RE: Question on ATM w/ FreeBSD

On Mon, 6 Sep 2004, Harti Brandt wrote:

> On Sat, 4 Sep 2004, Ted Mittelstaedt wrote:
>
> TM>> If your card does not support VPI 1, you need a small ATM switch to move
> TM>> ATM PVCs from one VPI to another. Fore ASX-200BX is excellent small and
> TM>> cheap switch.
> TM>>
> TM>
> TM>Are any of the cards mentioned - Fore LE155, PCA-200, HE155, not support
> TM>VCI 1?
>    ^^^ VPI probably?
>
> The HE155 has a configurable VPI/VCI space of 12 bits that you can split
> between VPI and VCI. Per default the driver uses 2 VPI bits and 10 VCI bits.
>
> The PCA-200 definitely can do only VPI 0.
>
> For the LE155 I don't remember.

The LE155 can split the bits 0+12, 1+11, or 2+10, but the driver defaults
to 0+12 (VPI=0, VCI=0-4095).  Since there will be an ATM switch anyway for
the DS3-OC3, this should not be an issue.

Incidentally, the LE155 does not have a limit on the VPI/VCI combinations
for the transmit side, just the SAR on the receive.  So if RX traffic is
light and/or you don't mind spending CPU cycles doing SAR in software, you
could make a driver that had no VPI/VCI limits.  At one time, I was
thinking about doing this for an ATM/DSL access router.

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

I would definitely recommend the Fore switch over the SA100 (PSAX100). The
modules and spares will be a lot easier to find for the Fore.  Unless you
really want the dual power supplies of the ASX-200BX, you can get the same
switch cheaper by putting the SCP-ASXHA CPU board in the ASX-200WG.  In a
setting with no SVCs, I don't see any need to upgrade the CPU though.

For that matter, the older and larger ASX-200 switches would be just fine,
and you can probably buy them all day long for under $100 on ebay. Just
be sure to get a spare, as the hard drive won't last forever. (It's a
2.5" SCSI, and a bit hard to find.  Old Mac powerbooks are one source.)

All the best,

-Richard
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