This responds to the videostreaming/downloading post above (linked Msg# 4195) by another cabletv engineer. Again, I don't presume or imply the validity of what these folks are saying. Rather, the nature of the discussion itself is of interest here. What is interesting is the fact that, and I've picked up on this elsewhere, there doesn't seem to be an industry-wide simulation product that one can use for approximating line conditions on HFC plant. At least none that I've been able to identify, other than the one that is referenced in the discussion, used for ATM environments (which limits its utility to only one or two CM vendors, COM21's original ATM CM architecture, most notably). And that may say something in itself.
Denver Techie, Mark Laubach, if you're looking in, would you care to comment on the availability of HFC network simulators for IP over DOCSIS? TIA.
FAC
---begin:
[T]hanks for your replies. I am trying to find out if any one have done
multi-downstream testing for VOD type of service within a cable modem
domain.
As you pointed out, it is impossible to provide a feasiable video quality
in the current cable modem systems because only one downstream channel
is available in most of cases.
Besides the QOS in ATM, suppose that DOCSIS1.1 supports QoS, but I have no
ideas how this quality assurance does. One thing many people agaisnt ATM
is the header cost of almost 10%.
David, I totally agree with you: IP-streaming over the Internet is
always unsatisfied. We assume that a proxy server acts a cache agent for a
cable network domain, and this cable network provides some kind of QoS
like DOCSIS.
I am trying to simulate the multi-downstream IP streaming in cable modem
environment. NIST ATM/HFC simulator seems a good choice, but I am trying
to aviod the ATM header cost. I cannot find any other simulation tools.
Maybe I have to build a new MAC layer in NS to do the tests.
Could you give me some suggestions on this? I assume it is extremely
difficult to have experiments on real systems.
thanks,
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On Fri, 2 Nov 2001, <someone> wrote:
> greetings,
>
> My experiments with MPEG2 video over cablemodems have been mostly
> unsuccessful. I believe that bandwidth is the primary limit. I'm sending
> this message via a cablemodem at home. The University of Wisconsin-Madison
> has a project with Charter Business Networks to provide cablemodem service
> for UW students, faculty and staff. Traffic from these cablemodems is
> delivered over a direct fiber digital connection right back to our campus.
> However, Charter has limited the bandwidth of the cablemodems to 1.5 MBPS.
>
> Our College of Engineering and Computer Science Department have piloted an
> application they call eTeach. You can read about it at
> <http://eteach.engr.wisc.edu/>. It supports multiple synchronized windows
> with Windows Media Player, Powerpoint slides, and World Wide Web
> pages. They have converted their CS310 class to eTeach lectures so
> far. The problem is in getting all the clients running the correct version
> of Windows with enough memory and CPU speed, and the correct version of
> Windows Media Player. Also, viewing is only supported in labs with
> switched 100 MBPS Ethernet.
>
> Last year we shipped MPEG2 video of a live hockey game from Madison to
> Anchorage where it was broadcast by the public station up there. This year
> we're trying to exchange live women's basketball MPEG2 video over Abilene
> between Wisconsin, University of Indiana and Penn State.
>
> I'm working with a number of people on a new public television and radio
> network in the State of Wisconsin. The network will use MPEG2 video over
> an ATM network. Why not IP? First, this network will not be shared, so
> there are no other users to share the cost of the network. Second, the
> network will distribute one television and two radio networks, and IP has
> no quality of service feature. Third, the budget will only support DS-3
> bandwidth, which doesn't give IP video very much headroom. The only way we
> can do this network with QOS is with ATM.
> |
