2 Replies Latest reply on Jul 5, 2012 1:01 PM by thischarmingsam

    Using rtmfp on wireless LAN without server


      To explain my situation:


      I'm connecting 100 tablet devices via the same lan using a wifi router, without Internet access (using serverless e.g. "rtmfp:".) I'm using rtmfp to send chat messages between these devices, and using one client to issue trigger commands to the Rest of the connected clients, which include telling them to load content from a local apache server, draw graphics based on an array of values etc.


      To get 100 to receive a netgroup post simultaneously I have to put them in separate netgroups (5 in total) and then have one client which issues specific commands / is connected to all 5 groups.  I tested having then all in one netgroup, some of the tablets would not receive messages. When in the smaller netgroups (closer to the magic number 14) they respond instantly, same multicast ip for all groups.


      My questions are: would you expect this scenario (one wifi router, all clients connected to it) to produce detrimental results? Should a netgroup be able to support 100 members in this scenario?


      I need to upscale my application (AIR on android) to support 500+ devices and will do so by any means necessary, So any help and/or suggestions will be very very appreciated!





        • 1. Re: Using rtmfp on wireless LAN without server
          Michael Thornburgh Adobe Employee

          posting is never going to be "simultaneous", or even "fast". however, NetGroup.post() should reach all members of the group, within a few seconds, no matter how big the group is.


          a group of 100 clients on a LAN should totally work in serverless mode.


          are you sure you're using NetGroup.post() and not NetGroup.sendToAllNeighbors() to send your messages? sendToAllNeighbors() will only send a message to a peer's neighbors, which are the peers to which it is directly connected. a peer will not be directly connected to every other peer in a 100 member group. on average, in a 100 member group, i'd expect each member to have approximately 27 neighbors (2*log N + 13). some will have a few more, some a few less.


          if somehow your wireless LAN was partitioned when the members joined the group, the group could be partitioned into disjoint sets according to the physical partition. however, once the physical partition was healed, the IP multicast neighbor discovery should eventually repair the RTMFP group partition with very high probability.


          note that P2P on a wifi LAN actually takes twice as much wireless capacity as you think, since peers aren't directly communicating with each other. for one peer to send a mesage to another peer, the message has to go on the radio to the base station, which then retransmits it to the receiving peer, so the message is sent over the radio twice. and when you're talking about a lot of peers (like 100) doing a P2P operation at nearly the same time, you could run into situations where the peers jam the wifi network. you'll need to do some experiments to see how well your clients and base station handle that kind of scale.

          • 2. Re: Using rtmfp on wireless LAN without server
            thischarmingsam Level 1

            Thank you so much for your speedy feedback! I'll try testing it again with 100 tablets now I know what to look for. Is there anything you would recommend to accomodate the 500 tablets I've been asked to cater for?


            EDIT: Only using netgroup.post, not any other method.


            Thanks again