RE: [EFM] EFM Requirements
I don't think that "If you want high speed and long reach, you need more
pairs" is the only answer. A rate adaptive technology can offer high speed
on short loops and long reach with lower speeds.
From: Hugh Barrass [mailto:hbarrass@xxxxxxxxx]
Sent: Tuesday, August 14, 2001 9:52 AM
To: Lough, Andy
Cc: Vladimir Oksman; Sherman Ackley; Stds-802-3-Efm (E-mail)
Subject: Re: [EFM] EFM Requirements
Thanks for your input. I agree with *almost* all of it:
First - although reach and bandwidth are political issues there is a hard
limit governed by the Shannon capacity of the cable. If you want it to go
further, it will be slower; If you want higher speed, it won't go as far; If
you want high speed and long reach, you need more pairs. There is no free
I think it is vital that 802.3ah focus on all three media types (copper, p-p
fiber, p-mp fiber) as there are clearly applications that will not fit the
same solution as one another. It's no use inventing a hammer and simply
describing the whole world as a nail...
Secondly, with respect to compatibility and unbundling - the two issues are
closely related. However, I do not think we can get our requirements by
looking at any and every (non-standard) service that is out there and trying
to fit in around them. I suggest the starting point should be
standards-based compatibility. FSAN has defined spectral standards, these
have been adopted by NRIC-5 (committee of the FCC). It seems likely that
spectral compatibility on a cable will soon be regulated as closely as it is
in the airwaves. This makes sense as a cable binder behaves like a shared
medium at higher frequencies.
I think that the main difference in our viewpoints is the angle we are
looking from. I see the rate/reach as a technical problem (i.e. what's
possible) and try to meet the requirements from there. I see the
compatibility as a regulatory issue and expect that if we comply then others
This is a very healthy discussion for the group - it is very important that
we can align the expectations of the majority in order to make progress on
developing the standard.
"Lough, Andy" wrote:
> I see the key issues as being broken down into 3 simple areas (my frame of
reference is the EU market only)
> we need to consider the needs of all operators (telcos,ISPs, etc.). Rapid
deployment of Ethernet broadband services will only practically be achieved
over copper in the short to medium term. put simply it will be impractical
for carriers to install fibre everywhere due to deployment costs. Carriers
on the whole do not have the finances or ability to raise finances to cover
extensive fibre deployments (to every building currently copper connected).
This leaves the existing Copper as the main practicable medium for
deployment as an existing asset(excluding wireless which is outside the
scope of this forum).
> reach - reach is a practical issue. If we are to support all service
providers in a given market we need to be able to support longer distances
to ensure the maximum possible coverage from a given area, hence a maximum
potential subscriber area and thus the maximum possible revenues for that
carrier to sustain its business. This applies in all areas, rural
definitely, but also in city centres, where COLO opportunities are
congested, the need to span multiple areas via copper can clearly be
justified. For specific numbers that's down to opinion, 12Km is a hell of a
long way, I believe 6,000ft @30-40Mb+ and 12,000ft@15-20Mb+ would be ideal.
thus enabling both city centre and business focused services to be
covered(shorter loops high bandwidth) and more distant/home applications to
be served (at longer distances, longer loops lower bandwidth).
> bandwidth - Bandwidth needs to be focused on the applications, I believe
most thoughts are in the 20Mbps range (for home), however the key issue is
that it needs to be flexible such that a deployment of a technology doesn't
restrict the ability to service customer needs based on a technology
symmetry limitation (indeed inline with the basic principles set by the
original Ethernet standard).The SME market is one area I believe will demand
distance and BW above 6000ft@30Mb, for ASP type services, with fibre install
being negated by a suitable copper deployment. Allowing a service provider
to be ultimately flexible and using a single technology for deployment will
be a key advantage over current technologies - hence encouraging adoption of
Ethernet first mile propositions. We also need to consider that application
bandwidth requirements will only increase going forward as adoption
increases and service providers generate content based businesses, so we
should design in some s!
> re capacity upsides if at all possible to ensure longevity of the
> compatibility - For me this is THE most important issue. We have to keep
in mind the EU directive on unbundling the copper loops. This means any
particular service provider may have an SLA and contract with a customer
delivering copper based service over Ethernet - if another service provider
installs a service the next day in the loop that interferes/is interfered
with by EFM then it will become impossible for the local loop unbundling
to work, this will cause the whole broadband over copper deployment to fail
as those tasked with managing the local loop look to restrict access to both
service providers and technologies. As we are here to set a successful
technology standard to encourage the deployment of Ethernet in the First
mile, then compatibility in local loops must be allowed for.
> compatibility, if built in as an intrinsic part of the technology, should
also be considered when looking at the home end, where technology advances
and implementations both current and future are likely to evolve. We will
likely see a combination of current and new wireless , plus wired (copper
e.g. HPNA) and more likely power line technologies deployed at ever
increasing rates to meet the consumer needs. (power line has my personal
vote @ 15Mb-40Mb over the next 3 years). We cannot assume spectral
containment of these signals. using powerline for example it is impractical
to filter a power cct, and the signal leakage from the cables themselves
likely running in parallel to the copper telco cables will introduce
crosstalk that needs to be planned for.
