An anonymous reader sends us to Telephony Online for a story about Comcast's second attempt at traffic management (free registration may be required). After the heavy criticism they received from customersand the FCC about their first system, they've adopted a more even-handed "protocol agnostic" approach. Nevertheless, they're once again under scrutiny from the FCC, this time for the way their system interacts with VOIP traffic. By ignoring specific protocols, the occasional bandwidth limits on high-usage customers interferes with those customers' VOIP, yet Comcast's own Digital Voice is unaffected. Quoting:
"The shocking thing is just how big a Pandora's box the FCC has appeared to open — and it just keeps getting bigger. When the FCC first started addressing bandwidth usage and DPI issues, it quickly found itself up to its knees in network management minutia. Not long after that, it followed another logical path of the DPI question and asked service providers and Web companies about their use of DPI for behavioral targeting. Now it seemingly has opened up huge questions about what it means to be a voice carrier in the age of IP. It's not hard to imagine the next step: What about video? Telco IPTV services are delivered in roughly the same way as carrier VoIP services — via packets running on the same physical network but a prioritized logical signaling stream. Is that fair to over-the-top video service providers?"
If Comcast is having major network congestion then why did they automatically double everyone's download speeds? I got a letter a few days ago saying that I now get 12 down rather then 6. Seems like a BAD idea if they are having congestion issues...
Yeah because they buy non symmetrical DS3's and above amirite?
I doubt the problem is up at that level anyways. The price per byte on the backbone is so cheap it hardly matters. It's the few miles nearest end users - where most of the network actually is - that matters.
I wish they (all ISPs) would start honoring TOS flags and then start selling packages like X gigabytes of 1st class traffice, Y gigabytes of 2nd class traffic, and Z gigabytes of 3rd class traffic. Presumably people would use 1st for VOIP, 2nd for ssh or websurfing, and 3rd for bittorrent. But if somebody configures bittorrent to use 1st class, it's not the ISPs problem.
All that said, I have comcast's very slowest "broadband" - 768kbps (i.e. under 1 mbit), and vonage always works fine. I haven't noticed any congestion problems on their network.
Finally, why the submitter thinks video is such a dilemma is a bit of a mystery to me. 99.9% of video is download - not interactive video phones and such - so having some jitter isn't really a problem, easily solved with buffering. It doesn't need to compete on the millisecond scale with voice traffic.
The problem is that ISP's pay per megabyte for uploads. Downloads are free for them except for the cost of the line and equipment maintenance., etc. That's what this is really all about.
The problem is that the DOCSIS spec involves having your own little slice of frequency for downstream but everyone shares upstream. Your DOCSIS 1 stuff would let you dump 5 or 6 megabits to each of thousands (well, okay, maybe hundreds):) of subscribers at once if you could actually feed the data into your head end fast enough. But sending the data back upstream is done on a shared frequency. Some line cards have multiple frequencies (no idea what they are now; when I worked for Cisco Santa Cruz when they were developing the Cisco DOCSIS modem ref design firmware it was the MC11 and MC16, I think, the MC16 had six upstream channels) so that you could send the same downstream to a whole bunch of places, but segment their upstream and feed it into the different upstreams (inputs on the line card.) If you run out of bandwidth you can charge more, and buy more bandwidth. But if you run out of upstream bandwidth on the line card, you have to add a line card and go forth and physically segment your network.
You don't understand cable system design. The reason for the 6:1 ratio between upstream and downstream is not because Cisco (or anyone else) thinks you can oversubscribe the upstream spectrum, but because upstream carrier to noise ratios are much worse than downstream. Because of the lower CNR, upstream modulation has to have a lot more interleaving and error correction (and much lower symbol rates). It also helps isolate noise problems to a smaller service area.
Part of DOCSIS 3 spec is 64QAM upstream. Some operators are trying it now, and finding out that there's a whole new level of plant maintenance necessary to deliver a good upstream bit error rate. Meanwhile, the normal downstream carrier is 256QAM (6.4MSym/s symbol rate), which requires a 3dB improvement in CNR over 64QAM at the same symbol rate. As fiber is driven deeper into the cable network it will be much easier to increase the upstream modulation to 256QAM and downstream modulation at 1024QAM. Typical cable systems today use 16QAM modulation in the upstream, with a 3.2 MSym/s symbol rate.
And, it is fairly common to have multiple upstream carriers in a node (neighborhood). DOCSIS 3.0 adds support multiple downstream carriers* through devices called edge QAMS. The downside of that is most operators have 65 or so analog channels, several dozen digital cable channels, 4-5 VOD carriers, and one DOCSIS 2.0 carriers in the downstream. The push is to get rid of the analog channels, but that's politically unpopular since it would require all customers to get a set top box for every TV (someday tru-2-way TVs and set top boxes will be at Best Buy, but it's a long time coming). Once 3.0 is deployed, the typical system may have 3 or more bonded downstream carriers/service group, about 500 customers. End users will need a new modem to get full use of the channel bonding, but it should be worth it for the much greater increase in speed.
Finally, everyone always gets the "shared bandwidth" argument wrong. Most people think of DOCSIS like classic Ethernet, with a hub or daisy chain cable. This means that Ethernet NICs need to use CSMA/CA to avoid collisions. There is no way for a cable modem to hear another one, so the CMTS assigns a mini-slot to a cable modem when it is provisioned/registered (which essentially makes a TDMA channel). the ONLY time a modem is permitted to transmit is at it's assigned mini-slot. Over the years, CMTS software has improved, and operator's understanding of the configuration has become much more granular, to the point that bandwidth optimization is much better understood than it was 10 years ago, along with moving from 7200 series network engines to VXR and above (in the case of Cisco).
