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Rob
In Deo speramus, God Bless the USA
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join:2001-08-25
Kendall, FL
 ·Comcast
| reply to jtorre69
Re: Thanks Comcast!
said by jtorre69  :It's not that at&t does not care about the state of their network, it's just that with at&t you don't share your network connection with your neighbors. It doesn't matter if your neighbor downloads countless data .That's what makes dsl a better product than cable modem. That's why at&t doesn't have to resort to this. DSL is a shared medium, just like cable. The difference is at which point you begin sharing your connection with your neighbors on a DSL connection is not the same point on cable.
DSL is not a better product than cable modem. Whichever service is available in your area, and reliable, that is which service is a better product. Not to mention that cable tends to yield faster speeds than DSL, constantly. | |
jvanbrecht
join:2007-01-08
Bowie, MD
| said by Rob :DSL is a shared medium, just like cable. The difference is at which point you begin sharing your connection with your neighbors on a DSL connection is not the same point on cable. By your account above, it means every single link is shared across the entire internet from business to residential service.
By shared, they mean segment, not the entire company, Cable segments are a shared medium, DSL is not as its a point to point connection via a local loop from your house to the ISP (bypassing the switching equipment in the CO since DSL is not a switched medium) Yes, on the ISP side it becomes shared when it hits the ISPs backbone as well as its connections and peering points to tier 1 backbones. BTW, ATT is a tier 1 backbone, where as comcast is just a customers of a tier 1 provider. If the ISP does not have the accumulated backbone bandwidth to provide all their customers with sufficient service, that is not the users fault, regardless of how much they download. | |
Rob
In Deo speramus, God Bless the USA
Premium
join:2001-08-25
Kendall, FL
·Comcast
| said by jvanbrecht :said by Rob :DSL is a shared medium, just like cable. The difference is at which point you begin sharing your connection with your neighbors on a DSL connection is not the same point on cable. By your account above, it means every single link is shared across the entire internet from business to residential service. By shared, they mean segment, not the entire company, Cable segments are a shared medium, DSL is not as its a point to point connection via a local loop from your house to the ISP (bypassing the switching equipment in the CO since DSL is not a switched medium) Yes, on the ISP side it becomes shared when it hits the ISPs backbone as well as its connections and peering points to tier 1 backbones. BTW, ATT is a tier 1 backbone, where as comcast is just a customers of a tier 1 provider. If the ISP does not have the accumulated backbone bandwidth to provide all their customers with sufficient service, that is not the users fault, regardless of how much they download. AT&T may be a Tier 1, whereas Comcast isn't (though they have their CRAN Network), yet Comcast provides much faster speeds than AT&T does. Obviously Comcast is doing something right if they are usign AT&T's network, yet bringing faster speeds than the Tier 1 provider is! | |
djrobx
join:2000-05-31
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2 edits | reply to jvanbrecht
quote:
Yes, on the ISP side it becomes shared when it hits the ISPs backbone as well as its connections and peering points to tier 1 backbones
Oops, but wait, lots of AT&T DSL customers are serviced from a neighborhood RT where they share fiber back to the CO. And now AT&T is moving to a FTTN architecture where the "nodes" are placed almost exactly like cable nodes!
You also seem to overlook that the "Tier 1" internet connections don't generally start until your service is done riding an ATM network from your CO to a POP somewhere. There isn't a direct conneciton to Tier 1 going to each CO.
Bottom line the "not shared with your neighbors" argument is really dumb and always has been. Sharing happens on even the best technology out there (FTTH). "Never shared" made for a cute advertising campaign for Pacific Bell back in the day but AT&T has long since stopped because they know it no longer applies.
What matters is how well and how fast a company works towards keeping their network mantained. | |
jvanbrecht
join:2007-01-08
Bowie, MD
| reply to Rob
Thats a limitation on DSL, which is heavily reliant on line quality and distance. That is one advantage that cable has over DSL. I do not live in an ATT service area, so I am not sure what they are providing with their fiber service that they are deploying. Also, as I stated in another post further down, yes they are a customer of a tier 1 provider, and odds are they use either ATT or Verizon (used to be uunet, then mci) as their provider, and I suspect they are probably running OC3's or OC12's to provide the bandwidth they need. But thats not the problem with cable. The problem is in fact that cable is a shared medium (all users on a particular segment share the bandwidth available on that particular segment), and yes, a single user can very easily saturate that segment, but that is not the users fault, that is the fault of the operator offering services it cannot support to stay in the game and compete against others who are offering faster services.
I am not being anti comcast.. well actually I am, but my beef with comcast has less to do with their bandwidth problems, and more to do with their billing practices, but that is off topic. I also equally hate ATT and Verizon.. so I consider myself unbiased on this fact. Also consider my background, I have worked for UUNET (before they were murdered by MCI and then Verizon), RCN, AOL Time Warner and Roadrunner (also owned by AOL/TW). I understand the technology and its limitations.