> As engineers we like to see things in black and white, but the truth is
the world is grey. a perfect pair of copper doesn't exist, no one single
example customer requirement can represent the complete overall
> The key to our success is a standard that will do the most for the most
number of customers in the simplest way without imposed restriction. (pretty
much in line with the achievements of the original Ethernet standards)
> Andrew Lough, Mitel Networks
> -----Original Message-----
> From: Vladimir Oksman [mailto:oksman@xxxxxxxxxxxx]
> Sent: Monday, August 13, 2001 9:19 PM
> To: Sherman Ackley
> Cc: Stds-802-3-Efm (E-mail)
> Subject: Re: [EFM] EFM Requirements
> Dear Sherman,
> thank you very much for this significant and really helpful input. A
> of questions for clarification anyway.
> 1. By your experience only two MPEG-2 channels are required. Why, however,
> telcos were pushing so strong for 22Mb/s downstream for VDSL motivating
> a need in 3 video channels. Is there some specifics in video service over
> Ethernet you keep in mind?
> 2. You mentioned loop length of 10-12 km. It seems to me that the
> will allow 1-1.5 km. Does it still make sense to work on EFM?
> 3. You mentioned compatibility with HPNA. Here several questions come to
> A. Is it right that you assume EFM running over the home wiring?
> B. If yes, do you mean HPNA running over the same wire with EFM or
> different wires?
> C. What kind of HPNA do you keep in mind (there is no standard on
> Vladimir Oksman, Broadcom Corporation.
> Sherman Ackley wrote:
> > Service Provider Requirements for Ethernet in the First (two) Mile(s):
> > Sherman L. Ackley, CTO
> > The National Rural Telecommunications Cooperative provides services to
> > 350 member independent telephone companies who serve over 6 million
> > lines. Ethernet in the first mile is the most promising technology for
> > delivery of integrated voice, video and data services in the suburban
> > rural areas served by our Members. As the Chief Technology Officer for
> > NRTC, I would like to submit some practical requirements as seen by the
> > service providers most likely to implement this technology in the USA.
> > intent of this contribution is to help the study group prepare the
> > requirements document based on actual needs.
> > The user locations will be 90 percent residential and 10 percent
> > Of those businesses, 90 percent will have 10 or fewer PCs.
> > The system must work over standard high capacitance telephone outside
> > cable. Binder group integrity is not assured. The technology should
> > force removal of bridge taps and end sections. It needs to operate
> > degradation at binder group fills over 70%.
> > System reach is the most important aspect of the design. Ethernet in
> > first mile must operate over the longest reach possible. The number of
> > households and small businesses served by a node is proportional to the
> > square of the reach. For example, a reach of 3 km can serve about 100
> > single-family homes per node. Doubling the reach to 6 km increases the
> > served per node to 400. And with a 12 km reach, 1600 homes per node can
> > served. This assumes 100 percent subscribe. At 25 percent
> > short reach technology gets down to some dismal financial outlooks in
> > of cost per revenue producing subscriber as well forcing the
> > too many street corner server nodes.
> > Coexistence with HomePNA on the same cable pair is essential. This
> > will be necessary in over 75% of households served with Integrated
> > services. For example, a data stream of 10 Mbps will support two MPEG-2
> > high-resolution standard TV signals. The DSL will carry this to the
> > service set-top box/home gateway that can be located anywhere in the
> > The Gateway device will terminate the video and data for use at the
> > TV, it will then forward the second video and data over the same cable
> > to other set-top boxes and PCs within the house using HomePNA.
> > Peer-to Peer (or server to server) communications requires that the
> > be adaptable so that full rate is available upstream or downstream as
> > required by the user generated traffic. For example, it is now possible
> > record MPEG-1 video on a camcorder and e-mail it over the Internet.
> > Unfortunately, sending the e-mail over a conventional fixed data rate
> > ADSL/VDSL system takes forever for the 20 Mbps file.
> > There is little demand for sending three simultaneous MPEG-2 video
> > to the home. This is based on the analysis of over 20 million DBS and
> > digital cable subscribers. In fact, two streams are required in only 30
> > percent of households. It is far more economical to install a second
> > Ethernet Subscriber Loop (ESL) for the one in 100 who want three HDTV
> > than to burden all with the high costs required to support a higher bit
> > short reach technology such as VDSL.
> > In conclusion, long reach is of paramount importance. For delivery of
> > Standard TV signals, 10 Mbps at 12 km is required. For one HDTV plus
> > Standard TV, 20 Mbps at 12 km is desired. Also, the selected technology
> > should allow data to flow in either direction at the full data rate.
> > Finally, the technology should be spectrally compatible with HomePNA
> > requiring the use of a splitter at the residence.
> > Finally, feedback on these ideas from other service providers and
> > invited.