1 Reply Latest reply on May 26, 2011 10:54 PM by Michael Thornburgh

    Difference between Application-level multicast and peer-assisted network?


      The simplest application level multicast is done through


      someone.publish("xxx") to a netGroup -----> FMS rtmfp url -----> all players connected to the same netGroup and play from a netstream


      In peer-assisted networking,

      they ask for wantObjects and addHaveObjects. I wonder if in app. level multicast, these peers also ask for Objects?

      If so, how do they know the index of Objects?


      A live streaming from webcam doesn't have an ending index.

      Do they just keep asking for all objects starting from 0 ~ MAX_VALUE?

        • 1. Re: Difference between Application-level multicast and peer-assisted network?
          Michael Thornburgh Adobe Employee

          "peer-assisted networking" refers to all P2P modes of RTMFP Groups (P2P multicast, object replication, directed routing, and posting).


          NetStream.publish()/play() on a group NetStream is the P2P multicast mode.  under the covers quite a lot of fancy advertising, fetching, pushing, and tuning is going on all automatically.  multicast is always for live, continuous content, and all members of the group share approximately the same sliding window of stream fragments at any instant of time.  the size of the window is controlled by NetStream.multicastWindowDuration.  each member tries to get all the fragments in the current window.  members share information about the fragments in the window with each other.  P2P multicast is designed and optimized for a small number of publishers in a group sending continuous-form live media to all members in a limited amount of time.


          the wantObjects/haveObjects NetGroup calls are for the "object replication" mode.  here the objects and index numbers are under direct ActionScript control, and the intent is that each member should eventually have every object, no matter how long that takes.  object replication is designed for mesh-wide reliable consensus on a set of objects with all semantics of content and origin left to the ActionScript developer.


          posting is kind of like a multicast of a single message.  it is designed and optimized for a large number of senders infrequently sending single messages to all members.


          directed routing can be used for, among other things, creating distributed hash tables (DHTs) and is a complex subject.


          Matthew Kaufman described all of these modes in his talk at MAX 2009; the presentation is available on Adobe TV:



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