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When we speak of the Internet data transfers and protocols, the normal process (that I'm aware of) is this:

  • A request is sent to the server (some data uploaded)
  • The server processes the request (on remote server)
  • The response is sent back to the client (data downloaded)

However, how does a satellite TV's set-top-box go about updating its firmware? I am aware that it just fetches (or downloads data) directly from satellite, which is then deflated and installed on the system. But how does it manage to make the request for the download, since it can never transmit data up to the satellite as a "request".

This uni-directional data transfer baffles me, and I'd be glad if someone could explain the protocol please.

2 Answers 2

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The model you describe is just the traditional way the web works, but is not the only communication protocol used. Now I can't say for sure exactly what your provider is doing, but assuming they're using a traditional IP network the most common way of doing unidirectional communication is to use the UDP protocol on top of IP (in a previous life I worked a lot with satellite communications and we did everything over UDP).

The provider likely broadcasts updates to all clients and then the software on the set top box , which is always listening for updates, checks if it should accept the update and then responds accordingly.

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  • Thanks for the response, which suffices to give me home-work on UDP. Could then, "this unknown protocol" be used to broadcast static web-pages such that Internet content like Wikipedia (read-only) may be accessed anywhere directly through satellites? Just like GPS?
    – xibalban
    Feb 20, 2014 at 15:27
  • It could, but it wouldn't make much sense since it would have to be the provider just pushing pages down to clients. Since there is no connection from the client back to the server there is no way for the client to request a certain page (like when you click on a link), so you would only be able to see pages the provider decides it wants to show you.
    – heavyd
    Feb 20, 2014 at 15:31
  • @heavyd: Well, that makes sense for a limited number of devices - listen for firmware updates pushed down the link, if it matches the model you have, save it and apply. This obviously doesn't scale well, but might work. Not useful for anything with a large set of variations, e.g. web pages. Feb 20, 2014 at 15:34
  • How about broadcasting a web-package, where the user could choose which package to download (say, a certain static website). The package could then be deflated on the user device and may contain the whole website. It could reside on the device cache, allowing room for more downloads.
    – xibalban
    Feb 20, 2014 at 15:45
  • As piskvor mentioned that wouldn't scale well since you would have to broadcast every possible pages to all clients, the set top boxes would have to have enough storage to store all possible pages until a client selects which page they want to see.
    – heavyd
    Feb 20, 2014 at 16:02
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It uses Broadcasting. It is a channel (a Frequency, an ip address for internet analogy) preconfigured by the manufacturer to communicate and in this case send firmware updates to the receiver. Like Sat channels send audio and video data to your receiver.

It doesn't need to send a request because the channel is always emitting the firmware file, i think they send the file in a loop with a begining sequence preset. So the receiver looks for the begining sequence and start copying from that point.

Check this wikipedia page for more information : https://en.wikipedia.org/wiki/Broadcasting_(networking)

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  • Thanks, and you may like to join our discussion on @heavyd's answer. We are debating if websites could be broadcasted by satellites. Could turn out to be very useful for remote area information access directly to a mobile handheld device.
    – xibalban
    Feb 20, 2014 at 15:52
  • @xibalban: for broadcasting a web-package the inconvenient is that the user cannot interact (transmit a request back) unless he has an emission system (like in internet over Satelite). The only way he has to choose is by choosing another channel where another web-package will be broadcasted or to send him the complete website and he chooses locally from cache.
    – Arch User
    Feb 20, 2014 at 16:17
  • I was referring to the latter i.e. downloading the complete static website (or a section of the website) and viewing it from cache.
    – xibalban
    Feb 20, 2014 at 16:19

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