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Technical Questions

Discussion in 'DIRECTV - Coax Networking (private)' started by Sixto, Jun 22, 2009.

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  1. Sixto

    Sixto Well-Known Member

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    Curious about a few things ...

    For the receiver to DECA coax connection, do we think only power is provided, or the DECA is actually talking to and sending some data to/from the DECA thru the COAX port? I wonder how it knows it's there?

    When the receiver talks to the network thru the Ethernet port, do you think it actually does anything special because it's a DECA, or it doesn't care?

    I have all DHCP and it looks like each receiver got the same IP address, and shows the MAC address at the router the same as before, so to the rest of the network going thru the DECA is exactly the same?

    How do you think the network DECA works, it's just some sort of bridge from MOCA to Ethernet?
     
  2. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    yes.
    MoCA to MoCA is a "sub" network and outside it's "just a network".
    Much like having a fiber link.
     
  3. Sixto

    Sixto Well-Known Member

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    So the network DECA is somewhat like a switch? It just passes packets through both ways?

    So when the receiver boots, it searches for a DHCP server, just like before ... the request goes out the Ethernet port, to the receiver DECA, which converts the request to send it over the 500-600Mhz path, which then goes to the network DECA, which then converts it from the 500-600Mhz path onto the real Ethernet network, to the DHCP server?
     
  4. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "Seems right"
    You've got "packets" loaded onto RF and unloaded at the other end.
     
  5. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    Technically, I think the DECA is a bridge. A switch keeps track of MAC addresses and only forwards packets to the proper network interface that is known to have a MAC. A bridge is more transparent (stupid) and sends all packets all the way thru. (A hub is a multi-port bridge.)

    From what I can tell... The ethernet ports on the receivers might not even know the DECA is there. Take the case of a PI powered DECA on a HR20-100 or H23. The receiver wouldn't even know via the tuner port...

    I'm pretty sure that all the receivers do is supply power, tho they might do some work to recognize when DECA's are present and then turn on the 20V power. How that is accomplished, I'm not sure.

    Yes, a lot of speculation on my part. We'll see what further testing brings. :)

    Cheers,
    Tom
     
  6. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Since speculation is running rampant, I'll go so far as to say that the DECA doesn't even know/care about 13/18 volts as it simply has a voltage regulator that drops it down to 5 volts for the chips.
     
  7. Sixto

    Sixto Well-Known Member

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    Thanks Tom.

    So it seems that the receiver somehow recognizes that the DECA is there, turns on power to the DECA, and then the DECA can mimic a real network to the Ethernet port. And then the DECA bridges Ethernet-to-MOCA(500-600Mhz) two-way.

    And all the DECA's listen to 500-600Mhz and pass packets around.

    So technically, using a hardwired network, all attached to a real switch, packets would flow between two ports of the switch without other ports seeing the packets, while on a MOCA network probably every port sees every packet.
     
  8. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    I've done some more research and it seems like the DECA is smarter than I expected. Might very well be a switch between the DECA cloud and the hardwired network. But I'll keep playing.

    Cheers,
    Tom
     
  9. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    While you are very likely correct, the DECA is not expected to survive a PI-29V. Don't use a gray PI to power a DECA.

    Cheers,
    Tom
     
  10. dettxw

    dettxw MRVing

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    Any idea, other than the previously mentioned possible expansion of SWM channels, why in the world they chose to use OTA frequencies instead of something above 700MHz?
     
  11. Sixto

    Sixto Well-Known Member

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    Yep, be interesting to see if it's possible to hook a non-DVR to a DECA (powered by receiver) and check the throughput to a non-DVR on the other side, across a Gigabit network.

    For now will stick with the trial assignment :) but someday ...
     
  12. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    DOH!!
    Now you tell me not to use my 29 volt PIs.
    That's all DirecTV has given me for my SWM LNBs.
    [Actually the nervous nelly in me has kept them out of the loop]
     
  13. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "I have no idea", but we're using 1/2 the frequency of the CATV system.
     
  14. dave29

    dave29 New Member

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    Maybe it is because Direct has been trying to phase OTA out???
     
  15. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Doubt the AM21 would be here if DirecTV really wanted to phase out OTA,"but" diplexing has been unsupported for a fairly long time now.
     
  16. Sixto

    Sixto Well-Known Member

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    Yep, the availability of the AM21 does complicate the discussion, but for sure OTA has been referenced as unsupported for a while.

    It's always appeared that 12 SWM channels was more optimal to cover 95% of the user base, rather then the 8 available today.
     
  17. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "12" is to 9, as 11 is to 8.
    There is space for 3 new SWM channels above what we have now.
    There isn't space below what we have now, since the tuner needs to start at 950 MHz.
    Guide data & software downloads [to update to SWM] have to be in common between SWM & non-SWM.
     
  18. DJPellegrino

    DJPellegrino Godfather

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    Curiosity is killing me here..but before I try it I would like to run it past you guys.

    In my depiction below, I would like to add a 3-way splitter to the mix. On output 1 I'd like to run my internet connection, on output 2 I'd like to run the cable connection to the DECA. On output 3 I'd feed the standard room.
    From the DECA I'd connect the PI-21v and then the cable modem. From the cable modem I'd connect the router. Also, the network port from the DECA will be connected to one of the wired ports of the router.

    My thinking is, and based on one of Tom's comments, the PI power will be used by the DECA. The DECA is filtering the network traffic 500 - 600 mhz and sending it thru the network port. I assume all else is passed thru the coax thru to the modem. So as the router has something for the network, it will hit the DECA which will place it on the coax back thru to the STB's on the DECA network.

    Does this explain enough what I am looking to do?
    Basically I want to get network traffic to the STB's via the coax and eliminate the wireless.
    What causes of concern are there?

    Possible DECA Satelitte & Internet Setup.jpg
     
  19. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    ?? Splitter for the Internet? Is this cable internet you're trying to duplex into the SWM stream?
     
  20. DJPellegrino

    DJPellegrino Godfather

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    yes it is cable internet, but I'm not really trying to push it to all locations, even though it will end up that way. The other locations won't do anything with the internet traffic since there is no cable modem there that has been provisioned. I'm trying or want to try and use the existing coax to pass the local network traffic between units without the wireless connection I currently have. I am unsure if the signal from the DECA being back fed into the coax will disrupt anything up to an including the internet provider seeing a 500-600mhz signal on their line.
     

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