation (18.3), however, GCB is not subject to this limitation.
Thus GCB will be particularly useful for networks having very limited supply of network
transmission channels (e.g., IP multicast). Otherwise, CB can be employed to achieve better
performance.
=
4, but only 1.27% and 1.28% respectively when
m
=
18.7 Implementation and Benchmarking
In this section we address some practical issues in the implementation and deployment of open-
loop multicast streaming algorithms. Using CB/GCB as an example we explain the issues we
encountered during implementation of the system and describe some experimental results
obtained from benchmarking.
We developed the CB/GCB system implementation in C++, which runs in the Red Hat
Linux 7.0 operating system.We useUDP over IPmulticast as the network transmission protocol
and set up a testbed with off-the-shelf PCs connected by an IP-multicast-ready FastEthernet
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