*There is some use of multiple downstreams now, it has been in the spec since DOCSIS 1.1, but isn't needed on much more than a temporary basis. Individual modems can only tune one carrier at at time, so it is typically used to get more customers on a node than it is used to get higher speeds. However, some operators have used multiple downstreams to isolate business class customers from everyone else.
As a result, the term Tier 1 Network is used in the industry to mean a network with no overt settlements. An overt settlement would be a monetary charge for the amount, direction, or type of traffic sent between networks.
Common definitions of Tier 2 and Tier 3 networks:
* Tier 2 - A network that peers with some networks, but still purchases
start selling packages like X gigabytes of 1st class traffice, Y gigabytes of 2nd class traffic, and Z gigabytes of 3rd class traffic.
That seems like it would be a bit complex, and also problematic if they did not ship their own routers and instructions for configuring it.
Why not just sell pure bandwidth, and if people want to prioritize things, let them do it within their own networks? If I'm saturating my connection with BitTorrent, it's really up to me to QoS it down until Skype works. But, if I'm saturating my connection with BitTorrent, and someone else is having problems with Skype, that suggests they should buy more bandwidth.
I can see where TOS might be easier for the ISPs, let them squeeze a bit more out of their networks, maybe oversell a bit more and acknowledge that your torrent will slow to a crawl (but your voice will still work) during "peak" hours.
On the other hand, Amazon seems to be able to put a relatively cheap, relatively constant price on all network traffic to Amazon Web Services. I don't know if my bill is typical, but I pay $65 for fiber -- split evenly, that would be 300 gigs upload and 176 gigs download, or 150 gigs up and 265 gigs down... per month. I mean, I might do more than that torrenting, but not much, and I imagine that's a good deal more than Comcast currently provides.
It's probably the NSA's traffic cloning and storage system that can't keep up with trying to record all of America's VOIP calls. We're sorry, but this mailbox...United States of America...is full.
Comcast is having big issues in my area. The initial time to hook up to my ISP every day is between three and five minutes. That is lousy service. Now that they are providing phone service on the same cable lines if they cause a death due to net congestion or not being able to hook up to their service then huge damages as well as punitive damages should apply.
I don't give a hoot if they have to run two cables into every home this no
If someone is doing very high traffic, enough to get into Comcast's temporary "QOS Low" category, they are probably sending and full rate. If you are sending at full rate, the typical end-host NAT and buffering alone will cause bad quality for VoIP (search for VoIP and BitTorrent for a lot of such tales). There is nothing Comcast's network management really does to affect things in this case anyway.
Comcast's network management should only cause additional VoIP issues when the big transfer STOPS and the VoIP call is made within only a few minutes (before the user's link is reclassed back into the "QoS normal" category).
Did you read the part in the summary which said that Comcast VOIP was unaffected by this problem?
What was not mentioned is that Comcast's VOIP is out of band. I'm no comcast apologist (comcast's policies were the straw that broke the came'ls back and got me to move to a new house where I could get verizon FIOS) but this is less of an issue that it has been made out to be. From day one, comcast's VOIP has used seperate channels from their internet services. Their VOIP is limited to connecting to POTS or other comcast VOIP customers. It is not on the internet, it is only on a comcast private intranet.
From day one, comcast's VOIP has used seperate channels from their internet services.
I'm not sure that's really the issue. I'll admit a little bit of ignorance on the issue, but what would happen to your upload rates if Comcast opened those VOIP channels to normal data? Or what if they allowed VOIP to travel on those channels whether they were the VOIP provider or not?
Because I think the issue is that they're providing a limited amount of bandwidth to the home and complaining about congestion, meanwhile setting aside access for their own services. I can't blame them, since it probably m
To clarify... Comcast Digital Voice, like any PacketCable service, uses reserved capacity. It comes off of the cable modem channel, at the physical layer (minislots), and it keeps the telephone calls off of the Internet. CDV is NOT an Internet phone service at all. It's a separate access network, using MGCP-derived signaling and RTP/IP encapsulation of voice.
If the phone is not in use, then a tiny bit more capacity on the cable (100 kbps/call) is made available for data. If you think that's unfair, fine, but that's how PacketCable works, and it maximizes efficiency for the whole system. It's safe, legal, and non-fattening.
My home router actually had a 10Mbps Half Duplex WAN port for some odd reason. I had to find a new router to get the full 12 down speed they promised. Oddly 10 Mbps WAN ports are still very common on home routers, even brand new ones.
I don't know what's going on in my area, but Comcast sucks ass out here. The connection will just flat-out drop for 10-20 seconds at a time. Really fucks you up when you're trying to play a game online. They've had techs out here a few times with no results. Thank God I just found out that Qwest has their 7Mbps DSL service out here. I'm crossing my fingers and hoping that it's better than fucking Commiecast's godawful service.
Sometimes you have to keep on complaining. I had a similar problem that wasn't solved until they finally sent out a team of real technicians with a spectrum analyser. Even then, it took them several visits to locate the faulty equipment that was generating interference on the local cable distribution system.
Why do ISPs insist on being more than just a pipe? It's so dumb no one wants them to be anything else. Do they just not feel useful when they are a pipe?
Why do ISPs insist on being more than just a pipe? It's so dumb no one wants them to be anything else. Do they just not feel useful when they are a pipe?
