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    by: Natalina

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    1 : VIDEO OVER IP Chapter 9 : MULTICASTING Natalina Gusmao HCI & Robotics, KIST
    2 : Basic Concepts Applications Multicasting System Architecture System Impact Chapter 9 MULTICASTING Definition What is “Multicasting”? Multicasting: the process of sending a single video signal simultaneously to multiple users
    3 : BASIC CONCEPT Unicasting Multicasting Joining and Leaving a Multicast
    4 : BASIC CONCEPT Multicasting vs. Unicasting Unicasting Each video stream is sent to exactly one recipient Multicasting A single video stream is delivered simultaneously to multiple recipients
    5 : BASIC CONCEPT Unicasting Advantages Will work on standard IP networks, including the public Internet Each user has an independent video stream which allows the video source to offer each user playback controls The source can determine precisely which unicast destinations are allowed to receive the data stream and keep record of each recipient Disadvantages The video source must have enough processing capacity and network bandwidth to create a stream for each user There must be enough bandwidth in every segment of the network to deliver all the streams from the source to their final destinations The video source must know the correct IP address of every active viewer’s device
    6 : BASIC CONCEPT Multicasting Advantages The amount of network bandwidth required can be greatly reduced using multicasting They are only required to transmit a single copy of the stream Higher-quality video can often be used for multicasting Disadvantages Individual users cannot pause, rewind or fast-forward the content The network equipment must be multicast enable along the entire route from the source to every multicast destination Some firewalls and NAT devices can block protocols se in multicasting The burden on routers can be significant Controlling access to specific video content can be complicated on a multicast network When hybrid public/private networks are used, system installation can be complicated
    7 : BASIC CONCEPT Joining and Leaving a Multicast What users do if they want to watch multicast program? They must join in at whatever point the program happens to be in If a multicast program is already flowing through a network, users have the option of joining or leaving that multicast What router do after receiving a request from a user to “join” a multicast? The router must determine whether it is already processing the multicast for another user If it is, then the router simply needs to make a copy of the multicast stream and send it to the requesting user If its not, the router must request the stream from a device that is closer to the multicast source The request can send the steams to the user
    8 : BASIC CONCEPT Joining and Leaving a Multicast What about if users want to “leave” a multicast? Users’ device must sent a “leave” message to the router The router then stops delivering the stream so that the users’ bandwidth can be freed up for other users What router does if it no longer has any user that are requesting the stream? It must also leave the multicast If not, multicast network could easily become choked with streams that nobody is watching
    9 : APPLICATIONS IPTV Live Events Continous Information Continous-Presence Conferencing Some apps for the multicasting
    10 : Definition Why? APPLICATIONS IPTV Multicasting is a powerful tool for IPTV because it is well suited for private networks and it solves a number of problems IPTV system architectures are well suited for multicasting because many of them are custom-built, private networks
    11 : APPLICATIONS Live Events Live Broadcast Using Temporary Satellite Live Broadcast Using IP Multicast Past Present
    12 : Definition Another apps for multicasting is to send information that is continuously changing IP multicasting is used by a number of brokerage firms not only to transmit share data, but also to transmit live news feeds from a variety of sources that can effect prices APPLICATIONS Continous Information
    13 : Definition What is “Continuous-Presence Conferencing”? APPLICATIONS Continous-Presence Conferencing Continuous-Presence Conferencing: high-end form of videoconferencing in which the participants in each conference location can hear (and see) all the other locations during the entire conference through the use of multicasting Continuous-Presence Conferencing = telepresence or virtual meeting
    14 : APPLICATIONS Continous-Presence Conferencing Often used to create the “illusion” that all of the participants are in the same room Requirement Having enough displays in each room to show the video images coming from all the other room
    17 : Definition What is “SAP”? Function MULTICASTING SYSTEM ARCHITECTURE SAPs SAP = Session Announcement Protocol, an experimental protocol for broadcasting multicast information It is similar to the TV guide service that is broadcast on many cable TV system Used to inform multicast-enable receivers periodically about programs (such as video or audio streams) currently being multicast on a network What is the most important part of a SAP message? Perhaps, it is the multicast address of the multicast stream
    18 : What is the most important part of a SAP message? Perhaps, it is the multicast address of the multicast stream Why? Once the user device has this address, it can send a request to the network to join that multicast Common default SAP communications always take place on the multicast group address on port 9875 MULTICASTING SYSTEM ARCHITECTURE SAPs
    19 : Purpose of IGMP (Internet Grouping Management Protocol) Give information to routers about streams on a network that are being multicast Routers Responsible for forwarding and replicating multicast streams to all the devices that are entitled to receive the streams MULTICASTING SYSTEM ARCHITECTURE IGMP Join/Leave Example
    21 : Router Configuration Server Usage Bandwidth Example SYSTEM IMPACT
    22 : Router Configuration SYSTEM IMPACT Some functions that a router must perform Receive, duplicate, and forward SAP packets Process IGMP packets as required to determine when a device wants to join or leave a multicast Replicate multicast packets as needed to supply them to any requesting
    23 : Sever Usage SYSTEM IMPACT Unicasting server A server must create a separate stream for each receiving device For servers that serve numerous clients, this can be a huge processing burden Multicasting server Have relatively light burden compare to unicasting servers Because the network makes copies of the stream, only one stream needs to be provided by the source This can be accomplished with a low-cost, low performance server Because all the viewers watch the same steam at the same time, the server does not need to handle
    24 : Bandwidth Example SYSTEM IMPACT The big difference in these two illustrations: Amount or bandwidth needed A & source; A & other routers
    25 : THANK YOU!!!

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