The issue at hand here however is not the technology, well it kind of is, but not completely, the issue here is Comcasts policy, which in my opinion is lame. A police officer cannot give you a speeding ticket, and then not tell you what the speed limit is that you broke (assuming all the speed limit signs were removed from the road) | |
KrK
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| reply to djrobx
said by djrobx :Oops, but wait, lots of AT&T DSL customers are serviced from a neighborhood RT where they share fiber back to the CO. Yeah, but it would take an AWFUL LOT of bandwidth heavy users I think to reach the capacity of the RT's Fiber connection.
Anyone from AT&T care to comment on approx. how much bandwidth an RT has? Because if you figure the TOP speed a user can get is around 8mbps down/1kup (and most much lower then that) then even if the connections were maxxed it would take a quite a few of them to overload the RT, me thinks.
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"Regulatory capitalism is when companies invest in lawyers, lobbyists, and politicians, instead of plant, people, and customer service." - former FCC Chairman William Kennard (A real FCC Chairman, unlike the current Corporate Spokesperson in the job!) | |
jobias
join:2006-01-18
Knoxville, TN
| said by KrK :said by djrobx :Oops, but wait, lots of AT&T DSL customers are serviced from a neighborhood RT where they share fiber back to the CO. Yeah, but it would take an AWFUL LOT of bandwidth heavy users I think to reach the capacity of the RT's Fiber connection. Anyone from AT&T care to comment on approx. how much bandwidth an RT has? Because if you figure the TOP speed a user can get is around 8mbps down/1kup (and most much lower then that) then even if the connections were maxxed it would take a quite a few of them to overload the RT, me thinks. This is a silly argument.
Seriously, what do you think cable nodes use to connect to the headend? Coax? Really? Cause you'd be wrong.
Cable nodes and DSL RT's both use a fiber link to talk to their respective Headend/CO. (lookup HFC: »en.wikipedia.org/wiki/Hybrid_fibre-coaxial)
The primary difference is that RT's offer individual lines to the home, while Nodes run shared coax to the house.
As djrobx points out, the bandwidth usage becomes an issue in the same place. If an RT is significantly over-subscribed (I say significantly, because they are, just as with cable nodes, cell phones, and even normal phone service, slightly oversubscribed by design) you'll see the same exact issues occur in DSL as when a hog pops up on a cable network. | |
KrK
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2 edits | said by jobias :This is a silly argument. Seriously, what do you think cable nodes use to connect to the headend? Coax? Really? Cause you'd be wrong. No, it's not silly. Each DSL user is connected directly back to the RT or CO. (Often called dedicated run). At that point, the connections of all the DSL users on the RT is combined and goes over fiber back to the "Cloud" if you will.
That means to experience slowdown, the *entire RT* has to be overloaded to the point the fiber connection from the RT's capacity is exceeded.
Now, with Cable TV, it's different. YES, Fiber comes to the Node... But then the node goes out on Coax and connects many homes.... 500... I'm not really sure. To experience slowdown, if people on your Coax run are overloading it, you will slowdown. The bandwidth capacity of Coax is a lot less then fiber, and if you have dozens of homes on one run, it's a lot easier to overload the connection **BEFORE** it gets back to the Node which is where the fiber is.
Basically, yes, it's possible for an RT to be oversubscribed.... and everyone on that RT to experience slowdown.... *but* it's a *lot* more likely that a cable run with many users on it will experience slowdowns because simply put, there's a ton of people sharing one coax connection run back to the Node. So with DSL, all the users combined on an RT have to overload it's *fiber* connection, whereas with cable, all the users on that one run have to overload it's *Coax* connection.
I can't really explain it any clearer then this.
Cool, here's an image that shows it well:
Typical DSL setup. Note the direct connections to the RT's and CO's.
Now, typical Cable setup. Note the runs of coax from the node with tons of houses all on the same run.
'Nuff said, methinks. | |
David
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| reply to KrK
said by KrK :Anyone from AT&T care to comment on approx. how much bandwidth an RT has? Because if you figure the TOP speed a user can get is around 8mbps down/1kup (and most much lower then that) then even if the connections were maxxed it would take a quite a few of them to overload the RT, me thinks. Well I will put it like this. The alcatel 7300 DSLAM for Central offices at bare minimum for management and program controls only takes an OC-12 (that's just management control). Consumer traffic management now a days to the DSLAMs is as least a OC-48 or better. I forget what the actual is but it was told to us if they activated the test DSLAM in our office and maxed out it's connectivity for the consumer side, it would only be at 1/2 the bandwidth of the connection required to connect to it. That's assuming all useable ports and shelves! They advised in training class you can max one out, but you are not meeting "minimum requirements" if you do.
Remote terminals are given 4 Fiber optic connections 1 Digital POTS + 1 DSL + 2 spares. I believe the connections currently to them are configured for OC-48 currently and with just a flip of a switch can easily be 192's. Hell the RT sends an alarm to the central office if the bandwidth ever hits 50%. The RT's send alarms for all kinds of things including fan problems, cooling problems, and even power problems.