Because there isn't a lot of profit growth in being "just a pipe", and like all businesses, they would like to make more money.
Sadly with regards to Comcast, it's because they don't consider themselves primarily an ISP.
It's not that they are an ISP and they want to be something else. It's that they are "SOMETHING ELSE" and DOCSIS came around and they looked and said "Hey. While we're at it we could charge folk a few extra bucks a month and give them Internet too." So it's very easy to understand how they wish to ensure you use THEM for your VoIP and video-on-demand needs.
Seriously. Call their help line. Listen to their canned message while you're on hold. Does it say anything remotely close to "we want to be your ISP"? Nope. It says something like "we're happy to be your ENTERTAINMENT company".
Nothing really surprises me anymore about their horribly pathetic reliability once you realize their idea of what they are.
Bandwidth is a commodity. As such is interchangeable: the provider of a commodity is in competition with everyone else providing the same commodity. They have to differentiate themselves based on price, which they can only do by cutting costs and increasing efficiency. Though market competition is in our best interests as consumers, it isn't in theirs. The last thing a company wants is for market competition to work efficiently to drive down their margins. That's why they will do everything they can to avoid selling a commodity: product differentiation, branding, and so on - strategies that effectively create mini monopolies (you don't buy an MP3 player, you buy an iPod; you don't buy shoes, you buy Nike).
That's the main reason. Another, which applies especially to monopolies (hello telecoms!), is price discrimination. A company would like to charge each customer as much as that customer can afford to pay, but they don't want to lose business with a price that's too high. By developing different classes of service they can coax more money from those able to pay more. The classic example is first-class seating on flights. How much a customer is able to pay may also depend on how much the service is worth to them. It may not cost the telecom company any more to provide bandwidth for, say, VoIP users than for WoW players, but VoIP customers may be able to pay more because it saves them money elsewhere.
It is the role of good market regulation to ensure competition works effectively to drive prices down towards costs. That is broadly good for consumers and for the economy as a whole. Companies - especially incumbent companies - should be expected to do everything in their power to fight to break the market. And they do.
Why don't they just UPGRADE THE PIPES. My god every other first world country has huge bandwidth where these types of things aren't even a consideration. Yet comcast just whines because you can't run everything and be fair on tiny pipes.
because they want to milk the current technology and still profit from it as long as they can. I know I work with these guys. No need for FTTH until there's competition.
They'll just let the FTTH come in and then merge with that company or acquire them outright.
the typical slogan of "they bought us" comes into play here. As cable becomes telco that's just what happens. Only you have to wait until the market forces make that happen. Here in NY Verizon basically takes about 10 thousand households away fro
My god every other first world country has huge bandwidth where these types of things aren't even a consideration.
Every other first world country has immensely higher population density. Canada's population is overwhelmingly located in certain centers and the remote population of Canada has just as much trouble as the remote population of the USA.
This does not adequately explain why we don't have higher speed in the areas of extremely high population density, of course.
We can solve these problems by forming community ISPs to wirelessly handle the last mile solution, which works in most places. Using solar-powered (or hell, wind-powered, it's very easy) mesh networks would work practically everywhere. IMO we would ideally replace the internet entirely with an alt-power mesh network. You can cross hills by putting a wind generator on top, running PoE as far as possible and putting PoE APs at each end of the wire. Wind generators can be made entirely out of junkyard parts (as can a welder to build it with, if you are crafty. a plastic fuel tank, some jumper cables, some scavenged wire and you've got a welder. The wind generator itself is made out of body metal, a steering knuckle, a wheel, an alternator. Easier to make with an oil drum instead of the body metal, though.
The problem here is one of "meh". We have great ideas but never seem to execute. I put myself in this category.
I live in Finland which has about 5 million persons at a population density of 15.6 per sq.km, while the US has about 300 million at 31 per sq.km, or double Finland's population density. Actually, about half of Finland's population is near the south coast (especially around Helsinki and Turku), while I'm in a rural area 300km north of Helsinki, so our regional population density is a bit lower. The largest town within 200km has about 80,000 people.
I have fiber to the house with 100/10 service available. The service is eur55 per month, including IP TV. If it's possible in the countryside in Finland, then it should be possible in most of US, where local populations and population densities are higher.
In fact, there are substantial areas of the U.S. with quite high population densities and local populations greater than all of Finland. Example: New Jersey, with 8 million persons at 438 per sq.km, and many millions more in adjacent areas.
http://en.wikipedia.org/wiki/New_jersey [wikipedia.org]
Your argument based on population density is a load of bollocks. You're just screwed by your ISPs.
In fact, there are substantial areas of the U.S. with quite high population densities and local populations greater than all of Finland.
You don't calculate from the total area of the country. You calculate from the populated area. This is the same reason the comment below yours about Canada is wrong. Canadians are by and large clustered into population centers because most of their country is trees, rock, and snow. Americans are some of the most spread-out people in the "modern" world (all but attitude, anyway.) People are well spread out across the country, with a not that astoundingly high population.
We are getting screwed by our ISPs. Hard. And its easy because there is little to no competition.
We can go around and around on this all day, but this is my last try. There is little to no competition because of the miles and miles (and miles and miles) of right-of-way to be secured and equipped. Wireless has so far not been a workable solution not because of licensing but because of the area to be covered. It's only useful for the last mile because people in town have "good enough" internet access and it's usually pretty cheap. (With that said, we do allegedly have a wireless last-mile solution here i
The ISP supplying my workplace regularly blocks HTTP for up to hours at a time. Nothing else, just outgoing(!) port 80. First connections get dropped silently, then after a while it moves on to forged TCP reset packets when trying to connect to anything. Which is pretty worrying because they're the only ISP available here.
