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I hope my question is fine for this group, and if not, I'll remove it as soon as required. Hereis a shot description of our problem:

  • Our system has many clients (about 500) that should be updated via WiFi 802.11b through the same ftp server.
  • We can't modify the network setup (i.e. we can't use 802.11g/n client) but we can update firmware on the peers.
  • The size of the update is 200 MB and the clients access.
  • the clients can't be updated in different slice time, since they wake up and shutdown almost at the same time.

Since ftp unicast connections are a bottleneck, we are evaluating a multicast over WiFi approach. (something similar to the way TV producer use DTV channel to transmit firmware updates)

However I didn't find, on the web, many information about this idea on WiFi. I found something about broadcast video streaming, but nothing more. Is there someone that can provide me an idea, a well documented protocol in order to implement such a system? Furthermore, is there someone that, if so, can explain where our approach is wrong? Thanks a lot Giovanni

  • Not really sure how to answer this one as multicast is pretty well documented. Are you looking for software that would do this? If so, this wouldn't be the place to ask. However, I would throw in that using multicast on 802.11 will require that the wireless infrastructure is configured for it and your client devices would have to join a multicast group upon booting up. Also there are some performance issues you would want to consider when using multicast (as it by default will run at the lowest base speed, often 1 Mbps). – YLearn Jun 1 '14 at 12:46
  • Multicast will not work very well for file transfers (irrespective of using wireless media). You really can't use any TCP application with multicast. Imagine if you are sending a file to three clients, and one drops a packet. How would you retransmit? That is why all multicast apps are UDP. – Ron Trunk Jun 1 '14 at 18:06
  • @Ron, while generally speaking this is true, this is not always the case. One example of software that uses multicast for imaging quite successfully is Symantec's Ghost which can image multiple machines utilizing multicast. This is a feature often used in universities when they image computer labs or some larger companies imaging machines for hardware refreshes at scale (if they aren't paying their hardware vendor to do it for them). – YLearn Jun 2 '14 at 17:48
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mtftp would be what you're looking for. HOWEVER, you are very quickly going to learn wireless (esp. old 802.11b hardware) and multicast do not play well together. Outside Uverse circles, it's hard to tell what wireless APs can deal with multicast -- Uverse has wireless receivers fed from an isolated AP, but the limit of 2 STBs suggests they don't work so well either.

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  • First thanks everyone for the reply. I'm not searching for a SW, but for a protocol suggestion. I thought that there should be something similar to the DTV smartbox update system, using multicast udp packets, sent in a period, cyclic way. However it seems I was wrongmtftp I wasn't able finding any reference, can you link any doc about this topic? Thanks again – Giox79 Jun 2 '14 at 19:04
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    Sorry, I found it,tools.ietf.org/html/rfc2090 – Giox79 Jun 2 '14 at 19:10

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