Is Cable (Coax) Internet Half Duplex?

[Klueless]

I finally have a chance to upgrade the car lots I work at part time from (s)low speed DSL to 100x10 Mbps Internet through a "new" cable TV provider at a (finally) affordable price.

Our computer consultant strongly suggested I contact his network consultant and that guy is suggesting fiber between the two car lots and fiber based Internet. While I do see some advantages I do not see it being worth the extra cost.

In closing he said, no worries; because coax is half duplex and when "up" floods "down" (and vice-versa) you'll be calling me back.

Well I "think" I get his point; because coax is a single wire it "must" be half duplex. But, on the fip side, because the cable company is advertising up and down speeds the modem pair must be doing some serious hand shaking and flow control rather than leaving the coax vulnerable to being flooded with collisions (ala fat Ethernet). But then there's a lot of other stuff on that cable line that runs down the road so I really DON'T know how everyone gets their fair share on a single wire.

My gut says it's all histrionics and to go with the cheaper solution. But I'm a little intimdated because these guys are the experts and without their support I might have to go it alone and provision new routers, pull cable, provision a couple APs, figure out how to set up a VPN tunnel between sites and so on.

(On one hand I'm a little scared but on the other hand it'd be nice not spending my mornings picking up cars : -)

 

[sfx2000]

Are you talking about MOCA?

 

[ColinTaylor]

I don't know if there's something unusual about the "cable" service you're talking about, but AFAIK normal cable internet is not half-duplex. It's essentially the same as ADSL but across a broader spectrum. It's like radio, just transmitted down a wire instead of through the air. The frequency spectrum is divided into slots, some of which are used for upstream and some of which are used for downstream.

Or are you talking about a site to site link, rather than customer premises to internet?

 

[CaptainSTX]

I finally have a chance to upgrade the car lots I work at part time from (s)low speed DSL to 100x10 Mbps Internet through a "new" cable TV provider at a (finally) affordable price.

Our computer consultant strongly suggested I contact his network consultant and that guy is suggesting fiber between the two car lots and fiber based Internet. While I do see some advantages I do not see it being worth the extra cost.

In closing he said, no worries; because coax is half duplex and when "up" floods "down" (and vice-versa) you'll be calling me back.

Well I "think" I get his point; because coax is a single wire it "must" be half duplex. But, on the fip side, because the cable company is advertising up and down speeds the modem pair must be doing some serious hand shaking and flow control rather than leaving the coax vulnerable to being flooded with collisions (ala fat Ethernet). But then there's a lot of other stuff on that cable line that runs down the road so I really DON'T know how everyone gets their fair share on a single wire.

My gut says it's all histrionics and to go with the cheaper solution. But I'm a little intimdated because these guys are the experts and without their support I might have to go it alone and provision new routers, pull cable, provision a couple APs, figure out how to set up a VPN tunnel between sites and so on.

(On one hand I'm a little scared but on the other hand it'd be nice not spending my mornings picking up cars : -)

CATV and Internet over cable use channels/ frequencies. Think of the COAX cable as a medium over which the RF frequencies are transmitted instead of being transmitted over the air. It is not an electrical transmission over copper wires like old style POTs.

 

[sfx2000]

Or are you talking about a site to site link, rather than customer premises to internet?

That's why I was asking the question - DOCSIS is typically service to the premises, MOCA is quite a different thing - site to site/node to node over a private plant.

In any event, being half/full duplex is kinda moot, as it's a scheduled MAC layer, so whatever tech is in use, it should be able to hit speeds consistent with the RF conditions (COAX is RF over the coax cable at the lowest layers)

 

[coxhaus]

In the old days you had Ethernet and Arcnet which ran on coax. One was 50 ohm and the other was 75 ohm. You did not want to mix those up. It was hell to find the problem when you had miles strung out. Ask me how I know?

 

[sfx2000]

Ask me how I know?

I'll ask, but I think I know the answer

 

[coxhaus]

In the early days IBM was king. We had a 1 mile token ring on a campus. It was not coax but fiber.

 

[Klueless]

In the old days you had Ethernet which ran on coax.

Thank you everyone for your patience, kind replies and for (ding, ding) bringing me into the 21st century. I guess I did get caught up in the "old days" when you had Ethernet running (at 2 or 3 Mbps) over coax as a (half duplex) backbone to tie multiple buidings together.

Y'all reminded/taught me that just ain't the way things are anymore. "Slotted", "scheduled", etc.; I'm starting to get it, it may be shared but it ain't "half duplex". I was completely forgetting what new technology can do with aging media. That (s)low speed, 7 Mbps DSL line I complain about is the same copper pair I used to get 110 bps on.

Yep, I'm going to ignore my apparently self serving experts and go with plain ol' affordable cable Internet.