"Catch-22" implies a no-win situation. Comcast (and the other ISPs) have done this to themselves. They advertise unlimited Internet access (or make it seem like they're offering unlimited access) and then get upset when someone tries to use it.
The ISPs should start advertising their download speed, upload speed, and bandwidth caps openly. Offer additional speed and bandwidth for a reasonable price. And if your infrastructure is such that sometimes you'll need to throttle someone, make it clear upfront how and when such throttling will happen.
Right now, on Comcast's sale page, they only list the download speed of their connections. I couldn't find their upload speeds or the bandwidth caps (which I know to be 250GB). As far as I know, Comcast customers have no way to check to see if their being throttled or if they're near the bandwidth cap.
It's really no surprise then that customers are upset.
But Comcast does not. Comcast Digital Voice rides the same channel as cable modem. The only real difference between CDV and another VoIP product (ie Vonage, etc) is that the ATA is built into the cable modem.
Comcast is a cable company, right? So isn't this just because their VoIP can be put in a separate Docsis channel (and prioritised accordingly), while 'regular' VoIP is sent as normal data?
I don't want to spend an hour writing a treatise on this, but I do think I need to make a few things clear.
Several issues are convolved here, and the "right" answer to each individual issue is not obvious (at least not once one factors in political and business viewpoints), so the convolution is essentially a mess. Like the original poster of the story, I have to assume that the FCC decided intentionally to delve into the mess. Anyway, here are the real issues:
1. There is (as far as I know) no new technology here. The PacketCable specs, which define how cable operators (most of them, anyway) implement VoIP were released in 1999. Comcast (like other US cable operators) has been deploying this technology since about 2002. As far as I know, the only part of the spec that Comcast don't really implement is the security portion. In any case, the specs are public and have been so for nearly a decade.
2. There is a fundamental technical difference between over-the-top VoIP (i.e., service provided by a third party such as Vonage) and telephony provided by the cable company.
3. The cable company can differentiate between its VoIP (or any other service needing preferential Quality of Service (QoS)) and ordinary so-called "best-effort" traffic, which is what is used to carry everything else, including over-the-top VoIP.
4. The reason for this is that it is the only entity that has access to the Cable Modem Termination System (CMTS), which controls the microsecond-by-microsecond details of traffic flow over the plant between a customer and the cable operator's facilities.
5. It is reasonable (from the cable operator's point of view) that since it owns the CMTS (and CMTSes are not cheap either to acquire or to manage), it's not voluntarily going to let some other company control any part of its operation (especially since if that gets screwed up, the customer experience is impacted).
6. Looked at from the point of view of guarantees applied to services, this looks like a violation of net neutrality, since over-the-top operators have to fight for bandwidth against things like P2P and web browsing, while the cable operator's phone calls don't have to do so (they have QoS guarantees).
7. But there is no law against violating new neutrality (as far as I know, in the US anyway). IANAL.
8. One can also argue that although it *looks* like a violation of net neutrality, it is in fact not such a violation, since from the viewpoint of what is happening inside DOCSIS (the protocols used to manage bandwidth on the plant between the residence and the cable company), over-the-top VoIP looks completely different from the cable company's offering. From that technical viewpoint, they can be considered two different services, and hence it would (presumably) be fine even under net neutrality principles to treat them differently.
Those are the basic ideas (although of course I've just summarized; it would take a lot more space to really describe all the details). But the basic point here is that there are lots of issues and viewpoints, some business-related, some political, and some technical. And much though one might like to demonize one party or the other, in this particular case the issues don't really seem to lend themselves to such a simple analysis.
Disclaimer: this was a quickly-written post of my initial impressions given the rather sparse (and not unambiguous) information available.
"Comcast Digital Voice uses Internet Protocol and not the Internet. Comcast Digital Voice calls travel on our private, managed network -- not over the public Internet. That makes it superior to other 'Best Effort' services delivering phone traffic over the public Internet."
We're still not doing congestion control very well. DOCSIS 3.0 [cablemodem.com], the new cable modem/hub standard, has many congestion management features, but they're a collection of features, not an integrated strategy.
Realistically, there are two QoS options a congestion strategy for general IP-based networks can deliver:
Low latency, low bandwidth. This is what you want for VoIP and for the low-latency channel of games. For this to work, the network has to enforce the "low bandwidth" requirement by limiting the number of packets in flight. "Fair queueing" can do that on the network side. If you only have one packet in flight (i.e. you wait until each packet is delivered before sending the next one), you shouldn't see any packet loss. If you send more than that, you lose packets. TCP already plays well with fair queueing. UDP-based VoIP protocols that don't do adaptive congestion control need to be fixed.
High latency, high bandwidth For everything else.
There are fancier reservation schemes, where you can reserve bandwidth, but they only work when all the players in the path cooperate, which tends not to happen. But there's no reason not to get the simple mechanisms above right.
That is just way too much effort for pleasure. It's much simpler to twist a belt around your neck until you pass out. The rush is amazing! Every AC should try it a few dozen times a day.:-)
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I doubt the problem is up at that level anyways. The price per byte on the backbone is so cheap it hardly matters. It's the few miles nearest end users - where most of the network actually is - that matters.
