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Re: Cable Modem [really more about PPPoE]

  • From: Fletcher E Kittredge
  • Date: Tue Jun 26 12:12:46 2001

On Tue, 26 Jun 2001 10:28:16 -0400 (EDT)  Chris White wrote:
> The other would be to Wholesale the last mile connection to the ISP
> customer. In this scenario you need to hand off the end user traffic to
> your ISP customers.
> DHCP alone is not a viable option in this model. How do you get the end
> user traffic to the ISP and back in a pure IP environment? Policy routing,
> GRE, MPLS, force your ISP customer to interconnect at every location,
> etc.?

Hello Chris;

You provide frustrating few details and a statement "DHCP alone is not
a viable option in this model."  Could you restate more concretely
what is your design problem which can only be solved by
ATM/MPLS/PPPoE?  I hesitate to answer for fear that there is some
constraint I don't know about.

> At this point ATM and PPPoE become considerations each with its own 
> advantages. If the service offering is business class ATM may be preferred
> (required by your customer) for COS/QOS. From a configuration management
> standpoint PPPoE has advantages especially in a residential environment as
> you do not need to reconfigure the PVC when the end user changes
> providors.

What follows is not directed at you personally, but you happened to say
the wrong thing at the wrong time :)  Apologies in advance.

<rant>

I don't believe any of this "ATM is the way to do" COS/QOS crap.  I
have had it in my face for 10 years (my graduate work in the early
90's was performance of IP over ATM.  This just in: it sucks.)  IPoATM
has never worked; prove to me it will work, then we can talk.

Same goes for MPLS, with knobs on.

Fat pipes; big buffers; simple protocols; get out of the way.

</rant>

We avoided doing DSL (much) until Etherloop and Ethernet was available
because ATM sucks so much.  I don't have much sympathy for people who
decided otherwise.  They knew, or should have known, the problems with
the ATM pvc approach.

If IPoATM worked; Ethernet would have been dead long ago.

> In a wireless environment this becomes even more of a consideration as
> most of the current hardware is limited in ATM or L3 functionality...

I am sincerely sorry you are stuck using broken hardware.  As a person
who has thrived by deliberately passing up "the latest thing" until
the proper hardware was available to implement good designs, I urge
you to question your assumptions about whether using broken hardware
is a good idea.

> I do not intend to argue one technology over another, just to point out
> that there are reasons PPPoE exists and is in use.....

Reasons don't equate to good reasons :)

> A good network design also needs to consider the business model of the
> company it supports.

I couldn't agree more!  But the converse of that is true; the business
model of a network company should reflect good network design.  I
believe the only workable model for networking companies is to have
network engineers involved at the highest levels.  That is, they have
to have veto power over decisions.  I don't understand how people
think they can thrive in an industry in which they do not have at the
senior level deep knowledge of the product.

My undergraduate degree was in English; my graduate degrees are in CS.
I worked for nine years at BBN before starting this company.  Our COO
was an a EE and a practicing network/compuer engineer for years before
he got his law degree.  Our CFO was a CPA, but has been in the
commercial Internet business since its inception (ANS/AOL/UUnet).
Technical experience works for us, while I note success does not seem
to be widespread in the industry.

regards,
fletcher




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