Re: [EFM] Minutes of P2MP Optics conference 22nd Aug 20002
Kent,
Unfortunately the "required bandwidth" question is extremely complex and heavily
dependent on the service offering and usage models. We have installations with
>1000 subs served by a single gigabit link (with a mix of multicast and unicast
MPEG-2 - 4.5Mbps - video). The advantage of using EPON for this service is that
you could build slowly - start with high split ratios and increase the fiber
usage as service usage picks up.
Maybe some of the people on this reflector have experience in the CATV
distribution. I can remember some of the "rules of thumb" but I may be out of
date or inaccurate because it's a long time since I discussed any of this. If
the service is a mixture of multicast and unicast, then you can assume <20% take
rate for the unicast - this means that 160 channels will be used for 800
subscribers. Furthermore you can assume that 60% of subscribers will watch the
top 10 channels, the remaining 20% may be watching minority channels - say 50
channels between them. Thus the total channel requirement should be ~220 to
offer your 800 subscribers a top flight service package.
If you use MPEG-2, DVD quality then the b/w requirement would be 990Mbps - not
reasonable for 1 EPON (or even 1 pt-pt). If, instead you use MPEG-4 (or VHS
quality) then the b/w requirement is halved and should be reasonable for either
distribution.
I hope this helps - I'm no expert on video distribution, I suggest that you find
somebody with MSO experience to get much better statistics.
Hugh.
"Mccammon, Kent G." wrote:
> Hugh,
> You uncovered that I still have a copperhead mentality or should I say Bell
> Shaped Head. But, I am flying the fiber flag now. However, I sometimes can
> be observed attending copper subgroup meetings to participate in the latest
> vote in linecode battles.
>
> You answered my request with a GigE link between central office and a remote
> VDSL ONU. I was asking about the use of P2MP interfaces rather than P2P
> GigE for Hybrid Fiber/Copper architectures. With the expected efficiency of
> P2MP, could an operator feed 4 VDSL nodes with 200 subs each? Or would point
> to point GIgE be needed for each VDSL node? I like conserving my embedded
> feeder fiber if I can! I like single fiber P2P and PON for reducing fiber
> cost whether making the most use of what fiber is there or planning large
> deployments that scale.
>
> -Kent
>
> > -----Original Message-----
> > From: Hugh Barrass [mailto:hbarrass@cisco.com]
> > Sent: Friday, August 23, 2002 3:52 PM
> > To: Mccammon, Kent G.
> > Cc: 'gkramer@ucdavis.edu'; Thomas.Murphy@infineon.com;
> > stds-802-3-efm@ieee.org
> > Subject: Re: [EFM] Minutes of P2MP Optics conference 22nd Aug 20002
> >
> >
> > Kent,
> >
> > It's great to see you're flying the "hybrid fiber/copper" flag!
> >
> > Most video codecs are designed to spit out monotonic streams
> > of (nearly) equal sized frames. These frames will either be
> > at the MTU size or as long as the VSP dares to make them
> > (many will limit the frame size to 1024 bytes for
> > superstitious reasons). The data stream will consist of many
> > (i.e. >20) frames at the maximum size followed by one short frame.
> >
> > Note that a gigabit link will be able to carry 200-400
> > streams of unicast or multicast video, so it will take a
> > large number of subscribers to fill the pipe (& therefore
> > stress the efficiency).
> >
> > Hugh.
> >
> > "Mccammon, Kent G." wrote:
> >
> > > Glen,
> > > Referring to your comment about frame size distribution from actual
> > > traffic.
> > >
> > > > The size of unused slot remainder depends on frame size
> > > > distribution. This distribution for today's traffic is known and
> > > > there exist formula to calculate this unused remainder
> > (for the case
> > > > when assigned slot size has no correlation to the frame sizes).
> > >
> > > Does anyone in the group have a traffic sample from a network
> > > transporting digital video streams to give frame size distribution?
> > > For example, a traffic sample for digital video over fiber
> > to a VDSL
> > > ONU to serve several hundred VDSL lines to a residential gateway.
> > > That scenario may be a good one to look at for traffic on a
> > > residential GigaPON connected to multiple VDSL ONU
> > locations with data
> > > and switched digital video content.
> > >
> >