I wish they (all ISPs) would start honoring TOS flags and then start selling packages like X gigabytes of 1st class traffice, Y gigabytes of 2nd class traffic, and Z gigabytes of 3rd class traffic. Presumably people would use 1st for VOIP, 2nd for ssh or websurfing, and 3rd for bittorrent. But if somebody configures bittorrent to use 1st class, it's not the ISPs problem.
All that said, I have comcast's very slowest "broadband" - 768kbps (i.e. under 1 mbit), and vonage always works fine. I haven't noticed any congestion problems on their network.
Finally, why the submitter thinks video is such a dilemma is a bit of a mystery to me. 99.9% of video is download - not interactive video phones and such - so having some jitter isn't really a problem, easily solved with buffering. It doesn't need to compete on the millisecond scale with voice traffic.
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The problem is that ISP's pay per megabyte for uploads. Downloads are free for them except for the cost of the line and equipment maintenance., etc. That's what this is really all about.
Re:Congestion? (Score:5, Informative)
The problem is that the DOCSIS spec involves having your own little slice of frequency for downstream but everyone shares upstream. Your DOCSIS 1 stuff would let you dump 5 or 6 megabits to each of thousands (well, okay, maybe hundreds) :) of subscribers at once if you could actually feed the data into your head end fast enough. But sending the data back upstream is done on a shared frequency. Some line cards have multiple frequencies (no idea what they are now; when I worked for Cisco Santa Cruz when they were developing the Cisco DOCSIS modem ref design firmware it was the MC11 and MC16, I think, the MC16 had six upstream channels) so that you could send the same downstream to a whole bunch of places, but segment their upstream and feed it into the different upstreams (inputs on the line card.) If you run out of bandwidth you can charge more, and buy more bandwidth. But if you run out of upstream bandwidth on the line card, you have to add a line card and go forth and physically segment your network.
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Re:Congestion? (Score:5, Informative)
You don't understand cable system design. The reason for the 6:1 ratio between upstream and downstream is not because Cisco (or anyone else) thinks you can oversubscribe the upstream spectrum, but because upstream carrier to noise ratios are much worse than downstream. Because of the lower CNR, upstream modulation has to have a lot more interleaving and error correction (and much lower symbol rates). It also helps isolate noise problems to a smaller service area.
Part of DOCSIS 3 spec is 64QAM upstream. Some operators are trying it now, and finding out that there's a whole new level of plant maintenance necessary to deliver a good upstream bit error rate. Meanwhile, the normal downstream carrier is 256QAM (6.4MSym/s symbol rate), which requires a 3dB improvement in CNR over 64QAM at the same symbol rate. As fiber is driven deeper into the cable network it will be much easier to increase the upstream modulation to 256QAM and downstream modulation at 1024QAM. Typical cable systems today use 16QAM modulation in the upstream, with a 3.2 MSym/s symbol rate.
And, it is fairly common to have multiple upstream carriers in a node (neighborhood). DOCSIS 3.0 adds support multiple downstream carriers* through devices called edge QAMS. The downside of that is most operators have 65 or so analog channels, several dozen digital cable channels, 4-5 VOD carriers, and one DOCSIS 2.0 carriers in the downstream. The push is to get rid of the analog channels, but that's politically unpopular since it would require all customers to get a set top box for every TV (someday tru-2-way TVs and set top boxes will be at Best Buy, but it's a long time coming). Once 3.0 is deployed, the typical system may have 3 or more bonded downstream carriers/service group, about 500 customers. End users will need a new modem to get full use of the channel bonding, but it should be worth it for the much greater increase in speed.
Finally, everyone always gets the "shared bandwidth" argument wrong. Most people think of DOCSIS like classic Ethernet, with a hub or daisy chain cable. This means that Ethernet NICs need to use CSMA/CA to avoid collisions. There is no way for a cable modem to hear another one, so the CMTS assigns a mini-slot to a cable modem when it is provisioned/registered (which essentially makes a TDMA channel). the ONLY time a modem is permitted to transmit is at it's assigned mini-slot. Over the years, CMTS software has improved, and operator's understanding of the configuration has become much more granular, to the point that bandwidth optimization is much better understood than it was 10 years ago, along with moving from 7200 series network engines to VXR and above (in the case of Cisco).
*There is some use of multiple downstreams now, it has been in the spec since DOCSIS 1.1, but isn't needed on much more than a temporary basis. Individual modems can only tune one carrier at at time, so it is typically used to get more customers on a node than it is used to get higher speeds. However, some operators have used multiple downstreams to isolate business class customers from everyone else.
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The problem is that ISP's pay per megabyte for uploads. Downloads are free for them except for the cost of the line and equipment maintenance., etc.
Horse crap. ISPs pay the same for bandwidth usage up or down.
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Not the big guy's. http://en.wikipedia.org/wiki/Tier_1_network [wikipedia.org] I think Comcast is a Tier 2 and pays for some, but not all of their traffic.
As a result, the term Tier 1 Network is used in the industry to mean a network with no overt settlements. An overt settlement would be a monetary charge for the amount, direction, or type of traffic sent between networks.
Common definitions of Tier 2 and Tier 3 networks:
* Tier 2 - A network that peers with some networks, but still purchases
Re:Congestion? (Score:4, Insightful)
start selling packages like X gigabytes of 1st class traffice, Y gigabytes of 2nd class traffic, and Z gigabytes of 3rd class traffic.
That seems like it would be a bit complex, and also problematic if they did not ship their own routers and instructions for configuring it.
Why not just sell pure bandwidth, and if people want to prioritize things, let them do it within their own networks? If I'm saturating my connection with BitTorrent, it's really up to me to QoS it down until Skype works. But, if I'm saturating my connection with BitTorrent, and someone else is having problems with Skype, that suggests they should buy more bandwidth.
