Question on ATM w/ FreeBSD

[Ted Mittelstaedt]

> -----Original Message-----
> From: alex at pilosoft.com [mailto:alex at pilosoft.com]
> Sent: Saturday, September 04, 2004 6:11 AM
> To: Ted Mittelstaedt
> Cc: freebsd-atm at freebsd.org
> Subject: RE: Question on ATM w/ FreeBSD
>
>
> On Sat, 4 Sep 2004, Ted Mittelstaedt wrote:
>
> > When I got that response I followed up with a second query to the
> > carrier of whether the encap was RFC1483 Bridged or RFC1483 Routed.
> > Apparently that exhausted the meager store of ATM knowledge that the
> > technical contact had and the question was referred up the chain,
> > presumably to someone more knowledgeable.
> If you are dealing with ILEC ADSL in US, it is almost always
> 1483-bridged,
> that is, you going to have all (N) of your customers aggregated over (M)
> PVC. You'll have one PVC per "gateway router", no matter how many
> customers there are.
>
> > The owner of the ISP wants to go with this particular carrier because of
> > some deals we have setup would make it very cheap, much cheaper than
> > anyone else.  Unfortunately it looks very much like we would be the only
> > ISP in Portland OR that gets an Internet feed delivered via ATM.  (at
> > least, the only local one)  I think probably there's a few national
> > carriers with POPs here who use ATM on their backbones, no doubt.  But I
> > have a good bit of knowledge of our competitors here and highly doubt
> > none of the rest of them are doing this, most likely because they
> > wouldn't understand how to put it together.  Few of them are multihomed,
> > even.
> Let me guess - you want to put IP feed on the same ATM interface that you
> get your DSL customers on?

No.  We have 3 DS3 atm feeds, the DSL ones are one to Qwest and one to
Verizon.
The 3rd DS3 atm is an egress to another carrier that provisions frame
circuits
in our area.

All of these are only egress DSL.  No backbones (in this area at least)
provision
over ILEC atm clouds.

In any case bringing in feeds on the same DS3 as egress DSL to customers
would
mean attempting to run BGP on the same router the DSL is going out on.  It
would
be a terrible octopuslike configuration, all eggs in one basket, and prone
to
lots of trouble.

Our feed routers that run BGP are separate from our egress routers.  The
egress
routers that have the DS3s in them are in fact Cisco 7206's.  (nonVXR)
However
the 7206 is not a powerful enough platform to run BGP on nowadays when you
run
a full set of access lists.  The 7206VXR is barely adequate but it's much
more
expensive.  And Cisco IOS lacks many critical tools needed for
troubleshooting
problems, it is a very unsuitable backbone router.

>
> > As a result of this the salespeople of the carrier we are talking to
> > that services our market don't know diddly squat about atm.  I won't
> > post who it is so as not to embarass them.
> Portland is Verizontal area, isn't it?
>

Both Qwest and Verizon are ilecs here.  We are not talking to either of them
for this project.

As a matter of fact when we went to a DS3 with Verizon for DSL egress, none
of the Verizon techs could supply any information on how the DSL vc's would
come into our DS3.  I had to determine that by trial and error.  I still
don't
know exactly the optimal values for the burst rate.  120 seems to work with
Cisco IOS but nobody at Verizon could tell me how their atm switches were
configured for DSL.

> > > its Variable Bit Rate. In this case you should get either and IDT77252
> > > or IDT77211 based card (I don't know whether there are cheap 77252
> > > cards, but you find Fore LE155 with a 77211 for a handful of $ on
> > > ebay). Richard probably knows better to what extend the LE155 supports
> > > VBR.
> ILEC ADSL is almost always UBR, and don't need to worry about VBR support.
>
> On other hand, you *do* need to worry about your ATM cards supporting
> non-zero VPI, because your customers will be on VPI 1. Many cards don't
> support that.
>

The PA-A3-T3 cards for the 7206 are cheap and support this, in addition
to bandwidth shaping on a per-vc basis.

> If your card does not support VPI 1, you need a small ATM switch to move
> ATM PVCs from one VPI to another. Fore ASX-200BX is excellent small and
> cheap switch.
>

Are any of the cards mentioned - Fore LE155, PCA-200, HE155, not support
VCI 1?

> > My suspicion is that it's going to end up being Routed.  The reason why
> > is that we are already using a different group within this carrier to
> > provide Frame Relay to customers -ie: we buy Frame circuits from their
> > network to supply bandwidth to customers.  Basically it's ATM vc's from
> > us to their ATM switch which interworks it to a Frame circuit that the
> > end user sees on the usual T1.  That is of course a completely separate
> > DS3 than what we are looking at buying.  But the circuits provisioned
> > off that are Routed not bridged, and all5snap, and vbr.
> >
> > It would also almost certainly be a single VC on the DS3.
> >
> > DSL egress in this market, by contrast, is all Bridged, both
> with Verizon
> > and Qwest.  (we have both those ilecs here, ugh)  They both use vbr and
> > aal5mux.
> >
> > I have another question for you guys,- if I am using routed/vbr
> is there any
> > benefit to using a forerunner he155 and the fatm() driver as opposed to
> > a Fore LE155 with the idt() driver?  Also, what exactly is the
> difference
> > between a Fore LE155 and a Fore PCA-200 (which uses the hfa() driver I
> > understand)?
> >
> > You are right in there being no cheap IDT77252 cards out there.  I don't
> > have $2-3K on this project to throw into atm pci cards. :-(
> No real need to get HE vs LE. I am doing all of this on linux on LE
> card...
>
> > Has anyone worked with the Ascend/Lucent/Avaya PSAX gear, like the PSAX
> > 100? Is that an ATM switch that could run a VC from one interface to
> > another? The documentation on Avaya's site is very unclear plus the PSAX
> > 100 has been long discontinued.  But because of that they appear to be
> > rediculously cheap on the secondary market.
> Like I said, take ASX200BX - it is still supported.
>

The switch chassis themselves are cheap enough on Ebay.  But where you run
into trouble is the DS3 cards for them usually aren't included with the
switches, and are a lot harder to find secondhand.  Not impossible, though,
but rarer.

And I don't much care about the supported/unsupported aspect of the
equipment
I use anyway.  I'm the first line of support here.  And the user community
like the mailing list here, is the second line.  And it doesen't make a
lot of sense to spend $2K a year on a support contract with Cisco for a
used 7206 that you bought off Ebay.  For starters you don't get hardware
support anyway, and secondly, I've used Cisco support enough times in the
past to know that they aren't much good for the truly knotty problems.  If
we are buying used Fore switches/atm cards/ etc. I am not expecting any more
support than a copy of the user manual.  Remember this is all going into
a FreeBSD router that will be running BGP, so I'm already on my own for
support there, anyway.

The Lucent PSAX gear I've seen on the secondary market, some of it is
going for under $100.  Compared to a used Fore ASX200BX at $800+, to me that
is worth screwing with it - that is, if anyone can possibly confirm that
the PSAX even is an ATM switch.

Call Cisco support sometime and ask them why your 7206 running 12.0.7T
IOS reboots about once a month or so.  That's support for you.

Ted

> >
> -alex
>
>