Ironically the big problem for some RT's is they run out of ports for customers to connect to before they run out of bandwidth for one. I have never in my 7 years been here ever seen a bandwidth problem from an RT. I probably never will in my lifetime. The RT's have way more bandwidth than what they have ports for customers for. I mean it's something fierce on what those things have. From what I hear is some of the RT's now (and if you are close enough) will have Uverse capability right next to the DSL customers. Digital T1 customers and others even get provisioned out of there. One RT tech told me one day that he just got done turning up a DS3 connection from an RT. Those things are like lego blocks the possiblities are just endless.
Ironically they are working at the VRAD models to be the same way.
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KrK
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| THANK YOU.
In other words, AT&T DSL kicks ass. The chances of you experiencing slowdown at the Node level pretty much approach zero.
Now... How about if you raise the speed caps some  | |
codee
Premium
join:2001-10-01
Minneapolis, MN
| reply to KrK
said by KrK :Now, typical Cable setup. Note the runs of coax from the node with tons of houses all on the same run. 'Nuff said, methinks.
Do you SERIOUSLY think that there are still 2000 homes on a node?? 1000?? I hope you are joking with that picture because that is ridiculous....that is a good example of maybe 1999. I don't experience any slowdowns no matter what time of day it is. On a side note, I am totally against any sort of specific limit being stated by Comcast. It would probably be lower then what I sometimes use anyways, I mean look at the limits of the ISPs who DO state what they are - they're pretty low. Some months I may need to use 300+ gigs, and some I may use 50-75 gigs. I haven't ever recieved a letter/warning/bad behavior slip for anything before, and I'm pretty sure the limits wouldn't be as high as 300+ gigs. I like it the way it is now with no set limit. | |
KrK
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| I don't know how old that is, or how many homes are on a Node.
Perhaps a Comcast employee would care to comment?
Irregardless, however, whether it's 500 or 25, the point still stands.
They are all on one shared coax back to the node. If your neighbors are "hogging" the connection, it can get overloaded and slowed down.
Look this isn't a DSL vs Cable: Which is better bashfest. This is merely a description of the topographical differences of the systems, and lends itself to why there are or aren't caps and why they'd be necessary.
Peace.
--
"Regulatory capitalism is when companies invest in lawyers, lobbyists, and politicians, instead of plant, people, and customer service." - former FCC Chairman William Kennard (A real FCC Chairman, unlike the current Corporate Spokesperson in the job!) | |
David
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| reply to KrK
I didn't even say anything about the underground vaults. Those are and could be C.O. 's just on their own.
You can still slow down at a node, it's possible but typically your DSL and your Pots to the RT would have problems. We have whats called a "streaming RT" condition where the RT just keeps sending fragmented packets to the C.O. header and you can send no packets back to the RT or they all fail. Typically a switchover can fix it, however every now and then they have to go to the RT and change cards.
Those repairs are typically less than 4 hours. 90% of the time they are replacing a card at the RT while they are there or switch to the backup card and route that way till permanent repairs can be made. If the RT goes down hard they drive and change.
Now the areas they typically don't have a lot of bandwidth would be say small towns with DSL and such. For instance, say ozora, mo. Town of about 5,000 people and maybe say 300-500 live in town. an OC-48 for those customers might be overkill by quite a bit. Most times here they deploy a big dslam there as a "Master controller" and the adtran Dslams as a slave controller or the customer's side. Now they don't keep a lot of bandwidth for DSL here, but then again, how many customers in a small town are you expecting? You are not going to have say 1000-3000 customers like downtown STL on a given part of town. I can see the point here would be if they are not using enough traffic to really peak a OC-12 why give them a 48? At that point it's just overkill.
I remember last year there was a few different small towns in wisconsin that were getting another OC-12 between them and chicago for backhaul. The one and only OC-12 they had was and finally hit 50%. Before the traffic peaked 65% they had another one turned up and divided the traffic in like 1/2. I remember he said he checked his work like 6 months later and the original OC-12 was at like 30% and the other one just cracked 22%. Now how long was it before the 2nd OC12 was even required, it was 2+ years out. Even then he had it on the books to make them both 48's. Even if he did one this year and one next year, he would still have enough bandwidth available. Now that we have at&t's legacy network and SBC's legacy network, it's going to be interesting how they integrate everything. I am watching the changes on this side of the fence and it's just phenomenal.
I just for kicks and grins looked at my local dslam's percentages. Ya know on patch Tuesday it hit 12%? It's average for the month is 7%. Some days like labor day and Christmas it's at like 0%. I have seen a few days with goose eggs on the report. I am sitting here thinking I would take a pic if it ever hit 50%, but then again, I wonder how long I will be waiting? Or if the equipment or me will be retired by the time it happens?
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KrK
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| That's very good news. Awesome network management, really.
I'm very impressed. It's nice to know that if usage gets to 50% capacity the additional capacity is brought online.
It's overkill... in a great way. It's also pretty forward thinking. It suggests AT&T could deploy VDSL in a flash. Or break out more tiers. I guess the only thing that holds it back is the copper.
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"Regulatory capitalism is when companies invest in lawyers, lobbyists, and politicians, instead of plant, people, and customer service." - former FCC Chairman William Kennard (A real FCC Chairman, unlike the current Corporate Spokesperson in the job!) | |
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