I can see where TOS might be easier for the ISPs, let them squeeze a bit more out of their networks, maybe oversell a bit more and acknowledge that your torrent will slow to a crawl (but your voice will still work) during "peak" hours.
On the other hand, Amazon seems to be able to put a relatively cheap, relatively constant price on all network traffic to Amazon Web Services. I don't know if my bill is typical, but I pay $65 for fiber -- split evenly, that would be 300 gigs upload and 176 gigs download, or 150 gigs up and 265 gigs down... per month. I mean, I might do more than that torrenting, but not much, and I imagine that's a good deal more than Comcast currently provides.
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Re:Congestion? (Score:5, Funny)
I doubt the problem is up at that level anyways.
It's probably the NSA's traffic cloning and storage system that can't keep up with trying to record all of America's VOIP calls. We're sorry, but this mailbox...United States of America...is full.
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Is that why they instituted download caps?
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Comcast is having big issues in my area. The initial time to hook up to my ISP every day is between three and five minutes. That is lousy service.
Now that they are providing phone service on the same cable lines if they cause a death due to net congestion or not being able to hook up to their service then huge damages as well as punitive damages should apply.
I don't give a hoot if they have to run two cables into every home this no
Second Post... (Score:4, Funny)
How much is self intereference? (Score:5, Interesting)
If someone is doing very high traffic, enough to get into Comcast's temporary "QOS Low" category, they are probably sending and full rate. If you are sending at full rate, the typical end-host NAT and buffering alone will cause bad quality for VoIP (search for VoIP and BitTorrent for a lot of such tales). There is nothing Comcast's network management really does to affect things in this case anyway.
Comcast's network management should only cause additional VoIP issues when the big transfer STOPS and the VoIP call is made within only a few minutes (before the user's link is reclassed back into the "QoS normal" category).
Re:How much is self intereference? (Score:5, Insightful)
Did you read the part in the summary which said that Comcast VOIP was unaffected by this problem?
Parent
Re:How much is self intereference? (Score:5, Informative)
Did you read the part in the summary which said that Comcast VOIP was unaffected by this problem?
What was not mentioned is that Comcast's VOIP is out of band. I'm no comcast apologist (comcast's policies were the straw that broke the came'ls back and got me to move to a new house where I could get verizon FIOS) but this is less of an issue that it has been made out to be. From day one, comcast's VOIP has used seperate channels from their internet services. Their VOIP is limited to connecting to POTS or other comcast VOIP customers. It is not on the internet, it is only on a comcast private intranet.
Parent
Re: (Score:3, Interesting)
From day one, comcast's VOIP has used seperate channels from their internet services.
I'm not sure that's really the issue. I'll admit a little bit of ignorance on the issue, but what would happen to your upload rates if Comcast opened those VOIP channels to normal data? Or what if they allowed VOIP to travel on those channels whether they were the VOIP provider or not?
Because I think the issue is that they're providing a limited amount of bandwidth to the home and complaining about congestion, meanwhile setting aside access for their own services. I can't blame them, since it probably m
Re:How much is self intereference? (Score:5, Informative)
To clarify... Comcast Digital Voice, like any PacketCable service, uses reserved capacity. It comes off of the cable modem channel, at the physical layer (minislots), and it keeps the telephone calls off of the Internet. CDV is NOT an Internet phone service at all. It's a separate access network, using MGCP-derived signaling and RTP/IP encapsulation of voice.
If the phone is not in use, then a tiny bit more capacity on the cable (100 kbps/call) is made available for data. If you think that's unfair, fine, but that's how PacketCable works, and it maximizes efficiency for the whole system. It's safe, legal, and non-fattening.
Parent
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Ugh, screw Comcast (Score:2)
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To pipe or not to pipe. (Score:3, Interesting)
Re:To pipe or not to pipe. (Score:5, Insightful)
Why do ISPs insist on being more than just a pipe? It's so dumb no one wants them to be anything else. Do they just not feel useful when they are a pipe?
Because there isn't a lot of profit growth in being "just a pipe", and like all businesses, they would like to make more money.
Parent
Re: (Score:2)
Do you think it would help if we let them be tubes?
Just askin'
Re:To pipe or not to pipe. (Score:5, Funny)
That's just great. ColdWetDog (752185) replying to Frosty Piss (770223). Mod me offtopic, but at least smile as you do it.
Parent
Re: (Score:3, Insightful)
Unfortunately, I can't seem to find the "+1 Off-topic" option.
Re:To pipe or not to pipe. (Score:5, Insightful)
Sadly with regards to Comcast, it's because they don't consider themselves primarily an ISP.
It's not that they are an ISP and they want to be something else. It's that they are "SOMETHING ELSE" and DOCSIS came around and they looked and said "Hey. While we're at it we could charge folk a few extra bucks a month and give them Internet too." So it's very easy to understand how they wish to ensure you use THEM for your VoIP and video-on-demand needs.
Seriously. Call their help line. Listen to their canned message while you're on hold. Does it say anything remotely close to "we want to be your ISP"? Nope. It says something like "we're happy to be your ENTERTAINMENT company".
Nothing really surprises me anymore about their horribly pathetic reliability once you realize their idea of what they are.
