Car Pools & QOS

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Ben Crosby 12/5/2012 | 1:24:47 AM

re: Car Pools & QOS Graham,

Some good summary there. I'm still not convinced that two PVC's over the DSL link is necessary, but I need to think a little more before I post the details of why not.

I think you'll find some competent folks on this discussion thread who would happily participate in a triple play webinar. Maybe a panel discussion rather than a vendor led one ? ;)

Cheers,
Ben.

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arch_1 12/5/2012 | 1:24:45 AM

re: Car Pools & QOS Tony Li asks:
"Why do we end up arguing over a bunch of arithmetic?"

This is the basic question. I think the arguments occur because we forget to define what we are talking about.

If we restrict ourselves to the last mile (the Home<-->DSLAM link) then ATM v. Packet is important, but only because it affects jitter in the upstream direction.

If we are talking about triple-play DSL, Then we enter a different discussion. I personally think that this is a total loser, unless the vendor can offer a qualitatively different service from Cable. Unless there is a qualitative difference,
DSL will lose to cable.

the only way to win is to offer a new service, different from cable. If the vendor recognizes the difference between true real-time video and non-realtime video, there is an oportunity for diferentiation. Realtime video constitues a very small percentage of the content that people actually watch, but it is the only content that actually requires QoS differentiation. The true killer app is movies on demand. Movies on demand do not requre QoS, since they are not time-sensitive.

If you insist on emphasizing broadcast, you will lose. Cable is perfect for broadcast. Why should DSL attempt to compete with this? DSL should play to its strengths rather than attempting to emulate cable's strengths.

Cable offers a fixed set of broadcast channels, of which a small number are actually real-time. As a consumer, at any given time I want at most one of the real-time channels, OR I want a greatly expanded selection of non-realtime content (movies, etc.) The fact that cable treats thse the same is an artifact of the technology. DSL can win by differentiating real-time and non-realtime content, and offering a vastly expanded suite of non-realtime content. If instead the DSL industry strugles mightly to overcome serious technical obsticles, merely to deliver a functional equivalent of my existing cable service, then it will lose.

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paolo.franzoi 12/5/2012 | 1:24:45 AM

re: Car Pools & QOS
The reason is that the consumer gets to make this decision.

Question 1: Is a large channel lineup of real time content important? Well, we have no model for video services that is not that model. If you were the RBOC, would you bet you didn't need one? Would you really bet say $10B?

Question 2: What are these services? Why can cable not offer them? If not real time service is such a good idea, why would cable not do it?

See here is the problem. You are constructing a market concept and saying that your competitor is completely stagnant. He is not.

seven

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Tony Li 12/5/2012 | 1:24:45 AM

re: Car Pools & QOS
I think that the decision process for one or two PVC's is actually pretty deterministic. First, it's a function of link speeds, MTU's, and applications.

If there is only one PVC, then the DSLAM and CPE will introduce jitter of at least one MTU's time. Obviously, that time is a function of link speed. If that jitter is unacceptable for the anticipated applications, then you need a second PVC so that your high priority cells can be interleaved or have priority over low priority cells.

Why do we end up arguing over a bunch of arithmetic?

Tony

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Graham Beniston 12/5/2012 | 1:24:44 AM

re: Car Pools & QOS One thing I forgot to mention was the influence of regulation. Our designs for the UK 3 years ago got away with Video on Demand through the B-RAS because fo these issues. BT had to buy DSLAM backhaul bandwidth at the same price it charged to leased line and wholesale customers (DSLAM backhaul is a peculiar term when the asymmetry is firmly in the downstrean direction). This meant that high-percentage simultaneous use of VOD was too expensive, and the solution was to bundle 100 broadcast TV channels. At 5 Mbit/s MPEG-2 per channel this was just about do-able, with IGMP snooping for multicast to the DSLAMs (it did lead to some other interesting ideas, such as a joint satellite/DSL set top box with broadcast channels through the sat. link). So the spec called for limiting the number of simultaneous VOD sessions to 10%.

