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• What is ‘Streaming’
• Why Use Streaming?
• Streaming Technologies
• Streaming Products
• Windows Media Technologies
WHAT IS STREAMING ?
• Method of making audio, video and other multimedia available in real-time over the Internet or corporate intranets
• Streaming ensures no download wait
• No files to take up space on your hard disk.
• Streaming technology is not new • It has been around since the inception of the radio (1897). We just called it
• Streaming media is content that contains audio, video and other media types.
WHY USE STREAMING ?
• Streaming video can be used for live or recorded events
• Provides truly interactive, on-demand audio and video
• No need for time taking downloads
• Corporate communications and training
• The Internet was not designed for real time streaming.
• Limited bandwidth, latency, noise, & packet loss
• Retransmission and out of order packet delivery
• Live or on-demand streaming is a time critical application
• Sensitive to the variation in delay inherent in a shared access network like the Internet
• Majority of end users access the Internet over very narrowband dial up links
THE ‘streaming’ SOLUTION
• Streaming uses ‘Buffering’
• Buffering irons out the natural traffic variations inherent on the Internet.
• Streamed broadcast starts to play at the same time as more content is being downloaded
• Media file can be of any length and can run over Internet bandwidths
THE STREAMING MODEL
• The components of an end to end streaming system are:
• Client (Media Player)
• Streaming Server
• Streaming Media Production Tools
•Unicast • A separate copy of the data is sent from the source to each client that requests it.
•Broadcast • A single copy of the data is sent to all clients on the network
•Multicast • sends a single copy of the data to those clients who request it.
• The bulk of the traffic on today's networks is unicast
• A separate copy of the data is sent from the source to each client that requests it
• Unicast wastes bandwidth by sending multiple copies of the data
•A single copy of the data is sent to all clients on the network
•Broadcast wastes bandwidth by sending the data to the whole network whether or not the data is wanted
•Broadcast slows client machine - each client must process the broadcast data whether or not the broadcast is of interest
• Multicasting sends a single copy of the data to those clients who request it
• Multicasting takes the strengths of unicast and broadcast and avoids their weaknesses
• No matter how many connections, there's still only one connection at the server.
• With multicasting, the client must notify the server that it wishes to receive the multicast stream, eliminating the capability of on-demand content
• Comparison of network load per client when unicasting an 8-Kbps PCM audio stream and multicasting the stream
• Internet Multicast Backbone
•Most widely known and used multicast enabled network
•A virtual network consisting of those portions of the Internet, sometimes called multicast islands, on which multicasting has been enabled
•MBone has been in place since 1992 and has grown to more than 2000 subnets.
•Has been used to multicast live audio and video showing Internet Engineering Task Force conferences, NASA astronauts working in space, and the Rolling Stones in concert.
•MBone has successfully demonstrated the practicality and utility of using multicasting to send multimedia across the network.
MULTICAST ISLANDS AND TUNNELS
•Multicasts that must travel across areas of the Internet that are not yet multicast-enabled are sent as unicasts until they reach the next multicast enabled island.
HOW MULTICASTING WORKS
•Multicasting follows a push model of communications
•The user is simply instructing the computer's network card to listen to a particular IP address for the multicast.
•Multicast addresses are Class D IP addresses ranging from 126.96.36.199 to 188.8.131.52
•The computer originating the multicast does not need to know who has decided to receive it.
HOW MULTICASTING WORKS
•Clients must have a way to learn when a multicast of interest is available.
•Clients must have a way to signal that they want to receive the multicast.
•The network must have a way to efficiently route data to those clients who want to receive it.
•Multicasts are announced in advance so that clients know when a multicast is available
•On the MBone, multicasts are typically announced using the Session Description Protocol (SDP)
•The announcement information is multicast to a well-known IP address and port where clients running the session directory tool receive this information
JOINING MULTICAST GROUPS
• To signal that they want to receive a multicast, clients join the group to which the multicast is directed.
• The Internet Group Management Protocol (IGMP) handles this task
• Groups are dynamic: clients can join or leave at any time
•When a client joins a group, it initiates two processes • First, an IGMP message is sent to the client's local router to inform the router that the client wants to receive data sent to the group
• Second, the client sets its IP process and network card to receive the multicast on the group's address and port
•When a group has no members, it ceases to exist on the network, releasing network bandwidth.