Parent
Because then their service would be a commodity (Score:5, Insightful)
Bandwidth is a commodity. As such is interchangeable: the provider of a commodity is in competition with everyone else providing the same commodity. They have to differentiate themselves based on price, which they can only do by cutting costs and increasing efficiency. Though market competition is in our best interests as consumers, it isn't in theirs. The last thing a company wants is for market competition to work efficiently to drive down their margins. That's why they will do everything they can to avoid selling a commodity: product differentiation, branding, and so on - strategies that effectively create mini monopolies (you don't buy an MP3 player, you buy an iPod; you don't buy shoes, you buy Nike).
That's the main reason. Another, which applies especially to monopolies (hello telecoms!), is price discrimination. A company would like to charge each customer as much as that customer can afford to pay, but they don't want to lose business with a price that's too high. By developing different classes of service they can coax more money from those able to pay more. The classic example is first-class seating on flights. How much a customer is able to pay may also depend on how much the service is worth to them. It may not cost the telecom company any more to provide bandwidth for, say, VoIP users than for WoW players, but VoIP customers may be able to pay more because it saves them money elsewhere.
It is the role of good market regulation to ensure competition works effectively to drive prices down towards costs. That is broadly good for consumers and for the economy as a whole. Companies - especially incumbent companies - should be expected to do everything in their power to fight to break the market. And they do.
Parent
911 (Score:5, Funny)
If you have VOIP, don't set your kitchen on fire during high congestion periods. Please people, a little take a little personal responsibility.
I don't know (Score:5, Insightful)
Why don't they just UPGRADE THE PIPES.
My god every other first world country has huge bandwidth where these types of things aren't even a consideration. Yet comcast just whines because you can't run everything and be fair on tiny pipes.
the truth from someone in the know. (Score:2, Informative)
because they want to milk the current technology and still profit from it as long as they can. I know I work with these guys. No need for FTTH until there's competition.
They'll just let the FTTH come in and then merge with that company or acquire them outright.
the typical slogan of "they bought us" comes into play here. As cable becomes telco that's just what happens. Only you have to wait until the market forces make that happen. Here in NY Verizon basically takes about 10 thousand households away fro
Re:I don't know (Score:5, Informative)
My god every other first world country has huge bandwidth where these types of things aren't even a consideration.
Every other first world country has immensely higher population density. Canada's population is overwhelmingly located in certain centers and the remote population of Canada has just as much trouble as the remote population of the USA.
This does not adequately explain why we don't have higher speed in the areas of extremely high population density, of course.
We can solve these problems by forming community ISPs to wirelessly handle the last mile solution, which works in most places. Using solar-powered (or hell, wind-powered, it's very easy) mesh networks would work practically everywhere. IMO we would ideally replace the internet entirely with an alt-power mesh network. You can cross hills by putting a wind generator on top, running PoE as far as possible and putting PoE APs at each end of the wire. Wind generators can be made entirely out of junkyard parts (as can a welder to build it with, if you are crafty. a plastic fuel tank, some jumper cables, some scavenged wire and you've got a welder. The wind generator itself is made out of body metal, a steering knuckle, a wheel, an alternator. Easier to make with an oil drum instead of the body metal, though.
The problem here is one of "meh". We have great ideas but never seem to execute. I put myself in this category.
Parent
You should know... (Score:5, Insightful)
Every other first world country has immensely higher population density.
Wrong, unless you're saying that Finland, Sweden, and Norway are not in the first world. http://en.wikipedia.org/wiki/List_of_countries_by_population_density [wikipedia.org]
I live in Finland which has about 5 million persons at a population density of 15.6 per sq.km, while the US has about 300 million at 31 per sq.km, or double Finland's population density. Actually, about half of Finland's population is near the south coast (especially around Helsinki and Turku), while I'm in a rural area 300km north of Helsinki, so our regional population density is a bit lower. The largest town within 200km has about 80,000 people.
I have fiber to the house with 100/10 service available. The service is eur55 per month, including IP TV. If it's possible in the countryside in Finland, then it should be possible in most of US, where local populations and population densities are higher.
In fact, there are substantial areas of the U.S. with quite high population densities and local populations greater than all of Finland. Example: New Jersey, with 8 million persons at 438 per sq.km, and many millions more in adjacent areas. http://en.wikipedia.org/wiki/New_jersey [wikipedia.org]
Your argument based on population density is a load of bollocks. You're just screwed by your ISPs.
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Re: (Score:3, Informative)
In fact, there are substantial areas of the U.S. with quite high population densities and local populations greater than all of Finland.
You don't calculate from the total area of the country. You calculate from the populated area. This is the same reason the comment below yours about Canada is wrong. Canadians are by and large clustered into population centers because most of their country is trees, rock, and snow. Americans are some of the most spread-out people in the "modern" world (all but attitude, anyway.) People are well spread out across the country, with a not that astoundingly high population.
There ARE some sizable uninhabited reg
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We are getting screwed by our ISPs. Hard. And its easy because there is little to no competition.
We can go around and around on this all day, but this is my last try. There is little to no competition because of the miles and miles (and miles and miles) of right-of-way to be secured and equipped. Wireless has so far not been a workable solution not because of licensing but because of the area to be covered. It's only useful for the last mile because people in town have "good enough" internet access and it's usually pretty cheap. (With that said, we do allegedly have a wireless last-mile solution here i
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Comcast rolls out DOCSIS 3.0 to 3 more cities:
http://www.fiercetelecom.com/story/comcast-rolls-docsis-3-0-three-more-cities/2008-12-11 [fiercetelecom.com]
And Denver, Salt Lake City, and most of the west coast should be done before the end of 2009.
