 alchav
join:2002-05-17
Palm Desert, CA | reply to a333
Re: useless... said by a333:DOSCIS 2 shares the 50 megs among like 50 users, so comcast cant use it to offer those speeds to each and every sub. Now, hopefully, with channel bonding and the rest of it, DOSCIS 3.0 should be able to make those speeds possible. I agree with a333, Cable Companies and Telco's are laid out differently. Cable Companies work on a sharing Network, while Telco's Network starts at the Central Office. DOSCIS 3.0 or Fiber through a Cable Company will still have limitations. Like I said Verizon FiOS is the clear winner anyway you look at it. |
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 MattAll noise, no signal.Premium
join:2003-07-20
Jamestown, NC
kudos:12 | said by alchav:said by a333:DOSCIS 2 shares the 50 megs among like 50 users, so comcast cant use it to offer those speeds to each and every sub. Now, hopefully, with channel bonding and the rest of it, DOSCIS 3.0 should be able to make those speeds possible. I agree with a333, Cable Companies and Telco's are laid out differently. Cable Companies work on a sharing Network, while Telco's Network starts at the Central Office. DOSCIS 3.0 or Fiber through a Cable Company will still have limitations. Like I said Verizon FiOS is the clear winner anyway you look at it. You do realize FiOS' BPON and/or GPON architecture is shared at the neighborhood node right, not at the Central Office. |
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| reply to alchav
ODNs are shared -- a BPON distribution hub (in the metal box at the end of your street) splits 622/155 Mbps among 32 users. In other words, if all 32 Fios users on a hub took 20/20 service and maxed out the upstream they would only be able to get 4.84 Mbps each. |
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| Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable. |
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 espaethDigital PlumberPremium,MVM
join:2001-04-21
Minneapolis, MN
kudos:2
 ·Clear Wireless
| said by Heyya :
Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable. FiOS uses TDMA on the upstream as well to solve the "multiple speaker" problem in the same way as cable. Based on my understanding of FiOS, each neighborhood distribution would share 1 port on the head-end. The downstream light path is split to 32 homes with the head-end being the only speaker so there's no chance of transmit collision. Each of the 32 homes off the distribution node sees the same downstream data feed just like cable. On the upstream each home is fed into an optical combiner to go back to a common upstream node port. The reason you are limited to 155mbps upstream is because of the TDMA timing overhead to ensure that upstream data transmissions are handled in a controlled fashion and 2 ONTs don't transmit at the same time.
The biggest difference is network scaling; Verizon needs one head-end port per 32 homes, whereas Comcast can go as wide as 1 head-end port per 1000 homes in some cases. |
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Reviews:
 ·Comcast
| reply to Matt
Technicallity , they are shared at the block muxer. Meaning they are shared at the 32 sub block , where its muxed onto the main fiber ring. But in all real world speak they have less people packed on a "node".
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"It's always funny until someone gets hurt......and then it's absolutely friggin' hysterical!" |
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Reviews:
·Comcast
| reply to espaeth
said by espaeth:said by Heyya :
Thats incorrect. Fios uses two data lightwaves upstream and downstream and both are up to 622mbps on BPON. Plus its using TDM so its not actually shared like cable. FiOS uses TDMA on the upstream as well to solve the "multiple speaker" problem in the same way as cable. Based on my understanding of FiOS, each neighborhood distribution would share 1 port on the head-end. The downstream light path is split to 32 homes with the head-end being the only speaker so there's no chance of transmit collision. Each of the 32 homes off the distribution node sees the same downstream data feed just like cable. On the upstream each home is fed into an optical combiner to go back to a common upstream node port. The reason you are limited to 155mbps upstream is because of the TDMA timing overhead to ensure that upstream data transmissions are handled in a controlled fashion and 2 ONTs don't transmit at the same time. The biggest difference is network scaling; Verizon needs one head-end port per 32 homes, whereas Comcast can go as wide as 1 head-end port per 1000 homes in some cases. But did you know that Verizon can also add amplitude modulation on top of the time division ?just by updating the "headend" what it does is functionally make up to 4 muxes able to send on the same light wave at different timing intervals after a handshake , pretty neat stuff I say.
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"It's always funny until someone gets hurt......and then it's absolutely friggin' hysterical!" |
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