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INTRODUCTION ORBAN
MODEL
1010
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A special HTTP tunneling protocol that wraps RTSP/RTP packets inside HTTP
packets, only supported by Apple QuickTime Player, can be used to help cir-
cumnavigate firewalls and/or routers by using the same port that web serv-
ers/browsers use. The advantage to this is that streaming protocols are still
used for media content stream control and TCP/IP reliability is gained. The dis-
advantage is since it is less efficient, it adds server load, slight network over-
head and increased bitrate.
HTTP/ICY — Streaming Servers
Using a streaming server that supports HTTP/ICY protocols such as SHOUTcast or Ice-
cast, HTTP is fully capable of streaming media content to a client player. This is not
the same as HTTP media file download from a web server. Basically, SHOUTcast and
Icecast use HTTP to negotiate the connection between the server and clients, as well
as to send metadata and to use a file transfer to send the media content.
HTTP/ICY has the following properties:
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It can be used for live and file streaming (unicast only).
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It does not leave a copy of the media content on the user’s computer.
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It requires a streaming server and/or live streaming encoder.
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The stream will stop and re-buffer if data rate exceeds network connection
speed.
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HTTP/ICY uses TCP/IP protocol to ensure that all streaming packets are deliv-
ered, retransmitting if necessary. TCP is optimized for guaranteed delivery of
data, regardless of its format or size. For example, if your client media player
realizes that it is missing a data packet from the server, it will request the
server to resend that packet. Resend requests take time, take up more band-
width, and can increase the load on the server. If the network is congested,
you could begin to use more bandwidth for resends than for the media con-
tent itself. TCP is not designed for efficient real time delivery or careful band-
width control, but for accurate and reliable delivery of every bit. Therefore, if
your network bandwidth is greater than the data rate of the stream, which in
most cases it is, HTTP/ICY is a very accurate way to deliver streams.
•
Most firewalls, routers and network configuration schemes will pass HTTP/ICY.
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Figure 1-6: SHOUTcast DNAS Server/Client Transports