Comcast users think they've got it bad? (Score:3, Informative)
The ISP supplying my workplace regularly blocks HTTP for up to hours at a time. Nothing else, just outgoing(!) port 80. First connections get dropped silently, then after a while it moves on to forged TCP reset packets when trying to connect to anything. Which is pretty worrying because they're the only ISP available here.
Not a "Catch-22" (Score:5, Insightful)
"Catch-22" implies a no-win situation. Comcast (and the other ISPs) have done this to themselves. They advertise unlimited Internet access (or make it seem like they're offering unlimited access) and then get upset when someone tries to use it.
The ISPs should start advertising their download speed, upload speed, and bandwidth caps openly. Offer additional speed and bandwidth for a reasonable price. And if your infrastructure is such that sometimes you'll need to throttle someone, make it clear upfront how and when such throttling will happen.
Right now, on Comcast's sale page, they only list the download speed of their connections. I couldn't find their upload speeds or the bandwidth caps (which I know to be 250GB). As far as I know, Comcast customers have no way to check to see if their being throttled or if they're near the bandwidth cap.
It's really no surprise then that customers are upset.
Not agnostic (Score:5, Insightful)
If they are treating their own VOIP differently than other traffic then it isn't "protocol agnostic" at all.
Re: (Score:3, Interesting)
But Comcast does not. Comcast Digital Voice rides the same channel as cable modem. The only real difference between CDV and another VoIP product (ie Vonage, etc) is that the ATA is built into the cable modem.
DOCSIS? (Score:2, Informative)
Not an easy issue (or set of issues) (Score:3, Interesting)
I don't want to spend an hour writing a treatise on this, but I do think I need to make a few things clear.
Several issues are convolved here, and the "right" answer to each individual issue is not obvious (at least not once one factors in political and business viewpoints), so the convolution is essentially a mess. Like the original poster of the story, I have to assume that the FCC decided intentionally to delve into the mess. Anyway, here are the real issues:
1. There is (as far as I know) no new technology here. The PacketCable specs, which define how cable operators (most of them, anyway) implement VoIP were released in 1999. Comcast (like other US cable operators) has been deploying this technology since about 2002. As far as I know, the only part of the spec that Comcast don't really implement is the security portion. In any case, the specs are public and have been so for nearly a decade.
2. There is a fundamental technical difference between over-the-top VoIP (i.e., service provided by a third party such as Vonage) and telephony provided by the cable company.
3. The cable company can differentiate between its VoIP (or any other service needing preferential Quality of Service (QoS)) and ordinary so-called "best-effort" traffic, which is what is used to carry everything else, including over-the-top VoIP.
4. The reason for this is that it is the only entity that has access to the Cable Modem Termination System (CMTS), which controls the microsecond-by-microsecond details of traffic flow over the plant between a customer and the cable operator's facilities.
5. It is reasonable (from the cable operator's point of view) that since it owns the CMTS (and CMTSes are not cheap either to acquire or to manage), it's not voluntarily going to let some other company control any part of its operation (especially since if that gets screwed up, the customer experience is impacted).
6. Looked at from the point of view of guarantees applied to services, this looks like a violation of net neutrality, since over-the-top operators have to fight for bandwidth against things like P2P and web browsing, while the cable operator's phone calls don't have to do so (they have QoS guarantees).
7. But there is no law against violating new neutrality (as far as I know, in the US anyway). IANAL.
8. One can also argue that although it *looks* like a violation of net neutrality, it is in fact not such a violation, since from the viewpoint of what is happening inside DOCSIS (the protocols used to manage bandwidth on the plant between the residence and the cable company), over-the-top VoIP looks completely different from the cable company's offering. From that technical viewpoint, they can be considered two different services, and hence it would (presumably) be fine even under net neutrality principles to treat them differently.
Those are the basic ideas (although of course I've just summarized; it would take a lot more space to really describe all the details). But the basic point here is that there are lots of issues and viewpoints, some business-related, some political, and some technical. And much though one might like to demonize one party or the other, in this particular case the issues don't really seem to lend themselves to such a simple analysis.
Disclaimer: this was a quickly-written post of my initial impressions given the rather sparse (and not unambiguous) information available.
VOIP!=Internet (Score:5, Informative)
"Comcast Digital Voice uses Internet Protocol and not the Internet. Comcast Digital
Voice calls travel on our private, managed network -- not over the public Internet. That makes
it superior to other 'Best Effort' services delivering phone traffic over the public Internet."
Source (emphasis mine): http://www.comcast.com/MediaLibrary/1/1/About/PressRoom/Documents/ProductsAndServices/digital_voice.pdf [comcast.com]
Comcast's own Digital Voice is unaffected (Score:3, Insightful)
Well of course.
If they offer a netflix alternative expect that to be a better performer due to shaping as well.
Most people will just think the alternatives suck and choose comcast's service instead, never the wiser.
Better congestion control (Score:3, Informative)
We're still not doing congestion control very well. DOCSIS 3.0 [cablemodem.com], the new cable modem/hub standard, has many congestion management features, but they're a collection of features, not an integrated strategy.
Realistically, there are two QoS options a congestion strategy for general IP-based networks can deliver:
There are fancier reservation schemes, where you can reserve bandwidth, but they only work when all the players in the path cooperate, which tends not to happen. But there's no reason not to get the simple mechanisms above right.
Re: (Score:3, Funny)
That is just way too much effort for pleasure. It's much simpler to twist a belt around your neck until you pass out. The rush is amazing! Every AC should try it a few dozen times a day. :-)