LTV ISDNO20-M2, Руководство пользователя

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UDP ( U ser D atagram P rotocol) is a communications protocol that offers limited
service for exchanging data in a network which uses the Internet Protocol (IP).
UDP is an alternative to the Transmission Control Protocol (TCP). The advantage of
UDP is that, it is not required to deliver all data and may drop network packets when
there is network congestion. This is suitable for live video, as there is no point in re-
transmitting old information that will not be displayed anyway.
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Unicasting is communication between a single sender and a single receiver over a
network. This means that the video stream goes independently to each user, and
each user gets own stream. A benefit of unicasting is, incase one stream fails, it only
affects one user.
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Multicasting is bandwidth-conserving technology that reduces bandwidth usage by
simultaneously delivering a single stream of information to multiple network
recipients. This technology is used primarily on delimited networks (intranets), as
each user needs an uninterrupted data flow and should not rely on network routers.
2.6 How to stream H.264
Deciding on the combination of protocols and methods to use depends on your
viewing requirements, and on the properties of your network. Setting the preferred
method(s) is done in webpage.
RTP+RTSP
This method (actually RTP over UDP and RTSP over TCP) should be your first
consideration for live video, especially when it is important to always have an up-to-
date video stream, even if some images are lost due to network problems. This could
be configured as multicast or unicast.
RTP/RTSP/Multicasting provides the most efficient usage of bandwidth, especially
when there are large numbers of clients viewing simultaneously. Note however, that
a multicastbroadcast couldnot pass a network router unless the router is configured
to allow this. For example, it is impossible to multicast over the Internet.
RTP/RTSP/Unicasting should be used for video-on-demand broadcasting, so that
there is no video traffic on the network until a client connects and requests the
stream. However, as more and more unicast clients get connected, the traffic on the
network will increase and may cause congestion. Although there is a maximum of 10
unicast viewers, note that all multicast users combined count as 1 unicast viewer.
RTP/RTSP
This unicast method is RTP tunneled over RTSP. This could be used to exploit the
fact that it is relatively simple to configure firewalls to allow RTSP traffic.
RTP/RTSP/HTTP
These methods could also be used to traverse firewalls. Firewalls are commonly
configured to allow the HTTP protocol, allowing RTP to be tunneled.