I think the idea of mixing traffic for the video network with that for other networks is a laudable notion. Laudable but incoherent.
The reason is that it is unlikely that customers will like the channel switch time associated with deep network scanning for channels. That means that broadcast channels will be brought very close to the customer (say the end office).
The implication of this of course is that there is no statistical gain of this across the 3rd mile. So, whats the point of adding a layer 2 or layer 3 aware product? To add cost? To add delay?
You can argue whether Ethernet over SONET/SDH or WDM technologies are better. But content is likely to flow in layer 1 from Head End to End Office.
Incoherent probably isn't the right word, but this is a good point. But certainly many operators are already looking at unified IP access architectures, if not deploying them already (KDDI, for example). Even if broadcast channels are brought to the end office via layer 1 transport, there may be an increasing amount of video content that is multicast through the "3rd mile" of the network, relative to the location/distribution of content servers that may not be colocated with DSLAMs.
Incoherent probably isn't the right word, but this is a good point. But certainly many operators are already looking at unified IP access architectures, if not deploying them already (KDDI, for example). Even if broadcast channels are brought to the end office via layer 1 transport, there may be an increasing amount of video content that is multicast through the "3rd mile" of the network, relative to the location/distribution of content servers that may not be colocated with DSLAMs.
Scott
Do you mean to say that there will be multicast running across the VPLS domain? What are the ramifications of this? Do many VPLS implementations correctly prune multicast?
re: VPLS & the Third MileI have to agree with Scott here. Content/media servers are typically not co-located at the POP. Content providers are beginning to peer with other carriers such as MSOs at neutral exchanges in some places, but they would rather not if given a choice. Long-haul IP video distribution becomes real in this case.
Also, for the times when video is not using its bandwidth, it can be used by data and other less critical applications.
re: VPLS & the Third Mile What I am saying, is that there is no VPLS network involved.
To make this work, backhauling at layer one will be done. Doing anything else gives the chance of screwing up video. If there is no oversubscription (statistical gain), then there is no point in introducing a statical multiplexer (Switch/Router). Since traffic must be unblocked, there is no gain.
re: VPLS & the Third MileWell, there are VPLS networks involved in all the examples I cited, and they are carrying a mix of voice, video and data, and do a fine job of statistical multiplexing, since any on demand video traffic is inherently lumpy (more during the evening, weekends, etc.). Using a layer 2 service delivery mechanism like VPLS lets the operator traffic engineer their networks for the various traffic patterns that the triple play creates.
Layer 1 for broadcast traffic just doesn't hold up in most of these network implementations because it requires too much bandiwdth be delivered too deeply into the access network for no good reason. Multicast is what IP video is all about; I'm suggesting here that a VPLS is an excellent Layer 2 solution to support video multicast, plus provides some additional benefits of scalability and QoS.
In regards to minimizing channel switch delays, that is done at the DSLAM using IGMP snooping (associating members to multicast groups), so the use of VPLS in the third mile has no real impact on channel switching.
This isn't theoretical; it's operational today in some major networks, and indicates a growing trend.
re: VPLS & the Third MileWell, I think maybe the term third mile is confusing, then, because I envisioned it as not representing the core, but only the feeder/metro of an access network, so the realm of connectivity between/among end offices, POPs, and content hosting locations. In this case, VPLS makes a world of sense and is in operation today in the examples I provided.
A VPLS is created interconnecting DSLAMs with Ethernet uplinks or OLTs with Etehrnet uplinks to sites in the metro/region with content, softswitches, ISP routers, etc. VPLS is an improvement over traditional Ethernet connectivity because of the features of MPLS. Multicasting in this realm does in fact make sense, though I see your point that multicasting across the long haul doesn't always make sense.
re: VPLS & the Third Mile I think this is true on a metro basis as well Scott.
As far as I can tell, all the US carriers plan to Layer 1 to the End Office. Why? Again, there is no statistical gain for Video Traffic. If you have a 200 channel lineup and a 10,000 line CO do you will still be bringing a GiGE to the End Office for the content. There is no gain.
If we move to Unicast traffic there could be some gain, that would be based upon the way one chooses to engineer the network and the take rate of services. This creates an assumption that there will be a content source in every Metro. This could be true, but is not what I see the US carriers doing. I do see addins for local content and local ad insertions. But I think its cheaper to run a GigE around than build a second head end.
So, what WOULD be carried on this VPLS network? Shrug, you tell me. Traffic between distributed VoD servers?
So my vision of multicasted content is very different than yours. I don't see it growing beyond the GiGE size of pipe. Given that its pretty cheap to pipe around. If you want to make a case perhaps the UNICAST traffic (VoD or Network PVR) can use such a network. I guess so, would be my answer. Not sure what gain you get for it as I think a server in a metro area is going to be quite flat in distribution.
re: VPLS & the Third MileWell folks, once again. I'm confused. I agree with points, and I'm baffled by others. Things have already moved towards ethernet deployment to customers. Within most countries, cost of ethernet in the 'last mile' stretch of the network works out more cost affective when budgeted over three years than a standard [TE]1 circuit - providing within about 3.5Km. Compare the bandwidth between the two and the math is simple. Most companies CapEx over three years, and hell, in three years god knows how cheap things will have become. This has been evident for years though, and providers such as bredsbandbolaget, and manufacturers such as packetfront have made this clear. However, I don't see what VPLS and multicast have to do with one another. Ethernet tin is cheap, and is partly the reason it has been kicking ass in recent years. VPLS & MPLS in it's various forms are great tools for customer aggregation as ethernet by nature is pretty limited. But what are you suggesting here? Is VPLS coming in to play to keep stuff tidy? Or are you suggesting a profundity far greater, that I have missed?
Scott,
I think the idea of mixing traffic for the video network with that for other networks is a laudable notion. Laudable but incoherent.
The reason is that it is unlikely that customers will like the channel switch time associated with deep network scanning for channels. That means that broadcast channels will be brought very close to the customer (say the end office).
The implication of this of course is that there is no statistical gain of this across the 3rd mile. So, whats the point of adding a layer 2 or layer 3 aware product? To add cost? To add delay?
You can argue whether Ethernet over SONET/SDH or WDM technologies are better. But content is likely to flow in layer 1 from Head End to End Office.
seven