Oracle Video server, Manual

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Networking in the OVS System
2-34 Introducing Oracle Video Server
Best-Effort Delivery Ethernet uses best-effort delivery, which means that when
data is sent over the network, every effort is made to deliver the data. However, if
the receiving computer is turned off or if there is a network problem, the data is
lost. Ethernet does not notify the sending computer when a message is received or
dropped.
Demands of Video on LANs
A shared Ethernet network is sufficient for non-real-time applications such as
databases or word processors, in which delays of a fraction of a second in receiving
data are not critical and are often not noticed by users.
However, applications receiving video are time-sensitive and depend on
isochronous, or time-based, delivery. Data packets must arrive on time to be useful,
or the video suffers a brief interruption and the user notices a glitch in the video.
Glitch-free video is not easy to deliver on a shared Ethernet network because:
■
All data traffic from one computer to another is read by all computers on the
network.
■
Video cannot be delivered as a continuous string of packets, but as multiple
individual packets that compete equally with other applications for network
resources.
■
The large number of packets needed to deliver video consumes network
resources. For example, 20 video streams at an encoding rate of 1.5 Mbps
(Megabits per second) require a total network rate of 30 Mbps, which is much
greater than standard 10baseT Ethernet network rates.
■
A shared Ethernet network card can drop packets due to transmission timeouts
in heavy network traffic.
Once a video stream starts, it must continue and finish uninterrupted by other data
transfers or by glitches. To ensure uninterrupted video:
■
Video cannot be interrupted by other network traffic such as large file transfers.
■
The network must be capable of sustained data transfer rates that support the
maximum video encoded rate multiplied by the number of concurrent video
streams.
Switched Ethernet meets both of these requirements.