I do agree with brook seven that raising this percentage above 50% is likely to make the B-RAS at least too expensive if not infeasible. But an interesting discussion would be the effect of moving video traffic off the B-RAS. I don't think this would affect the overall QoS if you kept mulitple ATM PVCs from the DSLAM to the CPE, which I suggested was feasible, practical and cost efficient. The key is to dedicate fixed bandwidth to the PVCs. The idea that you should use the 5, 10 or higher Mbit/s link to the subscriber as "rubber bandwidth" is often not useful, and it is much more pragmatic to reserve a whole 5 Mbit's for video/TV only. The B-RAS wouldn't need to know about it then.

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arch_1 12/5/2012 | 1:24:43 AM

re: Car Pools & QOS I asserted that realtime video over DSL is an expensive functional equivalent of Cable TV, and the DSL should instead fulfill the true demand for non-realtime video.
-----------------------------------------------
brookseven asks:
Question 1: Is a large channel lineup of real time content important? Well, we have no model for video services that is not that model. If you were the RBOC, would you bet you didn't need one? Would you really bet say $10B?

Question 2: What are these services? Why can cable not offer them? If not real time service is such a good idea, why would cable not do it?
-----------------------------

Cable delivers multiple channels of broadcast video because that was what it was technically designed to do, not because that's what people want. In most homes, most of the time, the actual live customer is watching non-realtime video which happened to get delivered over this realtime technology. In a great many cases the customer recorded the material earlier on his TiVo, and is watching it now. for the vast majority of the time, on a vast majority of the channels, the material is pre-recorded at least days prior to transmission, and is therefore non-realtime video.

So I disagree with your characterization of the current cable market. Realtime video technology is used primarily to address a market demand for non-realtime delivery, and it only partially fulfills that demand. The remainder of the demand is fulfilled by video rental and purchase.

What we have is a system that is capable of delivering at most hundreds of realtime channels and which currently delivers less than ten real-time feeds, using the rest of the capacity to deliver an insufficiency of non-realtime feeds.

Why should the DSL industry spend tens of billions to implement an expensive substitute for this inadequate functionality?

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paolo.franzoi 12/5/2012 | 1:24:41 AM

re: Car Pools & QOS
See you miss the point....Cable can become a massive not real time video system by converting spectrum. It can do this anytime it wants.

Instead of taking the analog channels and turning them into digital ones...say turn 1/2 to digital channels and the other half to download content at say 2x DSL rates. Requires new setops but the plant will support it.

By the way, a very small minority own TiVo. They love it but it is a TINY number.

seven

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optoslob 12/5/2012 | 1:24:38 AM

re: Car Pools & QOS Arch,
I fully agree with you from a technical perspective, HOWEVER there are a few additional points that are worth considering.

- If Video over DSL looks like an exact copy of Cable / Satellite than they can leverage the existing Content contracts. If they are even a little different than suddenly they are back at the negotiation table hammering out contracts with every content owner. Keep in mind that these content owners are not very technically inclined, these are the same guys who thought they could kill P2P file sharing by just shutting down Napster. To say they are paranoid concerning technology is a gross understatement.

- RBOC's also want to provide CO based value added functions to the Video. So this will be things like PVR's (TiVo) but as a shared resource within the CO. So if the settop box has no storage capability, than even non real time video needs QOS.

optoslob

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sgan201 12/5/2012 | 1:24:30 AM

re: Car Pools & QOS Hi,
RBOC could deliver broadcast TV in a somewhat similiar and low cost fashion by putting a satellite dish on the CO. The broadcast TV can be deliverred to CO via satellite without massive outlay of the backhaul bandwidth and necessary network upgrade. The expensive CO backhaul bandwidth can then be used to handled VOD stuff. In this model, there is very little difference in the content delivery model between RBOC and the dish people. IN hace, RBOC can even cut a deal with the Satellite TV people.

Dreamer

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paolo.franzoi 12/5/2012 | 1:24:12 AM

re: Car Pools & QOS
You are correct dreamer that could work, if one were willing to put a headend in the office. Given headend costs, these are generally minimized.

seven

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