How does Comcast deliver dial tone? [telecom]

I was on a phone call with a friend who has phone service from Comcast, and I was reminded several times of why I dropped them: his voice would cut off for two or three seconds at a time, and he said mine would too.

Does anyone know why Comcast has so many problems with their phone connections?


Reply to
Bill Horne
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I hate to say it, but that's not unusual for Comcast.

When I lived in Atlanta, I was living in a house with others. We had Comcast cablemodem. When I moved in, we were only getting three hundred kilobits per second.

I spoke with the landlord and then we called Comcast.

I may have already told this story. They'd come out, confirm that I was only getting three hundred kilobits per second. They'd test for a while, then they'd tell us they were going to check it 'upstream'. I discovered that was just their way of giving up on fixing it and a polite way to vamoose.

I'd call again and ask what is going on with the 'upstream' check. They wouldn't know anything about it and send someone else to the house. And this process would repeat again and again.

Finally, I called the county franchise office and they escalated it through Comcast.

So this time they sent someone who knew what he was doing. He did something that none of the other repairman had done (he swapped out the cablemodem).

Miraculously, that's all it took to fix it. And none of the previous folks could figure that out. If one of them had, they wouldn't have had to make the other trips. And we were getting calls from the Comcast repair supervisor complaining to us about how many times they had to come out.

When Comcast cablemodem works, it works fine. But when you have problems, don't count on a fast resolution. You may have to lock horns with them or escalate it through your county franchise office.

Some of the other cable companies have similar problems.

When I moved from Atlanta to New Mexico, I discovered that Comcast was here, too. And I've used them a good bit. Fortunately, I've not had service problems as previously described in New Mexico.


At 11:43 PM 3/9/2011, Bill Horne wrote:

***** Moderator's Note *****

A. Because it disrupts the normal top-to-bottom flow of a written communication. Q. Why is top-posting bad?

Bill Horne Moderator

Reply to
Fred Atkinson


Reply to
Adam H. Kerman

Same problems as with any VOIP over a shared "party line" connection, latency and congestion. Phone calls are where latency shows up first, because you have to send and receive the packets in order and regularly, and the majority of them need to arrive on time and in order. If there was a huge buffer of data packets to keep it streaming constantly over a so-so connection (and allow time to resend any missing packets) there would be a huge time delay in the conversation

- like watching TV News conversations between the Anchor in New York and the Correspondent in Cairo when there is a 6 to 8 second delay because of multiple satellite hops.

There are a few hundred to a few thousand houses on the one segment of cable sharing the same physical layer and one node of backhaul (converted to a DS1 or DS3 on the cable system's fiber-optic backbone cable to the headend) to "The Internet" at large - and everyone using data (and the phone call is data) is sharing that one pool of bandwidth one at a time. You get a slice of time every few milliseconds to send and receive your packets, then the bandwidth goes to the next customer, and the next, and the next, and the next.... If the segment is overloaded you have to wait a while for your turn to come around again, and may not get to send and receive as large a packet as you want, and that will make the signal choppy and stuttered both ways.

This is exactly the same problem as the old first-generation Thin-net Ethernet for offices - everyone is on one loop of coax back to the server, and when the loads get too high and there are collisions between nodes it becomes slow for everyone. And if one user node has problems and is sending out bad data the whole system goes down. (Been there, Done that, Have the BNC tees and terminators...)

And when the cable segment is overloaded (as they often are) it can make voice service unusable. What's worse, the cable company can give priority for time slices to certain customers using their paid-for Comcast Phone VOIP and Premium Movies On Demand customers, making the service even worse for those using "free" Skype, Ooma, Magic Jack, BitTorrent or other services - IF the cable company doesn't deliberately sabotage their use to free up more bandwidth for their "paying customers"...

(Which is what "Network Neutrality" was originally intended to correct, the carrier's attitude that "some bits are more valuable to us than others, or are being sponsored, and they get priority..." But that whole idea has been corrupted - and is a whole 'nother discussion anyway.)

The cable company can split the segment in half (or more) and issue the dedicated backhaul channels to much smaller pools of customers - but they won't do it unless and until their premium subscribers are affected because it affects the bottom line, They have to roll a truck and invest in more physical plant to do it, and it raises the internal costs for a larger Internet feed and more servers at the headend... Much easier for them to single out the top few users of internet bandwidth in the area and cut off their service for "abuse" of their monthly traffic cap or calling it a "commercial use at residential rates" or some other lame excuse, and the service will get better for everyone else on the system - for a while...

Welcome to the United States - We invented fast internet, just can't get it into our houses. I'm at almost 18 KFt out from the CO (the hard limit) they won't put me on the U-Verse Remote DSLAM's (the perennial response is that "it's full...") and plain old DSL can only do 128K - and it's wheezing along at that. But that tiny little slice of bandwidth is *all mine*, not shared with all my neighbors.


***** Moderator's Note *****

I used to have DSL from Covad, which topped out at ~680Kbps, not even the minimum I had contracted for. Covad couldn't fix it.

I recently changed to (spit) Verizon DSL, which does 1,500Kbps with no problem. It seems that some cable pairs are more equal than others: 'twas ever thus, 'twill ever be.

Bill Horne Moderator

Reply to
Bruce Bergman


That may sound a little facetious to some people, but I wonder with our increasing reliance on Wireless connections of all sorts that this sort of thing will be an increasing issue over the upcoming decades?

The number of individuals on the planet reliant on Wireless connections must have exploded since the last 11-year Sunspot cycle.

-- Regards, David.

David Clayton Melbourne, Victoria, Australia. Knowledge is a measure of how many answers you have, intelligence is a measure of how many questions you have.

Reply to
David Clayton

You might be getting constant speeds because they have Interleaved your cable pair. I had major problems with very old cable and slow speeds, the Noc Tech set my line this way and all problems went away, that is unless it really rains hard.

Reply to

Comcast's phone service is based on PacketCable, which includes QoS features that give the phone traffic priority over data.

I'd be rather surprised if the problems were due to congestion on the cable system.

R's, John

Reply to
John Levine

[Moderator snip]

THE reason why voice over IP is a second class service. A dedicated circuit (i.e. a switched circuit connection) will always deliver better service than an IP connection. Unless, of course, one provides unlimited bandwidth...

Of course, cost prevails...


Reply to
Eric Tappert

Sounds sort of what I'm going through with a client right now. One of their sites has terrible network performance but they won't tell me anything about the properties of that network.

So I suggested sun spots, backhoe fade, etc.

Reply to

Nah. You're taking jobs away from the customer service reps at their network provider whose job it is to read from the excuse of the day calendar when misfiling trouble tickets. You want the recession to end at some point, don't you?

Reply to
Adam H. Kerman Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.