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Re: Cable Modem [really good network design]

  • From: Wojtek Zlobicki
  • Date: Tue Jun 26 15:15:32 2001

----- Original Message -----
From: "Fletcher E Kittredge" <>
To: "Wojtek Zlobicki" <>
Cc: <>
Sent: Tuesday, June 26, 2001 2:52 PM
Subject: Re: Cable Modem [really good network design]

> On Tue, 26 Jun 2001 14:27:29 -0400  "Wojtek Zlobicki" wrote:
> > > The Ethernet protocol was designed to adjudicate and route packets
> > > internal to one homogeneous, physical network.  It handles media
> > > access, security, reliablity and routing in that one physical network.
> >
> > What does Ethernet have to do with routing ?
> Routing in its original sense.  You stick an Ethernet frame in here,
> it traverses a number wires connected by boxes which make decisions as
> to which wire it should go out on.  It then pops out on the other edge
> of the network.  Magic!
> A network of Ethernet switches looks a heck of a lot like routers.
> They are certainly smarter than the IP routers of circa 1983.
> > The problem you dont really have one physical network. We are trying
> > to extend Ethernet into a logical network.
> Who is "we" in this statement?

Those using PPPoATM/E

> >  The
> > reason that I like PPPoATM is that the end device requires littel
> > intelligence , it knows one PVC, and all changes (linking them to the
> > ISP of choice, propogate easily downstream)
> Little intelligence to implement ATM?  Never heard that claim before.

Much easier to place a $300 CPE (Cisco 678 which speaks ATM).  Than a 1605
(chosen for the fact that its about the cheapest Dual Ethernet Router from
Cisco).  How do you propose that we bring Ethernet to the customer ?  The
now defunct CLEC that I worked for, used 678 and 1483 so that the 1605 did
the routing (as far as our netowork was concerened, we were
bridging/switching these customers, the fact that they ran IP was their

> Contrast the cost of an Ethernet chip with an ATM chipset.

ATM to the desktop never took off, whats wrong with Ethernet over ATM ?
With devices such as
IADS, it allows for easy differentiation of traffic.  Now you can cary voice
and data over the same
physical link without worry.  ATM is expensive in the core but inexpensive
at the customer prem ($300 for a ATM DSL modem is relativel cheap,
especially since it is a router , if you want it to be).

> > .RFC 1483 (Ethernet over
> > ATM, used in DSL and plausibly in cable ) is a great idea for business
> > but not suitable for home users.  Hardware that you speak of becomes
> > just too expensive.
> Define "great idea".  Compare and contrast with all the failed DSL
> providers which used ATM.  Use one DSL/ATM provider who is making money as
> an example.  No excuses please.

Market GLUT and not technology failed here.  I was able to completely
reprovision a customer in about two minutes in a PPPoATM network we ran.
PPPoATM allows for a easily managable resale strategy, if your sales staff
and wholesalers can't sell the service, thats not the fault of the

> How do you reconcile the cost of the hardware being too expensive with
> the statement above that ATM requires little intelligence?

> > It appears as if someone has thought of this before   Someone is
> > doing this already (I don't know the name of the company), taking
> > cable
> > modems and using wireless for intramodem communication (why re-invent
> > wheel)
> > instead of copper.
> That would be a good idea.
> regards,
> fletcher

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